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<br />was obtainable from \997 light-trap samples. In 1998, two larval razorback sucker were collected. These <br />specimens provide verification of spawning by the re-established population. <br /> <br />Studv Area: <br /> <br />The principal sampling area for this study will be the San Juan River between RM 128 and Mexican Hat (RM <br />53). We will attempt to makc one or more sampling foray in 2001 between Mexican Hat (RM 53) and the Clay <br />Hills boat landing (RM 2.9) just above Lake Powell in Utah. If conducted, this latter sampling effort would <br />include making collections in reaches of the San Juan River under the jurisdiction of the National Park Service. <br />Flow condition in 1999 were such that there were few low-velocity habitats avaiJable during the sampling <br />period. <br /> <br />Obiectives: <br /> <br />1. Determine the spawning periodicity of catostomids between mid-April-early June and examine potential <br />correlations with temperature and discharge. <br /> <br />2, Determine if reproduction by razorback suckcr occurred in the San Juan River (upstream of Mexican <br />Hat, UT) <br /> <br />3, Provide comparative analysis of the reproductive effort of eatostomids. <br /> <br />4. Attempt to validate presumed spawning period of San Juan River catostomids using data from the <br />razorback sucker and Colorado pikeminnow larval fish studies. <br /> <br />Methods: <br /> <br />Sampling for razorback sucker larvae will be conducted in the San Juan River between Four Comers (RM 128) <br />and Mexican Hat (RM 53) from mid-April through early June using sampling techniques that will provide <br />sufficient number of individual fish necessary to meet study objectives. Access to the river shall be acquired <br />through the use of either rafts or canoes. The tentative sampling schedule will be on a bi-weekly <br />(approximately) interval. <br /> <br />Sampling efforts for larval fish will be concentrated in low velocity habitats. Samples in those habitats will be <br />collected with small mesh seines and light-traps. Habitat type, length, maximum depth and substrate of the <br />habitat will be recorded. For seine samples, length and number of each seine haul will be determined. <br />Specimens will be preserved in the field for future laboratory processing. Catch per unit effort will be <br />determined as thc number of fish per m2 sample for seine samples and the number of fish per hour for <br />individuals collected in light-traps_ <br /> <br />Catch rate data and compared across and within sites by species. In addition, catch rate between and within <br />sites will be compared temporally (1997 & 1998 samples). Specimens will be distinguished and compared by <br />residence status (native versus non-native) and catch rate over-laid with the annual hydrograph. <br /> <br />15 <br />