As part of a larger survey on cumulative effects within the Saint John River basin (Canada), a fish survey was conducted near Edmundston (NB, Canada) in the fall of 1999 using slimy sculpin (Cottus cognatus) and white sucker (Catostomus commersoni). The discharge environment receives effluent from the pulp mill, a paper mill, three sewage discharges, and tributaries receiving agricultural runoff. Sculpin collected downstream of the sewage discharges and pulp mill effluent had greater growth, condition, and liver size but no significant differences in gonad size. Stable isotope data indicated slimy sculpin did not move between sites. Female sculpin collected downstream of the paper mill showed no significant differences in length, body weight, age, condition factor, liver size, and gonad size compared to fish from reference sites. Female white sucker collected downstream of the pulp mill did not differ significantly in any measured parameter compared to reference fish. Liver sizes of white sucker from the Saint John River were outside the range considered to be indicative of uncontaminated riverine sites. In 2000, sculpin collected downstream from a poultry‐processing facility had larger livers and lower condition factors, suggesting that the site is contaminated. We found no significant differences in sculpin length, weight, condition (except for males), and liver size in sculpin collected downstream from the pulp mill in October 2001. The responses of slimy sculpin and white sucker differed, perhaps in relation to differences in life history characteristics. Results from this study indicate the slimy sculpin is a suitable fish species for monitoring rivers that receive multiple industrial and municipal effluents.

This research examined the influence of acute changes of water temperature on the recovery processes following exhaustive exercise in juvenile Atlantic salmon (Salmo salar). White muscle phosphocreatine (PCr), ATP, lactate, glycogen, glucose, pyruvate, plasma lactate, and plasma osmolality were measured during rest and at 0, 1, 2, and 4 h following exhaustive exercise in fish acclimated and exercised at 12 degrees C and acutely exposed to either 6 degrees C or 18 degrees C water during recovery. An acute exposure to 6 degrees C water during the recovery period resulted in a severe reduction of metabolic recovery in salmon. However, metabolites such as muscle PCr and ATP and plasma lactate recovered very quickly (2-4 h) in fish acutely exposed to 18 degrees C during recovery. Overall, differences exist when postexercise metabolite levels are compared between acclimated fish and those fish acutely exposed to different water temperatures (either higher or lower). Taken together, the findings of the acute experiments suggest that at some point following exercise fish may seek warmer environments to speed the recovery process. However, the relationship between behavioural thermoregulation and recovery following exhaustive exercise in fish is not well understood.

Basic biological information was collected to assist in understanding the biology of selected small-bodied fishes for use in environmental monitoring programmes. Gonado-somatic index (I G ) and hepato-somatic index (I H ) profiles of female blacknose dace Rhinichthys atratulus, mummichog Fundulus heteroclitus and golden shiner Notemigonus crysoleucas were similar, decreasing gradually during the spawning season. I G and I H profiles of female northern redbelly dace Phoxinus eos peaked twice suggesting oocyte recruitment was continuous throughout the spawning season. Regressions of ovary mass to adjusted body mass (M A ) were more variable in dace relative to the other fish species. For female blacknose dace, variability in the relationship between ovary mass and M A was minimized by selecting either 2 year-old fish and fish that weighed 2-4 g.

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White sucker (Catostomus commersoni) are widely distributed in North America and are often used in environmental monitoring. Whole organism characteristics of three white sucker populations determined to be resident (outside of spawning) within small sections of the Saint John River, New Brunswick, were studied in 2001 and 2002. Significant differences in performance characteristics were present among sites. The differences can be interpreted as either improved sucker performance at Florenceville (upstream site), or decreased performance at Woodstock. Without further investigation it is difficult to identify whether the apparent improved performance is a response to nutrient enrichment, or increased mortality associated with the recent prevalence of lesions. Confounding factors are also present. Daily water level fluctuations resulting from an upstream dam discharge may change habitat availability and/or diversity, thereby altering the fish community. Liver sizes in Saint John River white sucker are considerably larger than in fish collected in Ontario, but are not relative to nearby New Brunswick river populations. This has implications for the importance of reference site selection and understanding the natural variability within a species (intra-specific variation) on multiple spatial scales.