Survival of Hatchery Raised Red Drum Exposed to Abrupt Salinity Increases—Simulating Bay Stockings

Abstract

As part of a stock enhancement program in Texas, Red Drum Sciaenops ocellatus are subject to a standard salinity acclimation protocol between the hauling trailer and stock site of 1 h per 10‰ salinity difference. In certain circumstances (hypersaline sites or drought) salinity differences can exceed 20‰ between hauling trailer and stock site. Information is needed on whether the current protocol is sufficient to investigate whether extending the acclimation time can improve survival. We conducted nine trials, each exposing pond-cultured Red Drum fingerlings to salinity increases of 10‰ (over 1, 2, and 3 h), 20‰ (over 2, 4, and 6 h), and no salinity change (control). Survival at 96 h following a change in salinity of either 10‰ or 20‰ was independent of the rate of increase in salinity. However, survival was lower among Red Drum subjected to an increase of 20‰ (survival, 61%) than to 10‰ (82%). Fish condition, length and weight of fish examined here had no significant effect on survival, across trials. Results suggest that hatchery personnel should select stocking sites within 10‰ salinity of the production pond and hauling trailer.

Received September 10, 2015; accepted December 24, 2015

ACKNOWLEDGMENTS

We thank Mark Fisher (TPWD) for providing statistical consultation and coordinating three anonymous reviews, as well as J. Anderson and D. Patterson (TPWD) for additional reviews. We are grateful to the Marine Development Center and Sea Center Texas for providing Red Drum fry to ponds at the Perry R. Bass Hatchery. We also appreciate the hatchery staff at the Perry R. Bass Hatchery for procuring healthy fingerlings used for this study. This project was funded by a grant from the State Wildlife Grants Program to TPWD (Federal Aid Grant T-94).