A New View of the Predation Cycle of a Planktivorous Fish, White Crappie (Pomoxis annularis)

Abstract

Predators are often categorized as either cruise or ambush feeding strategists. We present evidence that white crappie (Pomoxis annularis) are neither. Instead, the crappie swim intermittently and search only when stationary. If the crappie searched while swimming, one would expect the run speeds to be slower than the pursuit speeds, but no difference was found between these two measurements. Assuming that prey are located while swimming, a foreshortening of runs prior to pursuit would also be expected, but again, none was detectable. The duration of the search pause appears to be related to the detectability of the prey. Crappie also search during the pause immediately following the attack and ingestion of a prey item. The observation that the probabilities of detecting and pursuing a prey following a run or an attack do not differ significantly supports this conclusion. Also, the duration of the pause following a run or attack does not differ significantly over a wide range of temperatures. If these views are correct, white crappie could not forage optimally by either deleting located prey items from the diet or minimizing handling time. What they appear to be doing is creatively managing their search time.