IUCN Red List Assessment
Red List Category
Red List Criteria
IUCN Evaluation of the New Zealand Sea Lion, Phocarctos hookeri
Prepared by the Pinniped Specialist Group
A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
Pup production has declined at the Auckland Island (where 86% of the population breed) by 31% in the period 1997/98 to 2005/06. For the four years prior to this, pup production had increased by about 20% in the same region. Overall pup production has decreased by 17% between 1994/95 and 2005/06 at the Auckland Islands. Regular estimates of pup production prior to the mid 1990s are only available for one of the Auckland Islands (Enderby Island; where about 20% of the population breed) and production numbers at this site show no statistical trend since about 1980. Data from Campbell Island (where almost all of the remaining 14% of the population breed) is too intermittent and of insufficient precision to derive meaningful trends. The mean age of reproduction of female New Zealand Sea Lions is 10.75 yrs, with some females giving birth at 3 yrs and living as long as 27 yrs. Causes of the decrease in pup production since 1997 are not clear, but may be related to the scale of fishery by-catch or three unusual mortality events that resulted in very high pup mortality.
A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
Fishery by-catch of an estimated 1-2% of adult female New Zealand Sea Lions continues in association with the New Zealand squid trawl fishery. The recent, unusual mortality events have been diagnosed to have resulted from bacterial infections, but the underlying reason for their current frequency and scale of effect of not known, nor their potential for future epidemics.
A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.
If pup production since 1997 is primarily driven by by-catch and disease events, and these continue at current rates (mean of 4.1% decline in pup production since 1997), and we assume a three generation period of 30 yrs, then a decline of >70% will have occurred by 2027. This would qualify the species for EN under A3.
A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
If the rates of population decline since 1997 are less dependent upon the by-catch and epidemics (or these decline), and future rates of change average those prior to 1997, then the current dramatic decrease may be arrested and longer term trends may be <30% over 3 generations.
B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 kmÂ²; EN < 5,000 kmÂ²; VU < 20,000 kmÂ²
The EOO is > 20,000 kmÂ².
B2. Area of occupancy (AOO): CR < 10 kmÂ²; EN < 500 kmÂ²; VU < 2,000 kmÂ²
The AOO is > 2,000 kmÂ².
AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.
C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000
The number of mature individuals may be < 10,000, given that total population size (which included the juvenile cohorts) was estimated to be 11,700 and 12,500 respectively in 1994/95 and 1995/96, at a time when pup production was about 17% greater than the most recent 2005/06 estimate. When scaled down to current pup production sizes (9,700 and 10,400 respectively) and juvenile cohorts are removed, then the number of mature individuals is likely to be <10,000.
AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
Between 2000-2005 pup production at the Auckland Islands decreased by about 27%.
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
(a ii) % individuals in one subpopulation: CR = 90?100%; EN = 95?100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.
D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 kmÂ² or number of locations < 5
Does not apply.
E. Quantitative analysis
Indicating the probability of extinction in the wild to be: Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years
There has been no quantitative analysis of the probability of extinction.
Listing recommendation ? The New Zealand Sea Lion has a relatively small population (<10,000 mature individuals) and a limited distribution. Most reproduction is restricted to a very few sites. The best population trend data (for pup production) are from 1994. Estimates prior to this are less reliable, and include a smaller proportion of the whole population. There has been a marked (30%) decline in pup production in the last 10 years, at some of the major rookeries. The reason for the decline is not clear, but is likely to be a combination of on-going fisheries by-catch of adult females and a series of bacterial disease outbreaks. New Zealand Sea Lions qualify globally as Vulnerable (VU) under criterion A3(b). But, given the seeming increase in incidence and severity of disease outbreaks, and the EN (Endangered) status of some local populations, this species should be reviewed again within a decade.
- 1996Vulnerable(Baillie and Groombridge 1996)
- 1994Vulnerable(Groombridge 1994)