Abundance and Distribution of Sharks in Northeast Florida Waters and Identification of Potential Nursery Habitat

Abstract

Sharks are considered top predators in many marine ecosystems and can play an important role in structuring community ecology. As a result, it is necessary to understand the factors that influence their abundance and distribution. This is particularly important as fishery managers develop management plans for sharks that identify areas that serve as essential fish habitat, especially nursery habitat. However, our understanding of shark habitat use in northeast Florida waters is limited. The goal of this study was to characterize the abundance and distribution of sharks in northeast Florida estuaries and to examine the effect of abiotic factors on shark habitat use. A bottom longline survey conducted from 2009 to 2011 indicated that 11 shark species use the estuarine waters of northeast Florida during the summer months. Atlantic Sharpnose Sharks Rhizoprionodon terraenovae, Blacktip Sharks Carcharhinus limbatus, and Bonnetheads Sphyrna tiburo were the most abundant species and made up 81.4% of the total catch. Site, month, and bottom water temperature were the most important factors determining the presence and abundance of sharks and suggest both regional and seasonal variations in the use of northeast Florida waters. Depth, salinity, and dissolved oxygen were also important factors. Our data show that these waters serve as a nursery for Atlantic Sharpnose and Blacktip Sharks, with young‐of‐the‐year and juveniles being present in the summer months. Limited tag–return data reveal that juvenile sharks remain in these waters throughout the summer and that some return in subsequent summers. This is the first study to characterize the abundance and distribution of sharks and identify potential nursery areas in northeast Florida estuaries.Received October 10, 2012; accepted March 7, 2013

Ecological Drivers of Shark Distributions along a Tropical Coastline

“…Salinity and temperature have important physiological implications for sharks [ 20 , 68 ] and there are numerous examples of their influence on shark habitat use [ 3 , 14 , 36 ]. For example, the occurrence of immature scalloped hammerhead sharks in the north-eastern Gulf of Mexico increased with both salinity and temperature [ 15 ].…”

“…A wide range of abiotic variables are thought to influence the habitat use of coastal sharks (reviewed in [ 11 ]). For example, water temperature [ 14 ], depth [ 15 ], salinity [ 3 , 16 ], turbidity [ 17 ] and dissolved oxygen concentration (DO; [ 18 , 19 ]) have been identified as important factors for multiple species. Influences of abiotic variables may be dictated by a species’ physiological requirements [ 11 ].…”

Resource‐use dynamics of co‐occurring chondrichthyans from the First Coast, North Florida, USA

“…Recent studies on shark assemblages in the northeast Florida and southeast Georgia coast, a location commonly referred to as the “First Coast” as it was the first area of Florida colonized by Europeans, have demonstrated that this region provides an important habitat for a sizeable number of commercially and recreationally important shark species (McCallister et al ., ; Morgan ). Initial work examining shark abundance in First Coast estuaries demonstrated that at least 11 shark species use inshore waters in this region on a seasonal (late spring to fall) basis, with at least two species, the Atlantic Sharpnose shark ( Rhizoprionodon terraenovae , J. Richardson, 1836) and Blacktip shark ( Carcharhinus limbatus , J. P. Müller & Henle, 1839), making use of the site as juvenile refuge or “nursery” habitat (McCallister et al ., ). More recently, a follow‐up study expanded the total number of shark species that frequent First Coast waters to a minimum of 14 and also reported differences in species and life‐stage composition of catch from inshore estuarine waters and adjacent beach habitats, demonstrating the greater abundance of older ( i.e ., juvenile to mature) life stages in nearshore waters (Morgan, ).…”

“…Recent studies on shark assemblages in the northeast Florida and southeast Georgia coast, a location commonly referred to as the "First Coast" as it was the first area of Florida colonized by Europeans, have demonstrated that this region provides an important habitat for a sizeable number of commercially and recreationally important shark species (McCallister et al, 2013;Morgan 2018). Initial work examining shark abundance in First Coast estuaries demonstrated that at least 11 shark species use inshore waters in this region on a seasonal (late spring to fall) basis, with at least two species, the Atlantic Sharpnose shark (Rhizoprionodon terraenovae, J.…”

“…Initial work examining shark abundance in First Coast estuaries demonstrated that at least 11 shark species use inshore waters in this region on a seasonal (late spring to fall) basis, with at least two species, the Atlantic Sharpnose shark (Rhizoprionodon terraenovae, J. Richardson, 1836) and Blacktip shark (Carcharhinus limbatus, J. P. Müller & Henle, 1839), making use of the site as juvenile refuge or "nursery" habitat (McCallister et al, 2013). More recently, a follow-up study expanded the total number of shark species that frequent First Coast waters to a minimum of 14 and also reported differences in species and life-stage composition of catch from inshore estuarine waters and adjacent beach habitats, demonstrating the greater abundance of older (i.e., juvenile to mature) life stages in nearshore waters (Morgan, 2018).…”