MEDIA EMBARGO until NOVEMBER 12, 2002
Abstracts
(alphabetical by first author)
ALLEN, Y. (allenyc@lsu.edu)*, C. WILSON, H. ROBERTS, AND J. SUPAN; Oyster Geophysics Program, Department of Oceanography and Coastal Sciences, SC&E, Louisiana State University, Baton Rouge, LA. Using sidescan sonar to assess the impact and persistence of natural and anthropogenic disturbance to low‑relief oyster habitats in coastal Louisiana.
Traditional methods used to assess oyster reef distribution and condition are only able to provide subjective point information, which is often poorly georeferenced. Maps of oyster habitat in shallow waters are therefore typically extremely generalized, giving few details about the true distribution, character and dynamics of reefs. Sidescan sonar offers a significant advantage for oyster reef assessment in the turbid waters of coastal Louisiana. We used sidescan sonar in ultra‑shallow (<2m) waters to completely image over 19,000 ha in Louisiana estuaries in advance of an impending freshwater diversion project. We also conducted four years of intense annual surveys in a more restricted area (320 ha) with a diversity of reef types and culture intensity to examine natural and anthropogenic impacts on oyster reef extent and character. Our intensive surveys identified older stable reefs that had not been actively worked. Shell abundance and structure on these reefs were high, but oyster meat productivity was low. Areas of intense oyster culture were characterized by low relief reefs that frequently showed distinct evidence of scarring from dredging and other anthropogenic sources. Smaller scars caused by oyster dredging typically healed through the within time period of our study while larger anthropogenic scarring did not diminish over the four years. We also deployed the sonar towfish over an area immediately before and after both seeding and harvesting to establish a quantitative relationship with sonar reflectance. These relationships can be further used to predict the impact of harvesting and seeding on the extent oyster habitat.
ALEXANDER,
C. (clark@skio.peachnet.edu)*1, G. MCFALL2, T. BATTISTA3,
AND R. BOHNE2; 1Skidaway Institute of Oceanography,
Savannah, GA, 2Grays Reef National Marine Sanctuary, Savannah, GA, 3National
Ocean Service, Silver Spring, MD. Benthic habitat characterization of the
Grays Reef National Marine Sanctuary using sidescan, multibeam and GIS
techniques.
NOAA’s Grays Reef National
Marine Sanctuary has been completely mapped by the NOAA ship Whiting using
multibeam and sidescan sonar techniques. The
resulting data mosaics portray the geologic controls on the character of reef
habitat as well as the signatures of modern processes affecting the reef.
The multibeam data differentiate between the rocky and sandy habitats and
illustrate the influence of pre-existing geologic structure on the general
morphology of the reef. Sidescan data highlight the fine-scale detail of the rugged
reef surface, the influence of bioerosion on the reef surface and the dynamics
of mobile, unconsolidated sediments, which periodically alter reef benthic
habitats by covering and exposing rocky substrate. GIS techniques, coupled with the high-resolution sidescan
data, are being employed to automatically resolve and classify benthic habitats.
Diver observations of fish distributions will be compared to benthic
habitat distribution determined from the sidescan and multibeam datasets.
ALMEIDA,
F. (frank.almeida@noaa.gov)*1, P. VALENTINE4, R. REID2,
L. ARLEN2, P. AUSTER3, J. CROSS2, V. GUIDA2,
J. LINDHOLM3, J. LINK1, D. PACKER2, J.
VITALIANO2, and A. PAULSON2; 1National Marine
Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA, 2National
Marine Fisheries Service, Northeast Fisheries Science Center, Highlands, NJ, 3NOAA,
National Underwater Research Program, University of Connecticut, Groton, CT, 4U.S.
Geological Survey, Woods Hole Field Center, Woods Hole, MA. The effectiveness
of marine protected areas on fish and benthic fauna: the Georges Bank closed
area II example.
In late 1994, a
substantial portion of eastern Georges Bank was closed to commercial fishing
(Closed Area II) to assist with stock rebuilding. After about five years of closure, the southern portion of
CAII (south of 41º30'), exhibited a substantial increase in biomass and density
of sea scallops, Placopecten magellanicus,
and was reopened to the scallop fishery. Before
the industry was allowed entry into this area, we conducted a survey to monitor
the recovery of benthic habitat and fauna inside CAII.
Sampling sites were selected in a paired station design for an
inside/outside comparison; a grid design was used to monitor the remainder of
the inside area. At each station,
we conducted video transects, collected still photos, CTD casts, and sediment
samples for physical and chemical analysis.
A Smith‑McIntyre bottom sampler was then used to sample the benthic
community, followed by an otter trawl. Trawl
catches were sorted to species and all fish and invertebrates were weighed,
enumerated, and measured. Stomach
contents, maturity observations, and age structures were collected for selected
species at each station. Our
results suggest limited differences between the inside/outside paired stations
for species composition, community diversity, species richness, and trophic
ecology. Fish abundance and biomass was also similar inside and
outside the area; however, most individuals of a species were larger inside than
outside. The lack of other major
differences is likely a result of the fact that the seabed in the southern
portion of CAII is a relatively high‑energy sand habitat of low to
moderate complexity and has a relatively low vulnerability to trawling and
dredging. Other parts of closed
areas on the northeast shelf may exhibit stronger gradients for the same metrics
due to the presence of higher complexity gravel habitats and increased
vulnerability to bottom tending fishing gear.
The subtle differences in the size structure of fish species we observed
in CAII may have significant implications for the population dynamics of
commercially valuable species.
ANDERSON, JOHN T. (andersonjt@dfo-mpo.gc.ca);
Northwest Atlantic Fisheries Centre, Department of Fisheries and Oceans, St.
John’s, Newfoundland, Canada. Linking fisheries to benthic habitats
requires observations at multiple scales.
Management of commercial fisheries
typically occurs at the scale of fishing banks for annual periods. Spatial
structure within management areas is usually ignored. Historically, fisheries
observations have been at the scale of individual bottom trawl tows allocated
randomly within strata. Analyses of these data can reveal spatial structures
within bank-scale management units that are consistent over many years. We
interpret spatial stationarity as an indication of preferred habitats. In
Atlantic cod (Gadus morhua), we have
found that spatial structure is size dependent, where small juveniles occupied
different areas than larger conspecifics. Within these large areas of occurrence
we ask: how are juvenile cod distributed? Recent research on juvenile cod has
revealed spatial structure can be on the order of meters. However, relating
observations at small scales to larger areas remains a central problem facing
fisheries ecologists. Scaling-up requires definition of the spatial and temporal
heterogeneity of the fine-scale information and, secondly, correctly integrating
this heterogeneity to the larger scale. Integration requires information on the
spatial distributions of fish and their habitat associations from meters to
kilometres. Current technologies exist to carry out such observations. Our
recent research has combined acoustic and optical observational systems that are
capable of measuring fish and habitat distributions from meters to kilometres in
scale. Such combined observational systems should provide the descriptive basis
towards defining spatial heterogeneity and modeling this heterogeneity at larger
scales.
ANDERSON, T.J. (tara.anderson@noaa.gov); NOAA National Marine Fisheries Service. Santa Cruz Laboratory,
Santa Cruz, CA, and U.S. Geological Survey, Coastal and Marine Geology, Menlo
Park, CA. Understanding the complex nature of fish-seagrass associations.
Seagrass beds are rarely
homogenous entities. Instead, they form a mosaic that is structured at many
different scales. This has important implications for fish communities. However,
while seagrass beds are known to have higher abundances of fishes and greater
richness of species than unvegetated habitats, few studies have identified how
fish dispersions are modified by the spatial structure inherent in most
habitats. In this study a
multi-scaled observational (meters to 30 km) and experimental approach was used
to quantify the relationship between demersal fishes and subtidal seagrass areas
in Port Phillip Bay, Melbourne, Australia.
While most species were correlated with seagrass, either directly (e.g.
seagrass density and length) or indirectly (e.g. patchiness), seagrass alone did
not explain species distributions. Instead,
the association of a fish with it’s ‘preferred’ habitat was conditional on
the spatial structure of the habitat and the spatial location along the shore,
and that these landscape elements operated additively, or synergistically.
Additionally, a large-scale temporal dynamic both in the supply of larvae
and in seagrass health and presence also operated across all scales examined.
This study highlights that measuring the association between organisms and their
habitat requires many levels of information, ranging from understanding
individual habitat preferences at fine-scales, to understanding the
spatially-explicit structure of fish and habitat at landscapes.
Understanding and predicting fish assemblage structure in the face of
habitat change is no simple task, and relies heavily on the integration of
fine-scale empirical and landscape-level studies, but this study demonstrates it
is achievable.
ANDERSON,
T.J. (tara.anderson@noaa.gov)*1,2,
M.M. YOKLAVICH1, S. EITTREIM2, R. STARR3, L.
SNOOK4; NOAA National
Marine Fisheries Service. Santa Cruz Laboratory, Santa Cruz, CA, 2
U.S. Geological Survey, Coastal and Marine Geology, Menlo Park, CA, 3California
Sea Grant Extension Program, Moss Landing, CA, 4Moss Landing Marine
Laboratory, Moss Landing, CA. Fine-scale
distribution of groundfish populations: does habitat configuration and
patchiness matter?
At
a local scale, mobile organisms can exert considerable choice about their
occupancy of microhabitats. Fine scale habitat structure and patchiness can
modify the local distribution of fishes, and hence alter the strength of
interactions with each other and their environment. In this study we evaluated
the association of groundfishes with fine scale habitat composition and
structure. We integrated in situ fish
counts and habitat measures collected from the Delta submersible during
September 1994 with multibeam sonar data to explore how fine scale habitat
associations can be scaled to the larger landscape. This initial study
highlights both the importance of measuring fish-habitat associations at
multiple scales and the implications for ‘scaling up’ groundfish abundances
from fine scale transects to landscapes derived from broader scale habitat maps.
ARCHAMBAULT, P. (archambaultp@dfo-mpo.gc.ca)* and L. GENDRON; Department of Fisheries and Oceans
Canada, Institut Maurice-Lamontagne, Mont-Joli, Québec, Canada. The impact of scallop dredging on the American lobster (Homarus
americanus) in the Baie des Chaleurs, Canada.
