A novel approach to estimate postrelease survival for estuarine fishes

Effective adaptive management of aquaculture-based fisheries enhancement programs requires iterative feedback on the impact of stocking activities. For estuarine finfishes, postrelease survival is particularly challenging to assess where recapture rates are low or difficult to obtain. We describe a novel approach to assess short-term apparent survival of hatchery-reared fish stocked into open estuarine systems and address postrelease behavioral states to quantify weekly survival of common snook (Centropomus undecimalis) after one year of monitoring. Following a weekly spatial and temporal replicate-release design for two experimental releases, 1922 juvenile snook (133–281 mm fork length) were marked with passive integrated transponder (PIT) tags and released among two regions of Phillippi Creek, Florida. Marine-adapted PIT tag antenna arrays detected 79% of released individuals and provided daily resighting histories for analysis with multistate mark-recapture models. Resighting histories were best explained by short-term differences in apparent survival among the first few weeks, and long-term patterns in detectability driven by residency behaviors. Weekly apparent survival rates increased from between 0.25 and 0.52 after the first week to >0.9 after week five. Fork length positively influenced survival for both releases and water height positively influenced detectability for the fall release. The highest survival was observed for individuals released in lower Phillippi Creek in the spring, suggesting lower reaches of tidal creek systems provide ideal release locations for juvenile snook. Further application of this approach will help refine optimal release locations, times, and procedures, promote adaptive management of enhancement programs, and maximize the benefits of strategic, science-based stocking on receiving populations.