Trawling makes for skinny flatfish

10 December 2014

Source: NERC, Science of the Environment

Author: Tom Marshall

Trawling the seabed doesn't just remove some of the fishes living there; it also makes some of the survivors thinner and less healthy by forcing them to use more energy finding less nutritious food.

That's the conclusion of a new paper published in Proceedings of the Royal Society B, based on the work Dr Andrew Frederick Johnson undertook while studying for his PhD at Bangor University.

'We already knew that some species of bottom-dwelling fish in trawled areas were skinnier than those elsewhere, but until now it was assumed this was because they couldn't find enough food and went hungry,' he says.

Johnson's work sampling fish in the Irish Sea on Bangor University's research vessel Prince Madog shows that's not true; the stomachs of fish in trawled areas are as full as elsewhere, but they're full of different and less nutritious prey that the fish have to put more energy into finding. For instance, a fish with a bellyful of shellfish may feel full, but a lot of their meal is shell with no nutritional value. Much better to fill up on juicy worms - but these suffer more from the effects of trawling.

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