Self-feeding activity patterns in gilthead sea bream (Sparus aurata), red porgy (Pagrus pagrus) and their reciprocal hybrids

This study was conducted to monitor feeding activity of gilthead sea bream (Sa) and red porgy (Pp) and to investigate the hereditary effects on feedin g in their hybrids (female Sa X male Pp, female Pp X male Sa), obtained aft er artificial crosses. trill fish groups were held in 500-1 tanks under amb ient temperature (15-25 degrees C) and light conditions (daylength from 9 h 30 min to 14 h 48 min). Fish (initial body weight 100-165 g) were fed by m eans of self-feeders, which were connected to a computer, recording fish fe eding activity for a year. Results showed that there was a 24-h periodicity in all fish types over the experiment. Ln their daily feeding patterns, bo th parental species were diurnal: red porgies had a stable daily pattern ov er the experiment, while gilthead sea bream shifted their activity from a g eneral daylight fluctuation in warm periods to an afternoon peak in cold pe riods. The Sa X Pp hybrids showed intermediate feeding patterns compared to their parents in warm periods and a pattern that was similar to the red po rgy in cold periods, while the Pp X Sa hybrids had rather unchangeable dail y feeding patterns, which were not related to the parental ones. The propor tion of night feed demands increased in cold periods independent of fish gr oup. The relationship between temperature and feed intake was species-depen dent. Finally, this study indicated that feeding expression in hybrids was related to the combination of the parental genome, supporting our hypothesi s for a hereditary influence on feeding activity in fish. (C) 2000 Elsevier Science B.V. All rights reserved.