Energetic costs of activity in wild lake trout: a calibration study using acceleration transmitters and positional telemetry

Abstract

Acceleration telemetry transmitters offer the opportunity to estimate the cost of behaviours in free-ranging fishes, but a methodology to translate acceleration data into metabolic equivalents is still needed. This study extends previous calibration studies, explores how well tail-beat frequency transmitters fulfill their role, and presents a procedure to convert acceleration data into metabolic cost within a framework consistent with traditional fish bioenergetics models and thus facilitates comparisons of energetic costs between natural fish populations. These objectives were achieved by comparing data from lake trout (Salvelinus namaycush) in a laboratory setting with data from three natural populations. In the laboratory, tail-beat frequency, acceleration values, and oxygen consumption increased progressively with swimming speed. In the wild, individual swimming speeds estimated from positional telemetry were consistently underestimated by, but positively related to, transmitter-based acceleration values. The proposed rationale to estimate metabolic rate from acceleration data accounts for variation in fish mass and environmental temperature. We demonstrated how this novel method permits comparison of metabolic costs associated with the levels of activity typical of lake trout living in two different lakes.

Behavioral responses to annual temperature variation alter the dominant energy pathway, growth, and condition of a cold-water predator

“…First, increased reliance on Mysis and zooplankton would be less energetically efficient than foraging on larger prey fish or benthic invertebrates because predatory fish are more active when forced to feed on numerous, smaller prey (22). This increased energetic cost of feeding on small prey has been illustrated by studies that found predatory fish in lakes without pelagic prey fish had increased muscle activity and greater activity rates than those same species in lakes containing pelagic prey fish (23)(24)(25) and by studies showing that more active fish generally grow more slowly (26). Additionally, in oligotrophic lakes, the littoral zone is often more productive and smaller in volume than the pelagic zone (6,17), and therefore the probability of a lake trout's encountering prey would be higher in the littoral zone than in the pelagic zone, increasing foraging success but also reducing the time required to find prey.…”

Life at the top: Lake ecotype influences the foraging pattern, metabolic costs and life history of an apex fish predator

“…This empirical work inspired some of the first theoretical studies (Kerr, ; Kerr & Martin, ) on the links between prey size, growth and life history, and lake trout has served as a model organism in several more recent theoretical treatments (Giacomini et al., ; Quince et al., ; Shuter et al., ). In addition, lake trout has also been the focus of several recent empirical tests of that theory (e.g., Pazzia et al., ; Shuter et al., ) and is particularly suited to behavioural studies using acoustic telemetry (Cruz‐Font et al., ; Guzzo et al., ; Morbey et al., ).…”

“…The activity of 36 adult lake trout was studied using internally implanted acceleration–depth telemetry transmitters (V9AP, VEMCO, Nova Scotia, Canada; Table ). Transmitters were implanted in the posterior of the body cavity, following recommended procedures for fish (Harms, ), adapted to this type of transmitter (see Cruz‐Font et al., and Appendix S5.1 for details). Transmitter depth sensors were calibrated prior to implantation in fish.…”

“…The transmitters alternately measured and reported estimates of (a) depth (in m.) and (b) acceleration (A in arbitrary units—a.u.). Acceleration was measured on just the lateral and dorso‐ventral axes of the transmitter, in order to capture the acceleration of the fish's tail when engaged in the lateral, undulating movements associated with swimming (Cruz‐Font et al., ). The two‐axis values from each measurement were summed to yield a single sample value.…”

“…These expectations are particularly well suited to testing in the wild with acceleration telemetry (e.g., Cooke et al., ; Cruz‐Font, Shuter, & Blanchfield, ), and our objective in this study was to carry out such a test by: (a) generating extended (~20 days), temporally fine scale (~10 min) direct measures (i.e., the frequency of resting periods and the intensity of activity during active periods) of the feeding activity of an apex visual predator during a critical period in its annual growing season; (b) comparing those measures across populations that differ greatly in both the size and accessibility of available prey. Acceleration telemetry has been used in much recent work to assess the short‐term impact on fish behaviour of various anthropogenic manipulations (e.g., fisheries capture—Gutowsky et al., ; light pollution—Foster, Algera, Brownscombe, Zolderdo, & Cooke, ).…”