Fishes · Sharks · Thresher sharks

Pelagic Thresher Shark

Alopias pelagicus Nakamura, 1935

3 mCITES IIEndangered

914

The Pelagic Thresher Shark (Alopias pelagicus) is a fascinating and distinctive species found in the tropical and subtropical waters of the Indo-Pacific region, including the 🌊 Red Sea. These sharks are renowned for their extraordinarily elongated upper tail lobes, which can be as long as their bodies and are used effectively to stun prey, mainly small fish and cephalopods.

In appearance, the Pelagic Thresher Shark is sleek and slender, with a body that exhibits a bluish-gray coloration on the dorsal side and lighter shades on the ventral side. This counter-shading helps them blend into their open-water environment. They typically grow to lengths of about 3 to 4 meters, making them moderately sized compared to other shark species.

The 🌊 Red Sea offers a unique habitat for the Pelagic Thresher Shark, with its warm waters and rich biodiversity providing ample feeding opportunities. These sharks are usually found in deeper waters during the day, ascending to shallower depths during the night to hunt. They are mostly solitary creatures, though they can sometimes be observed in small groups, particularly around cleaning stations where smaller fish remove parasites from their skin.

In terms of behavior, the Pelagic Thresher Shark is known for its shy and elusive nature, often avoiding divers and boats. Despite this, the 🌊 Red Sea's clear waters sometimes offer exceptional encounters for those lucky enough to spot them.

Conservation-wise, the Pelagic Thresher Shark is under threat due to overfishing, bycatch, and illegal fishing practices. It is listed as Vulnerable by the IUCN Red List. In the 🌊 Red Sea, efforts are being made to protect this species through marine protected areas and conservation initiatives.

Overall, the Pelagic Thresher Shark is an integral species within the 🌊 Red Sea ecosystem, contributing to the ocean's health and the delicate balance of marine life in this region.

Why it's threatened

Biological resource use

Intentional use: (subsistence/small scale) [harvest] · Intentional use: (large scale) [harvest] · Unintentional effects: (subsistence/small scale) [harvest] · Unintentional effects: (large scale) [harvest]

The Pelagic Thresher is caught as target and bycatch in commercial and small-scale pelagic longline, purse seine, and gillnet fisheries. Most catch is taken as bycatch of industrial pelagic fleets in offshore and high-seas waters (Camhi et al. 2008). It is also captured in coastal longlines, gillnets, trammel nets and sometimes trawls, particularly in areas with narrow continental shelves (Camhi et al. 2008, Martinez-Ortiz et al. 2015, Temple et al. 2019).

The species is generally retained for the meat and fins (Clarke et al. 2006a_,_ Clarke et al. 2006b, Dent and Clarke 2015_,_ Fields et al. 2018), unless regulations prohibit retention. Under-reporting of catches in pelagic and domestic fisheries is likely (Dent and Clarke 2015). The species is highly valued by big-game recreational fishers, and although many practice catch and release, recreational fishing could be a threat due to post-release mortality that has been estimated for the congener Common Thresher as 78% for tail-hooked and 0% for mouth-hooked animals (i.e. all mouth-hooked animals survived) (Camhi et al. 2008, Sepulveda et al. 2015). For commercial fisheries, at-vessel hooking mortality for the congener Bigeye Thresher is high with between 49 and 68% of individuals caught found to be dead on haulback (Coelho et al. 2011, IOTC 2016).

Threat classification from the IUCN Red List.