Sensory and Behavioral Responses of a Model Fish to Oil Sands Process-Affected Water with and without Treatment.

If oil sands process-affected water (OSPW) is to be returned to the environment, a desire is that it not adversely affect aquatic life. We investigated whether a relevant model fish (rainbow trout, Oncorhynchus mykiss) could detect OSPW using its olfactory sense (smell) and whether exposure to it would result in behavioral changes. We also investigated whether ozonation of OSPW, which lowers the concentration of organic compounds attributed with toxicity (naphthenic acids), would ameliorate any observed adverse effects. We found that OSPW, regardless of ozonation, evoked olfactory tissue responses similar to those expected of natural odorants, suggesting that fish could smell OSPW. In 30 min OSPW exposures, olfactory responses to a food odorant and a pheromone were reduced to a similar degree by OSPW, again regardless of ozonation. However, olfactory responses returned within minutes of exposure cessation. In contrast, in longer (7 d) exposures, olfactory responses remained impaired, but not in fish that had received ozone-treated OSPW. In the behavioral assay, fish avoided an introduced plume of OSPW, and this response was not affected by ozonation. Taken together, our data suggest that fish smell OSPW, that they may use this sense to mount an avoidance response, and that, if they cannot avoid it, their sensory responses may be impaired, unless the OSPW has received some remediation.

Acute exposure to a common suspended sediment affects the swimming performance and physiology of juvenile salmonids.

To study the effects of an acute exposure to turbidity generated by suspended sediment, we examined swimming performance (Ucrit) and related metabolic parameters in individual and groups of juvenile trout at three different concentrations of calcium carbonate. To investigate differences among strains or provenience, we compared one strain of rainbow trout (Oncorhynchus mykiss; RBT) and one strain of brown trout (Salmo trutta; BNT) from a common hatchery and one RBT strain from a separate hatchery. In general, trout swum individually or in groups exhibited a decrease in Ucrit as turbidity increased. Both RBT strains were more similar to each other and were impaired to a larger extent in swimming performance than BNT, which was less impacted. For groups, indicators of aerobic metabolism were elevated while those of anaerobic metabolism were depressed. Specifically, citrate synthase activities and glucose levels tended to be greater while plasma lactate and LDH activities were reduced. Lactate and LDH levels in individually swum trout under sediment exposure suggest a greater similarity of fish from the same provenience. We suggest that acute exposures to environmentally relevant turbidities generated by fine suspended sediment may cause a reduced Ucrit, and that these changes may be related to changes in the utilization of aerobic and anaerobic pathways.

Variability in swimming performance and underlying physiology in rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta).

We investigated intra- and interspecific variation in swimming performance and related physiological parameters in two members of the salmonid family. For our comparisons, we sourced juvenile brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) from one hatchery and a second strain of rainbow trout from another. The hatcheries maintain genetic stocks obtained several decades ago from very different environments. We tested competing hypotheses: that there would be greater interspecific (across species) variation or that there would be greater intraspecific (within species) variation, owing to regional adaptations. To test these hypotheses, individual and small schools of five fish were taken to fatigue using the critical swimming speed test (U(crit)), and three post-exercise physiological metrics, packed red cell volume (hematocrit), citrate synthase and lactate dehydrogenase activity, were assessed. The majority of the results in swimming performance and hematocrit support that intraspecific variation was greater than interspecific variation, i.e. the location had a stronger effect than did genus. Variation in lactate dehydrogenase activity supported neither intra- nor interspecific variation as determining factors. In sum, our findings suggest that the performance of different species of salmonids from the same locale can be more similar than those of the same species from different areas.