Florida Museum of Natural History Ichthyology Department

Red List Assessments for Sharks and Rays

The 1996 IUCN Red List of Threatened Animals has now been published by IUCN. This Red List is the first to apply the new quantitative IUCN criteria for assessing and classifying the degree of threat to species from biological and environmental factors which can cause extinction. It has no specific legal force, but is used by governments and other organisations as a guide to setting priorities for conservation. It lists 5,205 threatened species (118 of which are marine fish) and includes 14 elasmobranchs. The 1990 and 1994 Lists included just three sharks, the whale shark (category of threat: Indeterminate), white shark and basking shark (Insufficiently Known). These assessments reflected the lack of data available for the species and the difficulty of applying the old Red List criteria.

New Red List criteria
The new criteria, published in 1994, are applied to two main aspects of extinction risk: small population and declining population. Most focus in the past in relation to extinction has been on the first category. However the new IUCN criteria also provide for the listing of declining populations, regardless of their population size. This is based on the conviction that rapid declines of large populations are at least as 'risky' as minuscule declines in tiny populations.

The key statistic for population decline is related to a period of time appropriate to the biology of the species in question - the three generation period. Such a decline may have taken place during the preceding three generations, or be projected into the future (for example where such a decline is likely to take place if current fisheries practices are not altered). Since it is obviously impossible to quantify precisely the size of elasmobranch populations, changes in indexes of abundance (such as catch per unit effort) may be used to infer changes in population size. The criteria also require the precautionary principle to be used. Thus, where a population decline is known to have taken place (e.g. as a result of fisheries), but no management has been applied to change the pressures on the population, the decline is assumed to be likely to continue in the future. If fisheries are known to be under way, but no information is available on changes in CPUE, data from similar fisheries elsewhere may be used by informed specialists to suggest likely population trends. Additionally, where no life history data are available, the known age at maturity of a very closely related species may be used to estimate age at maturity.

Testing the criteria
The revision of elasmobranchs in the Red List using the new criteria (initially presented in Species 19:16-22 - the Newsletter of the Species Survival Commission, December 1992) was first discussed at a Shark Specialist Group meeting in Bangkok, December 1993. Some members of the Shark Specialist Group (SSG) subsequently began, with advice from IUCN, to test the new criteria on a few species of elasmobranchs. This work gathered pace with the award of a grant from WWF's Endangered Seas Campaign to the SSG for carrying out Red List assessments on additional species in 1995. In November 1995 all SSG members were asked to become involved in this Red Listing work, so that a wider range of species could be assessed for the IUCN Red List and the SSG's Action Plan. A summary of draft Red List assessments for eight elasmobranchs, including examples of freshwater, deep sea, and coastal species, was circulated, together with a detailed worked example demonstrating how the assessment for the basking shark had been reached. SSG members were asked either to take the lead on undertaking assessments for individual species or groups of species, and/or to review those assessments already been made. As a result, a few additional draft assessments were produced.

Marine fish workshop, London A Marine Fish Red Listing Workshop was held in April 1996 at the Institute of Zoology, London, in collaboration with IUCN and WWF (see last issue of Shark News). Thirty-one participants from nine countries attended. The main aims were to evaluate the applicability of the new criteria to marine fish species, and to evaluate candidate marine fish for inclusion in the 1996 Red List. Draft species a s s e s s m e n t s produced earlier by members of the SSG were discussed and amended where necessary at the workshop, and some additional species assessed. Data were provided for discussion by several SSG members who were unable to attend.

The conclusions of the workshop were that the new criteria may, indeed, provide relative assessments of trends in the population status of species across many life forms. However, participants stressed that these criteria do not always lead to equally robust assessments of extinction risk, which depend partly upon the life history of the species. For example, using the 'A' criterion, a decline of over 50% or over 80% in the population of a species with high growth rate, high reproductive potential and early maturity does not necessarily mean that the species is Endangered or Critically Endangered with extinction. It may be a significant overestimate of the actual extinction risk. Indeed, a managed fishery for a teleost fish may aim for a 50% depletion of the unfished stock level in order to maximise yield. Nevertheless, it was recognised that when such fisheries result in a managed reduction in a species population to a new stable level, then the threatened status of the species will be removed from the Red List once the population has been maintained at its new level for the three generation period. This strategy will also ensure that a species is listed until the management has been demonstrated to be successful (history has repeatedly shown, both in terrestrial and marine environments, that management schemes are, in practice, rarely followed).

Caveats
While the reproductive capacity of elasmobranchs and their ability to recover from depletion is much lower than teleosts, some of the same considerations still apply, particularly for very wide-ranging species. However, it was agreed that the marine fish assessments produced at the workshop could be published in the 1996 Red List, provided that the preliminary nature of the marine fish assessments in general was highlighted and the need for further investigation of the issue recognised. The following caveat therefore appears in the introduction to the Red List:

"The criteria (A-D) provide relative assessments of trends in the population status of species across many life forms. However, it is recognized that these criteria do not always lead to equally robust assessments of extinction risk, which depend upon the life history of the species. The quantitative criterion (A1a, b, d) for the threatened categories may not be appropriate for some species, particularly those with high reproductive potential, fast growth and broad geographic ranges. Many of these species have high potential for population maintenance under high levels of mortality, and such species might form the basis for fisheries."

