Aquatic Environment and Biodiversity Annual Review 2012

AEBAR 2012: Protected species: Sea lions
essential amino acids and were of low to medium energy levels (Meynier 2010). This may indicate
that the nutritional content of prey species is not limiting the metabolic activity of NZ sea lions,
although vitamin and mineral content were not considered. Meynier (2010) also developed a bioenergetic
model and used it to estimate the amount of prey consumed by NZ sea lions at 17 871
tonnes (95% CI 17 738–18 000 t) per year. This is equivalent to ~30% of the tonnage of arrow squid,
and ~15% of the hoki harvested annually by the fisheries in the Sub-Antarctic between 2000 and 2006
(Meynier 2010). Comparison of the temporal and spatial distributions of sea lion prey, sea lion
foraging and of historical fishing extractions may help to identify the mechanisms whereby resource
competition might occur (Bowen 2012). The effects of fishing on sea lion prey species are likely to be
complicated by food web interactions and multispecies models may help to assess the extent to which
resource competition can impact on sea lion populations, such as those currently being developed by
NIWA (Project SA123098). In addition, multispecies models may provide a means for simultaneously
assessing multiple drivers of sea lion population change (a review of potential causes is given in
Robertson & Chilvers 2011) which may be a more effective approach than focussing on single factor
explanations for the recent observed decline in NZ sea lions (Bowen 2012).
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