PISCIVORY AND PREY SIZE SELECTION IN YOUNG-OF-THE-YEAR BLUEFISH - PREDATOR PREFERENCE OR SIZE-DEPENDENT CAPTURE SUCCESS

Young-of-the-year bluefish Pomatomus saltatrix become piscivorous at a very small size/age. When feeding on Atlantic silversides Menidia men idia in the laboratory, bluefish forage in groups and, unlike many oth er piscivores, tend to attack their prey tail-first. Attack distances, times and velocities as well as attack rates were not size-dependent. Handling times and attack success rates, however, were strongly deter mined by both predator and prey size. When given a choice of silversid e sizes, all bluefish sizes consumed primarily small prey. These resul ts suggest that bluefish attack all prey sizes upon encounter but capt ure primarily small prey. Size selectivity may be a passive process me diated by differential size-based capture success.