Data from: Life at the top: lake ecotype influences the foraging patterns, metabolic costs and life history of an apex fish predator

1.We used acoustic telemetry and acceleration sensors to compare
population-specific measures of the metabolic costs of an apex fish
predator living in four separate lakes. We chose our study species and
populations to provide a strong test of recent theoretical predictions
that optimal foraging by an apex fish predator in a typical aquatic
environment would be consistent with feeding to satiation rather than
continuous feeding. We chose four populations where the primary prey type
differed along a body size gradient (from small invertebrates to large
planktivorous fish) and along a thermal accessibility gradient (from
easily accessible coldwater pelagic prey to less accessible warmwater
epilimnetic and littoral prey). We expected that these gradients in prey
type would evoke distinctly different activity gradients depending on
whether predators fed to satiation (e.g. less frequent ‘rest’ detections
where primary prey are smaller/less accessible) or fed continuously (e.g.
fixed level of ‘rest’ detections under all prey conditions). 2. Our study
organism was a fall spawning, coldwater visual apex predator (lake trout).
Therefore, we focused our study on diel (early night, dawn, day, dusk,
late night) changes in metabolic costs associated with summer feeding
behaviour. The duration (~20 days) and fine temporal scale (~30 minutes)
of our behavioural data provided a uniquely detailed picture of intra- and
inter-population differences in activity patterns over a critical period
in the annual growing season. 3. In all populations, diel shifts in
activity were qualitatively consistent with that expected of a visual
predator (e.g. resting state detections were most frequent at night). 4.
Between-lake differences in daytime thermal experience were qualitatively
consistent with between-lake differences in the location of primary prey
(e.g. excursions to warm habitats were common in lakes with
epilimnetic/littoral fish as primary prey and relatively rare in lakes
with pelagic coldwater invertebrates/fish as primary prey). 5. Daytime
activity patterns were consistent with feeding to satiation rather than
continuous feeding: (a) individuals in all four populations exhibited
clearly delineated bouts of resting behaviour and active behaviour; (b)
the frequency of resting bouts and the resultant overall cost of daily
activity were strongly associated with the size and accessibility of prey
– in lakes with smaller and/or less accessible prey, predators rested less
frequently, exhibited marginally higher costs when active and had higher
overall daytime activity costs. Within each lake, similar changes in
activity occurred concurrently with diel changes in prey
accessibility/relative density.