stocking rainbow trout in private lakes
Our homeowners' association manages a 50 acre lake in Keizer that was formerly a gravel quarry. Depth varies from around 10' to 80' or more. Largemouth bass, crappie or bluegill, northern pikeminnow, and possibly chub have been found in the lake as well as some large carp and koi. We don't know how these species were introduced to the lake, but it may have been by flooding in the 1960s. It has been stocked with rainbow trout 2 or 3 times in the past10-15 years, but that population seems to be small, now. Homeowners want to re-stock rainbow trout large enough that winter resident cormorants won't be inclined to take them. We are seeking sound information about how to manage this fishery for the benefit of homeowners who like to fish with our desire to maintain a healthy lake ecosystem, waterfowl, good water quality, and other human recreation such as boating. I don't have much information about the biota of the lake; I don't know what trout food sources there may be or how many trout our lake can support. How can we get reliable information to make informed decisions about stocking our lake with trout?
I am not surprised by the diverse aquatic biota you describe for your pond. Most large ponds in the Valley would have 2 or more exotic species in them. Normally people would have stocked them for recreational fishing purposes or God knows why. Flooding tends to be the mechanism that helps them spread from one pond to others in the vicinity (and now they are all over the Valley). They all have very negative effects on the populations of our native fish. Hence, we don't recommend stocking them. Your interest in using rainbow trout is understandable, and I think that can be done with relatively low negative side effects on the native populations provided you use local stocks. That is the question perhaps. Where will your trout come from. My understanding is that Oregon has a number of approved trout breeders that people can buy fish from for pond stocking purposes. However, I suspect these breeders only have some genetic lines and in most cases they will not be representative of what is present in the many watersheds with have in the State. Therefore, by introducing some "domesticated" rainbow trout genetic lines in ponds all over the map, we may be affecting the long term viability and health of wild trout populations in our rivers. It is just for you to know because that (in addition to the competition and predation associated with the exotic species I mentioned earlier) would be one of the negative effects of releasing fish reared in captivity for generations into the wild. Hopefully your pond is well isolated and does not get flooded every year. I would also inquire about the possible use of triploid sterile trout, which would not reproduce naturally so they don't present the same threat to gene pools of wild stocks.
My advise to you would be to contact a person who is a great resources for pond owners in the Valley. His name is Brian Bangs and he is the biologist in charge of the Native Fish Investigations for Oregon Dept. of Fish and Wildlife. Phone: 541-757-4263 ext. 224. Cell: 541-908-1538 and email: Brian.Bangs@oregonstate.edu
Please let me know whether Brian can help you or not and if you have further questions by writing directly to firstname.lastname@example.org
Thank you for your response, Guillermo. I think that our small lake is very unlikely to ever flood over its current high banks, so the spreading of domesticated trout is probably not an issue. I will try to contact Brian Bangs for further advice.