Green sturgeon (Acipenser medirostris) COSEWIC assessment and status report: chapter 11

Limiting factors and threats

Sturgeon exhibit a combination of morphology, life history and habitat requirements that make them highly susceptible to negative impacts from human activities (Boreman 1997). Anthropogenic activities known to impact sturgeon include: exploitation (see Population sizes and trends), blockage of available freshwater spawning habitat through diking, damming causing inadequate flow regimes, channelization, elimination of backwater areas, dewatering of streams, destruction of thermal refugia, loss of deep pools, inundation of habitat by reservoirs, and exposure to bioaccumulating industrial and municipal pollution, (Boreman 1997, EPIC 2001, Adams et al. 2002). It is illegal to retain green sturgeon caught in both marine and freshwater in Canada (Department of Fisheries and Oceans [DFO] fishing regulations 2003). No assessment of mortality incurred by trawl caught green sturgeon has been done.

The long life span and late age of maturity make sturgeon vulnerable to chronic and acute effects of bioaccumulation. A fish contaminant survey of the Columbia River Basin between 1996 to 1998 found white sturgeon to have the greatest contaminant concentrations compared to all other species tested, of which various salmonids, two sucker species, walleye, pacific lamprey and eulachon (US Environmental Protection Agency [USEPA] 1999). White sturgeon also had the highest whole body concentrations of hexachlorobenzene (19 ųg/kg), DDT (787 ųg/kg), p,p’DDE (620 ųg/kg), Aroclors (173 ųg/kg), and dioxins were an order of magnitude higher in concentration than all other species tested. Although green sturgeon are less exposed to anthropogenic contaminants due to their marine migratory phase, there is the potential for exposure when entering freshwater to spawn and during estuarine concentrations.

There is a possibility of disease transfer from hatchery-raised sturgeon and wild sturgeon, however there is no evidence that this has ever occurred. There was a die off of white sturgeon in the Fraser River in 1993 to 1994. Thirty-four “huge sturgeon”, mostly females, were found (MELP 1997). Although no green sturgeon were reported, the possibility that some green sturgeon could have been affected exists as all affected sturgeon may not have been found.

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