Laserfiche WebLink
<br />1 <br />in the Green River, Utah and Colorado. In particular, Basinwide sampling was sufficient to <br />detect adults and larvae in many locations that were scattered throughout the Green River Basin. <br />Basinwide sampling also contributed information on the distribution and status of razorback <br />suckers stocked into the Green River since 1995. However, data collected under the Basinwide <br />sampling was too sparse to allow for more rigorous population level analysis and estimation of <br />vital population statistics such as adult population size, and recruitment and survival rates. Such <br />analyses were possible only when Basinwide sampling data were combined with data collected in <br />spring 1998 and 1999 when fish for brood stock development were captured. <br />Middle Green River adult population analyses, 1980-1999.-Negligible change in TL of <br /> <br />1 <br /> <br />1 <br /> <br /> <br /> <br /> <br />razorback suckers in the middle Green River, based on recaptures ofPIT-tagged fish since 1990, <br />mirrors the findings of other investigators for this and other populations of this species (Minckley <br />1983, Tyus 1987, Modde et al. 1996). With the exception of 1994 and 1995, the bulk of the <br />middle Green razorback sucker population since the early 1980's was composed of individuals <br />460 to 560 mm TL and most of those were 480 to 520 mm TL. Given the slow growth of these <br />fish, the likelihood of a fish growing out of a mode represented by a 20 mm-wide size increment <br />on a length-fi~equency histogram is very small. Modde et al. (1996) suggested that recruitment <br />was occurring during there study when length frequency histograms were stable and few <br />relatively small fish were noted from 1980 to 1992. Recruitment was either low ornon-existent <br />after 1992 when the razorback sucker population declined in spite of the presence of small fish in <br />the 1993 to 19951ength-frequency histogram. This suggested that length frequency histograms <br />be interpreted cautiously when making inferences about recruitment or mortality rates and in <br />conjunction with other data, as was done by Modde et al. (1996). <br />22 <br /> <br />