Laserfiche WebLink
<br />16 <br /> <br />Multiple linear regression was used to examine relationships <br />between flow/ thermal regimes and mean annual CPUE and total <br />length. Although a positive correlation (r=0.69) was found <br />between catch rates on the Colorado River and average flow during <br />the growing season, none of the relationships approached a <br />significant level due to high variability associated with a small <br />sample size. These analyses reiterate the need for continued <br />research and to incorporate similar data collected prior to the <br />inception of the ISMP to bolster these relationships. <br /> <br />The most common other fish species collected during sampling <br />was the red shiner (Appendix V). Riverine habitat conditions <br />that were conducive to increased squawfish production were also <br />apparently better for production of exotic species such as red <br />shiners and fathead minnows, as they also increased in 1988. <br />Other species commonly encountered included sand shiners, channel <br />catfish, and bluehead and flannelmouth suckers. <br /> <br />DISCUSSION <br /> <br />One of the most significant findings of the first 5 years of <br />ISMP sampling has been the increasing catch rates of late <br />juvenile and adult squawfish. In 1989 and 1990, the catch rates <br />of squawfish in the lower Green River increased dramatically. <br />When taking into account physical conditions and concurrent <br />results from other locations in the basin during those two years, <br />it appears that there was a real shift in the population <br />structure and not an artifact of sampling technique. Length <br />frequency histograms indicate recruitment on a scale <br />unprecedented in recent years. There is a need to continue to <br />track this population and glean as much life history (through the <br />PIT tagging program) and ecological (through the initiation of <br />feeding preference studies and age and growth research) <br />information as possible. <br /> <br />Young of the year sampling in 1988 revealed extremely high <br />(relative to the other four years) concentrations of squawfish <br />throughout the Green River. However, in 1990 our catch rates had <br />dropped to a record ISMP low on he lower Green River. The point <br />to be made is that from a biological and hydrological standpoint <br />we are monitoring a highly variable system, reiterating the need <br />for continued effort. While several relationships appear to <br />affect production of young squawfish in the Upper Basin, <br />monitoring should be continued to enable statistical comparisons <br />of data. <br /> <br />There is also a need to accurately determine ages of late <br />juvenile squawfish captured on the Green River. Although McKay <br />and Hawkins (1990) found that juveniles in the 1989 sample were <br />from the 1986 cohort, it is important to exclude the possib1ity <br />of recent increases in squawfish in the lower Green River being <br />