Mining activity

[2short]

Are the majority of N Cal streams altered by mining activity? Are there areas where the miners didn't turn the landscape upside-down? If you've fished both types of terrain did you find one or the other to be more fisher friendly?
Thanks
2short

[Darian]

2Short (for what Wading ),.... Anyway,.... As history will bear out, placer mining was big in the middle to end 1,800's.... It's still practiced on many rivers throughout NorCal( e.g. Gold dredging).... Check out the Yuba River Gold Fields or upriver in the Downieville area some time.... Virtually all of the major rivers on NorCal have been heavily mined in their lower reaches for placer deposits....

In most cases, the damage from Hydraulic mining activities is quite evident but nowhere more evident than at the Malakoff Diggings outside of Grass Valley or in the Yuba Gold Fields outside Marysville where large dredgers still carry out gold recovery and other operations.... Some of the lasting evidence of gold recovery operations (of all sizes) are the large rows of scoured rock deposits on river banks and mercury deposits remaining in alluvial deposits from gold recovery operations on all of the valley rivers.... Mercury was used to extract placer gold from "concentrate" and gold miners/Panners weren't real careful how they handled all of that Mercury.....

As I was saying, Mercury is used in one of the steps in recovering gold from the final stages of concentration (....in pans, sluice boxes, etc.).... This Mercury remains in the bottoms of all of these rivers, even today. It can be panned, right now, from alluvial sands at places like Negro Bar in Lake Natomas....

Mercury is ingested by micro-invertabrates in the water and is converted by them to Methyl Mercury where it enters the food chain. It works it way up the food chain in that form until it reaches fish which are then caught and, maybe, eaten by us.... Good case for catch/release, hmmm

The large deposits of rock on the sides of all valley rivers is the remaining evidence of Hydraulic/Dredge Mining techniques employed to remove and concentrate large amounts of placer gold for processing. Hydraulic mining was banned by the State Legislature either late in the 1,800's or early 1900's as it was seen to be extremely destructive.....

In answer to your question, "Are there areas where the miners didn't turn the landscape upside down?", I'd say, the higher up a river course you go, the better your chances of finding areas where placer mining was not carried out. Divers still practice dredge mining of placer deposits around Downieville on the Yuba River....

However, in spite of our best efforts to destroy our fishing grounds, nature always find a way to overcome. There's very good Trout/Steelhead/Salmon/Shad fishing on the Yuba River and I can't think of too many rivers that've been and continue to be mined more intensively....

I've fished both types of water since moving to this area and I'd say the Yuba River is one of the better fisheries in California. It certainly has its share of environmental concerns and has several dams built on it but its very resilient.....

Give it a shot and good luck.....

[Brian]

Wow Darian , you sound like you have a masters on local mining history and its impact on fisheries.
Thanks for the great information

[SteelieD]

Darian! Nice reply! I consider myself educated now... well sort of anyway !

[2short]

Darian,
yep wading and streamside hiking was where I was going when I asked about "fisher friendly".
You mentioned Mercury in the stream systems, are the levels high enough to cause a health risk, or does anyone really know?
2short

By-the-way, your reply was very informative, thanks.

[Darian]

Actually,.... Mercury levels in local river beds and dredger tailngs is quite high; altho, not so visible... . Mercury unchanged by micro-organisms will remain in sediments until removed by man or ingested by invertibrates.... According to everything I've read, Once in the food-chain, the Mercury is converted to Methyl Mercury which can be stored in our tissues and is dangerous at high levels of concentration .

About three years ago, a TV news item featured a piece on how easy it was to disturb the mercury in local river bed deposits. A guy with a gold pan panned several large drops of Mercury from the edge of Lake Natomas near Negro bar in just a few minutes panning.... . Gives ya an idea how prevalent Mercury is in this area.... One complicating factor is that Mercury occurs naturally as well as us contributing our leavings....

Gold miners/panners didn't do much in the way of recovering the Mercury used to recover gold from concentrates.... Let's face it, that wasn't high on their list of things to do on any given day and, let's be fair, they didn't necessarily understand the long term impact of their actions... . Mercury, being very heavy, sinks like a stone into the sediments of any body of water. Unless it's disturbed or ingested by some micro-organism, it just stays where it drops (doesn't seem to diffuse and disperse like it does out of water)... .

SOoooo,.... I guess it's safe to say that eating resident fish in areas of high Mercury concetrations is probably not a good idea considering the potential consequences... . On the other hand, it inadvertantly contributes to one of the benefits of catch/release... . This is not so much of a problem in some anadromous species but eating resident fish probably involves some level of risk for humans... . That's why the DFG has all of those warnings in their reg's. (Good for them )

Info about all of this used to be available thru a newsletter produced by the State Bureau of Mines & Geology titled: Mineral Information Service. Interesting publication....

Now, for an ol' fart like myself, I'm gonna continue to eat fish on occasion
cause I figure its too late for me.... Besides, I heard quality Single Malt Irish Whiskey makes you immune to Mercury poisoning. :P

OK, go catch some fish

[DonCooksey]

Here is a pretty good source of information from the EPA on health risks of mercury in fish, including tables and charts showing typical levels in different fish species and recommendations about consumption.

http://www.epa.gov/waterscience/fishadvice/advice.html

Interesting that rainbow trout tend to have one of the lowest amounts of methyl mercury of freshwater fish, with largemouth bass being one of the highest. Of course, it all depends on where they are caught. Also, older and larger fish have more than younger fish in general. I grew up in Michigan, where we had advisories on consumption of lake trout and other predatory fish that accumulate mercury, as well as PCBs. I was always told that you could minimize your exposure by avoiding as much fat as possible (removing skin, avoiding the belly area, etc.). That may have been related to PCBs rather than mercury - does anyone know about that?

I probably eat way too much fish that have mercury, mostly saltwater species, like tuna and mahi mahi, but I'm not planning to get pregnant anytime soon, and hey, I'm hardly shaking at all today.

[Darian]

Hey Don,.... Look on the positive side, you can always tell what the barometric pressure/temperature is....

[Hairstacker]

Darian and Don, this has been a very informative thread, thank you! Yeah, I too have found it interesting that mercury levels can vary considerably between species of fish, with black bass being among the worst. I understand large striped bass also accumulate mercury to levels high enough to where they shouldn't be eaten (and thus there's NO reason to keep 'em). I've also read that swordfish shouldn't be eaten period, even if you buy it in a supermarket.

Finally, I've learned that if you are persistent, you can find studies posted online that show the results of testing for mercury in specific waters like the Delta but I've only seen a few of these. What I have seen, though, has convinced me not to eat fish from the Delta, Central Valley, or Sierra foothills, except for stocked trout. The other thing that is not clear is just how much mercury from fish can be tolerated by your body -- it seems to me that nobody REALLY knows this, although advisory levels have been established. I put back all the fish I catch anyway, so I don't worry much about it.

[2short]

Sounds like compund interest for the large predatory fish. Everybody they eat already has mercury built up in them so they may reach eleveted levels faster. I think I saw something similar to this on "Killer Instinct" that show where the barefoot Ausi goes around catching snakes and other biting, stinging, constricting animals. He was collecting croc eggs for testing from various sites to help gauge the health of that paticular river system. I guess they test the eggs cause eggs don't bite off peoples arms. Chickens.
2short :P