Biologist Peter Moyle Discusses Effects of Suction Dredge Mining
Biologist Peter Moyle Discusses Effects of Suction Dredge Mining
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.
(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.
3 Comments
I have been a member of CalTrout, I am a life member of Trout Unlimited and I have dredged on my claim in a small creek in Plumas county. I have not trapped any fish in my dredge, and most if not all invertebrates also survive the trip over the riffles of the sluice box and simply go back into the creek. The change in channel structure I create is small and temporary. The material moved is from one place in the existing stream bed to another in the existing stream bed and within a ten foot section at any given time. In the Summer months, the wild Rainbows of the creek prefer to stay in the deeper pools I create even after I finish for the season. I do not agree that gravels disturbed by fish during spawning are more stable than dredge tailings. For that matter, seasonal runoff fluctuations cause a greater disturbance, regardless of whether the site was dredged or not, yet the effects are often positive for aquatic life when viewed over time. I do know of areas that once were spawning areas until the gravels became too locked up due to impeded flows and subsequent silt deposits.
[…] Dr. Peter Moyle points out, suction dredge operations can harm fish, especially endangered steelhead and salmon. Impacts include disturbance of spawning gravels, […]
Mr. Moyle, if you want to do real research, spend a few days with someone that dredges and get hands on experience. That’s is what real research is about. As far as Cal Trout, you guys should be ashamed of yourselves trying to shut down an industry where many are avid fisherman. Don’t cut off you nose despite your face.