Striped bass survival in Lake Blackshear, Georgia during drought conditions: implications for restoration efforts in Gulf of Mexico drainages

Abstract

Endemic striped bass Morone saxatilis (Walbaum) populations in Gulf Coast rivers have declined dramatically since the 1940s as a result of anthropogenic activities that limited access to historical spawning areas and adversely affected cool-water springs. Efforts to restore these populations to self-sustaining levels have been under way since the 1950s and continue to the present. In 1998–1999, we fitted 27 adult Gulf-strain striped bass with radio transmitters and released them in Lake Blackshear, Georgia. We used data on their survival, habitat use, and movement patterns to assess the potential long-term survival of fingerling striped bass stocked in this lake since 1996. Overall, we re-located only 27% of tagged fish in cool-water springs, and all radio-tagged striped bass that remained in the lake died during summer. Drought conditions based on rainfall and groundwater withdrawals during the study caused some cool-water springs in Lake Blackshear to stop flowing. Lake temperatures >27°C for 13 consecutive weeks, die-offs of non-tagged fish, intermittent spring flows, and widespread mortality of tagged fish suggest that the long-term survival of stocked striped bass in Lake Blackshear probably will be poor. Successful re-introductions of Gulf-strain striped bass to rivers and reservoirs in their historic range will depend on the presence of cool-water springs. The persistence, abundance, and sizes of springs in this region are heavily dependent on the periodicity of droughts and the magnitude of groundwater use. Regional climatological data indicate that droughts occur about every 3 years. Therefore, better management of groundwater withdrawals during drought periods will become increasingly important to maintain aquifer levels (and cool-water springs) needed for restoring native striped bass to Gulf Coast rivers.