While the suction dredge issue in California may be moot for the next five years if the current budget deal holds, uber-biologist Peter Moyle writes about his concerns with suction dredge mining, many of which are focused on intrusions into cold-water refugia (stressing fish), and direct effects:
The effects of suction dredging on fish are well described in the peer-reviewed papers Harvey (1986) and Harvey and Lisle (1998) and in the numerous citations in the two DFG review documents (see below “Further Reading”). The effects vary according to size of stream, fish species present, season of dredging, and frequency and intensity of dredging. Direct effects include trapping invertebrates and small fish in the dredges, altering the habitat that supports fish food supply, and changing channel structure to make it less favorable for fish. In the Klamath, piles of dredge tailings in the Salmon and Scott Rivers and their tributaries create attractive spawning grounds for salmonids. But these tailings are so unstable that they are likely to scour under high flows, greatly reducing survival of the embryos placed within the gravel.
The effects of suction dredging on fish are well described in the peer-reviewed papers Harvey (1986) and Harvey and Lisle (1998) and in the numerous citations in the two DFG review documents (see below “Further Reading”). The effects vary according to size of stream, fish species present, season of dredging, and frequency and intensity of dredging. Direct effects include trapping invertebrates and small fish in the dredges, altering the habitat that supports fish food supply, and changing channel structure to make it less favorable for fish. In the Klamath, piles of dredge tailings in the Salmon and Scott Rivers and their tributaries create attractive spawning grounds for salmonids. But these tailings are so unstable that they are likely to scour under high flows, greatly reducing survival of the embryos placed within the gravel.
(Read Moyle’s entire article here)
CalTrout believes that the impacts of suction dredge mining will vary widely depending on the size of the river and the makeup of the fish who inhabit it, and that blanket regulations for the entire state won’t protect stressed fish populations in specific areas.
We said so when we presented our comments to Fish & Game’s proposed regulations, and we will remain vigilant on the suction dredge issue.
