The effect of prey morphology and size on handling time in a piscivore, the largemouth bass (Micropterus salmoides)

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Abstract
Handling time for prey of different sizes and morphological types was studied in the largemouth bass (Micropterus salmoides). Prey ranged in size from about 1/10 to 2/3 the length of the bass. Handling time increased rapidly with prey of increasing size. For prey of equivalent length, crayfish were the most time-consuming morphological type to handle and swallow, followed by bluegill (Lepomis macrochirus), yellow perch (Perca flavescens), brook stickleback (Culaea inconstans), bluntnose minnow (Pimephales notatus), and finally bullfrog tadpoles (Rana catesbeiana). The ratio of prey length to bass length that minimized handling time per unit weight of prey consumed, for prey types common in the diet of largemouth bass, was 0.22 for tadpoles, 0.24 for yellow perch and crayfish, and 0.29 for bluegill. Comparison of the experimentally derived optimum prey size based on handling time with that consumed by three natural populations showed that bass commonly chose prey of similar or smaller size than the optimal predicted. The reasons for this are discussed.