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Last modified
7/14/2009 5:01:47 PM
Creation date
5/22/2009 6:27:11 PM
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UCREFRP
UCREFRP Catalog Number
9481
Author
Mueller, G., G. Bryant and T. Burke
Title
Changes in Fish Communities Following Concrete Lining of the Coachella Canal, Southeastern California
USFW Year
1989
USFW - Doc Type
Journal of the Arizona-Nevada Academy of Science
Copyright Material
YES
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a <br />ISSUE 1, 1989 CHANGES ^V FISH COMMUNITIES FOLLOWING CONCRETE LINING OF THE COACHELLA CANAL <br />Information collected in 1980 (Minckley et al. 1983), <br />prior to lining the first 78 km of the Coachella Canal <br />(Reach I), allows for a comparison offish communities <br />on a pre- versus post-project basis. Additional infor- <br />mation, available from studies made during the same <br />dewaterings in 1980 and 1984 but conducted 100 km <br />further downstream (Reach II) (Beaty et al. 1981, <br />Beaty 1984), provide somewhat of an experimental <br />control (Table 3). <br />Comparisons of fish diversity (number of species), <br />density (fishlm2), and biomass (grams/m2, Table 4) <br />demonstrate that, in nearly all instances, values for the <br />lined canal are lower than those in earthen sections. <br />The only exception was a slight increase in fish den- <br />sity (8.9%) when compared to Beaty's 1984 data. Even <br />with that increase, overall biomass dropped more than <br />30%. The data suggest that concrete lining led to <br />changes in species diversities of -14.3 to -62.5%, den- <br />Table 3. Comparison of the Relative Abundance (%) of Major Fishes Taken from Lined and Unlined Sections <br />of the Coachella Canal. <br /> Reach I <br />Pre-lining <br />1980 <br />(Minckley et al. <br />1983) <br />Post-lining <br />1984 <br />1980 <br />(Beaty et al. Reach II <br />1984 <br />1981) (Beaty 1984) <br />Channel catfish 78.8 96.6 83.3 86.1 <br />Threadfin shad 0.2 1.1 0.3 0.0 <br />C~'p 1.0 1.0 0.3 4.9 1! <br />Red shiner 11.5 1.2 0.0 2/ 1.2 <br />Largemouth bass 2.6 Tr. 31 2.2 1.9 <br />Sunfish 5.1 0.0 1.1 3.5 <br />Flathead catfish 0.9 0.0 1.1 2.4 <br />Tilapia 0.0 Tr. 11.2 0.0 <br />Black crappie 0.0 0.0 Tr. 0,0 <br />Striped bass 0.0 0.0 0.0 0.1 <br />Total 3,527 3,439 4,714 1,092 <br />fishlm2 0.229 0.089 0.147 0.034 <br />g/m2 49,369 4.367 12.035 6.245 <br />1/ =sample included five experimental grass carp (Ctenopharyngodon idellus) <br />2/ =not included in analysis. <br />3/ = Tr. less than 0.05 percent. <br />sities of +8.9 to -83.8%, and biomass of -30.1 to <br />-92.2%. <br />These declines undoubtedly reflect corresponding <br />reductions in the type and diversity of aquatic habitat. <br />As predicted by Minckley et al. (1983), fishes adapted <br />for swiftly flowing water continued to maintain rela- <br />tively high populations. Conversely, those fishes <br />dependent upon cover and more lentic conditions were <br />signficantly reduced or eliminated. For example, <br />largemouth bass, other centrarchids, and flathead cat- <br />fish (Pylodictis olivaris) contributed 7.9 to 15.6% to the <br />earthen canal's total community. In the lined canal a <br />single largemouth bass was the only fish to represent <br />that group (0.035%). <br />Changes in relative abundance were less obvious. <br />Channel catfish remained the dominant species. <br />Catfish in the earthen section represented 78.8 to 86.1% <br />of the total catch compared to %.6% for the lined canal. <br />Although the earthen canal enjoyed a greater degree <br />of species diversity, the majority of species contributed <br />a small portion of the overall community. <br />While the above comparisons assume that Reach II <br />data provide an experimental control, it must be <br />recognized that the relatively low values for 1984 could <br />also be the impact of either the upstream, lined section <br />of the canal, or of maintenance activities. Regardless, <br />trends in either case (i.e., valid or invalid 1984 control) <br />suggest decreases in diversity density, and biomass <br />after lining. <br />The first, 78-km, lined section of the Coachella <br />Canal represents a relatively short section compared <br />to the entire canal system in southern California. <br />
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