Amazing results in that study, jpsdad
Further, I believe all of the state biologists hate the invasion of zebra mussels in our large reservoirs. Now that is has been well over a decade in many locations, I wonder what their fish population surveys are showing as the response? I suspect their professional journal publications may have some interesting articles.
Regarding, the RES. I am sure they were consuming mussels when mussels were small enough. They reach a size however, that are too large for RES to consume. In the later years, I suspect that fewer and fewer mussels were being recruited each year due to competition for food by the large standing weight of mussels. Catchscratch, to what extent mussels provided food for the RES? I don't know. It seems plausible that RES faired better in ponds without mussels ... IF ... snails were more abundant when mussels were absent. I'll not venture a guess.
FishingRod, I think it seems very intuitional that before Swingle performed his study, many would have bet that results would have been the opposite. Seems to make sense that supporting a large standing weight of mussels would remove energy from the food web available to fish. And yet there appeared to a be a benefit. This benefit may have been what Swingle suggested, OR, it may be multifaceted. For example, their presence may benefit periphyton production. Their presence on the bottom, does increase bottom surface area and provide substrate for periphyton and habitat for organisms. I don't know. Also, if the water is clearer, it may reduce foraging energy expenditures making foraging more efficient for fish. I don't know. But this much I can say, I have yet to find any study documenting that native mussels are detrimental to fish. So I posted Swingle's findings so that people may not be discouraged by their presence in their ponds. The biggest problem is the potential for cutting the feet of barefoot swimmers, IMHO. One species, is called the heel splitter, I presume because its shells have been documented to split heels.
Regarding invasive mussels, they are impacting food webs and restructuring them. Such an effect is called a trophic cascade. In the end, the effect for fish standing weights may be positive. This seems to be the case for Lake Erie. But just keep in mind that trophic cascades reshape the community and that in this reshaping there are winners and losers. Some losers could be extirpated if they are not able to adapt. There will always be costs to some and benefits to others. The same is true of introducing native mussels to your pond. The food web will be different with them than without them. But the energy available for retention in stocked fish combinations does not appear to be negatively impacted by the presence of native mussels. In Swingles study, there was a 46% increase in fish standing weights associated with their presence.
