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<br />o <br />C) <br />l'~ <br /> <br />~....1. <br /> <br />r-.:, <br />Ci) <br /> <br />Fish species common in summer collections were also common in autumn <br />collections, Plains killifish and western mosquitofish were generally more common in <br />autumn lhan summer collections. Between 1993 and 1995 total autumn abundance of <br />fishes (Reaches combined) did not change appreciably. Total abundance in 1996 (a low <br />spring runoff and summer flow year) was substantially less than in preceding years, In <br />1997, total abundance was the lowesl of the study. From 1993 through 1996, Shannon- <br />Wiener Diversity declined bul increased in 1997 to the second-highest value of the study. <br />Tolal abundance of fishes in Reach 5 peaked in 1993 and 1996 and was lowest in 1997, <br />Between 1993 and 1995, Shannon-Wiener Diversity changed little, declince in 1996, and <br />was highesl in 1997. Red shiner was the most abundanl species in autumn collections in <br />Reach 5 in all years, except 1997 (high spring runoff and summer flows) when speckled <br />dace was mosl abundant. Falhead minnow and specked dace were usually the second- or <br />third-most common species. FIannelmouth sucker and bluehead sucker were rare in <br />1996, a low spring runoff and summer flow year. Colorado pikeminnow, likely stocked <br />individuals, was the third-most common species in Reach 5 secondary channels in 1997. <br />Roundtail chub was found only in 1997. No attribute of summer discharge was <br />significantly related 10 any commonly-collected species, exceptlhe positive relationship <br />between autumn abundance ofweslem mosquilOfish and days discharge < 500 cfs, <br />Attributes indicalive of low summer flow were negatively related 10 aulumn abundance <br />of native species. Mean summer discharge was negatively related 10 red shiner <br />abundance. Between 1993 and 1996, total abundance of fishes in Reach 4 declined <br />slightly, bul abundance in 1997 was considerably less than in preceding years. Shannon- <br />Wiener Diversity changed little from 1993 through 1996 and increased slightly in 1997, <br />Red shiner was the most abundant species in all years and fathead minnow or speckled <br />dace were second-most abundant in all years. Neilher flannelmouth sucker nor bluehead <br />sucker was common during autumn in Reach 4 secondary channels and bluehead sucker <br />was absent in 1996, Colorado pikeminnow and roundtail chub were found in Reach 4 <br />secondary channels in 1997, but not in preceding years. Elevated summer flows were <br />negalively correlated with summer abundance of nonnalive red shiner, fathead minnow, <br />channel catfish (significantly) and western mosquilofish; fathead minnow abundance was <br />significanlly, and positively, related 10 days summer discharge < 500 cfs. Autumn <br />abundance of native flannel mouth sucker, bluehead sucker, and speckled dace were <br />negatively, but not significantly, related to days summer discharge < 500 cfs. Total <br />abundance of fishes in Reach 3 peaked in 1995 and was leasl in 1997. ShannOn-Wiener <br />Diversity declined from 1993 through 1996, but increased in 1997. Red shiner was <br />always the mosl abundanl species in Reach 3 and fathead minnow or speckled dace were <br />always second- or third-mosl common, except in 1993 when channel catfish was third- <br />most common. Flannelmouth sucker was uncommon in all years and bluehead sucker <br />was absenl in 1993. Colorado pikeminnow and roundtail chub were found in 1997. No <br />attribute of summer discharge was significantly related to autumn abundance of any <br />commonly collected species. Speckled dace abundance was negatively related to days <br />discharge < 500 cfs. <br /> <br />In most years (1993 through 1997), summer abundance of fishes was usually <br />greater in summer than aulumn; in Reaches 5 and 4 differences were substantial. <br />Between summer and autumn (years combined) abundance differences were lypically <br /> <br />III <br />