First record of young-ofthe-year Scalloped hammerhead shark , Sphyrna lewini ( Carcharhiniformes : Sphyrnidae ) from Isla del Coco National Park , Costa Rica

The Scalloped hammerhead shark, Sphyrna lewini is a coastal and pelagic circumglobal species that resides within coastal warm temperate and tropical seas. Sphyrna lewini exhibits strong intraspecific segregation: neonates and young-of-the-year spend the first part of life in coastal inshore waters (nursery grounds), while adults migrate offshore, returning to protected nursery habitats for mating and pupping. On December 3, 2014, at approximately 19:00 hr, four young-of-the-year S. lewini were caught with hand line in Wafer Bay, Isla del Coco, Costa Rica (5°32’42.4” N 87°03’45.3” W). A total of three males (total length (TL): 73, 73, 76 cm) and one female (TL: 75 cm) were recorded. The presence of these individuals at Isla del Coco suggests that a pregnant female gave birth in or near Wafer Bay, which may be a nursery ground for S. lewini. We recommend further study to evaluate the presence and movements of young-of-the-year and juvenile S. lewini in Wafer Bay to determine if this was an isolated incident or if the bay is a nursery ground for S. lewini. Rev. Biol. Trop. 64 (Suppl. 1): S201-S204. Epub 2016 February 01.

The Scalloped hammerhead shark, Sphyrna lewini (Griffith & Smith, 1834) is a coastal and pelagic circumglobal species that resides within coastal warm temperate and tropical seas (Bigelow, & Schroeder, 1948;Compagno, Krupp, & Schneider, 1995).In the Eastern Pacific, the species ranges from southern California and the Gulf of California to Panama, Ecuador, Peru and northern Chile (Compagno et al., 1995;Bustamante, 2014).
Sphyrna lewini is highly impacted by anthropogenic activities, including overfishing and as bycatch in fisheries (Miller et al., 2013).Baum et al. (2003) reported a rapid decline in large coastal and oceanic shark populations in the Northwest Atlantic, and estimated that scalloped hammerhead sharks declined by over 75 % in the past 15 years.As noted recently, abundance of S. lewini in Isla del Coco Nationa Park, Costa Rica, has decreased by approximately 45 % during the last 21 years (White, Myers, Flemming, & Baum, 2015).In 2008 the IUCN Red List classified S. lewini as Endangered, and in 2013 it was included on the Appendix II of CITES.
Sphyrna lewini is caught by different fisheries in oceanic (longlines) and coastal waters (artisanal), as consequence of the strong spatial segregation between adults and juveniles.In fact, pups and juveniles live in nursery areas located in coastal waters of estuaries, bays and mangroves, where rich nutrient waters provide food and protection from predators (Clarke, 1971;Branstetter, 1987;Castro, 1993, Duncan, & Holland, 2006).Springer (1967) defines nursery areas as "coastal areas that are geographically separated from adult feeding grounds".However, Heupel, Carlson & Simpfendorfer (2007) propose a new definition, which "requires three criterion for an area to be identified as a nursery: (1) sharks are more commonly encountered in the area than other areas, (2) sharks have a tendency to remain or return for extended periods, and (3) the area or habitat is repeatedly used across years".
In Wafer Bay, on December 3, 2014 at approximately 19:00 hr, four young-of-theyear S. lewini were caught with hand line and a modified size five circular hook (5°32'42.4"N -87°03'45.3"W), at 12 m deep with a sea surface temperature of 29ºC (Fig. 1).Identification of the species was attained by analysis of the following distinctive characters outlined by Compagno et al. (1995) and Compagno, Dando & Fowler (2005): 1-a indentation located in the center of the margin of the head and two lateral slits respect to the principal; 2-the dorsal surface and flanks are gray-brown and the tips of the pectoral fins are dark, almost black; 3-the second dorsal fin is elongated almost until the beginning of the precaudal peduncle.
Based on previous studies, we conclude that the S. lewini captured in Wafer Bay most likely have not completed the first year of life.The presence of these individuals at Isla del Coco suggests that a pregnant female gave birth at Wafer Bay, which may be used as a nursery ground for S. lewini.This is the first record of young-of-year hammerhead sharks from Isla del Coco National Park (Bussing, & López, 2005;Garrison, 2005; Sibaja-Cordero, 2008 ;Zanella, López-Garro, Golfín-Duarte, & Saenz, 2012;Nalesso, 2014).
Although this report is not consistent with the traditional concept of nursery areas, because Wafer Bay is not located in coastal waters, the estuarine ecosystem offered by the Genio River could be used as nursery ground for pups and juveniles of S. lewini.In conclusion, we recommend further study to evaluate the presence of young-of-the-year S. lewini in Wafer Bay to clarify if this was an unusual event or if the bay is a nursery ground for the species.

ACKNOWLEDGMENTS
We thank the personnel of Isla del Coco National Park and Isla del Coco Marine Conservation Area for their assistance.We also acknowledge the Fundación Amigos de la Isla del Coco for supporting the expeditions.