The linkage among ecosystem perturbations, remediation, and the success of the Nipigon Bay fishery

Abstract

Since the inception of the commercial fishery in Nipigon Bay of Lake Superior, walleye (Stizostedion vitreum) and lake sturgeon (Acipenser fulvescens) have been extirpated and the abundance of lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis), and northern pike (Esox lucius) has declined significantly while the abundance of lake whitefish (Coregonus clupeaformis ) and lake herring (Coregonus artedii) has increased. Systemic stresses including eutrophication, airborne contribution of contaminants, and exploitation (reduced by closure of the commercial fishery in 1988) remain but may not impair populations of lake whitefish and herring, which interact less with tributaries and nearshore waters. Improvements in habitat, through water flow management in the Nipigon River, removal of logs in the nearshore, shoreline and stream restoration, cessation of log drives, as well as artificially increasing adult abundance have resulted in resumption of some limited reproduction by walleye and increased egg deposition and early life survival by brook trout. Multiple stresses are still ubiquitous in the Nipigon ecosystem, but relief of several stresses in tributaries and nearshore environments at least appears to have resulted in an initially encouraging response by two species dependent upon these areas.