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<br />6 Ecology of Bonytail and Razorback Sucker <br /> <br />from other sources. Currently, the facility is raising bony tail to <br />meet state and federal stocking requirements in the Green and <br />Colorado Rivers. <br />The Native Fish Work Group (NFWG) of the lower <br />Colorado River basin began activities on Lake Mohave in <br />1989 as a multiagency work group for the purpose of prevent- <br />ing the disappearance of razorback sucker from the reservoir <br />(Mueller, 1995). Efforts to have wild fish spawn in isolated <br />backwaters gradually evolved to collecting wild larvae from <br />the reservoir and raising them to a size large enough to ensure <br />survival. During the past decade, more than 500,000 larvae <br />have been collected and transferred to Willow Beach NFH for <br />initial rearing (Tom Burke, Bureau of Reclamation [BaR], <br />oral. commun., 2004). Some fish are moved to other locations <br />for further grow-out, while others are reared on-site (fig. 5). <br />Stocking programs have expanded in recent years due <br />to the increased demand for cultured fish. As a result, several <br />other culturing facilities were modified or built to help <br />meet production goals (table I). Other locations that are or <br />recently have been used to grow-out razorback sucker include: <br />Bubbling Ponds, Arizona; Niland, California; golf course <br />ponds in Page, Arizona and Boulder City, Nevada; Parker, <br />Arizona; and Lake Mohave backwaters (Mueller, 1995; Muel- <br />ler and Wick, 1998). <br /> <br /> <br />Fig. 5. Aerial view of Willow Beach National Fish hatchery located <br />downstream of Hoover Dam at Willow Beach, Arizona. During <br />the past decade the hatchery has installed solar panels and <br />heat exchangers to increase water temperatures to optimize fish <br />growth. Photo courtesy of Chester Figiel, U.S. Fish and Wildlife <br />Service. <br /> <br />Stocking Programs and Relative Success <br /> <br />Stocking projections for the Colorado River Basin in <br />2005 include 55,000 large (> 15 cm) bony tail, 98,000 large <br />(>30 cm) razorback sucker and tens of thousands of razorback <br />sucker larvae (Roger Hamman and others, U.S. Fish and <br />Wildlife Service [USFWS], oral commun., 2005). The vast <br />majority of these fish originate from the Ouray, Willow Beach, <br />Grand Valley, and Dexter hatcheries (fig. 6, table 1). <br /> <br />The following is a brief description of a few of the major <br />stocking efforts. <br /> <br />Central Arizona <br /> <br />Reintroduction programs resulted in limited success <br />(Minckley and others, 1991; Mueller, 2003; Burdick, 2003; <br />Clarkson and others 2005). The 1980's attempt to reestablish <br />razorback suckers in historical habitats within the Gila River <br />basin in Arizona failed. More than 12 million small suckers <br />were stocked but less than 200 were encountered (Minck ley <br />and others, 1991). Marsh and Brooks (1989) showed that <br />resident catfish could decimate an entire stocking within a few <br />days. These losses prompted hatcheries to shift toward stock- <br />ing larger fish that have improved survival (Mueller, 1995; <br />Burdick and Bonar, 1997; Ryden, 1997). The Arizona Game <br />and Fish Department (AGFD) continues to stock razorback <br />sucker in the Verde River; bony tail have not been stocked due <br />to political issues with water users and developers. <br /> <br />Senator Wash, California <br /> <br />Senator Wash Reservoir is a Bureau of Reclamation <br />(BaR) operated off-site pump-back storage facility located <br />just upstream of Imperial Dam. Razorback sucker established <br />a small population when the reservoir was initially filled in <br />1966. Population estimates during the mid-1980's placed <br />the population at approximately 50 fish, which prompted a <br />stocking program (Ulmer and Anderson, 1985). The popula- <br />tion was augmented between 1987 and 1990 with nearly 4,800 <br />razorback suckers, and recent estimates place the population <br />at nearly 1,000 fish (Laura Lesley, [AGFD], oral commun., <br />2004 ). <br /> <br />Lake Mohave <br /> <br />A stocking program in Lake Mohave was started to <br />augment the declining native population of razorback suckers <br />in 1992 (Mueller, 1995). Roughly 84,000 fish were stocked <br />during 1992-2003, but survival has been low. Marsh and <br />others (2005) have estimated that a population of approxi- <br />mately 1,500 young adults has been established, and survival <br />is closely correlated to size. Survival rates dramatically <br />increase when stocked fish are >30 cm and nearly double for <br />fish >35 cm (fig. 7). Spawning continues but young continue <br />to be lost to predators. Viable young are collected from the <br />reservoir and raised in isolated ponds to perpetuate the genetic <br />diversity of the community (Dowling and others, 2005). <br /> <br />Lake Havasu <br /> <br />A concerted effort to stock more than 30,000 large <br />bony tail and razorback suckers began in 1993. The majority <br />