THE BEHAVIORAL BASIS OF PREDATOR-PREY SIZE RELATIONSHIPS BETWEEN SHRIMP (CRANGON-CRANGON) AND JUVENILE PLAICE (PLEURONECTES-PLATESSA)

The shrimp, Crangon crangon (L.) (Crustacea: Crangonidae), is a significant predator of the smallest sizes of plaice, Pleuronectes platessa L. (Teleostei: Pleuronectidae), during and immediately after the fish settle on sandy beaches when predation rate is strongly dependent on the size of both the predator and the prey. Laboratory experiments showed that this size-dependency is caused principally by the superior escape capabilities of larger fish once captured rather than differences in the ability of different sizes of shrimps to capture their prey. Fish that escape after capture are often wounded and some of these wounds may subsequently be fatal. Many shrimps capture and eat fish that are larger than their stomach volume resulting in long handling times and low prey profitabilities. For all sizes of shrimps used (36-65 mm total length) prey profitability (mg prey ingested min(-1)) increases with decreasing fish length.