|Scientific Name:||Stegostoma fasciatum|
|Species Authority:||(Hermann, 1783)|
|Infra-specific Taxa Assessed:|
|Taxonomic Source(s):||Eschmeyer, W.N., Fricke, R. and Van der Laan, R. (eds). 2016. Catalog of Fishes: genera, species, references. Updated 31 March 2016. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 31 March 2016).|
|Red List Category & Criteria:||Endangered A2bd+3bd ver 3.1|
|Assessor(s):||Dudgeon, C.L., Simpfendorfer, C. & Pillans, R.D.|
|Reviewer(s):||Dulvy, N.K. & Kyne, P.M.|
|Facilitator/Compiler(s):||Kyne, P.M., Walls, R.H.L., Simpfendorfer, C. & Chin, A.|
The Zebra Shark (Stegostoma fasciatum) is a broadly distributed continental and insular shelf species of the Indo-West Pacific. It is usually found within a narrow band of shallow coral reef habitat and soft bottom that is heavily fished throughout all of its range except Australia. It is taken in inshore fisheries (demersal trawls, floating and fixed bottom gillnets and baited hooks) and regularly seen in fish markets in Indonesia, Thailand, Philippines, Pakistan, India, Taiwan, and elsewhere. There are limited data on population declines in these areas, with the exception of the Gulf of Thailand, but the species is susceptible to capture in a wide range of fisheries, has a narrow habitat range with potential limited dispersal, shows strong site fidelity and forms aggregations which facilitate the rapid removal of individuals.
Population genetic analysis supports two subpopulations of the Zebra Shark: Indian Ocean-Southeast Asian and Eastern Indonesian-Oceania. The greatest levels of exploitation and ongoing threats for this species occurs in Southeast Asia, particularly Thailand through to Indonesia. Given little or no genetic exchange from unexploited areas it is suspected that this subpopulation has declined by at least 50% over the last three generations (51 years) and these threats are suspected to continue at these levels into the future. Therefore the Indian Ocean-Southeast Asian subpopulation is considered Endangered. The Eastern Indonesian-Oceania subpopulation is composed of regions with minimal exploitation to this species as well as regions of greater fishing pressure and habitat threats. In particular, the Zebra Shark in Australian waters is considered Least Concern due to minimal impacts from fishing, non-consumptive exploitation and habitat loss. However, population genetic and tracking studies suggest there is likely to be exchange between Australian waters and the Arafura Sea in Eastern Indonesian waters where extensive trawl fishing occurs and has been increasing in intensity over the last 30 years. Based on the ongoing fishing and habitat threats posed by these trawl fisheries in the Arafura Sea and the potential impacts on Zebra Sharks migrating from adjacent regions, reductions of at least 20% of its population size within three generations (51 years) are suspected and the Eastern Indonesian-Oceania subpopulation is assessed as Near Threatened.
By combining the subpopulation assessments according to relative area (the Indian Ocean-Southeast Asian subpopulation has approximately 70% of the available habitat; the Eastern Indonesian-Oceania subpopulation has approximately 30% of the available coastal habitat), and given the ongoing threats from fishing and habitat loss across much of its range and suspected reductions of over 50% of its population size within three generations, this species is assessed globally as Endangered.
|Previously published Red List assessments:|
|Range Description:||The Zebra Shark is found in inshore waters of the continental and insular shelves of the Western Pacific and Indian Oceans (Compagno 2001).|
Native:Australia (New South Wales, Northern Territory, Queensland, Western Australia); Bahrain; Bangladesh; Cambodia; China; Fiji; India; Indonesia; Iran, Islamic Republic of; Japan; Kuwait; Madagascar; Malaysia; Maldives; Marshall Islands; Mozambique; Myanmar; New Caledonia; Oman; Pakistan; Palau; Papua New Guinea; Philippines; Qatar; Saudi Arabia; Singapore; Solomon Islands; South Africa; Sri Lanka; Sudan; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Tonga; United Arab Emirates; Viet Nam; Yemen
|FAO Marine Fishing Areas:|
Indian Ocean – eastern; Indian Ocean – western; Pacific – western central; Pacific – northwest; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The Zebra Shark comprises two distinct subpopulations based on the population genetic analysis of 13 microsatellite loci and mitochondrial ND4 sequences: Indian Ocean-Southeast Asian subpopulation and Eastern Indonesian-Oceania subpopulation (Dudgeon et al. 2009).|
Indian Ocean-Southeast Asian subpopulation
Population size information for the Indian Ocean-Southeast Asian subpopulation is limited. Zebra sharks are reported from fish markets across the region (Pillans and Simpfendorfer 2003). An ongoing photo-identification program in Thailand has identified approximately 250 individual Zebra Sharks in the Krabi Province in the Andaman Sea with most records from 2012–2015 (Spot the Leopard Shark Thailand, unpublished data). In contrast, only two sightings of Zebra Sharks have been reported from the Gulf of Thailand over this time. Vidthayanon (1997) and Compagno (2001) report the species as having declined in the Gulf of Thailand. Recent fish market surveys support substantial population declines in the Gulf of Thailand as the Zebra Shark was not sighted at landing sites in this region (Krajangdara 2014). Surveys of SCUBA dive schools operating in the Gulf of Thailand have recorded a significant reduction in sightings between the 1990s and 2000s from an average of one shark sighted per dive to <0.25 sharks sighted per dive (Ward-Paige and Lotze 2011).
