9481 - Laserfiche WebLink

Home Browse Search

i ISSUE 1, 1989 CHANGES IN FISH COMMUNfI'IES FOLLOW~IG CONCRETE L[MNG OF THE COACHELLA CANAL 3 Table 1. Absolute Fish Numbers and Densities in the Lined Coachella Canal, California, November 1984. Species Samples (#) Observed 1/ Total No.lm2 Canal Section A (2,977m2) Channel catfish 405 - 2/ 405 0.136 95.5 Threadfin shad 18 - 18 0.006 4.2 Carp 1 - 1 Tr. 31 0.2 Subtotal 424 - 424 0.142 99.9 Canal Section B (8,064m2) Channel catfish 1,039 0 1,039 0.129 97.9 Threadfin shad 16 0 16 0.002 1.5 Carp 6 0 6 Tr. 0.6 Subtotal 1,061 0 1,061 0.132 100.0 Canal Section C (10,785m2) Channel catfish 230 30 260 0.033 96.8 Threadfin shad 3 0 3 Tr. 0.8 _ Red shiner 9 - 9 0.001 2.4 Subtotal 242 30 372 0.034 100.0 Canal Section D (19,647m2) Channel catfish 1,322 197 1,519 0.01' 46.0 Threadfin shad 0 2 2 Tr. 0.1 Carp 28 0 28 Tr. 1.8 Red shiner 32 - 32 Tr. 2.0 Largemouth bass 1 0 1 Tr. 0.1 Subtotal 1,383 199 1,582 O.OQk1 100.0 Entire Reach (41,473m2) Channel catfish 2,996 327 3,323 0.089 96.6 Threadfin shad 37 2 39 Tr. 1.1 Cep 35 0 35 Tr. 1.0 Red shiner 41 - 41 Tr. 1.2 Largemouth bass 1 0 1 Tr. Tr. Totals 3,110 329 3,439 0.069 99.9 1! =Observed counts following seining effort. 2/ =Not included in the analysis. 3/ Tr. =Less than 0.0005 fishlmz or 0.05 percent Although individual catfish exceeded 1.5 kg, mean weightlfish for the entire sample was 41 g. Upon analysis it was discovered that the subsample was biased toward larger fish (mean weight = 87 g), which made it impossible to project valid confidence inter- vals for a biomass estimate of fish remaining in the canal. However, it should be noted that the estimated portion contributed only 5.2% of the projected total biomass. The other four species encountered were rare, constituting only 3.3% of the overall population. Overall relative abundance of threadfin shad was 1.1%, with densities less than 0.0005 fishlm2. As with chan- nel catfish, abundance was slightly higher in Section A (4.2%) than in other sections (0.1 to 1.5%). Common carp represented 1.0% of the total collection. While numbers were relatively low, carp comprised 24.8% of total biomass {Table 2) and 40.4% of biomass in