Species group report card – sharks and sawfishes Supporting the marine bioregional plan for the North-west Marine Region prepared under the Environment Protection and Biodiversity Conservation Act 1999 Disclaimer © Commonwealth of Australia 2012 This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Commonwealth. Requests and enquiries concerning reproduction and rights should be addressed to Department of Sustainability, Environment, Water, Population and Communities, Public Affairs, GPO Box 787 Canberra ACT 2601 or email [email protected] Images: Striped Nudibranch – C.Zwick and DSEWPaC, Raccoon butterfly fish – N.Wolfe, Display of colourful coral – Tourism WA, Red and yellow feather star (crinoids) – Tourism WA, Whale tail – Tourism WA, Snorkelling in Ningaloo Marine Park – Tourism WA, Green Turtle – Tourism WA, Black tip reef shark – N.Wolfe, Whale Shark – GBRMPA, Sea Grass Meadow – Lochman Transparencies CONTENTS Species group report card – sharks and sawfishes ..............................................................1 1. Sharks and sawfishes of the North-west Marine Region .........................................................3 2. Vulnerabilities and pressures ...................................................................................................7 3. Current protection measures ..................................................................................................14 References ................................................................................................................................15 Attachment 1: Sharks and sawfishes occurring in the North-west Marine Region ........20 iii SPECIES GROUP REPORT CARD – SHARKS A N D SAW FISH ES Supporting the marine bioregional plan for the North-west Marine Region prepared under the Environment Protection and Biodiversity Conservation Act 1999 Report cards The primary objective of the report cards is to provide accessible information on the conservation values found in Commonwealth marine regions. This information is maintained by the Department of Sustainability, Environment, Water, Population and Communities and is available online through the department’s website (www.environment.gov.au). A glossary of terms relevant to marine bioregional planning is located at www.environment.gov.au/ marineplans. Reflecting the categories of conservation values, there are three types of report cards: • species group report cards • marine environment report cards • heritage places report cards. While the focus of these report cards is the Commonwealth marine environment, in some instances pressures and ecological processes occurring in state waters are referred to where there is connectivity between pressures and ecological processes in state and Commonwealth waters. 1 | Supporting the marine bioregional plan for the North-west Marine Region | Species group report card – sharks and sawfishes Species group report cards Species group report cards are prepared for large taxonomic groups that include species identified as conservation values in a region; that is, species that are listed under Part 13 of the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and live in the Commonwealth marine area for all or part of their lifecycle. All listed threatened, migratory and marine species and all cetaceans occurring in Commonwealth waters are protected under the EPBC Act and are identified in the relevant marine bioregional plans as conservation values. Species group report cards focus on species for which the region is important from a conservation perspective; for example, species of which a significant proportion of the population or an important life stage occurs in the region’s waters. For these species, the report cards: • outline the conservation status of the species and the current state of knowledge about its ecology in the region • define biologically important areas; that is, areas where aggregations of individuals of a species display biologically important behaviours • assess the level of concern in relation to different pressures. 1 | Supporting the marine bioregional plan for the North-west Marine Region | Species group report card – sharks and sawfishes 2 1. Sharks and sawfishes of the North-west Marine Region The North-west Marine Region has a rich fauna of cartilaginous fish (sharks and rays) owing to the diversity of marine environments found across its waters. Of the approximately 500 shark species found worldwide, 94 are found in the region—19 per cent of the world’s shark species (DEWHA 2008). Four species of cartilaginous fish listed under the EPBC Act are known to occur in the North-west Marine Region: grey nurse shark, white shark, whale shark and green sawfish. Two other species of listed cartilaginous fish may infrequently occur in the region (Attachment 1). Of the cartilaginous fishes known to occur in the North-west Marine Region, this report card focuses on the six species listed in Table 1. These species were selected following consideration of their conservation status, distribution and population structure within the region, life history characteristics and the potential for the populations in the region to be genetically distinct from populations elsewhere. Sawfishes North-western Australia probably represents some of the last relatively healthy populations of sawfish in the world (Stevens et al. 2008). The dwarf sawfish,Pristis clavata, freshwater sawfish, Pristis microdon, and green sawfish, Pristis zijsron, occur mainly in inshore coastal waters and riverine environments of tropical northern Australia (Pillans et al. 2010). The freshwater sawfish and green sawfish are wider-ranging in the Indo-west Pacific, while the dwarf sawfish has been confirmed only from northern Australian waters. Given considerable declines in the global (and Australian range) of sawfishes, northern and north-west Australia may contain the last significant populations of these sawfishes. Important areas for sawfishes adjacent to the North-west Marine Region include the Pilbara coast, King Sound, and lower reaches of the Fitzroy, May and Robinson rivers for the dwarf sawfish; King Sound, and the Fitzroy, Durack, Robinson and Ord rivers for the freshwater sawfish; and Cape Keraudren for the green sawfish (Stevens et al. 2008; Thorburn et al. 2003, 2007, 2008). Sawfishes generally inhabit inshore coastal, estuarine and riverine environments. The dwarf sawfish is primarily a coastal and estuarine species and juveniles appear to use estuarine waters only (Thorburn et al. 2008). There is, however, a single record from a riverine environment, more than 100 kilometres from the estuary (Thorburn et al. 2003). The freshwater sawfish has been recorded in north-west Australia from rivers (including isolated water holes), estuaries and marine environments (Stevens et al. 2005). Newborns and juveniles primarily occur in the freshwater reaches of rivers and in estuaries, while most adult freshwater sawfish have been recorded in marine and estuarine environments (Peverell 2005; Thorburn et al. 3 | Supporting the marine bioregional plan for the North-west Marine Region | Species group report card – sharks and sawfishes 2007). It is believed that mature freshwater sawfish enter less saline waters during the wet season to give birth (Peverell 2005) and freshwater river reaches play an important role as nursery areas. The green sawfish has predominantly been recorded in inshore coastal areas, including estuaries and river mouths with a soft substrate, although there have been records of sawfish offshore in depths up to 70 metres (Stevens et al. 2005). This species does not occupy freshwater habitats. Short-term tracking of movement patterns has shown that dwarf sawfish occupy a range within the coastal fringe of only a few square kilometres and show site fidelity (Stevens et al. 2008). The species spends slack high tide resting in mangrove areas and becomes active on mud and sand flats during tidal movement, presumably feeding (Stevens et al. 2008). Short-term tracking has shown that green sawfish appear to have limited movements that are tidally influenced, and they are likely to occupy a restricted range of only a few square kilometres within the coastal fringe, with a strong association with mangroves and adjacent mudflats (Stevens et al. 2008). Sawfishes feed close to the benthos on a variety of teleost fishes and benthic invertebrates, including cephalopods, crustaceans and molluscs (Compagno & Last 1999; Last & Stevens 2009; Pogonoski et al. 2002; Thorburn et al. 2007, 2008). Grey nurse shark Grey nurse sharks (Carcharias taurus) are listed as separate populations under the EPBC Act. The west coast population is listed as vulnerable and the east coast population is listed as critically endangered. The western subpopulation has been recorded from the North West Shelf in the north, to Cocklebiddy in the south (RB McAuley, unpublished data). Grey nurse sharks are most commonly found on, or close to, the bottom of the continental shelf, from close inshore to depths of about 200 metres (McAuley 2004). The grey nurse shark is more commonly found in temperate waters. The North-west Marine Region represents the northern limit of the west coast population. Grey nurse sharks feed primarily on a variety of teleost and elasmobranch fishes and some cephalopods (Gelsleichter et al. 1999; Smale 2005). Reef-associated