USE OF A POPULATION-MODEL TO ASSESS THE IMPACT OF LONGLINE FISHING ONWANDERING ALBATROSS DIOMEDEA-EXULANS POPULATIONS

An age-structured model of a wandering albatross Diomedea exulans popu lation is developed to simulate population trends over time, using dem ographic parameters from the population at Possession Island, Crozets, during 1968-1986. The simulation results portray a population decreas ing at a rate of 2.29% per year, which concurs with global population trends. Sensitivity analyses of model parameters indicate that both ad ult and juvenile mortality are contributing to the decrease. Wandering albatross mortality is presumed to have increased as a result of deat hs caused by longline fishing vessels; such deaths are likely to be re latively more frequent among young, naive birds. The model is used to investigate the potential impacts of new longline fisheries such as th at for Patagonian toothfish Dissostichus eleginoides in Antarctica. As suming longline fishing operations affect juveniles more than adults, there is a time lag of 5-10 years before further decreases in populati on numbers are reflected in the breeding population. Also, because wan dering albatrosses are long-lived, population growth rates take approx imately 30-50 years to stabilize after a perturbation. Consequently, c aution must be exercised when interpreting population trends; short-te rm (<20 year) estimates may not provide good indications of long-term trends.