Detection of food limitation in health of white sucker (Catostomus commersoni) 5 years after the closure of a bleached kraft pulp mill

Recovery of fish after implementing better management of effluent or following the closure of pulp mills is not well studied. Results from existing studies suggest the predominant responses observed during the operation of mills would predict a pathway of recovery, but this hypothesis has not been tested at mills with variable effects on fish. Multiple studies done at a mill in northern Ontario showed variable responses in white sucker (Catostomus commersoni), including effects on reproductive endpoints. Data from most years failed, however, to meet strict definitions of response patterns used in Environmental Effects Monitoring. After the permanent closure of the mill in 2006, white sucker were collected in 2011 to determine the status of fish. We predicted that no effects would be observed in white sucker after the mill's closure. Five years after the closure of the mill, however, female white sucker showed statistical food limitation. Males showed a similar trend, but fewer statistical differences. These changes, coupled with reduced catch rates, have not been previously observed downstream of this mill. Our results suggest that recovery of fish after the closure of mills may not be clearly associated with effects found during operation. The absence of recovery after closure may more broadly suggest relevance of effects of operational mills.

Use of portable ultrasonography to determine ovary size and fecundity non-lethally in northern pike (Esox lucius) and white sucker (Catostomus commersoni)

The objective of this study was to investigate the feasibility of using field-based portable ultrasonography to accurately estimate ovary weight, gonadosomatic index (GSI) and fecundity in large-bodied fish species. These reproductive endpoints were estimated using ultrasound on prespawning female northern pike (Esox lucius) and white sucker (Catostomus commersoni) and compared with actual measured values determined post mortem. Using five cross-sectional ultrasound images in pike, estimated ovary weight and fecundity, but not GSI, were significantly correlated with measured values. All endpoints were overestimated by 21 to 23% using ultrasound in pike. In a subsequent experiment using 20 cross-sectional ovary images, estimated ovary weight, GSI and fecundity were significantly correlated with measured values in white sucker. Although underestimated by 5 to 12% using 20 cross-sectional images, there were no statistical differences among estimated and measured mean ovary weight, GSI and fecundity in white sucker using this approach. Based on the variances for GSI estimations in both species, power analysis indicated that the ultrasound technique could detect a 25% change in GSI using sample sizes of <20 fish. This study illustrates the utility of portable ultrasonography as a promising non-lethal technique for assessing reproductive endpoints in the field.

Responses in a Fathead Minnow (Pimephales promelas) Lifecycle Test and in Wild White Sucker (Catostomus commersoni) Exposed to a Canadian Bleached Kraft Mill Effluent

To evaluate currently available bioassays for their use in investigating the causes of pulp and paper mill effluent effects on fish reproduction, the responses of wild white sucker (Catostomus commersoni) collected from the receiving environment at the bleached kraft mill at La Tuque, Quebec, were compared with responses of fathead minnow (Pimephales promelas) exposed to effluent in a laboratory lifecycle test. White sucker collected at effluent exposed sites had increased liver size but none of the reproductive effects that had been documented in earlier field studies at this site. Exposure to 1, 3, 10, 30, and 100% bleached kraft mill effluent (BKME) in the lab led to significantly decreased length, but increased weight and liver size in male fathead minnow. Female length was also decreased and liver size was increased at high effluent exposures. Most effluent concentrations (1 to 30%) significantly increased egg production compared with controls. The fathead minnow lifecycle assay mirrored the effects seen in wild fish captured downstream of the BKME discharge. These results will be used to select short-term fish tests for investigating the causes of and solutions to the effects of mill effluents on fish reproduction.

Influences of Human Stressors on Fish-Based Metrics for Assessing River Condition in Central Alberta

Economic developments in Alberta have resulted in widespread changes in land use that may deteriorate river conditions for fish. Fish assemblages were characterized with index of biological integrity metrics for the heavily-developed watershed of the Battle River, Alberta. Metric relationships with human stressors were quantified using regression and information theory methods. Although the fauna comprised 14 native species, 50% of the catch was white sucker (Catostomus commersoni Lacepede, 1803). Five statistically unrelated metrics were identified as being responsive to stressors: two trophic guilds, one habitat guild, one reproductive guild, and one measure of community structure. Regression showed that the cumulative effect of human developments, indexed as road density in the basin, was negatively linked to the relative abundance of lithophils and positively linked to the relative abundance of omnivores. Agriculture also threatened the integrity of fish assemblages. Stream sections with higher cattle densities in their basins had fewer lithophils and benthic invertivores; whereas stream sections with higher nutrient concentrations contained fewer species, as well as fewer top carnivores, but more true omnivores. Understanding effects of human footprints that are expanding in western Canada will be critical to the successful management of aquatic resources.