Speartooth Shark

About the Speartooth Shark

The Speartooth shark is a very rare species found in both freshwater and saltwater. It is often found at the bottom floor of rivers. They are native to Western Pacific areas like northern Australia and New Guinea. The Speartooth shark is threatened by bycatch in commercial and recreational fishing activities and by possible habitat degradation which is decreasing their population. It is mainly caught by illegal gillnetting or hook and line fishing.

The Speartooth shark has a short, wide head and a flattened snout. It’s teeth on the upper jaw wide and triangular with serrated edges while it’s teeth on the lower jaw are narrow and spear-like with serrations only near the tip. Largest Speartooth shark found was that of a female with a length of 175cm/5.74 ft. The large sets of jaws were examined and indicate that the size can go up to up to 2m/6.6ft and possibly 3m/9.8 ft. The Speartooth sharks give birth to live young. Their size at birth is estimated to be 59cm/1.94 ft.

Like other river sharks the Speartooth shark has been adapted to living in cloudy water with low visibility. They are suggested to be primarily fish eaters.

Very few specimens have ever been recovered. The estimated population of mature speartooths is about 2,500 individuals. Although a protected species in Australian waters, it is subject to incidental capture in commercial fisheries and some illegal recreational retention. In PNG, it is retained for its meat and fins in largely unregulated fisheries. Based on current levels of threat, a continuing decline of at least 10% is projected over the next three generation lengths (54 years) and the Speartooth Shark is assessed as Vulnerable C1.

The species is caught as bycatch in subsistence, small-scale, commercial, and recreational fisheries and although retention is prohibited in Australia, it is retained in Papua New Guinea for its meat and fins by small-scale fishers. The Speartooth Shark occupies large tidal rivers, estuaries, and coastal waters. This habitat specificity increases the susceptibility to the impacts of human activities, particularly fishing and habitat modification (Grant et al. 2019). In Australia, the species is incidentally caught in commercial inshore gillnet, line, and pot fisheries, and is subject to minor levels of Indigenous harvest, and illegal recreational take (Field et al. 2013, DoE 2015b, Kyne and Feutry 2017, Lyon et al. 2017, Dwyer et al. 2019, Kyne et al. 2021). The Speartooth Shark was assessed as at high-risk in a cumulative risk assessment of all fisheries across northern Australia, mainly due to its susceptibility to capture in gill nets and suspected low productivity (Salini et al. 2007). The level of illegal recreational take is unknown; however, it is of concern due to the low population size and restricted distribution of the species including reliance on riverine habitat by juveniles (Kyne and Feutry 2017). The species is known to have a high mortality rate when captured in gillnets (Pillans et al. 2009) and juveniles are susceptible to capture in pots targeting Mud Crab (Scylla serrata) (Dwyer et al. 2019). Post-release mortality rate when discarded from other commercial fisheries is unknown; however, adoption of best handling guidelines may improve survival (Kyne and Pillans 2014, DoE 2015b). Habitat modification such as water extraction and barriers in rivers, such as dams, barrages, weirs, and poorly constructed road crossings, may affect habitat quality and impede movement patterns of the Speartooth Shark (DoE 2015b, Dwyer et al. 2020).

In Papua New Guinea, this species is caught in small-scale riverine and inshore fisheries and may be subject to habitat degradation in the Gulf of Papua and South Fly District associated with mining and logging activities (White et al. 2017b, M.I. Grant unpubl. data 2021). It is incidentally captured in a relatively recently developed high-value fishery for swim bladder (also known as fish maw) that targets mainly Barramundi (Lates calcarifer) and Scaly Croaker (Nibea squamosa) in estuarine and coastal habitats (M.I. Grant unpubl. data 2021).

Retention of this species is prohibited in Australia, although there is some illegal recreational take with Glyphis spp. being used as bait (Kyne and Feutry 2017) as well as some legal Indigenous harvest. In Papua New Guinea, the meat is used for local consumption and the fins are sold to local buyers through both legal and illegal markets for export (White et al. 2017a, Busilacchi et al. 2021). Glyphis spp. fins have been reported in the international trade, occurring in Hong Kong and China (Cardeñosa et al. 2020a, Cardeñosa et al. 2020b).

In Australia, the species is listed as Critically Endangered on the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). However, this listing was undertaken when the species was considered be to extremely rare and possibly thought to be extinct in part of its historic Australian range (the Bizant River, Queensland). A recent reassessment demonstrates that the species does not meet the criteria for listing as Critically Endangered and recommends a down-listing to Vulnerable (Kyne et al. 2021). Listing on the EPBC Act means the species is a ‘Matter of National Environmental Significance’ and is protected under the Act. The species is subject to a national multi-species Recovery Plan which aims to improve the population status and ensure anthropogenic activities do not hinder recovery (DoE 2015a).

In the Northern Territory, the Speartooth Shark is listed as a Vulnerable species under the Parks and Wildlife Conservation Act 2000, and a no-take species under the Fisheries Act 1998 and Fisheries Regulations. In Queensland, it is listed as a no-take species under the Queensland Fisheries Act 1994 and Fisheries Regulations 2008. Most Northern Territory rivers are closed to commercial net fishing and a core part of the species’ distribution, the Alligator rivers, is within Kakadu National Park and World Heritage Area, providing a significant conservation benefit to the juvenile population there. In Papua New Guinea (PNG), there is currently no species-specific regulation for the Speartooth Shark (White et al. 2015).

Given its recent documentation in Western Australia (P.M. Kyne and A.V. Harry, unpubl. data 2021), there is a need for legislative protection in that jurisdiction. There is also a need for targeted surveys in the Bizant River, Queensland, to confirm its presence/absence there since the last records are prior to 1983 (Pillans et al. 2009). Species distribution models have suggested the species also occurs in other unsurveyed locations (Udyawer et al. 2021). Surveys should utilize appropriate methods and target the species’ preferred salinity and turbidity ranges (Pillans et al. 2009, Kyne and Pillans 2014). More urgent is the implementation of effective management measures in PNG.

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