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net and used a motor boat to scare or `drive' fish from inside the backwater toward the river channel, thereby ensnaring fish in the net (see Osmundson and Burnham, 1996 for more details). This procedure made netting an 'active' rather than a passive capture method. Three passes were made through the entire upper study area each spring. Two passes were made through the lower study area each spring. During each pass, we netted every backwater we suspected adult Colorado squawfish might use. In some portions of river, where backwater habitats were rare, both shorelines were electrofished with a 4.9-m, jon boat equipped with a Coffelt WP-15 (Coffelt Manufacturing, Flagstaff, Arizona) using pulsed DC current. Captured fish were scanned for a PIT tag, and tagged if one was not detected. PIT tags (Biomark, Inc., Boise, Idaho) were implanted in the body cavity using a hypodermic needle after fish were anesthetized with Tricane methanesulfonate. Each PIT tag had a unique, 10- digit, alpha-numeric code that was read with an electronic scanner and recorded in the field. PIT tags were inserted 2-5 mm posterior to the base of the left pelvic fin. Samples of five to eight scales were removed with forceps from between the lateral line and insertion of the dorsal fin. The scales were placed between wax paper and kept in labeled envelopes. Maximum total length (TL), as defined by Anderson and Gutreuter (1983), was measured and fish were released after recovery from the anesthetic. We supplemented our data with additional capture records obtained from various sources, including those from a pilot netting and PIT-tagging exercise we conducted in the upper reach during 1990. The Colorado Division of Wildlife contributed 1991 through 1995 capture records and some recapture data was provided by the Utah Division of Wildlife Resources (UDWR); both agencies conduct annual electrofishing surveys of the river. U. S. Fish and Wildlife Service (FWS) capture records from a 1994-1996 survey of the lower 3.5 km of the Gunnison River (Burdick 1996), and from a 1995-1996 survey of flooded ponds near RK 262, were used. Length frequency data collected by FWS in 1982 were also utilized. Calculation of Growth The standard approach used in describing ages of fish is not intuitive. When the length of a fish at age 1 is reported, age 1 is not its first birthday'(or hatchday) as one would expect but rather its first winter, i.e., the time when growth slows down or stops for the year and closely packed circuli are laid down. In the Northern Hemisphere, the convention is to standardize all birthdates as January 1 (Jearld 1983). A fish captured between its first and second winter period is described as being age 1+, implying that it is greater than one year old when in fact it may not have reached its first real birthday. Because we used measurements of fish rather than back-calculated estimates of length, we deviated from this convention and attempted to describe the length of Colorado squawfish at their approximate summer birth date. A-4