The Zebra Shark is likely to be locally extinct from several locations throughout Indonesia. In particular, extensive SCUBA surveys for fish diversity assessments at sites across the Indonesian Archipelago have recorded none (Bali, Anambas Archipelago, Timor-Leste, Triton Bay and Cenderasih Bay in West Papua) or very few Zebra Sharks (Southwest Sulawesi; North Sulawesi; Raja Ampat) (Erdmann, pers. comm., 23 March 2015). The Zebra Shark was observed regularly (3-7 animals per dive) on dive sites at Berau Archipelago off East Kalimantan during surveys in 1997 but none were observed on subsequent surveys in 2002 and 2004 (Erdmann, pers. comm., 23 March 2015).
Eastern Indonesian-Oceania subpopulation
The Zebra Shark is found in large aggregations (20-50 animals) over sand near reef systems in parts of its Australian range (Pillans and Simpfendorfer 2003, Dudgeon et al. 2008). Abundance estimates based on mark-recapture analysis of photo-identification surveys of mature individuals are available for an unexploited aggregation in southern Queensland, Australia: 458 (95% CI = 298-618) (Dudgeon et al. 2008). Genetic effective population size estimates based on microsatellite data closely approximate these census sizes (377, 95% CI = 274–584) (Dudgeon and Ovenden 2015) suggesting the aggregation is composed of breeding adults. This population extends along the Queensland coast with genetic evidence of some segregation from northern Australia.
Population estimates for areas outside of Australia are unknown. Anecdotal reports from Conservation International staff at Raja Ampat in Eastern Indonesia suggest that the Zebra Shark used to be common on the large sandy regions around the reefs but are now rare.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The Zebra Shark occurs in tropical and subtropical, shallow inshore and offshore waters, often found on and around coral and rocky reefs and on sandy plateaus near coral, at depths down to at least 62 m. They are often observed resting on the bottom as well as swimming near the surface as both juveniles and adults.|
The Zebra Shark demonstrates seasonal movement patterns in subtropical locations towards the latitudinal extent of their distribution (Dudgeon et al. 2013). Regular seasonal movements of over 1,000 km and a larger movement of over 2,000 km along the Queensland coast in Australian waters have been recorded using acoustic tracking methods (C. Dudgeon, unpublished data). Aggregations along coastal sites in southern Queensland and northern New South Wales occur during the warmer months of each year (Dudgeon et al. 2008, Dudgeon et al. 2013). The species demonstrates strong site fidelity to particular reefs in Australia (Dudgeon et al. 2013) and Thailand (Spot the Leopard Shark Thailand, unpublished data), which may make them more susceptible to targeted fishing.
The Zebra Shark is an oviparous species. Size at birth ranges between 20 and 36 cm total length (TL). Reproductive periodicity in the wild is unknown. Captive aquaria animals have demonstrated annual egg laying periods of up to 3 months with 40–80 eggs laid per year (Robinson et al. 2011) with up to 25% of eggs resulting in hatchlings (Squire Jnr, pers. comm., 22 Jul 2014). Age of maturity of captive female sharks is approximately 6-8 years of age based on the commencement of egg laying (Thomas, pers. comm., 18 Feb 2015; Robinson, pers. comm., 11 Jan 2015) and 7 years of age for males (Watson, pers. comm., 18 Feb 2015). Adults reach a maximum size of 246 cm TL with no sexual dimorphism evident (Dudgeon et al. 2008) and live over 28 years in aquaria (Thomas, pers. comm., 17 Feb 2015). Generation length estimates based on 6 years first age at maturity and 28 years maximum longevity for female sharks is 17 years.
|Generation Length (years):||17|
|Use and Trade:||Zebra Sharks are landed whole and used for their fins, skin (dried), meat and cartilage (White et al. 2006). Zebra Sharks are kept in aquaria around the world. They breed well in aquaria and eggs and adults are also taken from the wild for aquaria stock. They are valuable within the recreational SCUBA diving industry, particularly in eastern Australia waters (C. Dudgeon. pers. obs.), near Phuket in Thailand (Anderson 2002), and elsewhere.|
The Zebra Shark is susceptible to capture in a wide range of inshore fisheries and although there is no direct evidence of population decline in the Indo-West Pacific, market surveys suggest this species is much less common than it used to be (L.J.V Compagno and W.T. White, pers. comms., 2003, Pillans and Simpfendorfer 2003). Surveys from 2004-2012 in Thailand indicate that the Zebra Shark is regularly landed at fish markets on the Andaman Sea but was not recorded from the Gulf of Thailand (Krajandara 2014). However, photographs show Zebra Shark available for auction at the Samut-Sakorn fish market near Bangkok in Thailand in 2012 (Arthur Jones Dionio, pers. comm). The geographic origin of these animals is unknown as Thai fleets also operate in foreign waters (Chen 1996). The Zebra Shark is reported from fisheries operating out of Taiwan (Chen et al. 1997), Myanmar (SEAFDEC 2004), Bangladesh (Hoq et al. 2014), India (Theisavigamani and Subbiah 2014), the Persian Gulf, the Oman Sea (Valinassab et al. 2006, Henderson et al. 2007), and Zanzibar (Shehe and Jiddawi 1997). Fish market surveys in Indonesia during April 2001-March 2006 recorded 77 Zebra Sharks with almost all coming from trawl fishery bycatch in Jakarta (Dharmadi et al. 2015).
