Best practices for common snook stock enhancement identified through iterative release experiments

Research on stock enhancement of Common Snook Centropomus undecimalis in southwest Florida has recently prioritized using passive integrated transponder (PIT) tags to monitor released fish. Autonomous antenna arrays deployed around release sites allowed for continuous sampling of PIT tagged fish, increasing post-release observations to estimate survival and establish best practices. A series of 25 iterative stocking experiments from 2015 to 2023 have generated data on 333 unique release groups (mean sizes = 112–287 mm FL) spanning a suite of stocking times, locations, and protocols. Stocking experiments were conducted with 45,958 juveniles, with ∼65 % being PIT tagged (100 % tagged for replicated studies and 10 % for larger, one-time releases). Mark-recapture models regularly indicated that survival is high and constant around 35 days post-release, providing a consistent point in time to assess experimental impacts. The diversity of stocking efforts resulted in survival rates to day 35 ranging from 0 % to 50.9 % of individuals. A step-wise modeling approach examined the spatial, temporal, and procedural factors for each unique release group to identify best practices with the goal of > 20 % survival to day 35, which occurred for 68 release groups. Although low-surviving groups (<10 %) can occur at any time, many were anecdotally associated with experimental designs with high-handling or stressful environmental times. We determined best practices for stocking Snook in southwest Florida to be releasing large juveniles into the mouth, lower, or middle reaches of tidal creeks in May, June, or September, using acclimation cages when stocking into locations considered to be high predation risk or environmentally stressful, and waiting an additional year between releases following a high-survival stocking event. • Iterative release experiments identified best practices for stock enhancement. • Antenna arrays rapidly collected post-release observations of PIT tagged fish. • Lower tidal creek reaches improved post-release survival of Common Snook. • May, June, and September provided optimal stocking timeframes. • Release success is highly variable, but best practices nearly doubled survival.