Fish and ecosystem health as determined by parasite communities of lake whitefish (Coregonus clupeaformis) from Saskatchewan boreal lakes

Abstract

In northern Canada, there is increasing concern about the potential negative impacts of industrial activities on wildlife and ecosystems. Therefore, a study was conducted on lake whitefish (Coregonus clupeaformis) from Montreal and Reindeer lakes, Saskatchewan, to assess fish health and condition, and ecosystem integrity of these northern lakes. In Montreal Lake, all fish were infected by !2 parasite species. The most prevalent parasite at this site was the larval trematode Ichthyocotylurus erraticus, which was detected in all fish examined. All Reindeer Lake whitefish were shown to harbour !1 parasite species. The most prevalent parasite (found in 87.9% of fish) at this locality was the larval trematode Diplostomum sp. Macroscopically visible pathogenic changes were not noted. Gross energy values of whitefish were 4.40 ± 0.88 MJ/kg and 5.14 ± 1.14 MJ/kg for Montreal Lake and Reindeer Lake, respectively, indicating that fish have sufficient energy stores to withstand stressful conditions. The parasite communities were species-rich and diverse, with Shannon diversity indices of 2.12 (Montreal Lake) and 2.02 (Reindeer Lake). The ratios of allogenic/ autogenic as well as planktonic/benthic parasite species did not indicate atypical environmental conditions. Together the findings suggest that in both lakes there is currently no significant anthropogenic impact on the whitefish populations and ecosystem health.

Intestinal Nematodes Affect Selenium Bioaccumulation, Oxidative Stress Biomarkers, and Health Parameters in Juvenile Rainbow Trout (Oncorhynchus mykiss)

“…Gross energy content of fish (i.e., energy released as heat when completely combusted) is often assessed as a measure of general health and condition, , and, in theory, it reflects total energy available to the fish to cope with energy-demanding situations. Healthy fish should reveal GE concentrations above 4 MJ/kg body weight to withstand long-lasting stressful conditions .…”

“…Complete development of the nematode in the definitive host from the time of acquiring infection until egg production takes approximately two months. 31 As a consequence, 28 days prior to onset of Se-Met exposure, rainbow trout from the two Se-Met + parasites groups were fed pieces of lake whitefish (Coregonus clupeaformis) intestines containing cysts with larval (L3) R. acus 32 to produce mean infection levels of 25−30 parasites/fish. This infection method has been verified previously in rainbow trout during a pilot study, obtaining 75% infection rate.…”

“…Nematode samples were frozen at −20°C until Se analysis; some R. acus samples were transferred into 4% formalin for species identification. 31 Selenium Analyses. Details on determination of Se in control and spiked food, R. acus cysts (to obtain information on Se concentration of the larval parasites prior to infection of rainbow trout), nematodes, and rainbow trout muscle are given in the Supporting Information.…”