Rationale
(Changed due to Not applicable)
The regional breeding population of Cape Gannet Morus capensis, although numbering 240 000 mature individuals, is confined to only three colonies in South Africa, which are vulnerable to catastrophic events. In light of this, the species satisfies the criterion for Vulnerable under D2 (population with a very restricted Area of Occupancy (less than 20 km2) or number of locations (less than 5) such that it is prone to the effects of human activities or stochastic events within a very short period).
Distribution
Cape Gannets are endemic to Namibia and South Africa, where they breed on just on six islands, three of which (Mercury, Ichaboe and Possession islands) are in Namibia and the remaining three (Bird Island, Lambert's Bay; Malgas Island, Saldanha Bay; and Bird Island, Algoa Bay) in South Africa (Crawford et al. 1983). The AoO of 30.3 ha is the total area of the three South African breeding islands combined.
Population
The regional population has undergone fluctuations but overall has increased from 100 000 mature individuals in 1956/57 to 270 000 mature individuals in 2005/2006 (Crawford et al. 2007). By 2011, the population had dropped to 242 000 mature individuals (Crawford et al. 2012). The Lambert's Bay colony was abandoned in 2005 due to predation by Cape Fur Seals Arctocephalus pusillus (Crawford et al. 2007) but has since been recolonised and in 2011 contained about 18 000 mature individuals. The Malgas Island colony has fluctuated but generally followed a downward trend and now hosts 60 000 mature individuals, while the Bird Island colony has increased and now holds 166 000 mature individuals (Crawford et al. 2012). The total regional population is estimated at 242 000 mature individuals. The confidence in this estimate is high.
Population trend
The regional breeding population declined by 1.14% per year over the 49 years between 1956-1957 and 2005-2006 (Kemper et al. 2007), equivalent to c. 47% over 60.6 years (three 20.2-year generations). The confidence in this population trend estimate is high.
Threats
Cape Gannets are vulnerable to changes in their prey distribution and have been affected by the shift in fish distributions (Roy et al. 2007); the majority of chick mortalities at breeding islands is attributable to starvation. Gannets switch to feeding on fishery discards when pelagic fish are not available (Pichegru et al. 2010). However, a diet of fishery discards decreases chick growth and survival rates (Batchelor and Ross 1984). Gannets are also affected by oil spills (Altwegg et al. 2008, Wolfaardt et al. 2009) as well as by chronic oiling (Parsons and Underhill 2005). Seal predation is a major threat at Malgas and Bird (Lambert's Bay) Islands with seals being known to take between 29% and 83% of fledglings (Makhado et al. 2006). Seal attacks caused the temporary abandonment of the Lambert's Bay colony in 2005/2006 (Crawford et al. 2007). Chick predation by Great White Pelicans Pelecanus onocrotalus is an increasing threat at Malgas Island (de Ponte Machado 2007). Gannets are also subject to accidental mortality as bycatch in the trawl (Watkins et al. 2008) and longline fishery industries. Heavy storms may reduce breeding success or destroy colonies.
Conservation
Underway
All breeding colonies enjoy some degree of protection (Lambert's Bay and Bird Island are nature reserves while Malgas Island is part of West Coast National Park) and have been declared Important Bird Areas (Barnes 1998). Rehabilitation centres such as SANCCOB in Cape Town and SAMREC in Port Elizabeth successfully rehabilitate oiled or otherwise incapacitated birds. The Department of Environmental Affairs conducts monitoring of the population size. The issue of bycatch in the trawl and longline fisheries is being addressed using bird scaring lines, line weighting and night setting. The species is protected under Sea Birds and Seals Protection Act, 1973 (Act No. 46 of 1973), Marine Living Resources Act (Act No. 18 of 1998): Publication of Policy on the Management of Seals, Seabirds and Shorebirds: 2007 and the National Plan of Action (NPOA) for Reducing the Incidental Catch of Seabirds in Longline Fisheries 2008.
Proposed
The prevention of oil pollution by increasing controls over the cleaning of ship's tanks is an important measure. The maintenance of seabird rehabilitation centres is essential.
Research
* Research into the foraging patterns of Cape Gannets is being undertaken by the Percy FitzPatrick Institute of African Ornithology in collaboration with the Department for Environmental Affairs and Agriculture, Forestry and Fisheries. This research will help to identify Marine Important Bird Areas in the region.
