Fisheries Behavioral Ecology - Abstracts
Buckel, J.A. and A.W. Stoner. 2004. Negative effects of increasing group size on foraging
in two estuarine piscivores. Journal of Experimental Marine Biology and Ecology 307:183-196.
Abstract
The effect of predator density on per capita ingestion rates in two estuarine predators, age-0
bluefish (Pomatomus saltatrix L.) and age-1 striped bass (Morone saxatilis W.), was examined in a
121,000-l research aquarium. Group size treatments were 3, 6, 12, and 24 predators; each treatment
was provided with 100 prey (mummichog killifish, Fundulus heteroclitus L.) during a 22-h feeding
trial. The behaviors of predator and prey were recorded. Predator type and group size had a
significant effect on per capita ingestion rates. Bluefish had significantly higher per capita ingestion
rates compared to striped bass. For bluefish, per capita ingestion rate was highest in the three
predator group, while for striped bass, individuals in the six predator treatment had the highest
ingestion rates. From these maxima, per capita ingestion rate values declined to their lowest values in
the 24 predator treatment for both species. Several factors that may be responsible for lowered per
capita ingestion rates at higher group sizes include predator interference, prey depletion, and antipredator
behaviors of prey. For juvenile bluefish and striped bass being a member of a relatively
large group may lead to decreased individual ingestion rates. Given that large group sizes of these
species occur in nature, we conclude that these foraging costs must be outweighed by benefits of
group membership.
Last updated
27 April, 2007
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