Spiny softshell turtle (Apalone spinifera) COSEWIC assessment and status report: chapter 7

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Population Sizes and Trends

Research conducted since the completion of the original status report in 1985 (Campbell and Donaldson) suggests that the southwestern Ontario subpopulation may be approximately 800-1000 individuals (Fletcher 1999). However, the long-term study did not mark individuals so an accurate or precise estimate of population size is not possible. It is impossible to determine to what extent the Canadian population has declined as there are no published historic estimates of densities for the population. It would appear that the population has decreased dramatically if one compares a 1792 journal entry from the Chatham area of the Thames River which states that “hundreds of soft-shelled river turtles were scooped off floating logs to make supper that everyone enjoyed” (Gray 1956) to 1997 survey work which located fewer than 10 individuals in the same area (Fletcher 1997).

The Quebec subpopulation appears to be stable, but much smaller, consisting of probably no more than 100 individuals (P. Galois, pers.comm.). As with the Ontario subpopulation, there are no historic population estimates that would allow for an accurate determination of the extent of population decline. Current research in Ontario indicates that parts of that subpopulation may be subject to significant future decline as the turtles of most areas appear to consist solely of older adults (recruitment appears to be almost zero). Habitat loss has been significant throughout the entire Canadian range so that not only has the range shrunk, but it has become more fragmented within this region (Spiny Softshell Turtle Recovery Team 1997). There are no estimates on the amount of softshell habitat lost or the percent of habitat that has been altered in some way along the rivers (although it would be well over 50% along the Thames). Habitat is currently being lost, but less rapidly than it was years ago. Patrick Galois and the author both agree that even if the population is not declining, a future increase in the population may not be possible as there is a lack of suitable additional habitat.