Size-structured patterns of piscivory of the longfin inshore squid (Loligo pealeii) in the mid-Atlantic continental shelf ecosystem

Abstract

The longfin inshore squid (Loligo pealeii) dominates the landings in the USA mid-Atlantic continental shelf region, yet the potential ecological effects of harvesting this species are not known. Because squid feed on a wide variety of prey items, including juvenile stages of commercially important fish species, a full exploration on the predatory role of squid in this ecosystem is warranted. We examined the seasonal diet contents of L. pealeii and evaluated the importance of size constraints in governing patterns of piscivory. Our analyses showed that piscivory was dictated by size constraints, with larger squid demonstrating higher rates of piscivory than small squid. Squid were piscivorous at smaller sizes in the winter and spring than during the summer and autumn. Also, the frequency of piscivory was highest during the winter and spring, coincident with the time period when the number of vulnerable prey species was greatest. Our findings suggest that the frequency and intensity of piscivory are likely to be related to the duration of time that prey are vulnerable to predation, which in turn is dictated by the relative body sizes of L. pealeii and juvenile fishes.