Lobster fishers in eastern Canada
often complain that scallop dredging is responsible for local declines in
lobster landings of the American lobster through destruction of lobster habitat.
In Baie des Chaleurs, although scallop dredging is restricted to depths over 18
m to 27 m, depending on the season, it nevertheless occurs in areas where
lobster is known to be present at certain times of the year. The aim of this
project was to determine to what extent scallop fishery spatially overlaps
lobster grounds and to examine the impact of scallop dredging on lobster
habitat, more specifically in terms of loss of bottom complexity. Such a loss
could affect the survival of lobster at different stages of its life, especially
cryptic juvenile stages. The study was concentrated in two localities, for which
fisheries managers have received site-specific request to assess the link
between these two fisheries. Seasonal adult lobster distribution was examined
from lobster fishing activity and from off-season experimental fishing. Location
of dredging activities was obtained from scallop fishers logbooks. Habitat, in
overlapping areas, was characterized using an acoustic device. Furthermore,
abundance of juvenile and adult lobsters was evaluated along transects running
across the overlapping area. Additionally, experimental dredging was performed
at one depth and a “Before-After-Control–Impact design” was used to
identify the immediate impact of the scallop dredge on habitat complexity and
benthic community. Results will be discussed in relation to the possible
mechanisms explaining how lobster landings could be affected by scallop dredging
activity.
ARREGUIN-SANCHEZ, F. (farregui@ipn.mx);
Centro Interdisciplinario de Ciencias Marinas del IPN,
La Paz, Baja California Sur, México. Scientific advice to manage
benthic fisheries in Mexico: present status and perspectives.
As in many countries, the
tradition of scientific guidance for fisheries management in Mexico has been
based on the population dynamics of the target stocks. Most work developed for
management responds to the need to protect fisheries from intensive
exploitation; and in general terms, it is aimed at avoiding recruitment or
growth over-fishing. For this, different strategies have been implemented:
closures in time and space, minimum legal sizes, number of licenses, catch
quota, control of fishing effort, proportional escapement, and others. The type
of measure applied depends on the specific life strategy and problem. Complexity
of analytical tools also varies according to the degree of knowledge required,
from a general and simple population dynamics study to a formal and complex
simulation experiment including risk and uncertainty analysis. Other management
initiatives requiring scientific advice are aimed at conservation of some stocks
involving closures, use of excluders, as well as natural reserves and protected
areas closed to exploitation. Management is frequently conducted by federal and
local governments, but in some few cases co-management has been put in practice.
Mexico recognizes the importance of precautionary management principles emerging
from international forums, and a strong effort is being developed in this way.
Recently an ecosystem-based approach has alternatively supported management
schemes, but even when more information is clearly offered, the main problem is
that ecosystem-based management requires participation of all ecosystem users (i.e
all fleets) which in some cases results in negative benefits for some of them in
order to improve ecosystem health, global yields or stocks recovery. An
ecosystem approach is also being used to evaluate the impact of fishing on the
dynamics and structure of ecosystems, in which a strong effort is being
developed. This scientific work is aimed at supporting ecosystem health,
conservation and sustainable exploitation as common criteria. All the above
situations are illustrated with fisheries from all the littorals of Mexico.
BAIRD, S.J. (s.baird@niwa.cri.nz)*,
N.W. BAGLEY, B.A. WOOD, A. DUNN, and M.P. BEENTJES. National Institute of Water
and Atmospheric Research, Kilbirnie, Wellington, New Zealand. The spatial
extent and nature of mobile bottom fishing methods within the New Zealand EEZ,
1989–90 to 1998–99.
Temporal-spatial representation of
fishing effort distribution for the main mobile bottom fishing methods used in
New Zealand waters was investigated using 10 years of commercial effort data,
from 1989–90 to 1998–99. Tow position data were used to map the changes in
fishing patterns for fisheries using otter trawls on the bottom by collating the
number of fishing operations and the area swept into 22 km² blocks. The
intensity of effort varied between fishing years: many 22 km² blocks were
trawled more than 10 times, representing a swept area of more than 10 km². In
most fishing years a median of 2 tows were made in each block (with the third
quartile at 4–6 tows) and the maximum number of tows in a block was 370. Swept
area values were scaled to vessel power and graphic representations of these
data indicated areas trawled by heavier ground gear. Transects of selected areas
for each fishing year showed large differences in the monthly spread of effort.
Analyses of data for other otter trawl effort (predominantly inshore) and
shellfish dredge effort are based on larger fishery areas because fine-scale
position data were not collected. At this scale, spatial and temporal
relationships between fisheries with different gear types were evident. Ground
gear components used in the main otter trawl and dredge fisheries are described.
The requirements for consistent data collection and the application of this work
to a wider understanding of the impact of fishing in New Zealand waters are
discussed.
BARNES, P.W. (pbarnes@usgs.gov)*,
G.W. FLEISCHER, J.V. GARDNER, and K.M. LEE; U.S. Geological Survey, Menlo Park,
CA. Using laser technology to
characterize substrate morphology of lake trout spawning habitat in Northern
Lake Michigan.
As part of a strategy to
re-establish devastated native lake trout stocks, six areas of offshore and
coastal Lake Michigan habitat were mapped with SHOALS bathymetric lidar in late
summer 2001 in cooperation with the U.S. Army Corps of Engineers.
Decimeter elevation/bathymetric data referenced to IGLD85 datum were
obtained on a 4 m grid over a total area of about 200 km2 in water depths from 0
to 30 m. Shaded relief and
color-coded depth images were developed within coarser regional gridded
bathymetry and subaerial DEM as a basis for maps and initial interpretation.
Sparse substrate samples, underwater diver and useful but local video
observations supplement the morphologic information.
Three geologic regimes are present in the area and form the basis for
substrate, habitat and morphologic classification.
Devonian and Silurian carbonates underlie the region.
Morphologic scarps and bedding(?) lineations suggest bedrock at or near
the surface at all of the mapped areas, but confirmation is lacking.
Overlying bedrock are glacial deposits including compacted clay tills and
outwash gravel and sand. The
orphology and video observations suggest NW-SE basal till lineations and small
(1-3km) cobble and boulder moraines with outwash deposits. Post-glacial
reworking appears minimal in depths greater than 10m. Modern sand deposits
appear as thin down-drift (to the east) bedforms, sand sheets and depositional
lobes, except along the coast of Little Traverse Bay where well developed,
en-echelon nearshore bars are present at the head of the bay.
Laser waveform data is being analyzed for benthic albedo information and
biologic data is being incorporated with the morphologic and geologic
observations toward classifying and mapping preferred lake trout spawning
habitat
BEAULIEU, S.E. (stace@whoi.edu)*1,
H. SINGH1, and K.L. SMITH JR.2; 1Applied Ocean
Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods
Hole, MA 02543, 2Marine Biology Research Division, Scripps
Institution of Oceanography, La Jolla, CA. Analyzing time-lapse photographs
of the sea floor for changes in benthic community activity.
Time-lapse photographs or repeated
photographic surveys of the sea floor can be used to study the response of
benthic fauna to a natural or anthropogenic disturbance.
We are interested in the responses of epibenthic megafauna to a
temporally varying food supply, or flux of particulate matter to the sea floor.
At a deep-sea study site, we have amassed ~10 years of time-lapse
photographs, taken once per hour, of ~20 m2 of the sea floor.
We would like to analyze this 10-yr time series for seasonal changes as
well as long-term trends in the benthic community.
In addition to species composition, abundance, size, and activity of
megafauna (with an activity index based on area traversed per unit time), we
would like to trace sediment features such as mounds and tracks.
Because manual analysis of the large number of photographs is very
labor-intensive, we developed image-processing routines that make it easier to
analyze oblique photographs, such as detecting organisms and their tracks.
Our methods include: 1) digitizing the film, 2) adjusting light on the
images (histogram equalization), 3) converting oblique photographs to plan view,
and 4) automated image processing, with routines based on edge detectors and
morphological operators. We will
present results for a 4-mo time series at the deep-sea site, with natural
disturbance from a massive accumulation of phytodetritus on the sea floor. We plan to use these algorithms for photographs taken in
other soft-bottom habitats, including images transmitted in real-time from the
Hawaii-2 Observatory in the abyssal Pacific.
BENTLEY, S. J. (sjb@lsu.edu)*1,
W.F. PATTERSON2, Y. ALLEN3, W. VIENNE1, and C.
WILSON3; 1Department of Oceanography and Coastal Sciences
and Coastal Studies Institute, Louisiana State University, Baton Rouge, LA, 2Dauphin
Island Sea Lab, Dauphin
Island, AL, 3Department of Oceanography and Coastal
Sciences and Coastal Fisheries Institute, Louisiana State University, Baton
Rouge, LA . Geoacoustic and
geological characterization of juvenile red snapper habitat; Northern Gulf of
Mexico continental shelf.
Laboratory and small-scale in
situ experiments have demonstrated juvenile red snapper display an affinity
for low-relief shell-rubble habitat; however, the spatial extent and temporal
variability of large-scale shell-rubble features on the Mississippi-Alabama
shelf are unknown. Moreover, the seabed geology of the entire region in general
is poorly known, with little significant research conducted since the 1950's.
Therefore, to develop a geological understanding of quality juvenile snapper
habitat in the region, we have undertaken a program of sidescan seabed mapping
and seabed sampling in areas on the northern Gulf of Mexico continental shelf
that historically produced high, median, and low juvenile red snapper catch
rates in trawl surveys. Preliminary results of sidescan surveys and grab samples
indicate highest juvenile snapper catch rates are found near irregular
low-relief ridges of shell and sand, with CaCO3 content to 100%. The
ridges are elevated 1-2 m above the surrounding seabed and generally orient
along NW-SE axes. Surrounding seabed is more typical of the Holocene
transgressive sand sheet, composed of fine-medium muddy sand with shell content
<10%. Most shell material found on the ridges appears to be fragments of the
oyster Crassostrea (now highly
encrusted by epibionts), indicating ridges are of estuarine origin, and are
probably remnants of coastal shell reefs formed during the Holocene
Transgression (i.e., during the past ~6000 y). Ongoing research focuses on
elucidating origin of the ridges, developing a geoacoustic fingerprint for
quality juvenile red snapper habitat, and examining temporal and spatial
variability in juvenile snapper habitat utilization patterns.
