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<br />8 <br /> <br />Prairie Naturalist 26(1 ): March 1994 <br /> <br />and lower catches of northern redhorse, white suckers, and longnose suckers, in <br />1991 than in 1992. The flow of the Laramie River differed between the study years. <br />Mean_daily flows dwing the sampling months were substantially greater in May and <br />June 1991 (3.9 and 5.7 m3/second, respectively) than in 1992 (1.1 and 1.3 m3/ <br />second, respectively), but there was little difference in July and August (range = 1.2- <br />2.1 m3/second). It is likely that catch rates of common carp, channel catfish, and <br />smallmouth bass were enhanced by higher flows with associated greater turbidity <br />and current velocity or the ability of the fishes to migrate over water diversion dams <br />in 1991. Similar patterns of higher catches with greater flows have been described <br />for common carp and channel catfish in other streams (Mayhew 1973, Hubert and <br />Schmitt 1982). Reduced catch rates of northern redhorse with higher flows also <br />were observed by Hubert and Schmitt (1982) on the Mississippi River. <br />A seasonal pattern of hoop net catches, with highest catch rates in early <br />summer and a decline into late summer and fall, has been observed among several <br />studies (Smith and Hubert 1989, Gerhardt and Hubert 1989, Hubert and O'Shea <br />1991). Higher catch rates of common carp, channel catfish, and smallmouth bass <br />during early swnmer in the Laramie River likely were associated with spawning <br />activity. <br />The habitat in which hoop nets are placed can influence catch rates (Hubert <br />and Schmitt 1982, Holland and Peters 1992). There was little variation in habitat <br />among the eight study sites in the Laramie River with a couple of exceptions. Site <br />3 (Fig. 1) was at the upstream end of a pool fonned by a water diversion dam. Sites <br />4, 5, and 6 had slightly higher gradients and more rocky substrate than other sites. <br />Higher catch rates of smallmouth bass and longnose suckers at Sites 4, 5, and 6 may <br />be associated with these habitat features. <br />Mesh size has been related to catch efficiency and species selectivity of hoop <br />nets. Holland and Peters (1992) found increasing catch rates with decreasing mesh <br />size in the Platte River, Nebraska, and this relation has been supported by other <br />studies (Starrett and Bamickol 1955,Hesseetal. 1982). Hubert and Schmitt (1982) <br />observed higher catch rates in larger-mesh nets, but substantial species selectivity <br />was noted. Species selectivity of hoop nets with different mesh sizes also was noted <br />by Starrett and Bamickol (1955). Small-mesh hoop nets may be selective for fishes, <br />such as catfish, associated with instream cover (Starrett and Barnickol1955, Hubert <br />and Schmitt 1982, Holland and Peters 1992). Small mesh sizes may provide more <br />shade orreduction in current velocity to attract cover-oriented fishes. The two types <br />of hoop nets used in the Laramie River had identical mesh at the cod ends, but D nets <br />had smaller mesh (3.8 cm bar measure) than the round nets (5.0 cm) at the open end. <br />The D nets may have provided more shade or cover; however, the D nets seemed <br />to be selective only for northern redhorse, a schooling species not associated with <br />instream cover. <br />The catch rates for fishes in both types of hoop nets in the Laramie River <br />downstream from Grayrocks Dam (approximately 50 fish/lOO net-nights) was <br />about an order of magnitude less than in the Powder River and Crazy Woman Creek, <br />