Patterns of intra-estuarine movement of adult weakfish (Cynoscion regalis): evidence of site affinity at seasonal and diel scales

The views and opinions expressed or implied in this article are those of the author (or authors) and do not necessarily reflect the position of the National Marine Fisheries Service, NOAA. Abstract—Fine-scale movements of and use of habitat space by individual marine fishes can structure broader population dynamics, yet little is known about these traits. This lack of key information applies to the economically and ecologically important sciaenid weakfish (Cynoscion regalis), which is seasonally distributed in estuaries and coastal habitats along the Middle Atlantic Bight, where it feeds and spawns. We examined movements of adult weakfish in a southern New Jersey estuary using acoustic telemetry at both seasonal (n=29 fish) and diel (n=9 fish) scales. From June through November 2008, a majority of tagged and redetected weakfish (12 of 20; 60%) established areas of localized residency. Several fish made excursions of varying distances (1.0–5.9 km) from these regions before returning after 1–2 weeks. At the diel scale, most weakfish (7 of 9; 78%) resided as a local aggregation during the day and made nighttime excursions beginning around sundown (1930 hours). No fish were detected within 0.5 km of their area of localized daytime residency after 2230 hours. These findings are new evidence of the affinity of adult weakfish within specific localities across ecologically relevant timescales and offer further insight into the importance of estuaries in the life history of weakfish. Population connectivity in fishes is directed by the movements and space-use patterns of individuals in populations. We must first understand these individual behaviors to fully understand the role of population connectivity and how it informs tools used to maintain sustainable fisheries (Mittelbach et al., 2014). Fine-scale movements and related patterns of site affinity and homing have been examined extensively in terrestrial (Bright and Morris, 1991; Costello, 2010) and avian (Hoppes, 1987) species, and improvements in our ability to track marine animals with greater resolution, in both time and space, have shed light on similar behaviors (March et al., 2010). Studies of fine-scale movements of fishes have elucidated their ability to home back to relatively small geographic areas (Mitamura et al., 2009), keep restricted home ranges (McGrath and Austin, 2009), and maintain site affinity at timescales that range from daily (Humston et al., 2005) to yearly (Ng et al., 2007). Effects of scale, although important for examining ecological processes, are neglected too frequently during evaluation of animal movements (Levin, 1992; Schick et al., 2008). Therefore, obtaining appropriately scaled data on the movements of exploited marine fishes is an increasingly warranted goal (Pittman and McAlpine, 2003). Estuarine movements of adult weakfish (Cynoscion regalis) are poorly understood despite their relative importance within the estuarine food web, their economic contribution to both recreational and commercial fisheries (Able and Fahay, 1998), and most recent coast-wide population decline (NEFSC1). Weakfish range from the Gulf of Maine during some years (Collette and Klein-MacPhee, 2002) to the southwest Atlantic coast where they maintain year-round residency. They are seasonal residents in the northern portion of their range within the Middle Atlantic Bight between New York and Virginia, where migrations move south and offshore in the fall and north and inshore in the spring (Shepherd and Grimes,