CORVALLIS, Ore. Marine resource managers often gauge the health of species based on overall biomass, but a new study of predator-prey relationships in the Bering Sea found that it isn't the total number of individuals that predators care about it's how densely they are aggregated.
It's more than searching for an easy meal, the researchers say. Predators need to balance how much energy they expend in searching for food with the caloric and nutrient value of that which they consume. When prey doesn't aggregate, however, the search for food becomes much more difficult affecting the health of the predators' offspring and the vitality of their overall population.
Results of the study were published this week in the journal PLOS ONE. The study was part of the Bering Sea Integrated Ecosystem Research Project, which was funded by the North Pacific Research Board and the National Science Foundation.
"We had to think very differently about these interactions, trying to see the world from the predators' point of view," said Kelly Benoit-Bird, an Oregon State University marine ecologist and lead author on the study. "When we first tried to identify good foraging locations for predator species we looked at areas of high prey numbers because it makes sense that they'd be where the food is. But the results didn't match what we might have expected.
"Predator populations that should have been doing well, based on prey numbers or biomass, were in fact not doing well," added Benoit-Bird, an associate professor in OSU's College of Earth, Ocean, and Atmospheric Sciences. "What we discovered is that smaller aggregations of prey are more attractive to predators if they are sufficiently dense."
The findings are particularly important, scientists say, because almost all fisheries management is based on biomass tons of fish and not how those fish may be distributed in the sea.
In their study, the researchers looked at
|Contact: Kelly Benoit-Bird|
Oregon State University