Significance of Cannibalism in Larval Walleye (Stizostedion vitreum)

Abstract

Cannibalism by larval walleye (Stizostedion vitreum) was studied to determine the ecological consequences and implications of cohort cannibalism in intensive culture systems and in natural communities. Two categories of cannibalistic behavior were observed. Trunk attacks were the most frequent (92%), and nearly always (98%) resulted in the escape of the victim; however, victims suffered a 19% mortality rate within 24 h of the attack. Tail attacks were less frequent but almost always resulted in ingestion of the victim. Tail attacks had a mean duration of 3.5 h and were more easily observed than trunk attacks (mean duration = 20 s). Under conditions of unlimited food, cannibalism could not be shown to confer an advantage in either growth or survival upon cannibals. The rate of cannibalism increased as food density decreased, but depended on the availability of light. Trunk attacks among larval walleye may be a higher source of mortality than the more commonly observed tail attack behavior.