Field estimates of food consumption of the searobin Prionotus punectatus (Bloch, 1797) on the continental shelf off Ubatuba, southeastern Brazil

Abstract

Daily ration and population food consumption of juvenile and adult searobin Prionotus punctatus (54-314 mm total length) were estimated for the southeastern Brazilian shelf off Ubatuba (23°35'S, 45°00'W). Samples were collected during 24hour-tisheries in three periods during 1987/88. P. puctatus is a diurnal invertebrate feeder, its maximum stomach fullness occurred during the afternoon. Instantaneous gastric evacuation rates were estimated from the data, and daily ration was subsequently computed for total food intake, as well as the dominant prey items, comparing the results off three widely-used methods. The total daily ration for juveniles (total length< 150 mm, average mass 15 g) was estimated at 11.6% body wet mass in January 1987 (summer). The daily ration for adults ranged from 2.7-3.4% body wet mass in winter July 1988 (average body mass 80.6 g), and from 3.1-4.1 % body wet mass in summer December 1988 (average body mass 110.0 g). The mean food consumption rate of the population was estimated at about 17 year-I, corresponding to a gross efficiency of 7.3%.