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Old 11-11-2011, 09:27 AM
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stoneflynut stoneflynut is offline
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Population estimates: If you mark X number of fish and anglers catch Y numbers of marked fish, it provides a ratio that can be applied to estimate the entire population size.

Growth rates: When fish are marked, their length and weight are recorded. Each time they are recaptured, you then have a time interval and a new set of measurements that tell biologists how fast the fish is growing.

Year class success: Marked fish allow biologists to follow individuals over time and determine how well that cohort has performed throughout its lifetime. This works particularly well when stocking, say, fingerlings. It can be used to gauge a particular strain of rainbows; the productivity of a certain water; depletion rates that help determine how frequently a water should be restocked.

And, yes, movement of marked individuals. Past studies have shown that Lees Ferry trout do not move downstream with any significant frequency. Recruitment of trout within the system (Colorado River) is known to be localized and not dominated by large in-stream migrations.

Asking other questions during the interview: Biologist often design interviews to gauge an anglers satisfaction with their experience. Such questions as 1) How many fish did you catch today? 2) How satisfied were you with your catch? 3) How would you rate the quality of your overall experience today? 4) Would you rather catch more smaller fish or fewer larger fish? Yes, that is an often asked question of anglers because it tells the managers how to best manage the fishery to attain the highest angler satisfaction. Some fisheries are more family oriented and best managed for a higher catch rate to satisfy the younger anglers and provide a meal back in the campground. Best to stock higher numbers of smaller fish in that fishery. Kids have more fun catching 4, 10" trout than one 14" trout. But as anglers gain more experience, they start to look for that "memorable fish." That term is actually used in fisheries management to refer to a fish the angler will want to photograph and will remember for many years. Lees Ferry is, once again, starting to produce 20" 'bows. Those are memorable but it takes a lot of protein to grow one. Bag limits can be used to reduce competition among smaller fish and allow more individuals to pass through a possible "bottle neck" that inhibits their growth to the memorable category.

Every fish population has a limiting factor in its environment that prevents the population from growing larger or individuals from growing larger. A carefully designed bag limit or size limit or slot limit can help create the kind of fishery anglers have said they want. By asking as many questions as an agency can afford to collect (creel surveys, data analysis, report writing all take time and money), they can help move a fishery toward what the anglers have said they want at any particular fishery.

Fisheries management is a complex set of variables confounded by the vagaries of weather and the environment. Most certainly I've missed some here, but hopefully you get the idea. When I'm interviewed by a creel clerk, I always do my best to accurately report my information and experience.

Last edited by stoneflynut; 11-11-2011 at 09:31 AM.
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