This discussion was first published on Nov 30 2010 as part of the 2010-2011 Red List update.
Initial deadline for comments: 31 January 2012.
Black-footed Albatross Phoebastria nigripes is currently listed as Endangered under criterion A4b,d, on the basis that its population is projected to decline by more than 60% over 56 years (estimate of three generations), as modelled using a moderate scenario for fisheries bycatch of 8,000 birds per year (Lewison and Crowder 2003). It has been suggested, however, that the demographic parameters for this model, namely survival probability, growth probability and fecundity, were based on data from the 1960s and 1970s, for which it was incorrectly assumed that no bycatch took place (Arata et al. 2009). This implies that in Lewison and Crowder’s (2003) model, the basic parameters for a stable population with no additional mortality were actually estimated from a population already experiencing significant bycatch, and were thus underestimated. This appears to have lead to an overestimation of the declines that would result from the annual bycatch scenarios tested by Lewison and Crowder (2003), by counting this source of mortality both within the demographic parameter estimates and within the simulation scenario, effectively doubling the impact of fisheries (Arata et al. 2009).
Nevertheless, likely bycatch levels are still predicted to cause a decline in the population, albeit not as rapid as previously forecast (Arata et al. 2009). Other studies on this species have confirmed the impact of fisheries bycatch on survival (Verán et al. 2007) and the annual population growth rate (Niel and Lebreton 2005). Annual bycatch was estimated at 5,228 birds in 2005, which, if doubled to account for underestimation, approaches the maximum Potential Biological Removal (PBR) level of 11,980 birds, which is calculated to be the maximum level of off-take possible without causing a decline (Arata et al. 2009). The maximum PBR level for this species has also been estimated at 8,850 birds per year (Niel and Lebreton 2005) and 10,000 birds per year (Cousins and Cooper 2000). It still remains necessary, however, to robustly model the future impact of bycatch on this species.
There is also uncertainty over the historic population trends of this species. Monitoring data from three colonies in Hawaii, representing over 75% of the world’s population, suggested that numbers may have decreased by 9.6% from 1992 to 2001 (USFWS data per E. Flint 2003, Gilman and Freifeld 2003). However, linear regression analysis of log-transformed counts at the same colonies suggests that the species’s population has remained stable since at least 1957 and has increased overall since 1923 (Arata et al. 2009). Confusingly, an earlier variation on the same analysis found a decline between 1992 and 2005 (Arata et al. in prep., cited in Naughton et al. 2007), highlighting the importance of considering time scales when analysing this species’s population trend. Matrix modelling suggests that its population is currently stable or increasing slightly (Arata et al. 2009).
The recent analysis presented by Arata et al. (2009) brings into question the validity of the species’s current Red List status. It suggests that the rate of projected decline should be lowered, which could result in the species becoming eligible for downlisting. Comments are requested regarding the various studies on this species and the implications for its historic and future population trends.
Arata, J. A., Sievert, P. R. and Naughton, M. B. (2009) Status assessment of Laysan and black-footed albatrosses, North Pacfic Ocean, 1923-2000. U. S. Geological Survey Scientific Investigations Report 2009-5131. Reston, Virginia: U. S. Geological Survey.
Cousins, K. and Cooper, J. (2000) The population biology of the Black-footed Albatross in relation to mortality caused by longline fishing. Honolulu: Western Pacific Regional Fishery Management Council.
Gilman, E. and Freifeld, H. (2003) Seabird mortality in North Pacific longline fisheries. Endang. Spec. Update 20: 35-46.
Lewison, R. L. and Crowder, L. B. (2003) Estimating fishery bycatch and effects on a vulnerable seabird population. Ecol. Appl. 13: 743-753.
Naughton, M. B, Romano, M. D. and Zimmerman., T. S. (2007) A Conservation Action Plan for Black-footed Albatross (Phoebastria nigripes) and Laysan Albatross (P. immutabilis), Ver. 1.0.
Niel, C. and Lebreton, J.-D. (2005) Using Demographic Invariants to Detect Overharvested Bird Populations from Incomplete Data. Cons. Biol. 19: 826-835
Verán, S., Gimenez, O., Flint, E., Kendall, W. L., Doherty, P. F., Jr. and Lebreton, J.-D. (2007) Quantifying the impact of longline fisheries on adult survival in the back-footed albatross. J. Appl. Ecol. 44: 942-953.
The following documents were sent by Craig Harrison on 19 January 2011 in reaction to this topic (not BirdLife documents):
12 October 2011: As can be seen from the attached news release, the U.S. Fish & Wildlife Service have decided against listing this species as endangered or threatened.
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