Gone Fishin’: Parasites are bugging area fish | SierraSun.com

Gone Fishin’: Parasites are bugging area fish

Each year questions arise on the appearance of the fish that some are catching in our local waters.

Most people fishing our local lakes have been reporting that the trout that they are catching have sores on them. This is not uncommon this time of year. The sores are caused by copepod parasites.

Typically there are two types that infect the trout population: they are Salmincola or Lernea parasites (also known as anchorworms). These external parasites cause the sores that show up on the skin of the trout that many are catching this time of year.

As I mentioned before, this happens each year. The primary cause is the water temperature. When water temperatures rise trout tend to be under stress. Most diseases such as these are related to low levels of dissolved oxygen, extremes in water temperature and crowding. Under stress the trout’s resistance to disease drops and disease organisms can establish themselves. This disease can be transmitted from fish to fish through heredity or by passage of the disease through the water, by nearness to a carrier animal or by the ingestion of an infected fish, snail, copepod, or other animal.

With low water levels in our local reservoirs so low, the likelihood of such an outbreak is always common. This year, the water levels are typically lower than they were last year at this time and that probably means that more fish will most likely be infected.

The California Department of Fish and Game (DFG) recently had an outbreak of these parasites in the trout and salmon populations in Lake Berryessa which were most likely caused by a combination of environmental and biological factors. As in our waters, water quality and fish densities have most likely contributed to the increase in parasite levels.

There is almost no effective method for treating fish and controlling the spread of these two parasites in lake dwelling fish. Reducing the number of rainbow trout planted or replacing them with brook trout and brown trout are options that the DFG may consider. Brook and brown trout are apparently more resistant to these parasites. While these fish are extremely bad looking, with proper cooking their consumption does not pose a human health risk according to the DFG.

However, most everyone that I talk to would not take one of these fish home and eat it. I would have to agree, even with the assurances, the fish just have an appearance that would suggest that there is something wrong with it. My motto would be “better safe than sorry” when it comes to eating fish with these parasites.

Typically, these parasites will drop off and the sores will heal as the water temperature cools and we get into our fall season. The fish caught late in the fall are typically well-conditioned and free of these parasites.

Hey, this is a great time to practice your catch and release technique!


Boca – (8,130 ac. ft.) Boca has been fishing fair and is very low. Water is being released at 127 CFS and 121 CFS is coming into the lake. In spite of the low water levels anglers are still having success. Anglers near the dam are still catching fish. Most anglers use nightcrawlers or Powerbait. Boats that can still be launched are having some success. Most were using a combination of flashers and a nightcrawler or minnow imitating lure. Kokanee fishing is fair to good for those experienced anglers that can get a boat in the water. Fly fishermen near the inlet have experienced fair to good action early and late. Nymphs and streamers have accounted for most of the fish caught recently. When it calms down, midges are very productive.

Donner Lake – Fishing has been fair to good. Anglers fishing for rainbows on the west end and near the launch ramp have had fair to good success. Nightcrawlers and Powerbait seem to be the main bait. Trollers using minnow imitating lures have had fair success.

Lake Tahoe – (Elevation 6224.83) Fishing has been good for mackinaw. Most fish are in the 5- to 7-pound range. A guide is highly recommended if you are fishing for mackinaw for the first time. Toplining and shore fishing is fair overall. No fishing is also allowed within 300 ft. of these tributaries.

Martis Lake – (Martis is restricted to artificial lures with barbless hooks. Zero fish may be bagged or possessed) Fishing has been fair. Most activity has been early and late with blood midges and callibaetis imitations. Most anglers are using nymphs such as the Hares Ear, Pheasant Tail, Damselfly imitations or the A.P. Streamers that imitate small fish, and woolly buggers are also good choices. For surface activity, patterns such as the Quigley Cripple, Martis Midge, Parachute Adams, and Griffith’s Knat are good choices.

Little Truckee River – (This area between Stampede Reservoir downstream to Boca Reservoir is now subject to artificial barbless lures with a two fish bag limit of fish 14 inches maximum) – (121 cubic feet per second) Fishing here has been fair in the stretch between Stampede and Boca. Fishing has been fair near the inlet area of the Little Truckee into Boca reservoir. This area changes almost daily. Nymphs and streamers are still the first choice if there are no fish on the surface.

Prosser – (8,583 ac. ft.) Prosser has been fishing fair. Fishing here is mostly with nightcrawlers or Powerbait. Fly fishermen near the inlets have taken a few fish mostly on nymphs and streamers.

Stampede – (162,412 ac. ft.) Stampede is fair. Most use the typical baits, nightcrawlers or Powerbait. Topliners have fair to good success for kokanee salmon. Most use a flasher of some sort and a kokanee bug or wedding ring with a piece of white corn. Kokanee should start to tightly school soon in anticipation of spawning. There is still good trout action, mostly subsurface, with nymphs such as the pheasant tail and the bird’s nest. There is some good surface activity early and late as well. Streamers are also working.

Truckee River – The release from the dam at Tahoe City is 383 cubic feet per second and near Truckee it is running at 382 cubic feet per second. Fishing has been fair throughout the river. Seasoned anglers have been doing well. Prince nymphs, Bird’s nests and pheasant tail nymphs have produced some fish as well as streamers. Dries include a parachute Adams, Quigley Cripples and an E/C Caddis. The key is to go small this time of year. Also hoppers during the day can still work.

Other Waters – Jackson Meadows has been fishing well. Davis and Frenchman lakes have improved this past week. Cooler nighttime temperatures are beginning to put fish on the bite. Great fall fishing is just around the corner.

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