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DISCUSSION Razorback suckers We were unable to locate a concentration of adult razorback suckers in the lower Green River as result of this study. One adult was collected in related efforts 43 miles below the mouth of the San Rafael River on May 16, 1995. Prior to the subject study and in recent efforts since, incidental collections of razorback sucker have been reported from the area (Table 2). Most notably were the two collections of adult razorback in the mouth of the San Rafael; one on May 14, 1996 collected during ISMP monitoring and the other on May 7, 1997 collected in a fyke net while light trapping in the area. A razorback sucker population or contingent of a larger population persists in the lower Green River as evidenced by the sporadic collection of adults and the collection of larvae. The size of the larvae and the timing of their occurrence in the lower 1~~~ r ~Q Green indicates spawning occurs somewhere in the lower portion of the river (Mutht is our feeling that continued spring sampling with fyke nets in the mouth of the San Rafael will reveal more adult razorbac~C suckers. And it is likely that the fish are either spawning in the Green River in the imme$iate vicinity of the San Rafael or in the San Rafael itself. The current Basinwide Monitoring program is designed to narrow down the distribution of larval razorback suckers and when they occur. _. Water temperatures typically warm in the lower Green River prior to those in the middle and upper sections. During 1994, the river temperature at Green River, UT warmed to a consistent 14 C on April 12, while it took another month (May 14) for this to happen near Jensen, UT. In the fall, the water temperatures at both Jensen and Green River, UT. dropped below 14 C the first week of October. The water temperature in the San Rafael River warms quicker than the ^ ,~,! mainstem Green River, usually in early April. Thermal data for the San Rafael River is limited therefore specific dates could not be determined. ®~` . ?~' In 1995 winter storms continued until late May for most of the state of Utah. While the '~~" temperatures at Jensen reflect this weather pattern, the river temperatures at Green River did not. ~~~ ~ The 14 C threshold was reached on Apri123 at Green River, Ut, while similar warming did not ~` occur till June 26 at Jensen, Ut (refer to Figure 2). San Rafael warming was also delayed; water temperatures did not reach and maintain 14 C until sometime in late April or the first half of May. DRAFT 15