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Integrated Statistical Modeling for Hawaiian Albatross Populations

Progress Reports (PDF): FY 2008, FY 2007, FY 2006, FY 2005, FY 2004, FY 2003

Project Overview
The potential impact of longline fisheries on albatross populations has been a concern (Croxall, 1998) since Weimerskirch et al. (1997) showed evidence of a detrimental effect of longline fisheries on the population dynamics of the wandering albatross, Diomedea exulans. Accidental bycatch of individuals of the three North Pacific albatross species (Phoebastria albatrus, P. immutabilis and P. nigripes) has also raised the possibility that population level impact needs to be assessed for these three species. In particular, Cousins and Cooper (1999) reviewed the available knowledge on population biology of the black-footed albatross, P. nigripes, to determine if bycatch in the longline fisheries might pose a significant threat.

Based on a comparative approach, Niel and Lebreton (2001) showed that suspected levels of bycatch for the black-footed albatross were large enough to possibly affect population growth. Similar concerns exist for the Laysan albatross, P. immutabilis, which, although more numerous than black-footed albatross, tends to exhibit large variation in breeding numbers.

Over the years, Laysan and black-footed albatross populations have been monitored in various ways, on a very incomplete and irregular basis. The types of data include banding of chicks, resightings (and band identification) of breeders, censuses on the breeding colonies, and estimates of bycatch. The various sources of demographic information have not yet been combined and appraised in a systematic statistical way to develop a comprehensive assessment of population status for Laysan or black-footed albatross. Furthermore, there are a number of peculiarities in the the demography of these birds which pose special problems for the parameter estimation and modeling, such as late age of maturity, low reproductive output, high adult survival rate, and long term pair bonding behavior.

The combined effect of these complications argues for the need for an integrated statistical modeling approach, in order to make best use of all the available information, while providing realistic quantification of the true uncertainties in the model conclusions and predictions. Integrated modeling is based on the combination of likelihoods corresponding to probability models for all relevant observables and parameters as they are linked by an underlying dynamical model (e.g., Hampton and Fournier, 2001). The purpose of this project is to develop integrated statistical models for black-footed and Laysan albatross populations, with a view to quantifying the effects of past and present levels of bycatch on these species, and to provide a basis for answering the following questions:

  • Are the estimated levels of bycatch having a biologically significant effect on population growth?
  • How do the effects of bycatch compare to the roles of natural environmental variation on ocean productivity, and pollutants and plastic ingestion, in driving variation in the bird population dynamics?
  • Are the albatross populations declining?
  • Are changes in recruitment rates correlated with changes in the population densities? Are they correlated with the time course of development of the longline fishery?

Project researchers will assemble a consensus version of all the pertinent data, review the existing estimates of demographic parameters, and undertake further estimates of particular parameters wherever needed to resolve questions raised in the review. Access to critical data will be obtained through ongoing cooperative efforts with the U.S. Geological Survey (USGS), U.S. Fish and Wildlife, the Western Pacific Regional Fishery Management Council and the Northern Pacific Albatross Working group. The review of the existing estimates will be conducted in collaboration with J.D. Nichols of the USGS Patuxent Environmental Research Center (Laurel, MD) who has recently done survival analyses based on the banding data and is currently working on a separate but related project on the demographics of the North Pacific albatross populations.

Project researchers will then develop a spatially structured Leslie matrix model (Caswell, 2000), that will be used as the core of an integrated model using the Kalman filter and combining likelihoods for the various information sources available. Specific questions concerning the impact of bycatch, the potential for compensation by accelerated recruitment, the additional impact of accidental deaths in terms of pair re-formation after mate loss, consistency of trends across spatially distinct colonies, etc. will be examined by implementing the corresponding assumptions in the model, and by testing them.

The responsibility for the two main main components of the project, demographic parameter analysis, and integrated modeling, will be shared by the two groups participating, with a main role of J.D. Lebreton's group on the demography, and of D. Goodman's on the integrated modeling. Project deliverables will be a documented data base, a manuscript giving the results of the review of the demographic parameters, and a report on specifications for the model.

Year 1 funding for this 3-year project to be awarded January 2003.

Literature cited:
•Caswell, H. 2000. Matrix population models. Sunderland, Mass., Sinauer.
•Cousins K. and J. Cooper. 1999. The population biology of the Black-Footed Albatross in relation to mortality caused by longline fishing. Honolulu, Western Pacific Regional Fishery Management Council.
•Croxall, J.P. 1998. Research and Conservation: A future for Albatrosses? Pp. 269-290 in Albatross Biology and Conservation. Robertson, G. and Gales, R. (eds). Chipping Norton, Surrey Beatty & Sons.
•Hampton, J., and D. Fournier. 2001. A spatially disaggregated, length-based, age-structured population model of yellowfin tuna (Thunnus albacares) in the western and central Pacific Ocean. Mar. Freshwater Res. 52: 937-963.
•Niel, C. and J.D. Lebreton. 2001. "Using Demographic Invariants to Detect Overharvested Bird Populations from Incomplete Data." Conservation Biology, submitted.
•Weimerskirch, H., N. Brothers, and P. Jouventin. 1997. "Population dynamics of Wandering Albatross Diomedea exulans and Amsterdam Albatross Diomedia amsterdamensis in the Indian Ocean and their relationships with long-line fisheries: Conservation implications." Biological Conservation, 79: 257-270.

Principal Investigators:

Dr. Daniel Goodman
Montana State University
Department of Ecology
Lewis Hall
P.O. Box 173460
Bozeman, MT 59717-0346 USA
Phone (406) 994-3231
FAX (406) 994-2490
email: goodman@rapid.msu.montana.edu

Dr. Jean-Dominique Lebreton
Centre National De La Recherche Scientifique
Centre D'Ecologie Fonctionnelle et Evolutive
1919 Route de Mende
34 293 Montpellier Cedex 5
Phone 33-4-67-61-32-05
FAX 33-4-67-41-21-38
email: lebreton@cefe.cnrs-mop.fr

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This page updated August 7, 2008