<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 />
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