Several variables--first, the time of year. If the survey is conducted in the fall, you'll see different size classes of fish compared to what you see in the spring.
The survey's job is to get enough fish from samples to judge the overall condition of the fishery. For example, if the majority of bass captured are in the 10-14" size class and relative weights are 80-90, and we see two size classes of bluegills such as 1-2" fish and some 5-6" fish, that tells us something. But, if we capture 5 different size classes of bluegills and five or six size classes of bass and they bass are 92-95 relative weight, that tells us something else. When I evaluate a fishery, I'm not as concerned about what we don't see as I am what we actually capture. We want to capture enough fish for statistical confidence and to judge ratios of each species and then compare all the data to draw conclusions.
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