Recovery Strategy for Lake Sturgeon in Ontario
1.5
Limiting Factors
The life history traits exhibited by Lake Sturgeon, including large body size, delayed maturation, low natural mortality, longevity and high fecundity have allowed this species to survive short term extremes in environmental conditions and have contributed to the long term success of the species. The species has exhibited a remarkable ability to adapt to change over periods of many centuries. The decline of this species over much of its range, over a relatively short period of time (e.g., since the late 1800s) suggests that Lake Sturgeon are not able to adapt rapidly to changes in their environment caused by multiple stressors (e.g., high rates of exploitation coupled with habitat loss). Adaptation by populations or groups of organisms is generally measured over several generation times. Spawning periodicity, late age of maturation and the longevity of Lake Sturgeon may contribute to the inability of Lake Sturgeon to adapt rapidly to changes in their environment or to recover quickly from perturbation. Various life history stages of Lake Sturgeon (e.g., eggs, larvae, juveniles, sub-adults and adults) require specialized habitats, often located far apart. Existing subpopulations frequently require both lake and river environments to carry out life processes. Research has shown that Lake Sturgeon tend to move large distances to access preferred habitat. As such Lake Sturgeon may be vulnerable to many forms of instream development and the disruption of physical connections between preferred habitats.
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 may have been 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. Exploitation Exploitation (e.g., the legal harvest of fish) is not considered as a current threat to Lake Sturgeon recovery as recreational harvests and commercial harvests, for the most part, have been prohibited across Ontario. However, overexploitation was a key factor in the historical decline of Lake Sturgeon in Ontario (Harkness and Dymond 1961; Brousseau 1987). Prior to the mid 1800s, Lake Sturgeon had limited value and were considered a
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