Taxonomy
Assessment Information
- IUCN Red List Category and Criteria
- Vulnerable A2bd ver 3.1
- Assessment language
- English
- Year published
- 2019
- Date assessed
- 2018-11-07 00:00:00 UTC
Geographic Range
Population
There are no data available on the absolute global population size of the White Shark. Genetic data suggest one global population; however, there is some genetic structuring between ocean basins, potentially within ocean basins, and likely global male-biased dispersal and female philopatry (Pardini et al. 2001, Jorgensen et al. 2010, Gubili et al. 2012, O'Leary et al. 2015, Andreotti et al. 2016, Bernand et al. 2018). White Shark total abundances have been estimated for a number of regions: 5,460 in eastern Australasia in 2017 (uncertainty range: 2,909–12,802) (Bruce et al. 2018, Hillary et al. 2018); in excess of 2,000 in the Northeast Pacific in 2012 (Dewar et al. 2013, Burgess et al. 2014); and, in South Africa: 1,279 in KwaZulu-Natal in 1996 (Cliff et al. 1996), 908 in Gansbaai from 2007–2011 (95% CI: 808–1,008) (Towner et al. 2013), 723 in False Bay from 2004–2012 (95% CI: 466–980) (Hewitt 2014), 389 from 2008–2010 in Mossel Bay (95% CI: 351–428) (Ryklief 2012), and 438 for all of South Africa in 2011 (Andreotti et al. 2016), although there are concerns for the validity of this last estimate (Irion et al. 2017).
Population trend data are available from four sources: (1) standardized relative abundance in the Northwest Atlantic (Curtis et al. 2014); and standardized catch-per-unit-effort (CPUE) in: (2) the Northeast Pacific (Dewar et al. 2013); (3) the South Pacific (Reid et al. 2011); and, (4) the Indian Ocean (Dudley and Simpfendorfer 2006) updated with data to 2012 (S. Wintner pers. comm. 3/10/2018). The trend data from each source were analysed over three generation lengths using a Bayesian state-space framework (a modification of Winker et al. 2018). This analysis yields an annual rate of change, a median change over three generation lengths, and the probability of the most likely IUCN Red List Category percent change over three generations (see the Supplementary Information).
First, the Curtis et al. (2014) relative abundance was used to represent data on catches in the Northwest Atlantic as it is the longest and most comprehensive compilation of data available for the region. It includes fishery-independent longline surveys, observer data from the shark-target bottom longline fishery, and recreational fishing tournament data. The relative abundance trend indicates historically higher abundances in the 1960s followed by a declining trend until the mid-1980s, and then an increasing trend since the 1990s, when a range of management measures were implemented (Curtis et al. 2014). The three generation trend analysis of the Northwest Atlantic CPUE for 1961–2010 (50 years) revealed annual rates of reduction of 1.0%, consistent with an estimated median reduction of 80.8% over three generation lengths (159 years), with the highest probability of >80% reduction over three generation lengths. This probability of a high level of reduction is over a very long period of three generations; it has incorporated the reductions from historically higher abundances and projected an estimated trend based on those reductions for a considerable period beyond that of the time-series and is thus indicative of historic declines rather than the recent increasing trend since 1990.
Second, in the Northeast Pacific, White Sharks have mainly been taken in inshore net fisheries. Fisheries catch data were available from the California set net fishery which accounts for the majority of White Shark bycatch in that area; this indicated declines during the 1980s followed by a gradual increase from 1990s onwards (Dewar et al. 2013). Based on those data, information from photo-identification studies, and other researchers, the status review of White Shark in the Northeast Pacific concluded that the White Shark abundance was stable or increasing although there was some uncertainty around this conclusion due to the limited long-term abundance data for the region (Dewar et al. 2013). The trend analysis of the Northeast Pacific California set net fishery CPUE for 1980–2010 (31 years) revealed annual rates of increase of 4.1%, consistent with an estimated median increase of 602.1% over three generation lengths (159 years), with the highest probability of increases over three generation lengths.
