CONFINEMENT-INDUCED AND TRANSPORT-INDUCED STRESS ON RED DRUM JUVENILES - EFFECT OF SALINITY

Fingerling red drums (Sciaenops ocellatus; mean weight +/- SE, 28.0 +/- 0.9 g to 42.3 +/- 1.1 g) were acclimated to salinities of 2, 4, 6, 8, 16, or 35 parts per thousand (25-degrees-C) and then crowded in cages for up to 48 h. Fish in the intermediate salinities survived whereas most fish in the two extreme salinities died. Plasma osmolality values increased in fish confined in 35 parts per thousand salinity, decreased in fish confined in 2 parts per thousand water, and were stable in the fish confined in the intermediate salinities. All fish (weight, 20.2 +/- 1.2 g to 37.1 +/- 1.7 g) survived 9 h of simulated transport and a 3-d follow-up in 2, 4, 8, 16, or 35 parts per thousand salinity at temperatures of 25 or 30-degrees-C. Results of this study and others indicate that healthy red drum fingerlings tolerate confinement and transport well. Further, survival is enhanced if fish are handled and transported in water that is nearly isosmotic with the plasma of the fish (approximately 11 parts per thousand).