FISHERMEN are not waiting for their fisheries to collapse before targeting species further down the food chain.
Biologists have been worried that as overfishing takes its toll and top predators such as cod and tuna disappear, we will have to eat the more numerous beasts lower down the chain, such as jellyfish. Now they are surprised to find this is already happening.
Tim Essington and colleagues at the University of Washington, Seattle, found that in 30 of the 48 marine ecosystems they looked at round the world, fishing is indeed targeting species further down the food chain. In only nine was this because the top fish had disappeared. In most cases, people are catching lower-level species even while there are still top fish around. Yet all of more than 200 recent scientific publications the team surveyed assumed that moving down the food chain happens only after the top fishery collapses (Proceedings of the National Academy of Sciences, DOI:10.1073/pnas/0510964103).
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This is dangerous, says Essington, because what is actually happening 鈥� taking everything at once 鈥� poses risks that aren鈥檛 being recognised. 鈥淲e are trying to extract conflicting ecosystem services from our oceans,鈥� he says.