Bergmann,
M. (m.bergmann@bangor.ac.uk)*1,
H. Hinz1 M.J. KAISER1, and S.I. Rogers2; 1School of Ocean
Sciences, University of Wales-Bangor, Wales, United Kingdom, 2CEFAS
Lowestoft Laboratory, Lowestoft, Suffolk,
United Kingdom. Assessing dietary specialism and food niche breadth of
cod and whiting to identify possible ‘essential fish habitats’ in the Irish
Sea, UK.
Demersal fish assemblages are
intimately associated with benthic habitats where they spend a large part of
their time feeding and avoiding predators.
Bottom fishing activities can degrade seabed habitats and change benthic
communities by reducing their complexity. Thereby
they can also degrade essential fish habitats such that they can no longer
sustain the fish species associated with them.
Having established a relationship between cod (Gadus
morhua) and whiting (Merlangius
merlangus) and specific Irish Sea habitats from consultation with fishers
and ground fish surveys we wanted to learn what functional role these habitats
play, i.e. as
sources of prey and shelter from predators.
Habitats complexity of stations with high and medium fish densities was
assessed using side scan sonar, QTC ViewTM and underwater
photography. Young cod were
particularly abundant in a habitat with mixed sediments (low grain size
sediments between stones and shells) and emergent epifauna off Belfast Lough
(Northern Ireland). Dietary
specialism indicates a close association with a particular habitat, while
broader diets within and between different areas indicate a weaker association
of a fish species with a particular habitat.
The availability of prey organisms was assessed by sampling epifaunal and
infaunal organisms with a 2-m beam trawl and a Day grab.
Demersal fish for condition and stomach contents analysis were collected
by otter and beam-trawling. The
results from stomach content analysis of cod and whiting are discussed in
relation to the prey availability found in the study areas and food niche
breadth.
BIZARRO, J.J.1, J.M.
FIELD (JField@ci.pacific-grove.ca.us)*1, H. G. GREENE1,
R.N. LEA2, and J. deMARIGNAC1; 1Center For
Habitat Studies, Moss Landing Marine Laboratories, Moss Landing, CA, 2California
Department. of Fish and Game, Monterey, CA.
Habitat associations of upper slope rockfishes (Sebastes spp.) and co-occurring demersal fishes in Ascension Canyon,
California.
Due to their typical life history
patterns (slow growth, late age at maturity, extreme longevity) deep-water
rockfishes (Sebastes spp.) are
especially susceptible to overfishing, as evidenced by recent declines in most
commercially targeted stocks. To
establish effective Marine Protected Areas (MPAs), the interaction between
fishes and their available habitats must be determined.
Our objectives were to describe habitat associations for upper slope
rockfishes and co-occurring fish species within the headward part of Ascension
Canyon at both large (1 to 10s of kilometers) and small (10s to 100s of meters)
scales. Geologic structure and lithology were investigated using high-resolution
multibeam bathymetric and backscatter data.
These data were interpreted to produce habitat maps of the study area.
Seafloor features and fish assemblages were then surveyed using the Delta
submersible at 50-meter intervals between 200 and 350 m.
Thirty-two ten minute transects were completed between two distinct,
large-scale habitat types. At 200
and 250 m, stripetail (Sebastes saxicola}
and greenstriped (S. elongatus)
rockfishes were the dominant fish species.
At 300 and 350 meters, splitnose (S.
diploproa) and shortspine thornyhead (Sebastolobus
alascanus) were the most abundant rockfishes. Large and small-scale habitat associations of these and
several other commercially important demersal fishes were also determined.
BLOESER, J. (Jennifer@pmcc.org);
Pacific Marine Conservation Council, Arcata, CA. Development of a West Coast
cooperative research program, working together towards better information.
The Pacific Marine Conservation
Council (PMCC) is presently working with federal and state agencies, scientists
and fishermen to develop a West Coast Groundfish Cooperative Research Program.
This program will provide a clearinghouse for ongoing cooperative research
projects. It will also house the primary source of information on research
priorities, funding and contacts for interested scientists and fishermen.
The need for systematically combining the expertise of fishermen with the
scientific rigor of researchers has clearly emerged in the evolution of our
Rockfish Rebuilding Campaign, launched in 2001. Cooperative research programs provide a unique opportunity for
those interested in fisheries to collectively resolve complex issues. Through
collaboration, federal agencies and fisheries managers benefit from the
experience, equipment, and insights of fishermen, while fishermen participate in
designing and conducting the research to gather data for superior management of
the resource. PMCC strongly believes that sustainable fisheries depend upon
implementing standardized methods of collecting, analyzing and applying the
'experiential' data of fishermen to fisheries science. Cooperative research also
has the potential to improve communication and trust while elevating the level
of scientific understanding.
BLYTH, R. E. (osp818@bangor.ac.uk)*1,
M.J. KAISER1, G. EDWARDS-JONES2 and P.J.B. HART3;
1School of Ocean Sciences, University of Wales-Bangor, Anglesey,
United Kingdom, 2School of Agricultural and Forest Sciences,
University of Wales-Bangor, Bangor, Gwynedd, United Kingdom, 3Department
of Biology, University of Leicester, Leicester, United Kingdom.
Biological and socio-economic implications of a limited access fishery
management system.
Marine reserves are considered to
be effective conservation tools in tropical waters, but to date few studies have
determined the economic and biological implications of limited access fishery
management systems in temperate zones. The Inshore Potting Agreement (IPA), a
fishery management system operated off the south coast of the United Kingdom,
was conceived to reduce conflict between fishers that operate towed
bottom-fishing gears and fishers that operate static gears. This system has
operated on a voluntary basis since 1978, and covers an area of 480km2.
In this study, an interview survey of fishers, associated industry members and
interested parties determined the economic implications of the IPA. Long-term
recreational angling records from within and outside the area of the IPA were
analysed to determine possible biological benefits for large-bodied fishes. The
results suggest that the long-term maintenance of the IPA is likely to have
greater economic and social benefits for local communities than if the area was
open to all fishing activities.
BRANCATO, M.S. (mary.sue.brancato@noaa.gov)*
and C.E. BOWLBY; Olympic Coast National Marine Sanctuary, Port Angeles, WA.
Survey of fishing gear and fiber optics cable impacts to benthic
habitats in the Olympic Coast National Marine Sanctuary.
In September 2000 the Olympic
Coast National Marine Sanctuary (Sanctuary) initiated a long-term monitoring
program designed to assess impacts to the seafloor and the benthic communities
from different intensities of commercial bottom trawling and the placement of
two fiber optics cables on the seafloor in the Sanctuary.
Survey sites were selected based on side scan and bathymetry data and
bottom trawling records from Washington Department of Fish and Wildlife, Oregon
Department of Fish and Wildlife, National Marine Fisheries Service and vessel
traffic tracking information collected by the Sanctuary.
We conducted our first two years of monitoring using the Delta
submersible equipped with underwater cameras, box core and a benthic suction
device (slurp gun). In addition, a shipboard bottom grab was used to collect
bottom samples. Four distinct
habitat types were monitored along low and high intensities of bottom trawling
both along the buried cable route and parallel to the route.
The underwater surveys were conducted at depths of 120 to 330 meters
along silt/clay, sand, gravel/cobble or boulder with mixed sediments.
Physical, chemical, and biological parameters were monitored.
BREMNER, J. (julie.bremner@ncl.ac.uk)*1,
C.L.J. FRID1, and S.I. ROGERS2; 1Department of
Marine Sciences and Coastal Management, Dove Marine Laboratory, University of
Newcastle upon Tyne, Tyne and Wear, England, 2Centre for Environment,
Fisheries and Aquaculture Science Lowestoft Laboratory, Lowestoft, Suffolk,
England. Biological traits of
the North Sea benthos – does fishing affect benthic ecosystem function?
Assessments of species composition
provide valuable information about the effects of anthropogenic activities.
However, we must learn more about how ecosystems function and why changes occur
in order to fully understand the implications of our activities and how to
manage them appropriately. Recent interest in the factors structuring biotic
communities has led to the use of variables such as feeding groups and
size-spectra in benthic assessments. These have allowed progress in the
examination of systems’ functional makeup but only address part of the picture
in terms of how ecosystems work. Biological traits analysis aims to investigate
the attributes of species within a community in order to get a picture of how
systems function as a whole. This approach incorporates information on the
interactions both between species and between species and their environment. It
includes information on feeding interactions, size, life history, habitat
requirements and morphology as well as retaining information on species
distributions. It is hoped that ultimately the approach will reveal the major
rules structuring benthic ecosystems and highlight the degree of perturbation
they can tolerate before this underlying structure breaks down. This poster
describes the application of biological traits analysis to the benthic fauna of
the North Sea benthos. The region has been heavily trawled for centuries and
changes in species composition have been linked to fishing. This study
investigates the functional structure of the ecosystem and how the traits
present have responded to fishing disturbance.
BROTHERS, G. (brothersg@dfo-mpo.gc.ca)*1
and J.J FOSTER2; 1Fisheries and Oceans Canada, Fisheries
Management Branch, Northwest Atlantic Fisheries Centre, St. John’s,
Newfoundland, Canada, 2Aquaprojects Inc., St. John’s, Newfoundland,
Canada. Effect of shrimp
trawling on snow crab resource in the northwest Atlantic.
The decline of the Northern
Atlantic Cod stock and favorable environmental factors have led to an increase
in the Northern Pink Shrimp (Pandalus borealis) Total Allowable Catch
from 37,000 MT in 1996 to 112,000 in 2002.
