Tracking seed-dispersing piranha in the Amazon

Fish are probably not the first animals that leap to mind when thinking of seed dispersers. Squirrels are well-known examples, but researchers have recently tracked a species of frugivorous—that is, fruit-eating—piranha in the Amazon that distribute seeds over more than five kilometers of flood plains. As Daniel Cressey described in a Nature News article, “Although fish have long been suspected of having an important role in seed distribution, proof of their ability to carry fertile seeds such distances has been lacking.”

Ecologist Jill Anderson from Duke University and colleagues tracked the fish Colossoma macropomum—also called a tambaqui or pacu—during three flood seasons in Peru’s Pacaya-Samiria National Reserve. As they reported in a paper published today in Proceedings of the Royal Society Biological Sciences, these fish are dispersing seeds at some of the greatest distances ever reported by frugivores. And because the seeds are dispersed in flood plains, they have a good chance of germination once the waters recede. Ed Yong reported in Discover’s blog Not Exactly Rocket Science that “seeds find it slightly easier to germinate after a voyage through the tambaqui’s innards.”

By tracking these fish, Anderson also found evidence that the populations are depleted due to overfishing. That is, she was unable to find any fish close to maximum size within the three seasons she was tracking them. As Yong concluded his post, “Other species of fruit-eating fish are facing similar problems. So fishermen are not only depriving the Amazon of some of its most effective seed dispersers, they are also taking the best carriers out of the game. In doing so, they are disrupting alliances between fish and plants that have been going on for millions years. And they risk the future of the same flooded forests that provide them with their livelihoods.”

Photo Credit: Markg6

Author: Katie Kline

Moderator of EcoTone and ESA's communications officer.

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