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.

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SynopsisWe examined the winter survival of age-0 smallmouth bass, Micropterus dolomieu, in lakes at their northern limit of distribution in New Brunswick, Canada. Pre-and post-winter collections over a 3 year period suggested the smallest individuals, <50 mm total length, died during winter under ice. Experiments with wild, age-0 smallmouth bass held in lakes demonstrated a size-dependent survival where smaller individuals had greater survival with an increasing temperature of exposure, but the largest individuals had reduced survival at warmer temperatures. Survivors lost 22-54% of pre-winter energy reserves measured as ash-free dry weight, which was similar to wild individuals captured in spring. Body size at the onset of winter affects survival, but it also appears that temperature interacting with a suite of environmental and biological factors affect changes in energy use and therefore survival of age-0 smallmouth bass under ice in winter. Environmental Biology of Fishes (2005) 72: 111-122 Ó Springer 2005