Preliminary Assessment of a Nearshore Nursery Ground for the Scalloped Hammerhead off the Atlantic Coast of Florida

—This study provides information regarding an open-ocean, nearshore nursery ground for the scalloped hammerhead Sphyrna lewini off the Atlantic coast of Florida near Cape Canaveral. Neonate scalloped hammerheads collected from this region ranged in size from 385 to 500 mm in total length (TL) and were observed during May and June, when water temperatures ranged from 26.1°C to 28.8°C. Although nearshore gill-net sampling during the study period encompassed the Florida Atlantic coastline from north of Cape Canaveral (latitude 28°40’N) south to the Jupiter Island area (latitude 27°04’N), neonate scalloped hammerheads were collected only in waters near the Cape Canaveral area. The nearshore waters near Cape Canaveral served as a nursery ground for scalloped hammerheads in 1994 and 1997. Extensive fisheries-independent gill-net sampling within the adjacent northern Indian River Lagoon system (Banana River Lagoon and Indian River Lagoon proper) did not collect scalloped hammerheads, indicating that this estuarine area does not serve as a nursery ground for this species. Other shark species collected in the overall study area included juvenile nurse sharks Ginglymostoma cirratum (620–1,219 mm TL); juvenile blacktip sharks Carcharhinus limbatus (630–885 mm TL); neonate, juvenile, and adult Atlantic sharpnose sharks Rhizoprionodon terraenovae (305–1,000 mm TL); juvenile and adult bonnethead Sphyrna tiburo (430–1,150 mm TL); and neonate and juvenile bull sharks C. leucas (754–1,460 mm TL). Human access to a portion of the open-ocean area near Cape Canaveral is currently prohibited due to security issues at the adjacent National Aeronautics and Space Administration’s Kennedy Space Center and Cape Canaveral Air Force Station. This area closure has inadvertently created a marine reserve by eliminating fishing pressure on and significantly reducing vesselor shore-based human interaction with this nearshore habitat. The effects, if any, of this marine reserve on shark populations in the region are unknown, and studies regarding these and other aspects of shark abundance and distribution in the Cape Canaveral area are currently ongoing. * E-mail: Doug.Adams@MyFWC.com Introduction The scalloped hammerhead Sphyrna lewini is a circumglobal species that inhabits warm temperate and tropical seas. In the western Atlantic Ocean, this species occurs from New Jersey to Brazil, including waters of the Gulf of Mexico and Caribbean Sea (Bigelow and Schroeder 1948; Compagno 1984). Within United States waters, the scalloped hammerhead is classified as part of the large coastal shark species complex and is commercially landed in longline, gill-net, and driftnet fisheries. In the historical Florida commercial shark fishery, spanning from 1935 until 1950, they were considered among the most valuable species because they contained the highest potency liver oil among the common shark species available (Springer 1963). Although this species is currently caught in large numbers and its fins are of high value, it is typically considered less marketable than the more frequently landed blacktip shark Carcharhinus limbatus and sandbar shark C. plumbeus (Berkeley and Campos 1988; NMFS 1993, 2001). Recreational anglers in Florida routinely encounter the scalloped hammerhead. Although in Florida’s state waters there is currently no size limit for this or any other shark species, there is a recreational bag limit of one per person per day or two per vessel per day, whichever is less (FWC 2007). This bag limit applies to all sharks, with the exception of currently protected shark species where no harvest or possession is allowed (FWC 2007). Although information regarding nursery grounds for scalloped hammerhead is limited, nursery areas have been shown to include bays, 166 ADAMS AND PAPERNO sounds, and littoral zones (Sadowsky 1965; Clarke 1971; Branstetter 1987). Little is known about specific nursery grounds for this species off the U.S. Atlantic coast. In a review of shark nursery grounds in this region, Castro (1993) presented data on 16 neonate and small juvenile scalloped hammerheads (347–598 mm in total length [TL]) from Bulls Bay, South Carolina. He suggested that there is an extensive nursery for this species on the southeastern coast of the United States with the center possibly located off South Carolina. In Florida, a total of eight juveniles (479–695 mm TL) were collected in the Mosquito Lagoon basin of the northern Indian River Lagoon system on the Atlantic coast in May, August, and September 1977 (Snelson and Williams 1981). No other specimens, however, have been documented within the Indian River Lagoon system since then (Tremain and Adams 1995; Provancha et al. 1998; Kupschus and Tremain 2001). Additionally, Dodrill (1977) collected a free-swimming, 382-mm-TL neonate scalloped hammerhead in the surf zone of the Atlantic Ocean off Melbourne Beach, Florida, on 1 June 1975. Aubrey (2001) collected 11 scalloped hammerheads (457–969 mm stretched TL) in the Cape Canaveral, Florida nearshore area from 1995 to 1998. Three of these were classified as young-ofthe-year individuals (457–481 mm stretched TL) and were collected in August 1996 (n = 2) and August 1997 (n = 1). Estimates of large and rapid declines in the population of scalloped hammerheads in northwestern Atlantic waters have recently been proposed. Since 1986, the abundance of scalloped hammerheads in the northwest Atlantic has reportedly declined by an estimated 89% (Baum et al. 2003); however, critical evaluation of these results indicate that this estimate may be exaggerated based on incomplete analyses and dataset limitations (Burgess et al. 2005). Life history parameters indicate that scalloped hammerheads are potentially among the shark species most vulnerable to overexploitation (Branstetter 1990; Hoenig and Gruber 1990; Baum et al. 2003). Effective management and protection of coastal nursery habitats is critical for many shark species. Prior to developing effective management strategies for shark populations, additional information regarding these nursery grounds, how specific nursery habitats are used by individual species, and the interaction between juveniles and specific nursery environments is required (Pratt and Otake 1990; Pratt et al. 1998; NMFS 1999). This paper provides information regarding the occurrence of neonate scalloped hammerheads in an open-ocean, nearshore nursery off the Atlantic coast of Florida.