Another note in the marine fish listings section states: "The marine fish listings below represent the first attempt to interpret the conservation status of marine fishes according to the new IUCN Red List criteria. These criteria require further evaluation in order to assess how well they reflect extinction risk in marine fishes."

Members of the SSG will be helping with this evaluation and assessment of the 1994 categories and criteria. These will be revised once the majority of the problems of this sort have been identified and addressed. Indeed, at the World Conservation Congress in Montreal, the Species Survival Commission was committed to a review of the criteria, with special reference to marine species. This review will take place soon. Please send comments/contributions to Sarah Fowler.

SSG Red List revisions
The Red List assessments produced at the London workshop were circulated to SSG members and comments invited on these and any other species (from a priority shortlist of about 100 proposed for future attention). Some of the assessments were discussed in detail by SSG members and non-members through the American Elasmobranch Society's (AES) Elasmo-L discussion forum, and at an SSG meeting in New Orleans, June 1996. SSG members (and interested non-members) attending the World Fisheries Congress, Brisbane, Australia were also invited to attend a afternoon meeting on 31 July, when another full discussion of the Red List assessment categories and criteria took place. On this occasion additional population data were discussed, and all the species listed in London were reassessed on the basis of a general consensus or majority vote.

Despite the caveats already agreed at the London workshop, many SSG members at these meetings continued to express their concern about the way in which the population decline criterion (A) appeared to seriously over-estimate extinction risk, even though the criterion could readily be applied to a range of population data derived from catch rates and fisheries independent field research. Indeed, many members queried whether the Red List criteria were applicable to sharks, because they did not consider elasmobranchs particularly wide-ranging species) could really be at global risk of biological extinction. It was also considered that species with geographically distinct populations should be assessed on a population basis, not globally, particularly since data for many populations are lacking.

As a result of these discussions, the precautionary approach was generally disregarded and the extinction risk for many of the more common and wide-ranging elasmobranchs listed at the London workshop slightly downgraded where there was any doubt whether the estimated population decline was actually operating at a global level. Conversely, the threatened status of some of the more seriously threatened and rarer species or populations was actually increased.

These revisions were all immediately submitted to IUCN on the understanding that there was still just enough time to incorporate these amendments into the published Red List. Unfortunately, we later heard that preparation of the copy was too far advanced for changes to be made, although they were added to the Red List Web site. The published Red List therefore lists the assessments produced in London; these and the updated assessments from the Brisbane meeting are shown in the Table.

This list will continue to be updated and extended by the SSG as more information becomes available; comments and new data should be sent to Sarah Fowler for forwarding to the experts who provided the assessments. The next major revision of the elasmobranch Red List assessments (incorporating many additional species) will be published in the Shark Specialist Group's forthcoming Action Plan. Additionally, the most recent version of the list is always available for consultation on the World Wide Web: (http://www.wcmc.org.uk/data/database/rl_anml_combo.html).

Sarah Fowler, Acting Chair, Shark Specialist Group

The ocellate river stingray Potamotrygon motoro is in demand for the aquarium trade and is one of the SSG priorities for Red List assessment. Photo: Manoel Mateus Bueno Gonzalez.

Elasmobranchs assessed for the IUCN Red List of Threatened Animals
Species	IUCN Red List categories and criteria
	Published Red List	July 1996 revision (Brisbane)
Hexanchus griseus Bluntnose sixgill shark	VU A1d+2d	LR (nt)
Dalatias licha Kitefin shark	VU A1d+2d	LR (nt)
Rhincodon typus Whale shark	Data Deficient	No change
Carcharias taurus Sand tiger, gray nurse shark	EN A1ab+2d	VU A1ab+2d EN A1ab+2d, SW Atlantic & E Australia
Cetorhinus maximus Basking shark	VU A1ad+2d	No change
Carcharodon carcharias Great white shark	VU A1bcd+2cd	No change
Lamna nasus Porbeagle shark	VU A1bd+2d	LR (nt) LR (cd) in NW Atlantic, VU A1bd+2d in NE Atlantic
Carcharhinus limbatus Blacktip shark	VU A1bd+2d	LR (nt)
Carcharhinus obscurus Dusky shark	EN A1d+2d	LR (nt) VU A1bd+2d in US Atlantic
Carcharhinus plumbeus Sandbar shark	VU A1bd+2d	LR (nt) VU A1bd+2d in US Atlantic
Glyphis gangeticus Ganges shark	CR A1bcde+2cde, C2b	CR A1cde+2cde, C2b
Pristis microdon Greattooth/freshwater sawfish	EN A1bcd+2cd	No change CR A1abc+2cd in SE Asia
Pristis pectinata Smalltooth or wide sawfish	EN A1bcd+2cd	No change CR A1abc+2cd in NE & SW Atlantic
Pristis perotteti Largetooth sawfish	EN A1bcd+2cd	CR A1abc+2cd
Pristis pristis Common sawfish	EN A1bcd+2cd	No change
Bathyraja abyssicola Deepsea skate	Data Deficient	No change
Himantura chaophraya Giant freshwater stingray	EN A1bcde+2cde	VU A1bcde+2ce CR A1bcde+2ce in Thailand

VU: Vulnerable	EN: Endangered	CR: Critically Endangered
LR: Lower Risk	nt: near threatened	cd: conservation dependent	lc: least concern.

The IUCN/SSC Shark Specialist Group

Shark News 8: December 1996

Red List Assessments for Sharks and Rays

Elasmobranchs assessed for the IUCN Red List of Threatened Animals