Third, one of the longest datasets in the South Pacific is from the east coast of Australia shark meshing program in New South Wales (1950–2009) in which White Shark standardized CPUE markedly declined from 1950 to the 1990s after which it began to slowly increase (Reid et al. 2011). During this period there were modifications to net specifications and spatial and temporal effort, and since 2010, further changes have been implemented that include a reduction in net soak time (Reid et al. 2011, NSW DPI 2018). From 2008 to 2018, catches of White Sharks in the meshing program have fluctuated between 3 and 26 individuals annually, with increasing catches in the latter years (NSW DPI 2018). Further north along Australia's east coast, the standardized CPUE of White Sharks also declined significantly, by 92% over 54 years (1962–2015) in the Queensland Shark Control Program (Roff et al. 2018). The trend analysis of the NSW shark meshing program CPUE for 1950–2009 (60 years) revealed annual rates of reduction of 1.8%, consistent with an estimated median reduction of 95.8% over three generation lengths (159 years), with the highest probability of >80% reduction over three generation lengths. Since mid-1990s protection of White Sharks in Australia, adult White Sharks abundance has been estimated to have slightly declined or remained stable with population growth rates unlikely to be greater than 3% per year (Bruce et al. 2018, Hillary et al. 2018). Based on the current eastern Australasian abundance estimate and species demographics (assuming continued protection) there should potentially be an increase in the eastern Australasian abundance as the current juvenile cohorts enter into maturity (R. Bradford pers. comm. 07/02/2019).
Fourth, long-term standardized CPUE in shark nets off KwaZulu-Natal, South Africa beaches in the Western Indian Ocean fluctuated considerably but was stable over time (Dudley and Simpfendorfer 2006). The trend analysis of the shark net CPUE for 1978–2012 (35 years) revealed annual rates of increase of 0.1%, consistent with an estimated median increase of 13.1% over three generation lengths (159 years), with the highest probability of increases over three generation lengths. In the West Australian Indian Ocean, the White Shark modeled abundance is not predicted to have increased by more than 10% since 1997 when protection was enacted (Braccini et al. 2017).
Further to the above data and analyses, in the Mediterranean Sea, based on anecdotal records and limited fisheries data, the White Shark is suspected to have declined by at least 80% over 69 years from 1947–2016 (Soldo et al. 2016). With the exception of the Mediterranean Sea, in all other regions with data, the status review and studies indicate that the White Shark has declined during the 1980s and has begun to show signs of increasing since protection has been implemented.
Across the regions, the White Shark is estimated to be declining from historic levels in the Northwest Atlantic and South Pacific, and increasing in the Northeast Pacific and Indian Ocean. The trends among ocean regions are highly variable and while they are mostly based on long datasets, they are extrapolated over a very long three generation length of 159 years which increases the uncertainty in the estimated regional trends. With the exception of the Northwest Atlantic, they are also based on datasets from limited areas within each region and may not accurately represent the trend in White Shark across the entire region. Despite these caveats, the trend data are the best available and were used for the estimation of a global population trend; the estimated three generation population trend for each region was weighted according to the relative size of each region. The overall estimated median reduction was 53.8%, with the highest probability of a <20% reduction over three generation lengths (159 years). With a shorter three generation length of 88.5 years (see Habitat and Ecology section), the overall estimated median reduction was 39.4%, with the highest probability of a <20% reduction over three generation lengths. However, due to uncertainty in the estimated trends, expert judgement elicitation resulted in an estimated global population reduction of 30–49% over the last three generations (159 years), based on long-term abundance data and protections instigated in the 1990s that have since reduced catches. Therefore, the White Shark is assessed as Vulnerable A2bd.
