Norm sort of put me "on the spot," as I really don't know much about invertebrates. However, I have a book, so I can find enough info to be dangerous.
I'd guess that the scuds that Norm mentioned as being available are probably Gammarus lacustris. The invert book I am reading says that they reach a maximum of 22 mm (nearly an inch), and they are "found in a wide variety of habitats over the northern half of the United States."
Earlier, Bill mentioned Gammarus fasciatus. My book says they reach a maximum of 14 mm, and are "common in the upper Mississippi drainage, the Great Lakes drainages, and the Atlantic coastal plain down to NC."
These appear to be the two mostly widely distributed scuds in the Gammarus genus. However, there also is a widely distributed scud known as Hyalella azteca. They only reach 8 mm, but are "widely distributed and common." So, I doubt that I could tell these from a small (young) Gammarus without a microscope and a book.
One of our local baitfish dealers, Mark Froning at Dakota Wholesale Bait (605-693-4422), said he gets quite a few of the scuds in his nets, but only in the spring. He said he could collect and sell them most easily at that time.
The problems with transporting fish and invertebrates outside their native range is probably an issue that should be considered, as indicated by Cecil. There are no easy answers to this dilemma, and sport fisheries biologists really struggle with the issue right now. Guess I'll let it go at that!!
Dave
