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Degraded Fish and Wildlife Populations
IJC Criteria: An impairment will be listed when fish and wildlife management programs have identified degraded fish or wildlife populations due to a cause within the watershed. In addition, this use will be considered impaired when toxicity (as defined by relevant, field-validated, bioassays with appropriate quality assurance/quality controls) of sediment-associated contaminants at a site is significantly higher than controls.
SLR RAP Rationale for Listing:
1) Fish Populations
Since 1979, fish populations have been recovering due to formation of
the Western Lake Superior Sanitary District (WLSSD) and construction of
the WLSSD wastewater treatment plant which resulted in improvements in
water quality. However, fish populations are still adversely affected
by alterations and loss of physical habitat, proliferation of exotic species,
and possibly by exposure to toxic substances.
- Operation of the Fond du Lac dam has adversely affected walleye spawning success. Stranding and mortality of spawning adults and eggs has been observed under erratic flow conditions. Specific flow requirements for the St. Louis River species of interest are not adequately defined (Stage I Report, pps. IV-18 to IV-19).
- Lake sturgeon populations in the St. Louis River have plummeted since the 1800's when the fish were commercially harvested. The population reduction may be due to bad water quality in the past, overharvesting, or dam construction. At the present, there are no spawning lake sturgeon in the river (Stage I Report, PP. IV-19).
- The population of ruffe, an exotic fish first found at Minnesota Point in July 1987, now surpasses populations of native fish. In July 1990, ruffe was the second most abundant species found in U.S. Fish and Wildlife Service trawls of the St. Louis estuary. In 1991, ruffe was the most abundant species in the trawls (Stage I Report, pps. IV-20 to IV-21).
- Purple loosestrife, an exotic plant from Europe, has infested the estuary and has the potential to degrade fish and wildlife populations. The plant crowds out native vegetation yet provides little or no food or habitat for waterfowl and other animals. The thick growth of loosestrife can choke off or eliminate access to fish spawning grounds (Stage I Report, pps. IV-22, IV- 24, IV-69).
- In 1991 and 1992, Envirovet trawls in the Duluth-Superior harbor turned up fish with significant pathological alterations (Stage I Report, pp. IV-26).
- A number of fish sampled on Crawford Creek (tributary to the Nemadji River) in 1985 had spinal deformities and possibly tumors (Stage I Report, pp. IV-26).
2) Wildlife Populations
Little population data is available for wildlife with the exception of
colonial nesting birds, herons, and gulls. Populations of the common tern
and the piping plover (threatened and endangered species) have declined,
the heron population has been declining, and gulls and mallards have experienced
die-offs in the recent past. These problems are due to alteration or loss
of physical habitat and possibly toxic contamination.
- The piping plover, a federally endangered species, has not nested in the estuary since 1985 due to loss of suitable breeding habitat. Human development of historical nesting sites, natural succession of vegetation, rapid increases in competing colonial species, and human disturbance have all contributed to the demise of the piping plover in the AOC (Stage I Report, pp. IV-23).
- The population of great blue herons at the rookery near Billings Park on the Wisconsin shore has been declining in