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<br />San Juan River Larval Razorback Sucker Survey <br />Fiscal Year 2001 Project Proposal <br /> <br />Principal Investigators: Steven P. Platania <br />Division of Fishes - Museum of Southwestern Biology <br />University of New Mexico <br />Albuquerque, NM 87131 <br />(50S) 277-6005 platania@unm.edu <br /> <br />and <br /> <br />Principal Investigators: David L. Propst <br />Conservation Services Program <br />New Mexico Department of Game and Fish <br />State Capitol, Villagra Bldg, P.O_ Box 25112 <br />Santa Fe, NM 87504 <br />(505) 827-9906 d,jJropst@state.nm.us <br /> <br />Backl:round: <br /> <br />In 1994, the first series of razorback sucker (n~672) were stocked in the San Juan River between Bluff, Utah <br />and the Hogback, New Mexico. Mean length and mass of those individuals, at the time of stocking, was about <br />400 mm TL and 710 g, respectively. In 1995, 13 of the recaptured razorback sucker were tuberculate males and <br />six of those individuals were ripe. Four recaptured 1995 razorback sucker were determined to be female but, <br />unlike the males, none were sexually mature. In their 1995 report of activities, Ryden and Pfeifer (1996) <br />suggested that the majority of the experimentally stocked San Juan River razorback sucker reached sexual <br />maturity in 1995-96 and that spawning of these individuals might begin in the next two years, <br /> <br />The UNM-NMGF larval fish drift study, whose primary focus was determining spawning period, identifying <br />approximate location of spawning sites, and assessing effects of annual hydrology (and temperature) on <br />Colorado pikeminnow reproductive activities, provided similar information for other members ofthe <br />ichthyofaunal community, At the November 1996 San Juan River Biology Committee integration meeting, it <br />was suggested that a portion of the larval fish drift study be expanded to allow for documentation of razorback <br />sucker spawning. However, because reproduction by razorback sucker (March-May) occurred considerably <br />earlier than Colorado pikeminnow (June-July), separate investigations of spawning periodicity and magnitude <br />were necessary for each species. <br /> <br />The most significant potential difference identified between the two studies, besides temporal differences in <br />spawning, was that we were attempting to provide the first documentation of reproduction by individuals <br />(razorback sucker) whose spawning potential had not been determined. Sampling for larval razorback sucker <br />was being conducted with no assurance that the stocked population of adult razorback sucker would spawn in <br />this system. Conversely, we knew from previous studies that Colorado pikeminnow reproduction had and was <br /> <br />13 <br />