INTERACTIVE EFFECTS OF STOCKING SITE SALINITY AND HANDLING STRESS ON SURVIVAL OF STRIPED BASS FINGERLINGS

We evaluated the effects of prestocking handling and stocking site sal inity on survival and stress response during the first 48 h after stoc king for three size-classes of cultured striped bass Morone saxatilis (mean sizes: 20, 65, and 230 mm total length). Treatments were routine handling, tagging, and minimal handling. Routinely handled and tagged fish experienced normal hatchery procedures for a large-scale stockin g program. Minimally handled fish were transported directly from reari ng ponds to stocking sires at low densities. Fish were stocked at fres hwater or brackish (salinity, 0-7 parts per thousand) sites. Survival in cages was monitored for 48 h after stocking, and cortisol concentra tion was measured to indicate stress levels. Handling before stocking, stocking site salinity, and the interaction of these factors signific antly affected survival and cortisol levels. For the two larger size-c lasses, minimally handled fish had high survival rates (>99%) and low cortisol levels (less than or equal to 18 mu g/dL) at both stocking si tes. Routinely handled and tagged fish had intermediate survival (80-9 9%) and cortisol levels (15-18 mu g/dL) at the brackish site and had l ow survival (6-48%) and high cortisol levels (26-36 mu g/dL) at the fr eshwater site. For the smallest size-class, survival of minimally and routinely handled fish was 83-99% at the brackish site and 0-3% in fre shwater. Brackish receiving waters appear to ameliorate the stress cau sed by routine handling and tagging procedures, which results in highe r rates of short-term survival.