Do sawfishPristisspp. represent South Africa's first local extirpation of marine elasmobranchs in the modern era?

Abstract

Largetooth sawfish Pristis pristis and green sawfish P. zijsron were not uncommon in catches made in KwaZulu-Natal (KZN) on the east coast of South Africa in the mid part of the last century but apparently have disappeared from this area. This paper traces the decline in sawfish catches from 1951 and assesses the current population status and local extinction risk, based on historical and current records up to 2012. Records were collected from research surveys, literature, media and museum specimens, and through contacting researchers and conservation managers who have worked in KZN coastal and estuarine areas. A total of 150 green sawfish, 7 largetooth sawfish and 89 unidentified sawfish records were located. Most sawfish (115) were caught during a four-year (1967-1970) gillnetting survey conducted by the Oceanographic Research Institute in the St Lucia estuarine system while 91 were caught in the bather protection nets installed and maintained along the KZN coast by the KwaZulu-Natal Sharks Board. Sawfish ranged from 63 to 533 cm total length (TL). Sawfish caught in the estuarine environments (mean TL 162 cm [SD 72], n = 95) were significantly smaller than those caught in the inshore marine environments (mean TL 310 cm [SD 109], n = 83), confirming the importance of estuaries as pupping and nursery areas. The St Lucia estuarine system, given the high abundance of sawfish, was determined to be the most important nursery area in KZN. The last sawfish encountered in KZN, which was not identified to species level, was caught in the bather protection nets in 1999 and released alive. Extinction probability analysis indicates that sawfish no longer occur in KZN waters. Anthropogenic changes to the St Lucia estuarine system, as well as to other KZN estuaries, gillnetting for bather protection, and illegal fish harvesting, coupled with a non-adaptive life-history style, may have precipitated the disappearance of sawfish from KZN waters.Online supplementary material: The complete list of records and specimens for largetooth sawfish Pristis pristis and green sawfish P. zijsron located by consulting various data sources, primary literature, media, museums and local conservationists and scientists is available online in Supplementary Appendix S1 at http://dx.

BeyondJaws: rediscovering the ‘lost sharks’ of southern Africa

“…The largetooth sawfish Pristis pristis and the green sawfish P. zijsron have been assessed globally as Critically Endangered. Sawfishes are (i) typically found in shallow estuarine waters, (ii) subject to heavy fishing pressure, (iii) easily caught due to their large toothy rostra, and (iv) sensitive to anthropomorphic changes to their coastal habitat (Kyne et al 2013;Simpfendorfer 2013;Everett et al 2015). They may represent the first local extirpation of marine elasmobranchs from southern African waters (Everett et al 2015).…”

Fish conservation in freshwater and marine realms: status, threats and management

“…Understanding of the biodiversity impact of overfishing is compounded by its long history, the absence of systematic data collection for much of the world's coastal seas and oceans until recently, and the ‘shifting baseline’ psychology that means we are blind to changes prior to our human experience (Thurstan et al, ). As an example, overfishing is the main cause of decline and near extinction of iconic species including sawfishes (Everett et al, ; Dulvy et al, ), and the giant yellow croaker ( Bahabia taipingensis ; Sadovy and Cheung, ). These taxa depend on, and are highly catchable in, estuarine habitats (Figure ).…”

Habitat use and site fidelity of neonate and juvenile green sawfish Pristis zijsron in a nursery area in Western Australia

“…This species is believed to have undergone a major decline in the extent of occurrence (38%) within its former Indo-West Pacific range (Moore 2015, Dulvy et al 2016). The species is thought to have become extinct in most of eastern Australia and parts of southeast Asia and represents South Africa's first marine elasmobranch extinction (Everett et al 2015, Dulvy et al 2016. There are few reliable contemporary records of the species through out its former range, and most recent records are from northern Australia, whose coastal waters perhaps offer a globally important refuge for 4 of the pristids (Peverell 2005, 2015.…”