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

Abstract

<p>The Scalloped hammerhead shark, <em>Sphyrna lewini</em> is a coastal and pelagic circumglobal species that resides within coastal warm temperate and tropical seas. <em>Sphyrna lewini</em> 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 <em>S. lewini</em> 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 <em>S. lewini</em>. We recommend further study to evaluate the presence and movements of young-of-the-year and juvenile <em>S. lewini</em> in Wafer Bay to determine if this was an isolated incident or if the bay is a nursery ground for <em>S. lewini</em>.</p><div> </div>

First record of a potential neonate tiger shark (Galeocerdo cuvier) at a remote oceanic island in the Eastern Tropical Pacific

“…Considering the high biomass of apex predators at this near pristine ecosystem (Edgar et al ., 2011; Friedlander et al ., 2012) and the relatively small size of neonate sharks at birth, mortality of this individuals due to predation could be high (Branstetter, 1990; Heupel & Simpfendorfer, 2002). Wafer and Chatham Bays (north side of Cocos Island; Figure 1a) have been identified as important refugees for several juvenile and young‐of‐the‐year (YOY) shark species (López‐Garro et al ., 2012; Zanella et al ., 2012; Zanella, López‐Garro, Martínez, et al ., 2016; Zanella, López‐Garro, McComb‐Kobza, et al ., 2016). Nonetheless, the site where the neonate G. cuvier was recorded (Yglesias Bay) is located on the south side of the island, which has more exposure to wave action and stronger currents compared to the larger and more protected bays of the north (Cortés, 2016; Lizano, 2008) (Figure 1a).…”

“…Additionally, coral reef formations at Yglesias Bay are less extensive, complex and diverse than in Wafer and Chatham Bays (Alvarado et al ., 2016). Notably, one factor that all these bays have in common is the freshwater influx from rivers and waterfalls that increase suspended sediments and water turbidity, especially during the rainy season (July–November) (Zanella, López‐Garro, McComb‐Kobza, et al ., 2016). Because water turbidity offers some degree of protection from visual predators in shark nurseries (Heupel et al ., 2019; Yates et al ., 2015), the presence of turbid waters at Yglesias Bay could explain why a neonate of G. cuvier was found at this less complex habitat.…”