As well, an additional 365 new, <20 meter vessels have been added to
the existing fleet of 13, >50 meter vessels involved in harvesting the
resource. Shrimp and Snow Crab (Chionoecetes
opeilio) are known to cohabit the same area, and as such, many crab fishers
have expressed concern that shrimp trawling may be having a negative impact on
the crab resource. In 2001, a
two-phase study was begun to determine the interaction between shrimp trawling
and the crab resource. Phase
one of the study was conducted in a small area (0.5 x 4 miles) cohabited by crab
and shrimp. The experimental design called for three fishing trips to be
undertaken, the first directing for snow crab, the second directing for shrimp,
and the third directing for crab. Crabs sampled were examined to determine
‘new’ and ‘old’ leg losses and then released 10 miles from the study
area. Phase two of the study which
was undertaken in 2002, consisted of three, five-day shrimp trawling trips
carried out in an area 5 x 10 miles where shrimp and crab cohabit. The shrimp
trawl had three retainer bags attached underneath the trawl and behind the
footrope to capture the crab that passed over and under the trawl footrope.
12,000 crab captured in the retainer bags were examined for ‘new’ and
‘old’ leg losses and then released 10-miles from the study area.
Analysis of ‘old’ and
‘new’ leg losses were compared before and after trawling (phase I) and after
trawling and at various times of the year (phase II), and phase one and two data
were also compared. Results
presented (with confidence limits) that cover both phases indicate a low
percentage of recent leg loss, suggesting that shrimp trawling did not adversely
impact crab encountered during the two-phase study.
BROTHERS, G. (Brothersg@dfo-mpo.gc.ca);
Fisheries and Oceans Canada, Fisheries Management Branch, Northwest Atlantic
Fisheries Centre, St. John’s, Newfoundland, Canada. Promoting environmental
awareness and developing conservation harvesting technology for the fishing
industry.
The Fisheries Diversification
Program, a Canada / Newfoundland Cooperation Agreement, has four components. One
of which deals with Environmental Awareness and Conservation Technology. During
the past two years several projects have been carried out jointly with the
fishing industry. They include;
Awareness of Gillnet Environmental Impact, Cod by-catch in American Plaice
Gillnets, Impact of Scallop Fishing on Lobster Habitat workshop, By-Catch of
Juvenile Groundfish and Pelagic in Shrimp Trawls, American Plaice By-Catch on
Cod Longlines, Size Selectivity in Yellowtail Bottom Trawls, effect of Chaffing
Gear on Codend Selectivity, and Crab by-catches in Scottish Seines. The
methodology used and results obtained in each of these projects will be depicted
in a poster session. Results
obtained during some of the projects have produced changes in the way commercial
fishing is carried out and managed.
BROWN , E. (ftejb@uaf.edu)*1,
B. FINNEY1, S. HILLS1, and M. DOMMISSE2; 1Institute
of Marine Science, University of Alaska Fairbanks, Fairbanks, AK, 2Monash
University, Department of Geography and Environmental Science, Clayton,
Australia. Impacts of commercial bottom trawling on the sediment
characteristics and benthic community of essential fish habitat on the inner
Bering Sea shelf.
Evaluation of impacts to essential
fish habitat by commercial bottom trawling is needed to ensure long-term
sustainability of the ecosystems that support these fisheries. Changes in
sediment properties and benthic community composition resulting from bottom
trawling were determined, and compared to natural disturbance in a shallow,
sandy habitat in the Bering Sea. Our site is in the Nearshore Bristol Bay
Closure, where trawling is prohibited except for one commercial flatfish
fishery, and spans this fishery area and the Walrus Islands State Sanctuary,
which serves as a control. Acoustic data, cores, grabs and video were randomly
collected in the closed and fished areas, and immediately pre and post
experimental trawling. Wave and tide data from NDBC buoy 46035 were used to
estimate near bottom current speeds and the frequency and magnitude of sediment
resuspension events. Significant changes in the sediment grain size distribution
and chlorophyll a content indicate
shifts in the fine fraction to 2-3cm depth. Such changes may result from
redistribution by turbulence following the net, which differs in timing and
magnitude from naturally occurring wave-driven bottom currents. The implications
of these changes in the sediment structure are evaluated relative to shifts in
benthic communities. Of the epifauna, only the abundance of the dominant seastar,
A. amurensis is significantly reduced
after experimental trawling. This could be the result of direct removal as was
documented during fishing. Alternatively, a shift from a more dispersed
distribution pattern to dense feeding clusters associated with processing waste
may have biased our video analysis. Infauna analyses are in progress.
BROWN, J.K. (Jeff.K.Brown@noaa.gov)*, D.W. PRITCHARD, and
G.T. NOLL; NOAA National Ocean Service, Office of Coast Survey, Hydrographic
Systems and Technology Programs, Silver Spring, MD.
Distribution of acoustic backscatter imagery from NOAA hydrographic
surveys.
Congress appropriated $6.2 million in Fiscal Year 2002 spending for NOAA to
upgrade its hydrographic surveying equipment on board the four NOAA survey
vessels operating in support of safe navigation. This is NOAA's first fleet-wide hydrographic equipment
purchase since 1992. The NOAA Office of Marine and Aviation Operations,
together with the National Ocean Service's Office of Coast Survey, specified and
procured five Klein 5500 high-speed high-resolution side scan sonars—one each
for the NOAA ships RAINIER and RUDE, two for the WHITING launches, and one for
the BAY HYDROGRAPHER, which NOAA also uses as a systems test platform. In
addition, NOAA procured a Reson 8125 high-resolution multibeam echosounder for
each vessel, and installed a hull-mounted Kongsberg-Simrad EM1002 multibeam
echosounder aboard the WHITING. Ancillary sensors, software, and data
storage management purchased to facilitate the use of these systems will help
NOAA speed the hydrographic data to the nautical chart. In determining
equipment needs, NOAA placed primary focus on meeting Homeland Security
requirements in collaboration with the Naval Oceanographic Office. This
purchase upgrades NOAA's systems to 21st century technology so that
it can continue its mission to produce the navigation products essential to safe
and efficient maritime commerce. NOAA will also continue to develop
optimized algorithms and work processes, using these Commercial Off the Shelf
products, to share with and transfer to the entire hydrographic industry.
One of the secondary benefits to this upgrade plan is the increased ability to
apply these same technologies to the production of large area maps of benthic
habitat. The high-resolution echosounders and side scan sonars will create
exciting high-resolution digital terrain models of the underwater environment
and provide good estimates of large-scale variations in acoustic backscatter.
Demonstration of sample products will be the focus of the poster session.
CAHOON, L.B. (Cahoon@uncwil.edu)*1,
M.H. POSEY2, W.H. DANIELS3, and T.D. ALPHIN2; 1
Department of Biological Sciences, UNC Wilmington, Wilmington, NC, 2
Center for Marine Science, UNC Wilmington, Wilmington, NC, 3 302 Tate
Road, Belhaven, NC. Shrimp and
crab trawling impacts on estuarine soft-bottom organisms.
This project addressed some
possible impacts of trawling for crabs and shrimp in North Carolina estuaries on
populations of organisms associated with soft-bottom habitats. The organisms of
interest included benthic microalgae, demersal zooplankton, and macrobenthic
infauna, encompassing the lower trophic levels in the benthic food chain and the
essential trophic coupling that supports estuarine fishery production. The
approaches used in this project included sampling before and after experimental
trawling at several estuarine locations, sampling in areas actively trawled and
areas closed to trawling, and sampling during several seasons over two years to
address seasonal and inter-annual effects. Sampling began in February, 1999, and
ended in November, 2000 at six locations in the Pamlico River Estuary.
Experimental trawling had no significant effect on the biomass of benthic
microalgae, no consistent effect on the abundance of demersal zooplankton, and
only a slight but non-significant effect on the abundances of benthic
macrofaunal animals. Benthic microalgae were significantly more abundant in
untrawled locations than in trawled locations, with strong seasonal variation as
well. Abundances of demersal zooplankton were not significantly or consistently
different between untrawled and trawled locations. There were higher abundances
of benthic macrofauna in trawled locations than at untrawled locations, but only
at certain times of the year. Species dominance was fairly consistent between
trawled and untrawled areas, with only a few exceptions. While inter-annual
variation and substrate did have an effect, seasonal variation was far stronger
and seemed to have an overriding effect. We conclude that direct, negative
impacts of trawling activity on these soft-bottom organisms are small relative
to other sources of population variability. The soft-bottom communities we
studied experience considerable natural disturbance in these broad, shallow
estuarine ecosystems. Although trawling per se does not seem to have a
consistent effect on estuarine soft-bottom benthos, there are interesting
differences between trawled and untrawled habitats that merit further
investigation.
CALDWELL, P. (Phil.Caldwell@noaa.gov)* and P. SHERIDAN, NOAA
Fisheries, Southeast Fisheries Science Center, Galveston TX. Data sets
relevant to identification of essential fish habitat (EFH) on the Gulf of Mexico
continental shelf and for estimation of effects of shrimp trawling gear.
Our objectives were: to identify
data describing habitats, shrimp trawling, and other human activities on the
Gulf of Mexico continental shelf; to incorporate such data into a GIS format;
and to provide preliminary experimental designs for assessment of effects of
shrimp trawling on EFH. We developed 57 data layers describing habitat (benthic
organism densities, sand/silt/clay, digitized sediment and biotic community
maps), structures (bathymetry, State/Federal waters, safety fairways, oil and
gas, artificial reefs, bottom obstructions), and fishing (patterns of shrimp
fishing effort, experimental trawling sites/catches, closed waters). Best
opportunities for experimental trawling in closed waters lie in southern and
northwest Florida (permanent closures) and in Texas (seasonal closures).
Experiments in open waters need to account for seasonal closures, ambient
shrimping effort, and variations in sediments and their associated benthic
communities. Cross-Gulf replication is necessary to provide a fishery-wide
assessment of gear impacts. Most opportunities for replication exist at depths
of 18-27 m for both sand and mud habitats. Moving to waters only as deep as
46-55 m forces experiments to become more regional and less Gulf-wide in nature.
Benthic data are most dense off south Texas and Mobile Bay, less dense off
Florida, and are largely absent off west Louisiana and north Texas.
Non-extractive or no-take marine reserves could be used to study effects of
complete cessation of trawling on habitats and fauna (estimating recovery rates
of ecosystem components, conducting fishery-free gear impact studies). We
present only a few options - data sets are available on CD.
CARBINES*, G.D. (Carbines@storm.cri.nz);
National Institute of Water and Atmospheric Research, Dunedin, New Zealand.
The impact of oyster dredging on blue cod in New Zealand.
