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<br />i <br />i <".:) <br />,:.:J C) <br /> l\' <br />! ,;..\ <br />10- <br />I (;..1 <br /> <br />".) <br /> <br />:'_J <br /> <br />Instrument Co., Lake Success, NY), Each muscle plug was transferred to a plastic vial (Nunc <br /> <br />CryoTube, Kamstrup, Denmark) using a stainless steel forceps and then placed in a freezer. <br /> <br />Water temperature regimes were designed to simulate those at DNFH in an attempt to <br /> <br />maintain the reproductive cycle of the test fish in synchrony with adults of the same year class <br /> <br />that have been spawned successfully at DNFH. Water temperature in adult exposure tanks was <br /> <br />maintained at ambient laboratory temperature, which varied from 130C in January at the start of <br /> <br />the study to 230C in June when the spawning trials were initiated. Weekly water temperatures, <br /> <br />averaged across all tanks, are shown in Figure I. This temperature regime was similar to that in <br /> <br />holding ponds and raceways used for culturing Colorado pikeminnow broodstock at DNFH (R. <br /> <br />Hamman, V,S. Fish and Wildlife Service, written communication). <br /> <br />All fish were exposed under a photoperiod that simulated conditions at Shiprock, NM, <br /> <br />from January to September (Appendix A). The light was provided by a combination of <br /> <br />wide-spectrum and cool-white fluorescent bulbs controlled by a timer. The photoperiod was <br /> <br />adjusted on the first day of each month, <br /> <br />All adult exposure tanks were siphoned each day to remove uneaten food, fecal material, <br /> <br />and detritus. After siphoning, the water in each tank was filtered continuously for at least 2 <br /> <br />hours to remove suspended material (primarily disintegrated food pellets) and increase the <br /> <br />dissolved oxygen concentration. Filtration was accomplished by using a submersible pump (1.7 <br /> <br />amp, Little Giant Pump, Oklahoma City, OK) fitted with a nylon hose that conveyed the water to <br /> <br />a 25-~m polypropylene bag filter (Filter Specialists, Michigan City, IN) suspended over the tank. <br /> <br />The tanks were covered with nylon netting (48-mm mesh), except during filtration, to prevent <br /> <br />fish from jumping out of the tanks, <br /> <br />II <br />