Interannual variation in cephalopod consumption by albatrosses at South Georgia: implications for future commercial exploitation of cephalopods

Assessing the consumption of prey by predators in the marine environment is key to fisheries assessment and management. Although environmental and ecological variations can affect the consumption of certain prey by albatrosses interannually, this issue has not been addressed to date. In the present study, the interannual consumption of cephalopods by grey-headed and black-browed albatrosses was assessed while breeding at South Georgia between 1996 and 2000, by comparing consumption estimates from a reparameterised version of the South Georgia Seabird Impact Assessment (SGSIA) model. The reparameterised model showed that there are considerable interannual variations in cephalopod consumption in both albatross species, with the highest consumption occurring in 1996 (5787 tonnes; for black-browed albatrosses) and 1997 (11 627 tonnes; for grey-headed albatrosses), and the lowest in 2000 (2309 tonnes and 772 tonnes for grey-headed and black-browed albatrosses respectively). These interannual variations were linked to oceanographic conditions and changes in cephalopod abundance/availability to predators. The cephalopod species with the most commercial potential (Martialia hyadesi, Kondakovia longimana, Moroteuthis knipovitchi and Gonatus antarcticus) also showed considerable differences in their consumption by predators. Owing to the importance of these squid species in the diet of albatrosses, precautionary measures for future commercial exploitation are suggested.

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