Little is
known about the potential impact of dredging on the growth and abundance of
demersal fishes. Observations of blue cod (Parapercis colias) and oyster
(Ostrea chilensis) fishing patterns indicate that dredging by the oyster
fishery reduced localized catches and changed fishing patterns of blue cod
fishers in Foveaux Strait, southern New Zealand. Towed underwater videos were
then used to confirm the impact of dredging on habitat complexity and numbers of
blue cod. An analysis of the diet and growth of blue cod from undisturbed
biogenic reefs and reefs modified by oyster dredging further showed that diet
complexity and growth of juvenile blue cod are reduced by dredging for oysters.
However, stabilizing dredged habitat with fresh processed oyster shells shows
promising signs of regeneration of blue cod populations in only a few years.
CARLSON, P.R. (pcarlson@usgs.gov)*1, P N.HOOGE2, A
STEVENSON1, G COCHRANE1, and P DARTNELL1; 1U.S.
Geological Survey, Menlo Park, CA 94025, 2U.S. Geological Survey,
Gustavus, AK. Extensive iceberg reworking of lower Glacier Bay sediments
provides unexpected geohabitat.
Complex iceberg gouge patterns were discovered in glacial marine sediment in the
lower part of Glacier Bay, Alaska, in water depths ranging from 50-100 m.
Individual gouges are as much as 5 km long, a few tens of meters wide, and with
several meters of relief. Previous acoustic profiling in this part
of the bay had not been of high enough resolution or density of coverage to
detect the vast area of gouges that were visible on multibeam imagery collected
in June 2001. These gouges were formed by large icebergs that calved
repeatedly as the Little Ice-age Glacier, which completely filled the fjord
about 200 years ago, retreated up bay. Massive icebergs with drafts to 100
m calved repeatedly from the glacier, as it retreated up the fjord. The
dominant gouge orientation, roughly parallel to the fjord axis, suggests that
the strong tidal currents, up to seven knots through Sitakaday Narrows, were
responsible for moving the iceberg keels into and across the seabed.
Surprisingly, the gouges remain unburied in this environment of high
sedimentation. This, in large part, is because the glaciers have retreated
more than 80 km up fjord from Sitakaday Narrows, thus the amount of sediment
presently reaching the ice gouges is largely restricted to local runoff and
plankton debris. In addition, the >7 knot tidal currents through
Sitakaday Narrows, effectively keep the ice-gouged fjord floor scoured clean of
fine sediment. This multibeam imagery is being used in our joint study of
physical and biological characteristics of benthic habitats (primarily Halibut
and Dungeness crab) in Glacier Bay. The habitat results also will be
applied to fisheries problems in southeast Alaska, especially to Marine
Protected Areas.
CHANG, S. (Sukwoo.Chang@noaa.gov)*,
J. VITALIANO and F. STEIMLE; National Marine Fisheries Service, Northeast
Fisheries Science Center, James J. Howard Marine Sciences Laboratory, Highlands,
NJ. Habitat and species associations of demersal fish and benthic
invertebrates in the New York Bight apex.
The associations among
demersal fish and benthic invertebrate species with numerous habitat variables
were investigated in the data collected during the 12 Mile Dumpsite Study
(12MDS) in the inner New York Bight (July 1986 to September 1989).
The 12MDS study was unique because synoptic measurements were made at
numerous levels of the benthic ecosystem over the 39‑month study period.
Also, a number of federally managed resource species spend all or part of
their life cycle in the inner New York Bight and adjacent estuaries.
Factor analysis and canonical correlation analysis reveal strong to
moderate associations among fish species, between fish species and water and
sediment quality variables, and between fish species and invertebrate prey
species. Furthermore, strong to
moderate associations were also found among invertebrate species and between
invertebrate species and water and sediment quality variables. The approach of
using multivariate statistical procedures to explore the associations between
habitat variables and important resource fish species can be used to better
understand the essential fish habitat relationships of these species.
CHIAPPONE, M. (chiapponem@uncwil.edu)*
1, D.W. SWANSON2, and S.L. MILLER1; 1Center
for Marine Science and NOAA’s National Undersea Research Center, University of
North Carolina at Wilmington, Key Largo, FL, 2Division of Marine
Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science,
University of Miami, Miami, FL. Impacts to coral reef benthos from lobster
trap gear in the Florida Keys National Marine Sanctuary.
Growth in the Florida Keys
fisheries for spiny lobster (Panulirus
argus) and stone crab (Menippe
mercenaria) has resulted in increased numbers of traps and environmental
impacts. During 1998 alone, the stone crab and spiny lobster fisheries were
estimated to utilize a total of 750,000 traps and 540,000, respectively. Impacts
from gear are exacerbated when traps are lost due to severe storms. This study
evaluated the distribution, density, and impacts to coral reef sessile
invertebrates from lobster trap gear at 117 sites in the Florida Keys National
Marine Sanctuary during 2000 and 2001. Sites were stratified according to
benthic habitat type and fishing protection and encompassed 13 of the
Sanctuary’s 23 no-fishing zones. Diver surveys using transects were performed
to document the type, length, and number of biota impacted by lost gear. Surveys
yielded 86 incidences of gear totaling nearly 380 m, consisting mostly of buoy
lines and wood slats. Densities of gear among the three habitat types ranged
from 0.11 to 0.86 incidences/100 m2, with four to eight times greater
gear density in patch reefs compared to other habitats. The distribution of
lobster trap gear did not differ significantly between protected and fished
sites. Lobster trap gear, especially buoy lines, caused partial mortality or
complete mortality to 152 sessile invertebrates. Relative to hook-and-line gear
effects, lobster trap gear impacted sessile invertebrates varied less among the
organisms considered. Gorgonians (39%) and scleractinian corals (24%) were the
most commonly affected, followed by sponges (17%), colonial zoanthids (13%), and
milleporid hydrocorals (7%).
CHIAPPONE, M. (chiapponem@uncwil.edu)*1,
D.W. SWANSON2, and S.L. MILLER1; 1Center for
Marine Science and NOAA’s National Undersea Research Center, University of
North Carolina at Wilmington, Key Largo, FL, 2Division of Marine
Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science,
University of Miami, Miami, FL. Spatial distribution and benthic impacts from
hook-and-line fishing gear in the Florida Keys National Marine Sanctuary.
The spatial distribution and
impacts to coral reef benthos from hook-and-line fishing gear were assessed at
117 sites spanning 2000 km in the Florida Keys National Marine Sanctuary during
the summers of 2000 and 2001. Sites were stratified random with respect to
habitat type and fishing protection. Surveys encompassed patch reef, spur and
groove, and hard-bottom habitat types from 3 m to 12 m depth within and adjacent
to 13 of the Sanctuary’s 23 no-fishing zones. Diver surveys using transects
were performed to document the type, length, and number of biota impacted by
hook-and-line gear. From surveys of 34,000 m2 of benthic habitat, 361
incidences of gear totaling nearly 465 m were documented, yielding a domain-wide
density of 1.06 incidences/100 m2. Gear densities ranged from 0.82 to
1.35 incidences/100 m2 among the habitat types. In patch reef and
spur and groove habitats, no significant differences were detected in the
distribution of gear between protected and fished sites, while protected areas
in the hard-bottom habitat yielded more gear than expected. Hook-and-line gear
caused partial mortality or complete mortality to 434 sessile invertebrates.
Organisms with upright morphologies such as gorgonians (47%), sponges (18%), and
milleporid hydrocorals (18%) were the most frequently affected. Organism
density, gear density, and gear length are some of the factors influencing gear
impacts. For the habitats surveyed, hook-and-line gear is spatially pervasive in
the Florida Keys, indicates a pattern of non-compliance with no-fishing
regulations, and represents a low-level stressor to sessile reef invertebrates.
CHIARAPPA, M.J. (michael.chiarappa@wmich.edu),
Western Michigan University, Great Lakes Center for Maritime Studies, Kalamazoo,
MI. Occupational endurance and contested resources: managing the cultural and
economic tensions of Lake Michigan’s commercial fishery.
The establishment of commercial
fishing in the Great Lakes in the 19th century introduced
unprecedented economic considerations and ecological effects to the basin’s
benthic habitats. By the late 19th/early 20th century, the alarming
effects of overfishing this region’s benthic species—most of which were the
principal target species (lake whitefish, lake trout, perch, walleye, chub) of
the Great Lakes commercial fishery—was increasingly apparent to fisheries
scientists and policy makers. The Great Lakes commercial fishery managed to
weather these stock fluctuations until the end of World War II when the combined
ecological effect of overfishing, sea lamprey predation, and a disproportionate
alewife population dangerously reduced benthic dwelling species. With the
exception of lake trout, benthic species have recovered over the past 50 years.
But commercial fishers, particularly Lake Michigan’s, have not necessarily
enjoyed the benefits of this recovery. As Great Lakes states revised their
fisheries policies to enhance sport fisheries, commercial fishers faced
stringent restrictions in their harvesting technologies, in their fishing areas,
and in the implementation of quotas. Today, in spite of highly contested policy
debates, Lake Michigan’s benthic fisheries are comprised of two constituencies
that visibly utilize benthic habitats to maintain distinct cultural prerogatives
and economic goals. Euroamerican commercial fishers draw on their cultural life,
traditional ecological knowledge (TEK), and a legacy of economic adaptation to
maximize their limited share of the benthic realm. Native American fishers,
motivated by the maintenance of treaty fishing rights, are using the benthic
realm for economic empowerment and the recovery of tradition-bound
cultural/ecological awareness. Looking at TEK and the formulation of vernacular
environmental ethics, this paper will consider the benefits and problems that
have accrued to each group’s attempt to utilize Lake Michigan’s benthic
habitat to achieve historical and contemporary goals.
CHIARELLA, L.A. (Lou.Chiarella@noaa.gov)*1, D.K.
STEVENSON1, C.D. STEPHAN1, R.N. REID2, J.E.
McCARTHY2, M.W. PENTONY3, T.B. HOFF4, C.D.
