Rationale (Changed due to Increased knowledge)

The regional population of Crozet Shag Phalacrocorax [atriceps] melanogenis satisfies the criterion for regionally Critically Endangered under the reduction in population size criterion (an observed population size reduction of 80% over the last three generations based on direct observation).

Distribution

Found only at the Crozet and Prince Edward Island archipelagos in the south-west Indian Ocean.

Habitat View more ecological information

Population

In 2008/09, 81 pairs of Crozet Shag bred at Prince Edward Island (Crawford et al. 2009). In 2012/13, 148 pairs bred at Marion Island (Department of Environmental Affairs unpubl. data). The present population at South Africa's Prince Edward Islands is therefore c. 230 pairs. The confidence in this population estimate is high.

Population trend

In the 1951/52 breeding season, there were at least 178 nests at Marion Island (Crawford et al. 2003). In 1987/88, 589 pairs bred at Marion Island (Cooper and Brown 1990). In 1994/95, regular monitoring of numbers of Crozet Shags breeding at Marion Island commenced. In that season, 841 pairs bred decreasing to 344 pairs in 2001/02 (Crawford et al. 2003) and to 220 pairs in 2003/04 (Crawford et al. 2009). Numbers then increased to 598 pairs in 2006/07, before decreasing again to 148 pairs in 2012/13, the lowest count yet recorded (Crawford et al. 2009, 2014). Numbers breeding at Marion Island decreased by 82% between 1994/95 and 2012/13, a period of 18 years. The decrease between 1987/88 and 2012/13 was 75% in 25 years or 2.2 generations, equivalent to greater than 80% in three generations. In 1984, 120 pairs were recorded breeding on Prince Edward Island decreasing by 33% to 81 pairs in 2008. The confidence in this trend estimate is high.

Threats

Decreases at Marion Island have been influenced by poor breeding success (Crawford et al. 2003, 2009). Numbers breeding between 1994/95 and 2012/13 were significantly correlated with numbers of Gentoo Penguins breeding at Marion Island (r=0.799, n=19, p<0.001, Crawford et al. 2014). The two species have similar foraging distributions and diets and their decreases may have been influenced by reduced food availability (Crawford et al. 2003, 2009a). Antarctic Fur Seals Arctocephalus gazella populations are increasing at both Marion and Prince Edward islands (Bester et al. 2009) and their predation on Crozet Shags is a potential threat, as is that on eggs and chicks. Crozet Shags may be disturbed by humans in close proximity and by helicopters, particularly during breeding. There is a small but non-trivial risk of diesel spills while offloading fuel on relief voyages.

Conservation

Underway

There is no access to the Prince Edward Islands without a permit issued by South Africa's Department of Environmental Affairs. At Marion Island, breeding sites are categorised according to the Prince Edward Islands Management Plan as Zone 4. This is the strictest conservation area; no helicopter movement is permitted overhead, no casual access permitted and only limited research allowed. There are no visits to Prince Edward Island except for bona fide research and conservation purposes every 4-5 years. There are strict guidelines in place to avoid diesel spills at sea.

Proposed

A Population and Habitat Viability Assessment (PHVA) is recommended, as is a Biodiversity Management Plan, culminating in a National Species Recovery Plan. Monitoring of numbers breeding and breeding success at Marion Island should continue. The population census at Prince Edward Island should continue at intervals of about five years. Restrictions regarding access to breeding sites should remain in place.

Research

* The taxonomic status of birds breeding at the Prince Edward Islands needs to be clarified. If birds at the Prince Edward Islands are a different species to those at the Crozet Islands, the species will be of heightened global conservation concern.

* Understanding inter-annual and inter-colony differences in diets and relating these to breeding performance is required in order to understand the population dynamics of the species. Further information is also needed on survival.

* Factors causing the periodic relocation of colonies require investigation.