TEMPERATURE EFFECTS ON SPONTANEOUS BEHAVIOR OF LARVAL AND JUVENILE RED DRUM SCIAENOPS-OCELLATUS, AND IMPLICATIONS FOR FORAGING

Spontaneous behavior of young red drum Sciaenops ocellatus was examine d over a period of 8 h at two acclimation temperatures (21-degrees and 26-degrees-C) and after acute temperature changes between these level s. Three sizes of fish were used (xBAR = 9, 23, and 34 mmTL). Activity of fish acclimated to 26-degrees-C was greater than that at 21-degree s-C for fish of all sizes. Duration of pauses in spontaneous activity was generally lower at the warmer temperature. Effects of handling sta bilized after 2-5 h. The time course for activity after an acute therm al change followed the traditional model for thermal stress, with an e arly overshoot followed by a stabilized period. The overshoot was posi tive for upward transfers (21-26-degrees-C) and negative for downward transfers (26-21-degrees-C). Pause duration showed a time course rough ly inverse of the trend for activity, but pause frequency was inconsis tent. Effects of 5-degrees-C changes stabilized after about 2h. Result s indicate that a minimum adjustment period of 2-5 h is advisable when handling young red drum for research or for stocking into natural wat ers. The behavior of young red drum deprived of food at acclimation te mperatures suggests they are sweep, rather than saltatory, searchers.