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I rl rl rl fI II I fI I [I fl fl... . t :1 II i, :1 ~I 'I I Table 1.2. Standing crop estimates of common fish species based on IS-minute visual surveys (n = 25) on the Colorado River channel between Davis Dam and Lake Havasu during August 2000. Species Number Percent Weight (g) Fish/ha Kg/ha Common carp 1,222 56.3 1,824 36.2 66.0 Striped bass 516 23.8 677 15.3 10.4 Channel catfish 77 3.5 1,002 2.3 2.3 Black bass 47 2.1 716 1.4 1.0 F1annelmouth sucker 290 13.4 1,000 8.6 8.6 Razorback sucker 3 0.1 190 0.06 0.08 Others 17 0.8 1,000 0.5 0.5 Totals 2,172 100.0 64.4 88.8 Fish densities averaged 64.4 fish/ha and 88.8 kg/ha based on average weights of fish collected by trammel net. Relative abundance decreased with distance downstream as habitat diversity decreased. This approach appeared best suited for large fish and estimates were undoubtedly conservative since small, cover-oriented fish or those at depths >4 m were difficult or impossible to see. These surveys also excluded more productive backwaters where sampling suggested the majority of fish were found. Light Trapping 2000 Effort In 2000,24 overnight samples were collected between 21 February and 10 May for a total of384 trap hours of effort (Table 1.3). Sampling during the months of February and March precluded spawning of other fish species. Four flannelmouth sucker larvae were c.ollected, all from the Laughlin Lagoon area and two razorback sucker larvae were collected from Park Moabi. Table 1.3. Summary of the location, effort, number, and species taken in the 2000 larval light trap effort. Location # of sets Effort (h) RZB FMS Cyprinids Centrarchids Laughlin Lagoon 8 128 0 4 3,304 38 Boy Scout Camp 6 96 0 0 250 4 Park Moabi 6 96 2 0 0 0 Topock Bay 1 16 0 0 0 0 Pulpit Rock 3 48 0 0 0 0 24 384 2 6 3,554 42 6