IUCN Red List Assessment
Red List Category
Red List Criteria
Denham, J., Stevens, J., Simpfendorfer, C.A., Heupel, M.R., Cliff, G., Morgan, A., Graham, R., Ducrocq, M., Dulvy, N.D, Seisay, M., Asber, M., Valenti, S.V., Litvinov, F., Martins, P., Lemine Ould Sidi, M., Tous, P. and Bucal, D.
Dudley, S., Musick, J., Fowler, S.L., Kyne, P.M., Cavanagh, R.D. and Valenti, S.V. (Shark Red List Authority)
A large, widely distributed, tropical hammerhead shark largely restricted to continental shelves. Sphyrna mokarran is highly valued for its fins (in target and incidental fisheries), suffers very high bycatch mortality and only reproduces once every two years, making it vulnerable to over-exploitation and population depletion. Generally regarded as solitary, and is therefore unlikely to be abundant wherever it occurs. Previously observed from Mauritania to Angola, reportedly abundant from November to January in Senegal, and in October in Mauritania, stocks have since collapsed and it is recognized as one of the four most threatened species by member states of the Sub Regional Fishing Commission. Although there is very little species specific data available, the absence of recent records give cause to suspect a decline of at least 80% in the past 25 years. Fishing proceeds unmanaged and unmonitored, resulting in an assessment of Critically Endangered in the Eastern Atlantic. Although not targeted in the Northwest Atlantic and Gulf of Mexico it is taken as by-catch in several fisheries and suffers greater than 90% vessel mortality. Two time series data sets (pelagic logbook, large pelagic survey) have shown a decline in the catch of Sphyrna spp. since 1986. Difficulties in species identification and accurate recording make an assessment of this species very difficult, however low survival at capture makes it highly vulnerable to fishing pressure, whether directed or incidental. It is therefore assessed as Endangered in the Northwest Atlantic and Gulf of Mexico, based on a suspected decline of at least >50% over the past 10 years. The decline is poorly documented and has not been curtailed. In the Southwest Indian Ocean this species is assessed as Endangered based on a continued decline in catch rate of 79% reported for the period 1978 to 2003. It is uncertain whether these declines reflect highly localized stock depletion or whether they reflect a general decline in the Southwest Indian Ocean, but large numbers of longline vessels have been reported to be operating illegally in coastal waters of the western Indian Ocean where they are targeting primarily hammerhead sharks and giant guitarfish Rhynchobatus djiddensis. Sphyrna mokarran is found along the northern coast of Australia. A large increase in the illegal, unregulated and unreported (IUU) fishing in northern Australia in the last few years points to great concern that this species is being increasingly targeted for its valuable large fins. Recent Risk Assessments of northern Australian elasmobranchs indicate that it may be ?high-risk? however, due to a lack of data to form the basis of an accurate assessment, the species is considered Data Deficient in Australia at the present time. Further investigation of its status there is required. Given its vulnerability to depletion, low survival at capture and high value for the fin trade this species is considered to meet the criteria for Endangered globally based on the available evidence for declines of >50%. There is an urgent need for data collection in other parts of its range, but considering the high value of its fins and high fishing pressure in other parts of its range, similar declines are likely to have occurred elsewhere.
- 2000Data Deficient