I'm pursuing a biology degree at the moment. From most of what I see by example, and hear from my teachers, the actual number of organisms removed completely from a system is the primary concern when researching the general health of a given system. This is of course not the only aspect of a system that should be researched, especially when looking at a controversial issue such as survival rates of released fish, but in general, the amount of fish entering a system vs. the amount that actually spawn vs. the amount that leave are considered the most important aspects when looking at the health of the system. Because of all of this, the researchers involved here are probably focusing on the C&K areas, because they want to get numbers on how many fish are killed for sure. I don't nescesarily agree that this is the best way to perform the survey, but it's a good first step, and each individual researcher is at will to choose which aspects of the run he or she thinks the most important to its continued survival.

david