Photographs and video footage taken in Oranjestad Bay by a local dive shop in July 2015 showed 2 small sharks (estimated to be <65 cm TL), which were later identified as juvenile lemon sharks. More juvenile lemon sharks were observed throughout the spring of 2016 on the northeastern side of the island in the shallow waters of Zeelandia Bay (n = 3, one individual on 3 separate occasions). Here, only one individual estimated to be smaller than 65 cm in total length was observed on each occasion. In addition, 2 young lemon sharks (estimated to be <65 cm TL) also in the shallow waters of Oranjestad Bay were filmed in June 2016 (Fig. 1A). All observations described here occurred in shallow water (<2 m depth) and on sandy substrate.
Clear photographic evidence was available for 3 out of 5 observations, which enabled identification and estimations of the sharks’ total length (TL) (Fig. 1B). Key morphological characteristics were used to identify the species: (1) a second dorsal fin approximately equal in size compared to the first dorsal fin; (2) broad pectoral fins at their base; and (3) size of the observed sharks, all of which were estimated to be smaller than 65 cm TL, which is the upper limit of the reported size-at-birth for the lemon shark. Although all of the observed sharks were in the range of the reported size-at-birth for this species, estimation bias for observations from the surface should always be taken into account. Based on the growth curve for this species, it is likely that all observed lemon sharks are younger than 2 years of age. According to Morrissey and Gruber, the home range of lemon sharks of this age is approximately 0.68 km2. Sint Eustatius is located on the same bank as Saint Kitts (approx. 12.2 km) and Nevis (approx. 46.6 km), for which the presence of lemon sharks is unknown. The closest island with known presence of lemon sharks is Sint Maarten located at a distance of approximately 55.8 km to the northwest. Sint Maarten and Sint Eustatius are located on different banks separated by deep water, which juvenile lemon sharks are known to avoid. The limited home range of young lemon sharks combined with the distances to nearby islands and observations from the same bay for 2 consecutive years (Fig. 1A) indicate that the waters of Sint Eustatius are possibly an important site for juveniles of this species. Considering the limited home range of the juveniles, it is likely that the adult females were also present.
Although the species is not considered to be endangered on the IUCN Red List, threats like overfishing and habitat degradation remain undefined . There is currently no local management in place for this species, however, a network of protected areas across the species’ range, covering different life-stages of the species, could greatly improve conservation of shark species. Moreover, protection of nearshore habitats has been shown to be crucial to juvenile lemon sharks.
3 of the islands of the Dutch Caribbean, Saba (including the Saba Bank), Bonaire and Sint Maarten, have been designated as shark sanctuaries. In the waters of St. Maarten and Bonaire the capture of sharks is restricted. In the waters of Saba and Bonaire, further measures are planned to improve the protection of all sharks. Sint Eustatius, however, has not implemented protective management for sharks in its waters. The island currently has 2 marine reserves (Fig. 1A), but these do not cover the bays in which the lemon sharks were observed for 2 consecutive years. Young lemon sharks exhibit high natal site fidelity (i.e. remain in the same area for multiple years), which indicates that local management efforts could have great potential to effectively conserve juveniles of the species in the waters of Sint Eustatius.