I'm hoping someone can help me with a question regarding the Clinostomum parasite. When I stocked HBG in march of 2009, I also put in 25 male BG, of a considerably larger size, that I transferred over from another pond. There were no visible signs of parasite infestation in the native BG, or the smaller HBG. During my limited ice fishing forays this winter, I caught 3 native BG that were absolutely covered with yellow grubs. I'm aware of the bird, snail, fish, lifecycle of Clinostomum, so I know how they got in the pond, and my fish, I just don't understand why only the BG were so infested? There's approx. 500 HBG, compared to 25 native BG in that pond. I've only caught 8 Hybrids total since the initial stocking that had any visible parasites. And even then there were just a couple grubs per fish. Nothing like the native BG, their fins, tails, and gills were full, worst cases I have ever seen. My question is this: When the cercaria leaves the snail to find a fish host, what determines a suitable candidate? Is it the first fish that comes along, or are there factors at work that may tend to make certain fish more susceptible?
My guess is the regular bluegills are using a slightly different habitat than the hybrids and therefore are more susceptible, i.e. they are closer to the bottom in shallower water near the snails and the hybrids are more suspended out away from the snails feeding on perhaps pellets if you feed your fish.
The reason I say this is when the free swimming cercariae leave the snail, they only live for a very short period of time, and may not live long enough to penetrate fish farther out away from the snails.
Although the cycle may be the same, are you sure these are Clinostomum? I was under the assumption that they were muscle and fin borers vs. clinging to gills. There are parasites that can be mistaken for others. Or maybe I misunderstood?
Some parasites infect directly by ingestion of the snail and arthropods, and if this is one of them, your bluegills may be selecting snails(yes bluegills do eat snails), or certain arthropods while the hybrids are feeding on something else exclusively -- like pellets.
