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<br />8 Ecology of Bonytail and Razorback Sucker
<br />
<br />1.0
<br />0.9
<br />Cii 0.8
<br />>
<br />.~ 0.7
<br />ijl 0.6
<br />m 0.5
<br />.::- 0.4
<br />.~ 0.3
<br />u..
<br />0.2
<br />0.1
<br />0.0
<br />50
<br />
<br />
<br />150 250 350 450 550 650 750
<br />Total length at release (mm)
<br />
<br />Fig. 7. Comparison of razorback sucker stocking size compared
<br />with actual first year survival based on recapture data collected
<br />from Lake Mohave. Database includes >80,000 stocked fish. Graph
<br />courtesy of Paul Marsh, Arizona State University, Tempe.
<br />
<br />of these fish were stocked in Lake Havasu as part of the Lake
<br />Havasu Fisheries Improvement Program. Bony tail continue
<br />to remain extremely rate (1-2 fish per year); however, in
<br />2005 approximately 1,500 razorback suckers were discovered
<br />reoccupying a historic spawning bar near Needles, Califor-
<br />nia. Suckers are migrating to this area approximately 50 km
<br />upstream of the reservoir. Spawners returned to this site again
<br />in 2006, making it the largest repatriated riverine population of
<br />spawning fish in the basin.
<br />
<br />Lower Colorado River (Downstream of Parker Dam)
<br />
<br />The Colorado River between Parker Dam and the Mexi-
<br />can border has been the recipient of the second largest number
<br />of razorback suckers, an estimated 2.2 million fish (Jason
<br />Schooley, ASU, oral commun., 2005). Razorback suckers
<br />were first stocked in 1980 with more than 2 million small fish
<br />introduced between 1986 and 1990. Stocking has continued on
<br />an annual basis since 1995 using larger, but fewer, fish. Since
<br />2001, nearly 40,000 relatively large razorback suckers have
<br />been stocked. Current surveys have only recovered recently
<br />stocked fish, suggesting overall survival during the past two
<br />decades has been exceedingly poor. Recaptures have been
<br />too few to estimate population size or survival (Schooley and
<br />Thornbrugh, 2004).
<br />
<br />Upper Colorado River
<br />
<br />Razorback suckers and bony tail were first stocked in
<br />the Upper Basin in 1988 (Chart and Cranney, 1993; Pitts and
<br />Cook, 1997). Large-scale reintroductions began in 1998 with
<br />bony tail and razorback sucker being stocked in the Colorado
<br />and Green Rivers. Although, there is a specific "Green River"
<br />broodstock, razorback sucker stocked into the Green River
<br />include production from Grand Valley and Lower Basin
<br />hatchery facilities (Tim Modde, USFWS, oral commun.,
<br />
<br />2005). Today, stocking has expanded to include the Gunnison
<br />and Yampa rivers. Attempts to reestablish these fish have seen
<br />limited success; survival of large hatchery-reared fish remains
<br />poor (Bestgen and others, 2002). Recaptures have been
<br />inadequate to estimate population size. As experienced in the
<br />Lower Basin, survival appears closely correlated to stocking
<br />size (Burdick and others, 1995; Ryden, 1997).
<br />
<br />San Juan River
<br />
<br />Razorback sucker have been stocked in the San Juan
<br />River since 1997, and larvae have been collected in recent
<br />years (Mueller and others, 200 I; Brandenburg and others,
<br />2003; Ryden, 2003a and 2003b). During the past year, about
<br />a half dozen one-year-old fish were collected (Dale Ryden,
<br />USFWS, oral commun., 2005).
<br />
<br />Prognosis
<br />
<br />Larger adult razorback suckers produced in hatcheries
<br />are surviving and beginning to spawn, but no self-sustaining
<br />population has been produced. The predation problem remains
<br />unresolved. Recovery actions are treating the symptom (low
<br />numbers of fish) but have not effectively dealt with the prob-
<br />lem (predation). Predation continues to restrict natural recruit-
<br />ment throughout the basin (Minckley and others, 1991; Tyus
<br />and Saunders III, 2000; Mueller, 2003). Resource management
<br />agencies continue to wrestle with the conflict between native
<br />fish management and recreational fisheries, hoping somehow
<br />the two programs can be compatible. Unfortunately, there does
<br />not seem to be any evidence they can, and the results have
<br />manifested into a totally displaced fish fauna.
<br />
<br />Study Objectives
<br />
<br />The purpose of this report evolved with its writing.
<br />Initially, the goal was to summarize the work conducted at
<br />Cibola High Levee Pond (CHLP). This included reviewing the
<br />status of these two fish, identifying causes for their endanger-
<br />ment, and describing why natural recruitment was occurring
<br />at CHLP. However, it became increasingly evident that CHLP
<br />mimicked historical ecological features that disappeared when
<br />large water development projects harnessed the river. The abil-
<br />ity of these riverine species to produce young in small, isolated
<br />habitats may provide the key to their recovery. This belief is
<br />based on 25 years of personal observations combined with the
<br />fact that recovery programs have been unable to reestablish
<br />self-sustaining populations in the mainstem river.
<br />The report was expanded to elaborate on the function of
<br />isolated communities and how manmade sanctuary habitats
<br />actually mimic historical conditions that existed prior to large
<br />water development projects. Off-channel sanctuaries provide
<br />
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