Feeding Habits, Daily Ration, and Potential Predatory Impact of Mature Female Spiny Dogfish in North Carolina Coastal Waters

摘要

Though the feeding habits of Spiny Dogfish Squalus acanthias in the northwestern Atlantic Ocean have received much attention due to their potential interactions with fisheries, currently no estimate of daily ration specific to the northwestern Atlantic population has been determined. To assess the diet of these sharks in the southern extent of their range, stomach contents were collected from 255 Spiny Dogfish captured by bottom trawl in nearshore North Carolina waters; 244 were mature females. Prey items were identified and percent index of relative importance was calculated for each prey taxon and category. To determine daily ration, 15 mature female Spiny Dogfish were captured by hook and line in North Carolina waters and kept in captivity for 2 weeks of feeding trials. Dogfish were fed preweighed frozen Atlantic Menhaden Brevoortia tryannus and allowed to digest their prey for predetermined periods, after which remaining food was removed using stomach-tube gastric lavage. Gastric evacuation rates determined by feeding trials were combined with data collected from sampling stomach contents to determine the daily ration and the amount of important prey taxa consumed during the Spiny Dogfish overwintering period. Teleost fishes were the dominant prey category, and Atlantic Menhaden and Bay Anchovy Anchoa mitchilli were the most important prey taxa. Daily ration estimates ranged from 0.26% to 0.56% of the shark's body weight per day. Spiny Dogfish potentially consumed an equivalent of 1.55-3.33% of the Atlantic Menhaden stock while overwintering in North Carolina waters