Summary The field of acoustic telemetry has evolved rapidly and now permits the remote sensing of animal behaviour, movement, physiology and survival in environments, and species not previously possible. However, an inability to detect when a telemetered animal is consumed by a predator can complicate accurate interpretation of the telemetry data. In this paper, we describe the efforts taken to test the two generations of a novel prototype acoustic telemetry transmitter designed specifically to detect predation. Testing involved either staged predation events where tagged prey (Rainbow Trout Oncorhynchus mykiss and Yellow Perch Perca flavescens) were fed to captive Largemouth Bass Micropterus salmoides, or false‐positive testing where prey fish were tagged and held without the risk of predation. Metrics of interest were (i) the rate of correctly identifying the predation events, (ii) signal lag (i.e. the time required to detect a predation event), (iii) tag retention time in the predator's gut, and (iv) the rate of false‐positive triggering in both live and dead prey fishes. Staged predation events were successfully identified in 61/65 and 52/55 trials for generation 1 and 2 tags, respectively. Signal lag time was reduced in generation 1 tags (generally between 1 and 9 h) relative to generation 2 (3–29 h); although signal lag was highly variable. A generalized linear mixed model (GLMM) indicated strong evidence that signal lag and tag retention were both negatively correlated with water temperature, but were not affected by prey species and only slightly by individual predator traits. There was preliminary evidence that prey size may be an important determinant of both signal lag and tag retention. False‐positives in live fish were absent after 120 days for generation 1 tags (n = 31), however, the false‐positive rates were significantly higher (10/44) after only 66 days for generation 2 tags. False‐positives in dead fish showed that 20% of the generation 2 predation tags would falsely trigger 2–3 days post‐mortem. Testing of the novel predation tags was encouraging, however, further testing is recommended. Predation tags will be an important contribution to the field of acoustic telemetry, thus, permitting the improved data interpretation and less‐subjective estimates of predation rates in biotelemetry studies.

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Three size classes of yellow perch (Perca flavescens) were dosed with a polychlorinated biphenyl (PCB) mixture and allowed to depurate the chemicals over 1 year while reared in 5000 L experimental tanks maintained under ambient environmental conditions. During the summer, PCB elimination rate constants for small perch (mean  =  10.1 g) averaged approximately three times those calculated for medium-sized individuals (mean  =  45.9 g) and four times those determined for the largest fish (mean  =  86.7 g). Significant differences in PCB congener depuration were observed among the three size classes with negligible elimination of congeners of the octanol-water partition coefficient (log Kow) > 6.5 occurring for the two larger size classes. Over the winter months, medium and large perch eliminated PCB 19 only, the least hydrophobic congener, with no elimination of PCBs of log Kow > 5.8 observed for the smallest individuals. An increase in lipid-normalized PCB concentrations was observed during the overwinter period because of the depletion of lipids as an energetic reserve. For medium and large perch, this increase was sufficient to overwhelm any elimination achieved during the spring and summer seasons. These results demonstrate that the allometry of species bioenergetics and seasonal temperature fluctuations are responsible for the degree of chemical biomagnification observed in aquatic food webs.

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Abstract-Three populations of brown bullheads (Ameiurus nebulosus) were sampled in the Detroit River and analyzed for concentrations of persistent organic contaminants as well as incidences of external lesions and liver histopathology. Chemical analysis revealed that both the sediments and the bullheads of the Trenton Channel had the highest concentrations of organochlorine compounds, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons compared with the other two sites (Amherstburg Channel and Peche Island). Furthermore, the Trenton Channel bullhead population had a higher prevalence of external abnormalities such as lip and skin lesions as well as truncated barbels. Histopathological analysis of the livers revealed higher prevalences of cholangiocarcinomas, cholangiomas, and other lesions in the Trenton Channel population. These observations support the conclusion that the health of the Trenton Channel bullhead population in the Detroit River is affected by exposure to organic chemicals, primarily through exposure to contaminated sediments.