SELBERG5, and K.A. JOHNSON6; 1National Marine
Fisheries Service, Northeast Regional Office, Gloucester, MA, 2
National Marine Fisheries Service, Northeast Fisheries Science Center,
Highlands, NJ, 3New England Fishery Management Council, Newburyport,
MA, 4Mid‑Atlantic Fishery Management Council, Dover, DE, 5Atlantic
States Marine Fisheries Commission, Washington, DC, 6 National Marine
Fisheries Service, Office of Habitat Conservation, Silver Spring, MD.
Results of a workshop on the effects of fishing gear on benthic
habitats off the Northeastern United States.
A panel of experts in the fields
of benthic ecology, fishery ecology, geology, fishing gear technology and
operations were convened in October 2001 to assist the Northeast Region’s
fishery management councils in evaluating the effects of fishing gear on local
benthic habitats and identifying potential management measures. The panel
expressed greatest overall concern about impacts from otter trawls and scallop
dredges to structure forming organisms. Gravel
habitat was considered to be most at risk from gear impacts, followed by sand
and mud habitats. In some
circumstances the extent of impact in each habitat varied based on the
environment’s energy level (high vs. low energy). In general, bottom tending mobile gear was of greater concern
than fixed gear. Clam dredges were
rated as having the least effect of the mobile gears because of the limited
geographic area and the rapid recovery rates of the high energy sand environment
in which they are fished. Scallop
dredges were rated as having large effects in the gravel and sand habitats in
which they are fished. Panelists had the greatest difficulty reaching consensus
on the impacts of otter trawls due to their widespread use over a large variety
of habitat types as well as the numerous gear configurations employed.
The three primary management measures proposed to reduce fishing gear
impacts included effort reductions, spatial closures, and gear modifications.
CLARK, M.R. (m.clark@niwa.cri.nz)*,
A.A ROWDEN, and S.O’SHEA; National Institute of Water & Atmospheric
Research, Wellington, New Zealand. Effects
of fishing on the benthic habitat and fauna of seamounts on the Chatham Rise,
New Zealand.
Major deepwater trawl fisheries
occur for orange roughy on seamounts in New Zealand waters. These seamounts are
often small, and trawling can be concentrated in a very localised area. Seamount
habitat is thought to be productive, but also fragile, and there is growing
concern from fisheries managers, environmental groups, and the fishing industry
about effects of fishing on biodiversity and ecosystem productivity. This has
prompted research to examine the nature and extent of deepwater trawling impact
on seamount habitat in New Zealand. Results are presented from a recent survey
where video and still imagery were applied to classify benthic habitat, and a
new robust epibenthic sled used to sample the deepwater fauna. The study took
place on the Chatham Rise where a group of 8 seamounts in close proximity
allowed for a spatially unconfounded comparison of replicated fished and
unfished seamounts. Commercial fisheries data were analyzed to determine the
amount of trawling on each. Similarities within, and differences between, fished
and unfished seamounts were identified for distribution of trawl gear
modification of habitat; extent of live coral; macroinvertebrate assemblage
composition, taxonomic distinctness and size spectra . This study provided
information to help plan management strategies and develop effective management
practices to allow both conservation and exploitation of seamounts, although
more research is required. In May 2001, 19 seamounts throughout the New Zealand
region, including several features on the Chatham Rise, were closed to bottom
trawling as a precautionary measure.
CLAYTON, T.D.
(tclayton@usgs.gov)*1, J.C. BROCK1, and C.W. WRIGHT2;
1U.S. Geological Survey, Center for Coastal and Regional Marine
Studies, St. Petersburg, FL, 2Laboratory for Hydrospheric Processes,
NASA, Goddard Space Flight Center, Wallops Island, VA. Mapping seagrass
boundaries with waveform-resolving lidar: a
preliminary assessment.
For ecologists and managers of
seagrass systems, the spatial context provided by remote sensing has proven to
be an important complement to in situ
assessments and measurements. The
spatial extent of seagrass beds has been mapped most commonly with conventional
aerial photography. Additional
remote mapping and monitoring tools applied to seagrass studies include optical
satellite sensors, airborne multispectral scanners, underwater video cameras,
and towed sonar systems. An
additional tool that shows much promise is airborne, waveform-resolving lidar
(light detection and ranging). Now
used routinely for high-resolution bathymetric and topographic surveys, lidar
systems operate by emitting a laser pulse, then measuring its two-way travel
time from the plane to reflecting surface(s) below, then back to the detector
co-located with the laser transmitter. Using
a novel, waveform-resolving lidar system developed at NASA -- the Experimental
Advanced Airborne Research Lidar (EAARL) -- we are investigating the possibility
of using the additional information contained in the returned laser pulse
(waveform) for the purposes of benthic habitat mapping. Preliminary analyses
indicate that seagrass beds can potentially be delineated on the basis of
apparent bathymetry, returned waveform shape and amplitude, and (horizontal)
spatial texture. A complete set of
georectified digital camera imagery is also collected during each EAARL
overflight and can aid in mapping efforts.
Illustrative examples are shown from seagrass beds in the turbid waters
of Tampa Bay and the relatively clear waters of the Florida Keys.
COCHRANE,
G. R. (gcochrane@usgs.gov); U.S. Geological Survey, Menlo Park, CA.
Mapping rocky habitat using textural analysis of sidescan sonar images.
Highly reflective seafloor
features imaged by sidescan sonar in nearshore waters off the Northern Channel
Islands (California, USA) have been observed in subsequent submersible dives to
be areas of thin sand covering bedrock. Adjacent
areas of rocky seafloor, suitable as habitat for endangered species of abalone
and rockfish, and encrusting organisms, can not be differentiated from the areas
of thin sand on the basis of acoustic backscatter (i.e. gray level) alone.
We found second order textural analysis of sidescan sonar data useful to
differentiate the bottom types where data is not degraded by near-range
distortion (caused by slant range and ground range corrections), and where data
is not degraded by far-range signal attenuation.
Hand editing based on submersible observations is necessary to completely
convert the sidescan sonar image to a bottom character classification map
suitable for habitat mapping.
COGGAN, R.A.
(r.a.coggan@cefas.co.uk)*1,2,4, C.J. SMITH3, R.J.A. ATKINSON2,
K.-N. PAPADOPOULOU3, T.D.I. STEVENSON2, P.G. MOORE2
and I.D. TUCK4;1CEFAS Laboratory, Essex, United Kingdom, 2University Marine Biological Station,
Millport, Isle of Cumbrae, Scotland, United Kingdom, 3Institute of
Marine Biology of Crete, Iraklio, Crete, Greece, 4Fisheries Research
Services Marine Laboratory, Aberdeen, Scotland, United Kingdom. Fast-track
methods for assessing trawl impacts.
Traditional methods for assessing
the impact of towed demersal fishing gear are notoriously slow, taking years to
report and imposing undesirable delays in the provision of scientific advice on
which fisheries and environmental managers can act. There is a need to develop
rapid methods for assessing trawl impacts.
We evaluate and compare a suite of rapid methodologies covering a range
of readily accessible technologies including:
1.
Acoustic methods: sidescan sonar and bottom discriminating sonar (RoxAnn™);
2.
Visual methods: towed video sledge and ROV;
3.
Faunal sampling (epibenthic megafauna): tissue damage, community
analysis, population density, functional group composition; and
4.
Sedimentology: granulometry, geotechnical properties and sediment profile
imagery.
These methods were applied to
otter trawl fisheries in the Clyde Sea, Scotland and the Aegean Sea,
Mediterranean, at sites representing a range of trawl impacts. Novel methods of
analysis were developed for quantitative interpretation of sidescan and video
records. The scientific effectiveness, cost effectiveness and operational
constraints of the various methodologies are reviewed. We recommend suitable
approaches to the rapid assessment of trawl impacts taking into consideration
the variety of resources (such as time, equipment and budget) which may be
available. Assessments should employ complementary methods that operate on
different scales of resolution (eg. sidescan sonar with either faunal sampling
or ROV). Site-specific factors, such as topography and substratum type, will
influence choice of methods and survey design. These rapid methodologies can
provide results in a matter of days or weeks rather than the months or years
associated with traditional assessment methods.
COLEMAN, F.
C. (coleman@bio.fsu.edu)*1, C. C. KOENIG1, M. W. MILLER2,
S.A. HEPPELL3, S. S. HEPPELL3, and K. SCANLON4;
1Department of Biological Science, Florida State University,
Tallahassee, FL, 2National Marine Fisheries Service, Miami, FL, 3Oregon
State University, Department of Fisheries and Wildlife, Corvallis, OR, 4U.
S. Geological Survey, Woods Hole, MA. Fishing
effects on habitat: the potential consequences of removing such habitat
engineers as red grouper (Epinephelus morio).
Mass removal of species that
restructure the architecture of habitat and thus increase its complexity can
have multiple effects on ecosystems, including loss of biodiversity and altered
biogeochemical pathways. In this paper, we report on the contributions made to
habitat heterogeneity by the engineering capabilities of red grouper, Epinephelus
morio, throughout its life. We
demonstrate that this fish starts excavating habitat at first settlement,
provides important structure and enhances biodiversity in nearshore communities
of the west Florida shelf as juveniles, and contributes significantly to the
structure of low–relief continental shelf edge areas as adults.
We discuss the potential benefits of using side-scan sonar imagery to
track grouper-induced changes in habitat over time (developing a time-series of
images both within marine reserves and in nearby reference sites).
We also discuss the implications of red grouper fishery removals to
overall productivity of the continental shelf of the northeastern Gulf of Mexico
and the particular management problems presented by knowledge of this behavior.
Current management decisions to move the longline grouper fishery further
offshore may increase pressure on red grouper and other excavating species, such
as tilefish, have a significant negative influence on habitat heterogeneity,
with potential to cause cascading problems throughout shelf-edge communities.
COLLIE, J. (jcollie@gso.uri.edu)*1,
J. HERMSEN1, and P. VALENTINE2; 1Graduate
School of Oceanography, University of Rhode Island, 2U.S. Geological
Survey, Woods Hole, MA. Effects
of fishing on benthic habitats: assessment and recovery.
Habitat disturbance by mobile
fishing gear has been identified as one of the most pervasive ecosystem effects
of fishing. However, the degree of
effect depends on gear type, habitat type, and other factors. To quantify these
differences, a meta-analysis of published fishing impact studies was undertaken.
