Going Fishing

Figuring out where predators hunt for food seems like it should be easy: Just look for the places with the most prey. But it’s not quite that straightforward, scientists say in PLoS ONE. In the Bering Sea, predators are the most attracted to areas with dense patches of prey, even if the total number of prey isn’t that high.

When studying predator-prey links, researchers often look at the number or total mass of animals in a certain area — say, the average number of prey per square meter. But in the sea, prey such as fish can clump together in small, dense groups.

To find out which factors were most important in drawing predators, the team studied three species in the Bering Sea. Two bird species, the black-legged kittiwake and thick-billed murre, eat fish and invertebrates; the third species, the northern fur seal, hunts fish and squid.

The researchers surveyed part of the Bering Sea area to figure out how prey species such as fish and crustaceans were distributed. They also tagged the birds and seals to track where the animals were hunting.

The location of the predators wasn’t linked to the number or mass of prey, the team reports. Instead, the predators were more likely to be found where prey had formed dense patches. Fur seals, for example, often hunted in areas with patches of pollock, especially if those patches were close together. Roberta Kwok | 4 January 2013

Source: Benoit-Bird, K.J. et al. 2013. Prey patch patterns predict habitat use by top marine predators with diverse foraging strategies. PLoS ONE doi: 10.1371/journal.pone.0053348.

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