Sex Differences in Residency of Adult Spotted Seatrout in a Louisiana Estuary

Spotted Seatrout Cynoscion nebulosus is the most highly sought after recreational species along the U.S. Gulf coast. However, movement information for this economically and ecologically important species is currently limited to data from mark-recapture studies. We used remote acoustic telemetry, a high-resolution, fisheries-independent technique, to examine the residency of adult Spotted Seatrout (n = 172) in a Louisiana estuary, Calcasieu Lake (approximate to 300km(2)). An estuarine-wide array of 60 receivers was deployed for a 2.5-year period (May 2007-October 2009) to detect and quantify how long fish were present in the estuary and determine the proportion of fish that emigrated from the system. We then determined how these metrics (detection period and emigration) were related to fish size, sex, and season of release. Emigration was highly seasonal and occurred exclusively during late spring and summer when water temperatures exceeded 24 degrees C. Surprisingly, male Spotted Seatrout, regardless of their size, were more likely than females to permanently emigrate from the estuary (i.e., not return within the 1-year battery life of transmitters) as evidenced by their shorter mean detection periods (males = 134 d, females = 177 d) and higher incidence of emigration (29-42% of males, but only 14-16% of females emigrated). Assessment and management strategies for this species may be improved by explicitly considering this behavioral difference between sexes. Namely, conducting stock assessments at a finer spatial scale (i.e., estuarine-specific versus state-wide) appears warranted given the high estuarine fidelity of females (approximate to 85%), which exacerbates their potential for localized depletions due to anthropogenic stressors (e.g., fishing pressure, habitat alteration, or pollution).