Catfish face migration barriers

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Amazonian catfish make the longest known freshwater migrations, covering thousands of kilometres, but their epic voyages are threatened by new dams.

Brachyplatystoma catfish can measure up to three metres in length, and are top predators. To study their migrations, Fabrice Duponchelle of the Institute of Research for Development in Montpellier, France, and his colleagues analysed the strontium isotope ratio in ear bones from 37 Brachyplatystoma rousseauxii captured near breeding areas in the Amazon basin. The authors found correlations between the strontium make-up of the bones and that of rocks in different parts of the river system. They suggest that young fish migrate downstream in the lower Amazon, then return upstream as adults, swimming some 8,000 kilometres to the area where they were hatched.

Two dams built recently on the Madeira River could prevent the fish from reaching their spawning grounds, which could have ripple effects through Amazonian food webs, the authors warn.

J. Appl. Ecol. (2016)

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