Does annual variation in growth and sexual maturation of white sucker (Catostomus commersoni) confound comparisons between pulp mill contaminated and reference rivers?

Abstract

A previous study on the effect of pulp and paper effluents on white sucker (Catostomus commersoni), conducted in 1991 and 1992, in both effluent-exposed and reference rivers showed that fish grew faster at downstream sites than at upstream sites. However, in contrast with fish from a reference river, fish exposed to effluent showed no decrease in age or size at first maturity or increase in gonad size or fecundity in response to greater growth. The objective of the present study, conducted in 1993, was to test if differences in measures of growth and sexual maturation between fish populations in exposed and reference rivers would vary from year to year and whether such variation would affect conclusions concerning the effects of pulp mill effluents. Although size at age, fecundity, and age at first maturity varied between the two studies, patterns of demographic responses to pulp mill effluents, relative to reference populations, remained the same, i.e., conclusions about effects of pulp mill effluents did not change despite variation in demographic variables between years and sites. This study reaffirmed the view that only by including the fish populations in a reference river could effects due to bleached kraft mill effluent be separated from effects due to nutrient gradients.

Reproductive Disruption in Fish Downstream from an Estrogenic Wastewater Effluent

“…Nonestrogenic environmental factors characteristic of WWTP effluents (increased stream temperatures and decreased oxygenation), social factors (skewed sex ratio), or wastewater nutrients could account for some individual effects in effluent-site white suckers – . However, these factors are not likely to account for the full and widespread suite of disrupted reproductive end points observed in this investigation.…”

Three Decades of Swedish Experience Demonstrates the Need for Integrated Long-Term Monitoring of Fish in Marine Coastal Areas

“…Although it is not the responsibility of regular monitoring to provide a full understanding of all observations, the integrated monitoring should allow a primary analysis of observed changes to verify whether or not changes are relevant and related to environmental stressors. Monitoring should also provide opportunities to test whether annual variations of demographics of studied populations obscure changes that we wish to detect (Gagnon et al 1995;Bussieres et al 1998). When changes are detected but their relevance is unclear, this should lead to follow-up studies addressing the cause of the change and its further ecological significance.…”

“…The program is optimized to: (a) indicate trends in concentrations of certain identified chemical contaminants, (b) indicate response in individuals and populations of sentinel species caused by chemical exposure, and (c) indicate fish community response to eutrophication or other stressors that affect ecological conditions in coastal habitats. Identification of chemical impacts depends on the ability of the monitoring to distinguish changes in survival and energy allocation from changes associated with alterations in habitat and natural variability (Munkittrick 1992;Bussieres et al 1998). Several natural ambient factors may influence fish, e.g., season, temperature, salinity, feeding conditions and predation.…”

“…The response pattern indicated a metabolic disturbance stimulating growth and inhibiting reproduction, which differed from the response seen in cooling-water exposed fish. The importance of growth as a natural regulator of reproductive investment was evident from the studies by Gagnon et al (1995) and Bussieres et al (1998) on the reproduction of white sucker along productivity gradients in rivers contaminated with pulp mill effluents and in reference rivers.…”

“…The response model for Baltic perch is based on the model proposed by Colby (1984) and Gibbons and Munkittrick (1994). Data on native perch populations under different kinds of stress were used to elaborate the model, and additional support was provided by, e.g., the relations between growth response and reproduction in white sucker demonstrated by Gagnon et al (1995) and Bussieres et al (1998). The model aims to support analyses of observed patterns of energy allocation and reproduction, and it also includes predicted responses on the subcellular and cellular levels due to contaminant exposures.…”