Estimating site-specific spawning parameters for a spawning aggregation: an example with spotted seatrout

An understanding of individual variability in spatio-temporal spawning behavior is important to understand productivity and inform stock assessments and management actions. Spotted seatrout Cynoscion nebulosus, popular both with recreational anglers and researchers due to their accessibility and catchability, have frequently been the subject of reproductive studies at the population level. We used passive acoustic telemetry to estimate spotted seatrout spawning interval and period and investigate spawning behaviors at the individual level. A total of 43 spotted seatrout (27 females, 16 males) were acoustically tagged and tracked over 3 consecutive spawning seasons with a high-density array deployed at a residential spawning aggregation site in Tampa Bay, Florida. The probability of a fish being at the spawning site and instantaneous loss from the population (Z) was estimated using a Bayesian framework-Cormack Jolly Seber model. Most fish exhibited intra-seasonal site fidelity, with males and larger fish of both sexes exhibiting a greater probability of being at the spawning site. A similar pattern with total length and sex was seen in Z. There were sex-dependent differences in movement within the array, with females traveling a larger distance between single detections while males had a higher total distance traveled within the array. This study demonstrates how acoustic telemetry can be combined with Bayesian models to estimate sex- and length-dependent spawning parameters for an aggregating marine species that exhibits temporal migration to and from a spawning site.