Abstract
In Spring 2011, 200 adult white sucker were collected in four areas of the St. Louis River area of concern (AOC), located in Minnesota and Wisconsin, USA. The areas included the upper AOC as a reference area, the upper estuary, St. Louis Bay and Superior Bay. Grossly visible abnormalities were documented and preserved for microscopic analyses, as were five to eight representative pieces of liver tissue. A piece of dorsal muscle was preserved for stable isotope analyses and otoliths removed for age determination. The incidence of raised skin lesions (mucoid plaques) was high (31 %), however, microscopically only 4.5 % of the white suckers had neoplasia (papillomas). The remaining lesions were epidermal hyperplasia. Superior Bay had the lowest percentage of skin/lip lesions (10 %), while St. Louis Bay had the highest (44 %). St. Louis Bay also had the highest incidence of skin neoplasms (12 %). No hepatocellular neoplasms were documented, however bile duct tumors were observed in 4.5 % of the suckers. Foci of cellular alteration were observed in fish from all sites except the upper AOC. Stable isotope data indicated that most of the suckers relied on the St. Louis River AOC for the majority (>75 %) of their diet, indicating they were resident within the AOC and not in Lake Superior. The amount of diet obtained from the upper estuary was a significant predictor of skin lesion incidence. Hence, habitat use within the AOC appears to be an important risk factor for skin and possibly, liver lesions.
Highlights
The utility of effects-based monitoring to assess ecosystem health in the aquatic environment has received increasingThe carbon (C) or nitrogen (N) stable isotope composition, 13C:12C or 15N:14N, of fish tissue is a time-integrated marker of the fish’s diet
Liver and skin tumors in brown bullhead (Ameiurus nebulosus) and white sucker (Catostomus commersonii) in the Great Lakes and other geographical areas are associated with environmental degradation (Baumann 1992; Baumann et al 1996; Rafferty et al 2009; Pinkney et al 2011)
A similar habitat use pattern was observed among fish with liver neoplasms, it was not significant
Summary
The utility of effects-based monitoring to assess ecosystem health in the aquatic environment has received increasingThe carbon (C) or nitrogen (N) stable isotope composition, 13C:12C or 15N:14N, of fish tissue is a time-integrated marker of the fish’s diet. Liver and skin tumors in brown bullhead (Ameiurus nebulosus) and white sucker (Catostomus commersonii) in the Great Lakes and other geographical areas are associated with environmental degradation (Baumann 1992; Baumann et al 1996; Rafferty et al 2009; Pinkney et al 2011). For this reason, ‘‘fish tumors or other deformities’’, was one of the beneficial use impairments (BUIs) identified by the International Joint Commission (IJC) at Areas of Concern (AOC) by the U.S.–Canada Great Lakes Water Quality Agreement, Annex 2 of the 1987 Protocol (IJC 1989). Louis AOC can be delisted in regards to this particular BUI or if further remediation is necessary
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