This analysis showed that intertidal dredging and scallop dredging have
the greatest initial effects on benthic biota, while trawling has less initial
effect. Fauna in stable
gravel, mud, and biogenic habitats are more adversely affected than those in
less consolidated coarse sediments. Recovery
rate appears most rapid in these less physically stable habitats, which are
generally inhabited by more opportunistic species. The general paradigm about
how fishing ought to affect benthic communities is generally supported, but
there remain substantial gaps in the available data, which urgently need to be
filled. Our own field studies have focused on the gravel sediment habitat on the
northern edge of Georges Bank, which is an important nursery area for juvenile
fish. On cruises to this area since
1994, we have collected dredge samples and photographs from sites of varying
depths and with varying degrees of disturbance from otter trawling and scallop
dredging. Compared with the
disturbed sites, the undisturbed sites have higher numerical abundance, biomass,
and species diversity of benthic megafauna.
Undisturbed sites also have higher percent cover of colonial epifauna,
which provide a complex habitat for shrimp, polychaetes, brittle stars, and
small fish. Since 1995 we have been
monitoring the recovery of a previously disturbed area that was closed to bottom
fishing in December 1994. We have
observed significant increases in abundance (´8), biomass
(´7),
production (´4),
and epifaunal cover in the closed area. Results
of our study have been used by the New England Fishery Management Council to
designate a Habitat Area of Particular Concern for juvenile cod.
COTTERELL
S.P. (s.cotterell@plymouth.ac.uk); Institute
of Marine Studies, University of Plymouth, Drake Circus, Plymouth, United
Kingdom. Fish landings, discards and benthic material from otter
trawling in the western English Channel.
A fleet-stratified sampling design
was employed between 1998 and 2000 to study fish discards and landing and to
quantify the other incidentally caught material.
The studied techniques were <12m single boat otter trawling, <12m
paired demersal trawling and >12m single boat otter trawling.
Trips for <12m ranged from one to three days while those for >12m
boats were one to six days. These
boats operated out of the four principle English ports of ICES area VIIe,
western English Channel. On board
the boats and prior to any sorting by the crew a sample (~40kg) of the catch was
taken and all fish were identified and measured, and their fate (whether to be
landed or discarded) was noted. All
non-fish material was stored in the fish hold for later detailed analysis.
The non-fish material was categorised as benthos, or biogenic, inorganic,
or anthropogenic material. The
benthos was classified, weighed and measured.
Also, a system to assess its degree of damage was developed, allowing
length-weight regressions to be generated for the more common invertebrate
species. On average 60% (by weight)
of the haul was landed, 10% was bait fish, 20% was discarded and 10% was
non-fish material. Landing samples were compared to confidential catch
composition figures of trip landings. British
Geological Survey data was used to assess the substrate over which the trawl had
passed and benthos composition was compared to historical data sets.
From this study it would appear that economic overfishing would occur
before irreparable benthic disturbance for these techniques.
CRAEYMEERSCH,
J.A. (johan@rivo.wag-ur.nl)* and G.J. PIET; Netherlands Institute for Fisheries
Research. Changes in the epibenthos assemblages of the North Sea following
the establishment of a protected area, the "plaice box".
In 1989 a protected area in the south-eastern North Sea was established:
the “plaice box”. Data of the
by-catch of annual beam trawl surveys carried out since 1985 will be used to
determine the effect of the changes in fishing effort. A first analysis showed
significant changes in the species composition after the ‘closure’ of the
box. Changes, however, also occurred in the reference area (although in other
species), suggesting that in addition to changes in impact by bottom fishing
gear, other (climatic?) variables may have been involved. We will present the
results of further analysis using multivariate techniques. Changes in species
composition in the box area and in a reference area will be related to changes
in fishing effort, environmental variables and climate.
CRANFIELD,
H.J. (j.cranfield@niwa.cri.nz)*1, K.P. MICHAEL1,
G.CARBINES2, D.P. GORDON1, B. MANIGHETTI1, A.
DUNN1, and A.A. ROWDEN1; 1National Institute of
Water and Atmospheric Research Ltd, Kilbirnie, Wellington, New Zealand, 2National
Institute of Water and Atmospheric Research Ltd, Dunedin, New Zealand. Effects
of 135 years of oyster (Ostrea chilensis)
fishing on the benthic habitat, associated macrofaunal assemblages, and
sediments of Foveaux Strait, southern New Zealand.
Management of the oyster fishery,
and understanding of the impact of this longstanding fishery on the benthic
environment, has been facilitated through periodic surveys. Fishers’ and
institutional fishing records and the results of biological, acoustic, and
sediment surveys have been analysed to show how historical changes to benthic
habitat relate to fishing. The seafloor once consisted of bioherms, hundreds of
metres wide and many kilometres long, aligned with the tide, separated by
similarly wide swaths of relict pebble-gravel sediment. The macrofauna of
bioherms was dominated by bryozoa, (over 200 species), and bivalve molluscs,
(over 60 species). Oysters were localised on this habitat alone which was also
important for blue cod, Parapercis colias.
Much biohermal epifauna was removed as bycatch of the oyster fishery and oysters
were subsequently depleted locally more rapidly. Bioherm habitat was important
in the formation of biogenic sediments and the recruitment, growth, and survival
of both oysters and blue cod. The expansion of relict pebble gravel seafloor
with the erosion of biohermal sediments relates directly to areal expansion of
fishing as oyster beds were serially depleted. Mytilid bivalves and styelid
tunicates are identified as early colonisers of regenerating bioherms, and
helical circulation patterns in the tidal flow are implicated in the formation
of these linear structures within which fine sediments again begin to
accumulate. Regeneration of habitat and rebuilding of oyster and blue cod
populations in the absence of oyster dredging suggest that MPAs and rotational
fishing could be effective in conserving both habitat and fisheries.
CRYER, M. (m.cryer@niwa.cri.nz)*,
B. HARTILL, and S. O’SHEA; National Institute of Water and Atmospheric
Research, Auckland, New Zealand. Deepwater
trawl fisheries modify benthic community structure in similar ways to fisheries
in coastal systems.
Off north-eastern New Zealand, the
Bay of Plenty continental slope supports bottom trawl fisheries for gemfish (Rexea solandri), hoki (Macruronus
novaezelandiae),
tarakihi (Nemadactylus macropterus), and, most recently scampi (a
burrowing, deep-water lobster, Metanephrops
challengeri). Excellent information has been collected since 1988 on the
distribution of trawling effort in these fisheries, including the start and
finish location of each trawl tow with a precision of 1 minute of latitude and
longitude. Using a GIS, we linked these data to information on the invertebrate
bycatch of 66 research trawls, and explored the extent to which the composition
of our bycatch (as one index of benthic community structure) could be explained
by the frequency of trawling at a given site. Using multivariate ordination
techniques, we explained up to 65% of variation in the distribution of species
among samples, more than half of which was attributable to our indices of
trawling (mainly for scampi and gemfish). Qualitatively, the inferred effects of
deep-water trawling were similar to those of coastal fisheries; increasing
fishing activity was associated with reductions in species richness, diversity,
and the abundance of large or fragile taxa. The gross quality of information on
fishing effort has hitherto been a major constraint on our understanding of the
effects of fishing. This study is one example of the way good quality
information at the right (fine) scale can further that understanding, but
comprehensive information on the distribution of fishing effort may also allow
extrapolation of experimental studies to the wider scale of fisheries
management.
CUTTER, G. R.
(gcutter@cisunix.unh.edu)*1, L. A. MAYER1, Y. RZHANOV1,
and R. GRIZZLE2; 1University of New Hampshire, Center for
Coastal and Ocean Mapping, Durham, NH, 2 University of New Hampshire,
Jackson Estuarine Laboratory, Durham, NH. Quantitative ground-truthing of
biological habitat characteristics using video mosaic images.
Benthic habitats from the
Piscataqua River, New Hampshire, have been delineated using bathymetry derived
from multibeam echosounder data, an increasingly common methodology.
In addition to the standard approach of manual interpretation and
delineation, we have implemented automated methods for distinguishing regions of
different acoustic character. Despite
the good agreement between the resultant delineations using manual and automated
methods, we suggest that acoustic data depicts the physical habitat model (PHM)
of the seafloor and therefore any such delineation may have limited utility for
directly characterizing fauna. The
pending issue is how the acoustic-derived physical habitat model represents the
biological components of the system. By
assuming organism-substrate interaction relationships, a functional biology
model can be developed to link the PHM to fauna, however, without ground-truthing
data such models are merely conjectural. Two
methods of ground-truthing habitat delineations are common:
core or grab samples, and still camera or video imagery.
There is a disparity between biology represented by acoustic and optical
imaging and direct samples. There
is also a disparity between what different optical imagery techniques represent.
We show that common imaging techniques can misrepresent fauna and
biological habitat characteristics for substrates with no apparent biological
features or sparsely distributed fauna. We
describe the use and analysis of video mosaics as an imaging technique for
representing microhabitat characteristics and macrofauna as well as larger,
sparsely distributed organisms. We
relate those results to how the PHM represents certain fauna.
DEALTERIS,
J.T. (jdealteris@uri.edu)* and L. G. SKROBE; Department of Fisheries, University
of Rhode Island, Kingston, RI. A
paradigm for the management of fish habitat based on vulnerability and
availability, and an assessment of the impact of fishers on habitat and habitat
protection on fishers.
Fish habitat on the continental
shelf of the northeast United States was evaluated along three strip transects
for vulnerability or resilience to and frequency of disturbance by
mobile-fishing gear, and the relative availability. Each study area,
approximately 50x150 km, was sub-divided into 10x18 km sub-areas for data
analysis. Habitat value has been
directly related to structural complexity, and indirectly related to substrate
stability. Sediment and bottom
current data were used to assess substrate stability in each sub-area. The
relative availability of each habitat type within each study area was also
estimated from the sediment distribution data. Fishing effort data for mobile
fishing gears within each sub-area were averaged over an 11-year period to
estimate the area impacted by each gear type annually.
