REVIEW The population decline of the New Zealand sea lion

1. The New Zealand (NZ) sea lion Phocarctos hookeri is NZ’s only endemic pinniped and is listed as ‘nationally critical’. The species breeds in the NZ sub-Antarctic: 71 % of the population at the Auckland Islands (2010 pup production: 1814 39) and the remaining 29 % on Campbell Island (726 pups in 2010). 2. Pup production at the Auckland Islands has declined by 40 % since 1998 (1998: 3021 pups produced): only 1501 pups were born in 2009. This decline is directly linked to philopatric females not returning to breeding areas. While the Auckland Island population has declined, the Campbell Island population appears to be increasing slowly. 3. Potential reasons for the decline in the Auckland Island population, but not in the Campbell Island population, include non-anthropogenic factors: (i) disease epizoot-ics, (ii) predation, (iii) permanent dispersal or migration, (iv) environmental change; and anthropogenic impacts: (v) population ‘overshoot’, (vi) genetic effects, (vii) effects of contaminants, (viii) indirect effects of fisheries (i.e. resource competition