Longtail tuna played a similar ecological role in northern and
eastern Australia by consuming a range of prey categories (e.g.
pelagic and demersal fishes) in similar proportions. However,
the diversity and composition of the diet varied significantly
among regions, seasons and fish sizes. The diversity of prey in
the northern region was nearly twice that of the eastern region,
which probably reflects the higher diversity of fishes generally
found in the tropical northern region (Blaber 2002). Also, the
overall prey diversity, variation in diet composition and feeding
intensity was highest during autumn and winter and decreased
markedly in spring and summer. This pattern was consistent for
both regions, despite fish in each region having significantly
different diet composition. In the northern region, longtail tuna
primarily consumed small schooling pelagic species such as
Sardinella spp. and Stolephorous spp. during spring and summer,
while Stolephorous spp., Clupeidae sp. and Engraulidae sp.
were primarily consumed in the eastern region during this time.