A management paradigm based on the premise that the priority for habitat
protection is directly related to habitat vulnerability and inversely related to
habitat availability, is proposed. On Georges Bank, areas of vulnerable and
spatially limited gravel-cobble habitat were intensely fished, indicating that
dredge and trawl fisheries in these areas are problematic for the conservation
of fish habitat. Protection of these habitats will impact those fishers that
target that habitat. Other areas on Georges Bank are minimally impacted by
fishers, and are also resilient habitats. In the southern New England and
mid-Atlantic study areas, the nearly ubiquitous and resilient sand habitat was
intensely fished in localized areas and minimally in other areas. Since this
habitat requires minimal protection, there will be minimal impact on fishers.
DEW, C. B. (braxton.dew@noaa.gov)*
and R. A. McCONNAUGHEY; National Marine Fisheries Service, Alaska Fisheries
Science Center, Seattle, WA. Did bottom trawling in Bristol Bay’s red king
crab broodstock refuge contribute to the collapse of Alaska's most valuable
fishery?
The 1976 Magnuson Act effectively
eliminated the Bristol Bay no-trawl zone known as the Pot Sanctuary. Implemented
by the Japanese in 1959, the boundaries of this refuge closely matched the
well-defined distribution of the red king crab population's mature-female
broodstock, thus affording a measure of protection to the reproductive potential
of the stock. In 1980, the point at which the commercial harvest of Bristol Bay
legal male red king crab had reached an all-time high after a decade-long
increase, domestic bottom trawling in the broodstock sanctuary began with the
advent of a U.S.-Soviet, joint-venture, yellowfin sole fishery. As the number of
unobserved, domestic trawls in the broodstock area increased rapidly after 1980,
and anecdotal reports of “red bags” (trawl cod-ends plugged with red king
crab) began to circulate, the proportion of males in the mature population (0.25
in 1981 and 0.16 in 1982) jumped to 0.54 in 1985 and 0.65 in 1986. It is
unlikely that normal demographics caused this sudden reversal in sex ratio. Our
hypothesis is that alternating, sex-specific sources of mortality were at work.
Initially there were ten years (1970-1980) of monotonically increasing,
male-only exploitation, followed by a drastic reduction in the male harvest
after 1980 (to zero in 1983). Also beginning in 1980, there was an increase in
bottom trawling among highly aggregated, sexually mature females residing within
a previously protected area known to be the primary broodstock habitat and the
most productive spawning ground for Bristol Bay red king crab. There has been
considerable discussion about possible causes (e.g., meteorological regime
shifts, epizootic diseases) of the knife-edge collapse of the Bristol Bay red
king crab population in the early 1980s. Our discussion will focus on the
temporal and spatial nexus between the population’s collapse and the onset of
large-scale commercial trawling within the population’s primary reproductive
refuge.
DOOLITTLE,
D.F. (danield@vims.edu)*1, M.R. PATTERSON1, Z-U. RAHMAN2,
and R. MANN1; 1College of William and Mary, School
of Marine Science at the Virginia Institute of Marine Science, Gloucester Point,
VA, 2College of William and Mary, Department of Computer Science,
Williamsburg, VA. Decreasing habitat disturbance by improving fish stock
assessments: a new method of remote species identification and quantification.
A direct
link exists between the quality of fisheries data and the effectiveness of
fisheries management. Increasing
the quality and quantity of data on which stock assessments and management
decisions are based has been cited as a critical national issue (National
Research Council, 2000. Improving the Collection, Management, and Use of
Marine Fisheries Data. National Academy Press, Washington, D.C.).
We approach the challenge of limiting deleterious habitat impacts due to
fishing through the creation and demonstration of novel stock assessment and
habitat visualization tools. We
present here a new method of fish
species identification and quantification.
The technique uses a Radial Basis Function artificial neural network
classifier to discriminate and enumerate selected fish species from
high-resolution side scan sonar images. We
demonstrate this technology onboard a Fetch! class Autonomous Underwater Vehicle
(AUV) and provide examples of how such technologies could augment fisheries
stock assessment as well as essential fish habitat determination.
Ancillary benefits of this technology include the opportunity to
simultaneously characterize surficial bottom types and document habitat
utilization by species that are known to the classifier.
Such side scan sonar species identification tools would significantly
augment current stock assessment methods, provide new insight to habitat usage,
and allow more ecologically realistic models to be constructed.
DOUNAS C. (kdounas@imbc.gr)*1,
J. DAVIES2, P. HAYES2, C. ARVANITIDIS1, and P.
KOULOURI1; 1Institute of Marine Biology of Crete, Greece, 2Fisheries
Research Services, United Kingdom. The affect of different types of otter
trawl groundrope on benthic nutrient fluxes and sediment biogeochemistry.
The direct impacts of seabed
disturbance by otter trawling on the rate of nutrients’ regeneration from the
sediment to the overlying water column, and on the biogeochemical sediment
zonation, have never been studied. These impacts can have very important
implications for nutrient supply, and hence on primary production in the
continental shelf where most trawling activity is concentrated, and consequently
on fish production and fishing management. The labile fractions of sedimentary
organic matter, responsible for most sedimentary metabolism, are usually
concentrated on or near the sediment surface. Consequently the impact of trawling on sediment
biogeochemistry could be studied by the artificial disturbance of the sediment
surface layer. The part of a trawl rig that mostly contributes to this process
is the groundrope (more than 90% of the total conduct surface) which was finally
chosen for carrying out of trawling simulation experiments. The site selected
was the continental shelf of Heraklion Bay (Eastern Mediterranean, Cretan Sea).
Artificial nutrient fluxes were measured by applying a trawling simulating
sampler. Five different groundrope settings were used in order to estimate
potential quantitative differences in sediment biogeochemistry and nutrient
releases derived from the conduct of the groundrope with the seabed. Statistical
comparison of the results revealed that almost all biological active compounds
at the sediment surface are resuspended by a single passage of the simulating
gear. The implication is that the upper extremely thin layer of sediments
contains a considerable reservoir of dissolved and particulate nutrients in
concentrations, much higher than in the underlying sediment layers.
EMELYANOV V.A. (evasea2002@yahoo.com);
First Deputy Chief of the Natural Academy of Sciences of Ukraine, and Institute of
Geologycal Sciences of the National Academy of Sciences of Ukraine, Kyiv, Ukraine.
The theoretical and methodological basis of estimations of the
human-made influences (fishing and constructing) on the benthic habitats.
In the last few decades, human-made influences have
considerably increased on the upper part of lithosphere within the World
Ocean’s bounds as the benthic habitat. Some
scientific directions have attempted to solve numerous benthic habitat problems
related to increasing fishing and construction activities. But it is impossible
to do this effectively within the limits of traditional scientific directions,
resulting in the need to incorporate more ecological sciences with these
traditional scientific approaches to investigations and estimations of the
growing problems and the search for solutions. In particular, more and more
explorations have concentrated their attention on the many-sided investigations
of the compound characteristics of benthic habitats as a marine geo-ecological
system. But many terminological,
conceptual, methodological and other general questions have arisen from these
studies. Without answers to these questions, it is difficult to solve many
specific problems related to human-made influences on benthic habitats, as well
as the creation and steady development of marine and coastal areas. In this
paper, some new terms are presented, with their treatments, basic conceptions
and approaches, that are more applied in the modern benthic habitat’s
investigations and become an important component of the theory and methodology
of a new scientific direction—marine geo-ecology, of studying and solving many
benthic habitat problems related to fishing and construction activities.
ENS, B.J. (b.j.ens@alterra.wag-ur.nl)*1,
A.C. SMAAL2 and J. DE VLAS3; 1Alterra, Texel,
The Netherlands, 2RIVO-CSO, Yerseke, The Netherlands, 3RIKZ,
Haren, The Netherlands. Fishing
for shellfish in an internationally important nature reserve: do current
policies achieve their objectives?
The Dutch Wadden Sea is a nature
reserve of international significance. Fishing for shellfish is allowed as long
these activities do not cause significant harm to the natural values of the
area. In 1993 this objective was implemented in a new shellfishing policy via
two management policies: closed areas and food reservation. Thus, 26% of the
intertidal mudflats are permanently closed for fishery to restore important
habitats, particularly intertidal mussel beds and seagrass beds. To prevent food
shortages for shellfish eating birds, mainly oystercatchers and eider ducks,
caused by shellfish fishery, fishing for shellfish is not allowed when shellfish
stocks are below a threshold value. In 2003, this new shellfishing policy must
be evaluated. To this end, a major research program was initiated. It includes
testing the hypothesis that mechanised fishing for cockles has long-term
negative effects on the recruitment of cockles and other bivalves mediated by a
loss of fine sediments. It also includes detailed investigations whether
declining numbers of oystercatchers and recent high mortality among eider ducks
can be related to food shortages and if so, whether these food shortages are
linked to the current shellfishing practices. While the program relies heavily
on massive long-term monitoring of shellfish stocks, shellfish fishery
(including continuous registration of all fishing activities), benthic habitats
and bird numbers in combination with mathematical modelling, some field
experiments are also conducted. Most notable is an experimental test of the
hypothesis put forward by the fishermen that fishing on mussel seedbeds helps to
stabilise these beds. Preliminary results of the project will be discussed.
ESCOBAR-BRIONES,
E. (escobri@mar.icmyl.unam.mx)*1, A. GRACIA1, and G. T.
ROWE2; 1Unidad Académica Sistemas Oceanográficos y
Costeros, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma
de México, Mexico, 2Department of Oceanography, Texas A&M
University, College Station, TX. Understanding
chronic and event driven natural change to benthic habitats
(physical/biological): effect of sediment disturbance on sediment community
oxygen consumption (SCOC).
Sediment variables and changes in infaunal ratio have been known to determine the rates of sediment community oxygen consumption. Habitat disturbance may affect SCOC by changing the seafloor surface by resuspension or smoothing and the ratios of size, species composition, abundance and biomass of the infaunal components. Estimates of SCOC were made at 15 localities of soft-bottom sediments of the shelf and margin of the SW Gulf of Mexico in which trawling efforts vary from null (Campeche Bank), intermediate (Tamaulipas shelf) to high (Campeche Bay) in an extended time span. Oxygen demand was measured on board in replicated (n=4) experimental incubation chambers. Environmental conditions were maintained during the experiments. The SCOC rates were highest in the Campeche Bank where meio and macrofauna was dominant. L