Effects of alternative prey on cannibalism in age‐1 bluefish

Abstract

Age‐1 bluefish Pomatomus saltatrix were offered both age‐0 bluefish and age‐1 Atlantic silversides Menidia menidia in the following proportions: 0:1·0, 0·25:0·75, 0·5:0·5, 0·75:0·25, 1·0:0. Atlantic silversides were consumed in greater proportion than offered throughout all treatments suggesting strong selection for silversides. There was no evidence of prey‐switching. The behavioural processes leading to age‐1 bluefish selection of Atlantic silversides was investigated. The proportion of attacks on each prey species was distributed randomly, or slightly higher on age‐0 bluefish; however, capture success was greater on silversides than on age‐0 bluefish prey. Therefore, age‐1 bluefish did not actively select for silversides and the observed selection pattern is a result of passive processes. These findings suggest that prey switching between age‐0 bluefish and an alternative prey probably does not act as a stabilizing mechanism in the bluefish population and confirm the importance of capture success in determining piscivore selectivity patterns.