Habitat and Ecology
The maximum size is undetermined, but estimated at 600–640 cm total length (TL) (Compagno 2001). Males mature at 310–410 cm TL (Pratt 1996, Compagno 2001, Tanaka et al. 2011); the majority of females mature at 400–500 cm TL (Francis 1996, Tanaka et al. 2011) but have been reported as immature at 472–490 cm TL (Springer 1939, Compagno 2001); and, size at birth is 120–150 cm TL (Francis 1996). Reproduction is aplacental viviparous with oophagy and histrophy, with litter sizes of 2–17 and a suspected two to three year reproductive cycle (Francis 1996, Uchida et al. 1996, Mollet and Cailliet 2002, Bruce 2008, Domeier 2012, Sato et al. 2016). In the Northwest Atlantic, Northeast Pacific, and Western Indian Oceans, female age-at-maturity of 30–33 years and maximum age of 30–73 years were reported based on bomb radiocarbon validated ages (Hamady et al. 2014, Andrews and Kerr 2015, Natanson and Skomal 2015, Christiansen et al. 2016). Due to the accurate method of bomb radiocarbon ageing, these are possibly more accurate than the previous lower estimates of female age-at-maturity of 7–15 years and maximum ages of 18–30 years (Cailliet et al. 1985, Wintner and Cliff 1999, Bruce 2008, Tanaka et al. 2011, Hillary et al. 2018). Using the precautionary approach and the validated, most conservative bomb radiocarbon ages of age-at-maturity of 33 years and maximum age of 73 years, generation length is 53 years. The bomb radiocarbon maximum age is accepted as being likely >30 years, minimum of 44 years, and possibly maximum of 73 years. The female age-at-maturity is possibly more contentious and to explore the sensitivity of the global population trend analyses to the younger female age-at-maturity, estimates of female age-at-maturity of 15 years and maximum age of 44 years were also used, that led to a generation length of 29.5 years (see Population section).
| Habitats | Suitability | Major importance |
|---|---|---|
Threats
The White Shark fins and jaws have a high market value with large fins used as display items (Clarke 2004). Small white shark fins are also present in the international fin trade (Shivji et al. 2005). Jaws may be retained domestically as curios (CITES 2004). The meat may be used fresh for either local consumption or exported internationally.
The White Shark is caught as bycatch mostly in inshore fisheries in a range of gears, such as longlines, setlines, gillnets, trawls, hand-held rod and reel, and fish-traps; it is rarely caught in offshore pelagic fisheries (Bruce 2008, Lowe et al. 2012, Dewar et al. 2013, Lyons et al. 2013, Francis 2017, Onate-Gonzalez et al. 2017). The species has a relatively high post-release survival in net fisheries (Lyons et al. 2013, Benson et al. 2018). The White Shark is targeted in beach protection programs in Australia and South Africa that use drum-lines and gillnets; however, in some instances these programs release live sharks (Dudley and Simpfendorfer 2006, Bruce 2008, Reid et al. 2011, Braccini et al. 2017, Kock et al. 2018, Lee et al. 2018, Roff et al. 2018). A shark control program in Réunion Island targets Tiger Sharks (Galeocerdo cuvier) and Bull Sharks (Carcharhinus leucas), with no captures of White Sharks reported to date (Florida Museum 2019).
| title | scope | timing | score | severity |
|---|---|---|---|---|
Use trade
The White Shark fins and jaws have a high market value with large fins used as display items (Clarke 2004). Small white shark fins are also present in the international fin trade (Shivji et al. 2005). Jaws may be retained domestically as curios (CITES 2004). The meat may be used fresh for either local consumption or exported internationally.
Text summary
The success of actions agreed through international wildlife and fisheries treaties depends on implementation at the domestic level; for sharks, such follow up actions have to date been seriously lacking. The White Shark was among the first shark species listed under several wildlife treaties. Many fishing nations worldwide and the European Union have domestic regulations specifically aimed at protecting White Sharks.
In 2002, the White Shark was listed on Appendix I and II of the Convention on Migratory Species (CMS), which respectively obligates Parties to strictly protect the species and to work regionally toward conservation, specifically through the CMS Memorandum of Understanding for Migratory Sharks. In 2004, the White Shark was added to Appendix II of the Convention on International Trade in Endangered Species (CITES), which requires Parties to ensure that exports be accompanied by permits based on findings that parts are sourced from legal and sustainable fisheries.
In 2012, the General Fisheries Commission for the Mediterranean (GFCM) banned retention and mandated careful release for the White Shark and 23 other elasmobranch species listed on the Barcelona Convention Annex II. Implementation by GFCM Parties, however, has been very slow.
To prevent overfishing and allow recovery, it is recommended that all White Shark conservation commitments under international wildlife treaties be fully implemented. For CMS Parties, this includes strict protections. In addition, initiatives to prevent lethal contact, minimize bycatch mortality, promote safe release, and improve reporting of catches (including discards) are needed. At a minimum, White Sharks should be subject to catch limits based on scientific advice and/or the precautionary approach.