Background

The family Hexanchidae includes three genera and four described species: Hexanchus Rafinesque 1810, Heptranchias Rafinesque 1810, and Notorynchus Ayres 1855 (Ebert and Stehmann 2013). Hexanchidae sharks have a worldwide distribution in cold temperate to tropical seas. Most species in the family are deepwater inhabitants of the outer continental shelves, upper continental slopes, insular shelves and slopes, and submarine canyons down to at least 2500 m depth, occurring in both benthic and neritic (Carpenter 2002; Ebert and Stehmann 2013).

The sharpnose sevengill shark, Heptranchias perlo (Bonnattere1788), is uncommon through its range and many aspects of its biology are poorly known. H. perlo has been known to occur primarily in deep waters down to 1000 m (Compagno et al. 2005; Ebert et al. 2013).

The sharpnose sevengill shark occurrence in the Western Atlantic has been reported in Mexico, Jamaica, Bahamas (USA), Cuba and Panama (Bonfil 1997; Claro and Parenti 2001; Paul and Fowler 2003; McLaughlin and Morrissey 2004; Kyne et al. 2012; Benavides et al. 2014). The importance of this study lies in the fact that it represents the first confirmed record of occurrence of H. perlo in Guatemala’s Caribbean Sea. Currently, H. perlo is listed as “Near Threatened” by the International Union for the Conservation of Nature’s Red List (Paul and Fowler 2003).

Methods

On the 20th March 2016, two female sevengill sharks were captured by artisanal fishermen in Guatemala’s Caribbean Sea and landed in the coastal village of El Quetzalito, Izabal (15° 49.776 N, -88° 12.340 W) (Fig. 1). All specimens were captured with a 1000 m long bottom trammel net of 3.5 inches mesh size and one panel. Specimens were captured at approximately 200 m depth, based on known length of net deployed. All specimens were examined and identified to species level using identification guides (Compagno 1984; Compagno et al. 2001).

Fig. 1
figure 1

Study area with location (⋆) of capture in relation to the fishing village of El Quetzalito

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Both specimens were preserved in formaldehyde (10%) and subsequently transferred to ethyl alcohol (70%) for final preservation. Both sevengill shark specimens were deposited in the Laboratory of Biological Science and Oceanography, Centro de Estudios del Mar y Acuicultura (CEMA) of the Universidad San Carlos de Guatemala (USAC). The specimens are part of the collection registered to the Consejo Nacional de Áreas Protegidas (CONAP) under the reference number (Rf) 250 and 251. Measurements were taken on the sevengill shark specimens using a vernier calipers or measuring tape, as proposed by Compagno (2001). A total of 80 morphometric measurements were taken (Compagno 2001).

Results

Systematic account

Family: Hexanchidae

Genus: Heptranchias Rafinesque, 1810

Heptranchias perlo (Bonnaterre, 1788)

Common name: Sharpnose sevengill shark, cañabota (local name)

Material examined

Rf 250: female, 370 mm TL (Fig. 2a, Table 1); Rf 251: female, 280 mm TL (Fig. 2b, Table 1).

Fig. 2
figure 2

Heptranchias perlo: a. Rf250, female, 370 mm TL and (b). Rf251, female, 280 mm TL

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Table 1 Morphometric measurements (mm) of individuals of two female specimens of Heptranchias perlo
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Description

Small shark with seven pairs of gill openings. Slender body. Head extremely narrow and pointed, with large eyes and narrow mouth. Dorsal coloration brownish grey, with lighter coloration below. One spineless dorsal fin with black apex.

Discussion

This report represents the first record of H. perlo, in Guatemala’s Caribbean Sea. In the Caribbean of Central America, H. perlo has only been reported for Panama (Benavides et al. 2014). During a deep water fishery survey using bottom trawling along the Caribbean coast of Central America, three H. perlo individuals were captured in Panama (Benavides et al. 2014); one female (670 mm TL) and two male (750–820 mm TL), sizes greater than the specimens reported in this study. Additionally, the capture depth of H. perlo, approx. 200 m (this study), coincides with the range describe by the species (Ebert and Stehmann 2013; Benavides et al. 2014). Knowledge of H. perlo biology is limited. A reproductive study conducted in the southwestern waters of Kyushu, Japan report H. perlo maturity of female is reached between 950 mm and 1050 mm (Tanaka and Mizue 1977). Moreover, birth size of H. perlo is 260–270 mm (Tanaka and Mizue 1977), close to that obtained in this study for Rf 251 specimen (280 mm TL).

Globally, this species is of minor commercial importance and occurs mostly as bycatch in bottom trawl and longline fisheries which may have caused population declines where deepwater fisheries have been practiced in the last decade. According to artisanal fishers in the region, H. perlo is rarely captured by the area’s local fishermen, and is only captured incidentally when fishing with trammel nets. When captured, fishers rarely utilize the meat due to the species’ small size although they render the liver for shark oil.

Conclusion

To date, reports regarding shark diversity of Guatemala´s Caribbean Sea are scare (Thorson et al. 1966; Hacohen-Domené et al. 2016; Polanco-Vásquez et al. 2017). This study forms the first confirmed records of H. perlo in Guatemala’s Caribbean Sea and increase the number of known shark species in Guatemala. This report further increases the species’ range of distribution throughout the Caribbean and Central America. This study highlights the need for comprehensive deep-sea research surveys to obtain a more complete assessment of the region’s deep-water elasmobranchs.