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<br />e e <br />Possible Causes for Decline of Squawfish <br /> <br />8 <br /> <br />It must be assumed that the reduction in size, numbers, and <br /> <br />distribution of the Colorado squawfish is due to man's influence <br />upon its environment. Further, almost anything that m~n does to the <br />river will have an effect. The cumulative effect of man's intrusions <br /> <br />have obviously been negative. Have we done anything positive? Possibly <br />so (Walker Wildlife Area), but most likely anything we do from now <br /> <br />on will add another increment to the continued demise of this <br /> <br />species. <br /> <br />Possible causes of decline: <br /> <br />I. Stream Alteration <br /> <br />A. Dams <br /> <br />1. Reservoirs not suitable for successful reproduction <br />2. Flow patterns <br />a. more stable on an annual basis <br />b. less stable on a daily basis <br />3. Temperature <br />a. cooler summers <br />b. warmer winters <br />4. Turbidity reduced downstream <br /> <br />B. Irrigation <br /> <br />1. Increased leaching of soil <br />2. Return of fertilizers, pesticides, etc. <br /> <br />C. Dewatering (reservoir evaporation, irrigation, industry, human <br />consumption etc.) <br /> <br />1. Reduced flow <br />a. volume <br />b. velocity <br />c. concentrates salinity and other dissolved solids <br />2. Lowers wat~r level = reduced habitat <br />esp. backwaters (young) <br /> <br />D. Channelization <br />1. Eliminates slow moving backwaters and pools <br />2. Alters species composition <br />3. Destabilizes substrate <br />4. Descreases invertebrate biomass <br />5. Increases flooding and destroys vegetation cover <br />