Anecdotal reports suggest that a substantial decrease in Zebra Shark sightings in the Berau Archipelago, East Kalimantan was from fishers using a free diving harpooning catch method targeting Zebra Shark (Erdmann, pers. comm., 23 March 2015). Genetic analyses (DNA barcoding) of shark fins collected during market surveys conducted across Indonesia from mid 2012 to mid 2014 found the vast majority of landed species were pelagic sharks with common reef and carpet sharks (including Zebra Sharks) extremely rare. Given the extensive shallow coastal habitat around Indonesia that would support the reef and carpet shark species, the authors conclude that this is a strong indication of the collapse of reef shark populations in Indonesia, most likely due to overfishing (Semibiring et al. 2015). Documented large declines in shark and ray catches associated with corresponding increases in fishing effort in the Java Sea (Blaber et al. 2009) are likely to have a large impact on the Zebra Shark in Indonesian waters and may be representative of fishing impacts across the region.
Legal and illegal fishing pressure has increased substantially in the Arafura Sea over the last 30 years (Resosudarmo et al. 2009). Trawling was banned in 1980 in all waters of the Indonesian 200 mile Exclusive Economic Zone west of longitude 130 E. This resulted in concentrated trawling pressure in the eastern part of the Timor Sea and the Arafura Sea. Approximately 90% of the large industrial scale vessels are foreign-owned and aim to collect maximum possible biomass including elasmobranchs (Fegen 2003). Zebra Sharks are likely to comprise part of this catch given their presence as bycatch in trawl surveys from neighbouring regions (Okera and Gunn 1986, Ramm 1997, Roelofs and Stapley 2003). Thai vessels comprise the largest demersal trawl fleet (Fegen 2003) and the numbers of Thai vessels operating in the Arafura Sea have increased from reports of 150 vessels (Chen 1996) to approximately 700 vessels (Blaber et al. 2005). Fegen (2003) reports that the Indonesian government issued 1,500 trawl licenses between 1998 and 2001. Thai vessels offload their catch onto freezer ships (Blaber et al. 2005) which are then transported for sale in Thai fish markets including Samut-sakorn province, Samut-prakarn province and Songkla province (Chen 1996).
The Zebra Shark is found in inshore, shallow coastal areas including mudflat, mangrove and seagrass beds as juveniles and then move further offshore to coral and rocky reef areas as adults. Threats to these key habitats occur in Southeast Asia with substantial coastal development including prawn farming in coastal areas as well as up to 80% of corals bleaching in the Andaman Sea and Gulf of Thailand during periods of elevated water temperatures in 2010 (Yeemin et al. 2010).
Threats within Australia are likely to be minimal. There are no target fisheries and small numbers are captured as bycatch in the Queensland East Coast Inshore Finfish Fishery (Harry et al. 2011), the Northern Prawn Fishery (Zhou and Griffiths 2008), the Pilbara Trawl fishery (Western Australia Department of Fisheries 2010) and in nets deployed by the Queensland Shark Control program (Sumpton et al. 2011). However, they demonstrate a high level of survival and records for these fisheries indicate a 79.5-100% post release survival rate. Recent acoustic tracking studies demonstrate that Zebra Sharks undertake large seasonal migrations on the eastern Australia coastline with regular movements of over 1,000 km annually and larger distances of over 2,000 km recorded in six months (C. Dudgeon unpublished data). Therefore it is possible for Zebra Sharks to move from Australia into nearby regions with fishing pressure such as the Indonesian Arafura Sea and Timor Seas.
A prawn trawl fishery consisting of about nine vessels operates in the Gulf of Papua in southern Papua New Guinea where Zebra Shark are caught in low numbers and mostly as juveniles (L. Baje, National Fisheries Authority, pers. comm., 2015).
Within Australia, the Zebra Shark occurs within several marine protected areas including the Great Barrier Reef Marine Park and Moreton Bay Marine Park in Queensland.
The Gulf of Papua trawl fishery in southern Papua New Guinea is managed under national laws and regulations, and there are some seasonal closures in place; although bycatch reduction devices are not currently in place, there are plans to implement in the near future (L. Baje, National Fisheries Authority, pers. comm. 2015).
The Zebra Shark is protected under the Malaysian Fisheries Act, therefore catches are opportunistic and landings not reported (Last et al. 2010).
|Citation:||Dudgeon, C.L., Simpfendorfer, C. & Pillans, R.D. 2016. Stegostoma fasciatum. The IUCN Red List of Threatened Species 2016: e.T41878A68645890.Downloaded on 25 April 2017.|
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