Feeding Chronology of Yellowtail Flounder (Limanda ferruginea) and American Plaice (Hippoglossoides platessoides) on Grand Bank (NAFO Division 3N)

Abstract

A total of 1199 individuals of yellowtail flounder (Limanda ferruginea, Storer) and 970 individuals of American plaice (Hippoglossoides platessoides, Fabricius) were sampled from six hauls carried out in a period of 24 hours for studying the feeding chronology of these species. The main prey of yellowtail flounder (considered as total weight percentage) were Gammaridae (19.5%), Ammodytes dubius (10.1%) Annelida (6.3%), Mysidacea (6.0%) and Anthozoa (5.6%). The predominant preys in American plaice were Ammodytes dubius (72.3%), followed by Mysidacea (8.5%) and Echinarachnius parma (6.1%). Diet composition varied with size and timetable for both species. The feeding intensity index values in yellowtail flounder were scaled over 24-hr period, and in both species these values slightly decreased during the night and at dawn, but in American plaice there was more variability in the timetable values between the size ranges. The mean weight fullness index values over the 24-hr period in yellowtail flounder were lower than in American plaice. Also, both species presented different behaviour between the size ranges. No significant differences were noted (p<0.05) in the estimated values for feed intensity throughout the 24-hr period in any of the ranges of both species studied.