GHi Cecil. I'm not an expert on the Gammarus, but I'll pass on a few comments.
We do find a lot of the Gammarus in the wetlands up here (SD, ND, and MN). The more fish in a wetland, the fewer the Gammarus.
In our fishing lakes, they do persist with sport fish populations, but not nearly in the same numbers as in the smaller wetlands. However, our food habits studies with yellow perch certainly showed that the perch will find and eat the scuds!!
In sport fishing lakes, I'd say the most scuds (Gammarus) that I see are in the lakes with some submergent (rooted) aquatic plants. I suspect the plants provide some refuge from predation, and that keeps the scuds at a more moderate level. Lakes with a 15 or 20% vegetation band have more scuds than the lakes with 0% vegetation (lakes that tend to be more shallow, windswept, and/or have lots of common carp).
I'd say that in a pond with submergent vegetation, scuds would be a good supplemental food source, although they wouldn't support panfish by themselves. I'm sure that small bass, bluegills, and yellow perch would love them (hopefully not so much that they disappear from the pond).
I have never specifically stocked them into a pond without them, and then tracked it to see what happens. Which, of course, makes me wonder right now why I didn't do so!! :-)
Dave
