First characterization of shark nursery habitat in the United States Virgin Islands: evidence of habitat partitioning by two shark species

Abstract

Little is known of the diversity, demography, and essential fish habitat of sharks within the United States Virgin Islands (USVI) marine ecosystem. To examine species diversity and the relative abundance of elasmobranchs in this region, bottom-longline and hand-gear sampling was con- . Lemon sharks Negaprion brevirostris had the highest relative abundance based on log-transformed CPUE data (0.98 ± 0.15), followed by blacktip sharks Carcharhinus limbatus (0.91 ± 0.18), southern stingrays Dasyatis americana (0.28 ± 0.08), nurse sharks Ginglymostoma cirratum (0.08 ± 0.05), blacknose sharks Carcharhinus acronotus (0.06 ± 0.04) and the Caribbean sharpnose Rhizoprionodon porosus (0.03 ± 0.03). The relative abundance of all species was significantly higher in the summer (2.6 ± 0.2) than during the winter (1.1 ± 0.2). For the blacktip (N = 89 captures of 74 individuals) and lemon (N = 66, 48 individuals) sharks, which comprised the bulk of the catch, mean fork length (± SE) was 51.9 ± 0.63 cm and 59.9 ± 1.2 cm, respectively, representing primarily neonatal and young-of-the-year life stages. The recapture rates for blacktip and lemon sharks were 21% and 29%, respectively, and nearly all recaptures occurred within the bay, indicating a high degree of site fidelity. Capture information and limited acoustic tracking provided evidence of spatial and temporal habitat partitioning by these 2 shark species within the bay. Although the CPUE of both species was highest over shallow (<1 m) seagrass substrate, lemon sharks were found and tracked exclusively on shallow, mangrove-fringed seagrass habitat, while blacktip sharks utilized a wider area of the bay. Fish Bay was determined to provide important nursery habitat for young juvenile lemon and blacktip sharks in the USVI.

Distributions of Sharks across a Continental Shelf in the Northern Gulf of Mexico

“…In contrast to Atlantic sharpnose and blacknose sharks, blacktip sharks are known to use coastal waters and bays as nurseries (Castro 1993;DeAngelis et al 2008). Blacktip sharks were shown to have a high residence time in coastal waters in Terra Ceia Bay, Florida, before migrating south during winter months (Heupel and Hueter 2001;Heupel et al 2004).…”

Complexities of coastal shark movements and their implications for management

“…The potential importance of physical and biotic factors in habitat selection by sharks has been reviewed by Simpfendorfer & Heupel (2004) and has been addressed by approximately 75% (n = 79) of the studies included in our review (Table S1 in the supplement). Influences such as tide, water temperature, salinity, dissolved oxygen, substratum type and depth affect the distribution of coastal elasmobranchs, with greater responses for some species and size classes (Economakis & Lobel 1998, Ackerman et al 2000, Hopkins & Cech 2003, Simpfendorfer et al 2005, DeAngelis et al 2008, Vogler et al 2008, Campos et al 2009, Heithaus et al 2009b, Ubeda et al 2009). To date, depth and temperature have been measured with shark movement for many species, followed by tide, current, benthos type, salinity, prey and dissolved oxygen associations (Table 2).…”

“…The definition of site fidelity varies among studies, and the term is sometimes used synonymously with philopatry. Generally, all definitions of site fidelity refer to the repeated use of an area over time, for example 'area site fidelity' (Goldman & Anderson 1999); 'daily site fidelity' ; 'long-term site fidelity' (Huveneers et al 2006, Lowe et al 2006, DeAngelis et al 2008; 'seasonal site fidelity' (Dicken et al 2007); 'site attachment' (Gruber et al 1988, Wetherbee et al 2007, Yeiser et al 2008; and 'natal site-fidelity' (Chapman et al 2009). …”

“…Castro 1993, Simpfendorfer & Milward 1993, Yokota & Lessa 2006), but we still have a poor understanding of how species partition nurseries from other phases. It is only recently that some researchers have started to address habitat use of multiple species of coastal sharks and considered multi-species management in these areas (White & Potter 2004, Wiley & Simpfendorfer 2007, DeAngelis et al 2008, Yeiser et al 2008.…”

Fine-scale spatial and seasonal partitioning among large sharks and other elasmobranchs in south-eastern Queensland, Australia

“…We also report on the average size and sex ratio for the two most abundant sharks and analyse monthly trends in overall catch. Elsewhere, studies have observed spatial partitioning among sharks in inshore waters (White and Potter 2004;Pikitch et al 2005;DeAngelis et al 2008). Given the large number of netted beaches in the present study and the fact that environmental conditions surrounding the nets do differ, we expected spatial differences to occur in the elasmobranch assemblage, particularly between Gold Coast and Sunshine Coast beaches.…”