Are Hatchery Fish Healthy?

October 16, 2008

Question: I have been fishing the Owens River Gorge for the last 23 years and the fishing recently has been great, but the fish were full of parasites! I know that area was recently stocked and I can’t help but feel they stocked it with infected fish. In the more than 23 years I have been camping and fishing the lakes and streams in Bishop, I have never encountered that type of problem. What is going on here? Thanks. (Marie E.)

Answer:This is a common question asked by anglers. According to Dr. William Cox, Department of Fish and Game (DFG) Program Manager for Fish Production and Distribution, it is also common to think that the problem comes from the hatcheries, which it does not. Hatchery fish are fed a pasteurized diet which eliminates infective stages of metazoan (worm) parasites. None of our hatchery fish have worms. DFG pathologists do many examinations of our hatchery fish prior to planting to ensure that we are not planting diseased fish and worms are never found.

When a clean hatchery fish enters natural waters they can become infected with parasites existing in that water and usually the source is wild fish residing there. Also, as fish density increases, so does the likelihood that parasites will become a problem. Ironically, as the fishing gets better and better because of more fish, so does the possibility of wormy fish.

DFG values input from anglers which gives us good information on the status of our fish and fishery. We are happy to examine anglers’ catches for worms or other parasites or diseases. Please contact Dr. Mark Adkison at (916) 358-2830, for more information.

For those fish you’ve caught,