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20001 XYRAUCHEN TEXANUS IN LAKE MOHAVE 185 <br />TABLE 2. Monthly tracking summaries for sonic telemetry of 10 wild adult Xyrauchen texanus in Lake Mohave, Ari- <br />zona and Nevada, from November 1994 to July 1997. The average monthly distance traveled is an average of individual <br />monthly movements (total m month-1). <br />Month Julian day Average S No. observations <br />November 1994 34639 1216, 1658 16 <br />December 34669 488 563 25 <br />January 1995 34700 350 431 32 <br />February 34731 345 525 25 <br />March 34759 1100 2703 35 <br />April 34790 309 515 33 <br />May 34820 445 770 24 <br />June 34851 463 593 28 <br />July 34881 679 1256 27 <br />August 34912 686 2030 23 <br />September 34943 157 214 24 <br />October 34973 307 541 24 <br />November 35004 333 380 21 <br />December 35034 521 773 21 <br />January 1996 35065 199 261 17 <br />February 35096 262 390 10 <br />March 35125 247 335 30 <br />April 35156 479 1407 18 <br />May 35186 1730 2179 6 <br />June 35217 475 453 40 <br />July 35247 533 641 33 <br />April 1997 35521 2338 5017 11 <br />May 35551 510 399 14 <br />June 35582 576 806 17 <br />July 35612 477 685 6 <br />,Boldface numbers, P < 0.05 <br />by fish scarcity, logistics associated with river <br />hydraulics, sampling in remote areas, and poor <br />water visibility (Tyus 1987, Tyus and Karp <br />1990, Modde and Irving 1998). On the other <br />hand, researchers working in reservoir envi- <br />ronments are presented with a broader and <br />less fluctuating range of physical parameters <br />not found in natural river settings. For <br />instance, reservoir water visibility (> 10-15 m) <br />allowed direct observations, summer water <br />temperatures presented a stable but wide <br />thermal gradient (12°-30°C), flows ranged <br />from 0 to 2 m sec-1, depths exceeded 40 m, <br />and fish could choose both littoral and pelagic <br />habitats. Reservoir conditions allowed us to <br />observe spawning and document reproduction <br />through the collection of larval X. texanus <br />(Mueller 1989, Minckley et al. 1991, Mueller <br />1995). River studies have not shared in this <br />degree of documentation, and spawning typi- <br />cally has been inferred by transmitter move- <br />ment and in a few cases by collection of ripe <br />fish (Tyus 1987, Tyus and Karp 1990, Modde <br />and Irving 1998). <br />It has been widely reported that X. texanus <br />migrate to specific spawning areas (Tyus 1987, <br />Tyus and Karp 1990, Modde and Irving 1998), <br />and while spawning site fidelity has been <br />speculated, it has never been proven (Tyus <br />and Karp 1990, Scholz et al. 1992, and Modde <br />et al. 1996). Recently, Modde and Irving <br />(1998) speculated X. texanus may use multiple <br />spawning sites in the Green River; however, <br />this was not documented by observation or <br />collection of gametes or larvae. <br />Adult X. texanus in Lake Mohave typically <br />used broad, shallow shoreline habitats and <br />generally did not occupy deeper canyon habi- <br />tat typical of the lower or upper reservoir. Fish <br />were seldom found together except during <br />spawning (McAda and Wydoski 1980) and <br />exhibited movement rates and ranges similar <br />to those in riverine habitats (Tyus 1987, Tyus <br />and Karp 1990, Modde and Irving 1998). Indi- <br />vidual fish exhibited various degrees of seden- <br />tary and roaming behavior similar to other <br />stream fish (Funk 1955). <br />Xyrauchen texanus spawning in reservoirs <br />occurs from January through March, which is <br />earlier and typically 2-3 times longer than <br />riverine spawning (Minckley 1983, Minckley <br />et al. 1991). Highly social, these fish form