Author: Golder Associates Ltd. 2011. DRAFT Recovery Strategy for Lake Sturgeon (Acipenser fulvescens) – Northwestern Ontario, Great Lakes-Upper St. Lawrence River and Southern Hudson Bay-James Bay populations in Ontario. Ontario Recovery Strategy Series. Prepared for the Ontario Ministry of Natural Resources, Peterborough, Ontario. v + 74 pp.
About the Ontario Recovery Strategy Series
This series presents the collection of recovery strategies that are prepared or adopted as advice to the Province of Ontario on the recommended approach to recover species at risk. The Province ensures the preparation of recovery strategies to meet its commitments to recover species at risk under the Endangered Species Act (ESA) and the Accord for the Protection of Species at Risk in Canada.
1.6 Threats to Survival and Recovery
A number of factors have contributed to the historical decline of Lake Sturgeon. Current threats include habitat alteration and fragmentation, pollution, illegal harvest, exploitation, species invasions and climate change (Harkness and Dymond 1961;
Rochard et al. 1990; Birstein et al. 1997). These threats must be addressed in order to achieve recovery of Lake Sturgeon in Ontario.
The loss of habitat that occurred beginning early in the twentieth century is considered far less important than overfishing in contributing to their precipitous decline. In fact, many of the populations were reduced to remnant populations prior to major
environmental perturbations affecting Lake Sturgeon habitat, including dam construction in Ontario. The combined impacts of habitat loss, overexploitation, increased industrialization, pollution, and species invasions make it difficult to establish current
cause and effect relationships in Lake Sturgeon populations.
Habitat Alteration and Fragmentation
Lake Sturgeon is a long-lived, migratory species that requires distinct habitat types throughout its life cycle. Habitat suitability may be constrained by the management of water levels, river flows, the creation of dams and by food availability. Where a
particular life history stage occupies or congregates in discrete locations, they become more vulnerable to localized disturbance.
Studies on the Ottawa River indicate that Lake Sturgeon distribution, especially of juveniles, is positively correlated with unimpounded river habitat (Haxton and Findlay 2008). The Moose River basin is one of the most fragmented river systems in North America. The overall and cumulative impacts on the region’s Lake Sturgeon subpopulations is unknown (Seyler 1997a). However, Lake Sturgeon have been impacted in discrete sections of rivers that have been impounded (Gibson et al. 1984; Nowak and Hortiguela 1986; Payne 1987). In these cases, the effects of habitat alteration due to historical log drives (e.g., bark deposition and scouring) and dam construction (e.g., loss of riverine habitat and fragmentation) as well as overfishing contributed to localized declines in abundance and eventual recruitment failure.
Many hydroelectric dams were historically constructed at natural barriers on rivers (e.g., waterfalls), where the greatest potential to build hydraulic head and to generate power existed. The fast flowing habitat below these features likely represented spawning habitat for fish species such as Lake Sturgeon. Where dam construction has created artificial barriers to upstream migration and disrupted formerly continuous habitat, Lake Sturgeon sub-populations have become fragmented (Wozney et al. 2010; Wilson et al. in prep.). Despite the construction of barriers, Lake Sturgeon will spawn at the base of dams (Auer 1996b; Haxton 2006). In such cases, flow management to provide access to and from spawning habitat, the provision of suitable spawning substrate and suitable flows to facilitate hatching and larval drift is critical.