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i , <br />4 JOURNAL OF 7'f-~ ARIZONA-NEVADA ACADEMY OF SCIENCE <br />VOL. 23 <br />Table 2. Absolute (g) and Relative Weights (%) of Fishes Collected in the Lined Coachella Canal, California, <br />November 1984. <br />Species Samples (g) Observed 1/ Total (g) g/m2 <br />(est. g) <br />Canal Section A (2,977m2) <br />Channel catfish 16,602 - 2/ 16,602 5.577 93.6 <br />Threadfin shad 443 - 443 0.149 2.5 <br />Carp 684 - 684 0.230 3.9 <br />Subtotal 17, 729 - 17, 729 5.956 100.0 <br /> Canal Section B (8,046m2) <br />Channel catfish 43,465 0 43,465 5.390 88.2 <br />Threadfin shad 258 0 258 0.032 0.5 <br />CazP 5, 533 0 5, 533 0.686 11.2 <br />Subtotal 49,255 0 49,255 6.108 99.9 <br />Canal Section C (10,785m2) <br />Channel catfish 17,033 1,250 18,283 1.695 99.7 <br />Threadfin shad 37 0 37 0.003 0.2 <br />Red shiner 20 0 20 0.002 0.1 <br />Subtotal 17,090 1,250 18,340 1.700 100.0 <br /> Canal Section D (19,647m2) <br />Channel catfish 47,701 8,206 55,907 2.846 58.5 <br />Threadfin shad 0 38 38 0.002 Tr. 3/ <br />Care 38,637 0 38,637 1.967 40.4 <br />Red shiner 128 0 128 0.007 0.1 <br />Largemouth bass 940 0 940 0.048 1.0 <br />Subtotal 87,406 8,244 95,650 4.869 100.0 <br />Entire Reach (41,473m2) <br />Channel catfish 124,801 9,456 134,257 3.237 74.1 <br />Threadfin shad 738 38 876 0.021 0.5 <br />C azP 44,854 0 44,854 1.082 24.8 <br />Red shiner 148 - 148 0.004 0.1 <br />Largemouth bass 940 0 940 0.023 0.5 <br />Totals 171,480 9,494 181,175 4.367 100.0 <br />1/ =Observed counts following seining effort <br />2/ =Not included in the analysis. <br />3/ = Tr. Less than 0.05 percent. <br />Section D. Individual weight averaged 1,381 g/fish. <br />Only one largemouth bass was collected, and a small <br />(3-4 cm) Tilapia sp. was observed but evaded capture. <br />DISCUSSION <br />One interesting aspect of canal operations is the <br />option of drainage. This feature provides biologists <br />the opportunity of approaching absolute measure- <br />ments of species composition, density, and biomass <br />of the fish community. In natural, flowing systems, <br />similar approaches aze virtually unheard of, and <br />prediction accuracy is dependent upon sample size <br />and sampling bias. Normally, estimates are associated <br />with high confidence intervals. These factors were <br />greatly reduced in this study. <br />