Seasonal occurrence, relative abundance, and migratory movements of juvenile sandbar sharks, Carcharhinus plumbeus , in
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asonal occurrence, relative abundance, and migratory movements of juvenile sandbar sharks, Carcharhinus plumbeus, in Winyah Bay, South Carolina Caroline Collatos
& Daniel C. Abel & Kelsey L. Martin
Received: 17 July 2019 / Accepted: 31 May 2020 / Published online: 10 June 2020 # Springer Nature B.V. 2020
Abstract In the past decade along the U.S. East coast, the overfished western North Atlantic stock of Carcharhinus plumbeus has been recovering; however, research investigating C. plumbeus habitats and seasonal habitat shifts is lacking. Accordingly, we studied the seasonal residency, catch abundance, and distribution of juvenile C. plumbeus in Winyah Bay, SC, as well as their migration patterns along the western North Atlantic. We set 303 bottom longlines from May through September in 2016 and 2017 and deployed 11 Vemco (V16-4H) acoustic transmitters in juvenile C. plumbeus. Catch abundance did not differ by month or year (p = 0.45) and was not significantly influenced by any tested water parameter (p = 0.58). C. plumbeus catches were dominated by individuals measuring 81–100 cm precaudal length, and mean size only significantly differed by year (p = 0.02) with slightly larger sharks (86.8 cm PCL) caught in 2017 than 2016 (81.4 cm PCL). Tidal stage and Bay region were positively correlated with catches (p = 0.02). From August 2016 through January 2019, juveniles were detected in Winyah Bay from April to November for 1–302 nonElectronic supplementary material The online version of this article (https://doi.org/10.1007/s10641-020-00989-2) contains supplementary material, which is available to authorized users. C. Collatos (*) : D. C. Abel Marine Science Department, Coastal Carolina University, Conway, SC 29528, USA e-mail: [email protected] K. L. Martin Texas A&M University, Corpus Christi, TX 78412, USA
consecutive days (μ ± SE = 108.1 ± 32.6 days), with six juveniles exhibiting interannual return. Detection frequency and presence differed by Bay region, with most detections nearshore and in Lower Bay, fewest in Middle Bay, and none in Upper Bay. This study had two primary findings: monitored sharks utilized a previously unknown southern overwintering migration route, and Winyah Bay serves as a secondary nursery for C. plumbeus. Keywords Sandbar shark . Seasonal presence . Habitat . Nursery area . Migration . Acoustic telemetry
Introduction Sandbar sharks, Carcharhinus plumbeus (Nardo, 1827), are a slow-growing coastal shark that frequently occupy estuaries in their early life stages (Bigelow and Schroeder 1953; Springer 1960; Castro 1993; Merson and Pratt 2001; Grubbs and Musick 2007; Grubbs et al. 2007). In the past three decades, the western North Atlantic stock of C. plumbeus have been overfished, and they are currently listed as vulnerable on the International Union for Conservation of Nature Redlist (Musick et al. 2009). Catch data collected from 1975 to 2014 from six independent shark fishery surveys ranging along the US coastline from Virginia through Texas showed recovery of the western North Atlanti
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