North-western Australia as a hotspot for endangered elasmobranchs with particular reference to sawfishes and the Northern River Shark

摘要

Recent targeted surveys, together with the collection of sawfish (Pristidae) rostra from the general public, have demonstrated that the Kimberley and northern Pilbara are important refuges for sawfish, with four of the world's seven species found here. These comprise all of Australia's known sawfish species, including the three species protected under the Environment Protection and Biodiversity Conservation (EPBC) Act 1999, i.e. Freshwater Sawfish (Pristis microdon), Dwarf Sawfish (Pristis clavata) and Green Sawfish (Pristis zijsron). The Northern River Shark (Glyphis garricki), which was only described in 2008, has only recently been discovered in the Kimberley and is listed as Endangered under the EPBC Act. These species are listed as Critically Endangered on the IUCN Red List and collectively represent -45% of Australia's elasmobranchs that are listed as Vulnerable or higher under the EPBC Act. There is, however, limited information on the spatial extent of these species throughout Western Australia, particularly as most sawfish surveys have targeted only a few specific areas over a vast coastline. We therefore encouraged public participation in providing Pristis rostra, taken from the fish as curios, in order to extend the known locations of the species and relate these to life history stages based on their size. Here we report on the published records and our unpublished catches (n = 376) across three Pristis spp., and collate this with data from donated rostra, 73% (n = 283) of which were considered usable, in that catch locations were reliable and they were from Western Australian waters. We provide information on sawfish distributions in Western Australia and identify areas that are important as pupping grounds, nursery areas or harbour mature individuals. We also collate known records of G. garricki and provide information on the ecology of this and the EPBC listed sawfish species.