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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.


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 31 March, 2009

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