Food consumption by yellowtail flounder in relation to production of its benthic prey

Abstract

Yellowtail flounder Lvnanda ferruginea consumes a small but significant propobon of the production of its invertebrate prey. Using 2 different methods, 1 calculated rate of food consumption by yellowtail flounder at 3 sites off the New England coast, USA. The bioenergetic method sums the food required to satisfy the metabolic needs of the fish. The second method is based on weight of stomach contents and rate of food evacuation from the stomach. The bioenergetic method gave consistently higher results (1.4 to 1.6 kg fish-' yr-l) than the stomach-content method (0.5 to 0.8 kg fish-' yr-'1. Yellowtail flounder abundance was estimated with a method that uses commercial-catch data to standardize a survey: relative-abundance index. I multiplied consumption rates per fish by flounder density to obtain estimates of consumption per unit area, which range from 1.2 to 6.3 g wet wt m-' yr-'. Annual production of 6 important prey species was calculated from benthic samples collected concurrently at the same sites. Yellowtail flounder consumphon as a percentage of prey production was 6 to 12 %, 2 to 5 %, and 1 to 3 %, for the amph~pods Uncjola inermis, Encthonius fasciatus and Ampelisca agassizi, respectively; 11 to 34 O/O and 7 to 21 O/ O for the polychaetes Chone infundibuliformis and Nephtys incisa, respectively; and less than 1 % for the sand dollar Echinarach-nius parma.