Whale Shark (Rhincodon typus) Issues Paper

Department of the Environment and Heritage, May 2005
ISBN 0 6425 5082 4

Appendix 2

Advice to the Threatened Species Scientific Committee (TSSC) from Wildlife Scientific Advice Section (EA) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (the Act)

1. Scientific name, common name, major taxon group

Rhincodon typus, (Whale Shark)

2. How judged by EA in relation to the Environment Protection and Biodiversity Conservation Act 1999 criteria.

EA judges the Australian population of Rhincodon typus to be eligible for listing under the Environment Protection and Biodiversity Conservation Act 1999 based on relevant information on threats to its populations.

Criterion 1: It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a substantial reduction in numbers.

It is estimated that there has been a substantial decline of Whale Sharks due to fishing pressures in the waters of other regional nations (Philippines, Taiwan, India). In the Philippines the catch per unit effort (CPUE) between 1993 to 1997 declined from 4.4 sharks per boat to 1.7 sharks per boat. Catch data from India (where CPUE has declined between 1998 and 2000), Philippines (as mentioned above) and Taiwan (where the number of Whale Sharks caught each year has declined from 250 pa to 10 pa with similar effort levels) all point to declining populations.

There is no population estimate for Whale Sharks in Australia but they are known to grow slowly and also be slow to mature, and as such are vulnerable to overexploitation. The population appears to fluctuate annually, with the nominee identifying that 85% of the sharks at Ningaloo were immature males. This data would indicate a population dominated by juveniles, but it is unclear whether this is evidence of a decline in the Australian population as a consequence of age partitioning.

The species is wide ranging with individual animals known to migrate in the order of 12,000 kilometres over the course of a year. It is almost certain that the Australian population is shared with regional countries where there are strong indications of a decline in the species. The impacts of this decline regionally have however not been documented for the Australian population. The documented decline regionally in a shared stock could however be taken to meet this criterion as suspected to have undergone a decline.

With the global demand for shark fin being sustained, it is unlikely that the pressure on Whale Sharks will be relieved in the short to medium term. In spite of the recent protection of Whale Sharks in the Philippines hunting pressure on some regional stocks is likely to continue. The likelihood of a sustained decline exists if exploitation continues and a decline in Australian stocks over time can be inferred or suspected.

Therefore the nomination is eligible for listing as vulnerable under this criterion.

Criterion 2: Its geographic distribution is precarious for the survival of the species and is limited.

The proponent has identified the major threat as fishing in the waters of other regional nations. This contention is supported by data collected by nongovernment. There is no threat to the species habitat or food sources.

Therefore the nomination is not eligible for listing under this criterion.

Criterion 3: The estimated total number of individuals is limited: and (a) evidence suggests that the number will continue to decline at a substantial rate; or (b) the number is likely to continue to decline and its geographic distribution is precarious for its survival.

There are no reliable population numbers or indices that can be used to assess this criterion. The Whale Shark is uncommon, and numbers appear to fluctuate locally on an annual basis at Ningaloo with the nominee identifying that 85% of the sharks being immature males. This data would indicate a population dominated by juveniles but does not answer whether this is a consequence of age partitioning.

Due to a lack of quantitative data the TSSC is unable to assess the eligibility of this species under this criterion.

Criterion 4: The estimated total number of mature individuals is low.

There are no reliable population numbers or indices that can be used to assess this criterion. The structure of the population that has been monitored at Ningaloo strongly suggests a bias in the population towards juvenile male animals. This indicates that the number of mature animals is likely to be low and there will be a male bias. The numbers of mature animals has however not been estimated.

Due to a lack of quantitative data the TSSC is unable to assess the eligibility of this species under this criterion.

Criterion 5: The probability of its extinction in the wild is at least 10% in the medium-term future.

Without reliable population estimates the TSSC is unable to assess the eligibility of this species under this criterion.

3. Conclusion

The evidence presented in the nomination is judged to meet the criteria in the EPBC Act and Regulations.

The highly migratory nature of the species and the evidence of decline of the species in regional nations probably sharing the Australian stock of the species is recognised. The decline regionally is considered as likely to have lead to a decline in the Australian population that has not yet been documented.

4. Recommendation

TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by including in the list of vulnerable species:

  • Rhincodon typus, (Whale Shark)

Source: Department of the Environment and Heritage, 2003 (http://www.deh.gov.au/biodiversity/threatened/species/r-typus.html).