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<br />! <br />I, <br />t. <br />f <br /> <br />Razorback suckers have been reintroduced at several locations in the upper and lower basins, with <br />variable success, More than 12 million hatchery-reared larvae and juveniles were reintroduced <br />into riverine habitats in Arizona and California from 1981 to 1990, but most fish were lost to' <br />predation (Marsh and Brooks 1989, Minckleyet al, 1991, Mueller 1995), Smaller releases ih the <br />upper basin have not been evaluated (Ryden and Pfeifer 1995). Razorback suckers, including <br />wild adults and their progeny, are currently in several hatchery and holding facilities in Utah, <br />Colorado, New Mexico, Arizona, and California, <br /> <br />;.. <br />k <br />~~ <br /> <br />" <br /> <br />Movement <br /> <br />Adult razorback suckers may travel long distances during spring spawning season in both <br />lacustrine (lake) and riverine environments, In Lake Mohave, adults moved over 60 miles to <br />spawning locations (Marsh and Minckley 1989), and in the Green River, spawning migrations of <br />over 60 miles were also recorded (Tyus 1987, Tyus and Karp 1990), Outside of spawning <br />season, adult razorback suckers move much less; Valdez and Masslich (1989) reported movement <br />of less than 3 miles during winter months (November-February), <br /> <br />:: -~ <br />, <br />?~ <br /> <br />Habitat <br /> <br />"."t <br />~ft <br />;~ <br />~ <br />~ <br />~~ <br />r.~ <br />t;~~ <br />t> <br />...t~: <br />(I.~' <br />1t~ <br />\,. <br /> <br />Adult razorback suckers occupy a wide variety of lentic and lotic habitats, Mainstream portions <br />of moderate to large streams and rivers and associated the low velocity habitats (backwaters; <br />sloughs, oxbow lakes, seasonally inundated floodplains) were integral elements of the histori~ <br />riverine habitat (Bestgen 1990), Lotic habitats commonly used by adults include near shore runs <br />and shallow to deep channels adjacent to or over mid-stream sandbars (Holden and Stalnaker <br />1975, Tyus and Carp 1989), In addition, springtime congregations of razorback suckers found in <br />tributaries and off-channel impoundments demonstrate the importance of these habitats (Bestgen <br />1990), <br /> <br />~!:;.;. <br />t-. <br />v., <br />V~. <br /> <br />t!; <br /> <br />Riverine habitat oflarval razorback suckers have only recently been documented and includes <br />shallow, sheltered, shoreline habitats such as flooded tributary mouths, backwaters and inundated <br />floodplain areas (Muth 1995), Areas that are typically warmer and contain more abundant forage <br />than mainstem habitats. As they grow older and increase in size young fish appear to move into <br />sheltered main-channel habitats such as backwaters and other low velocity habitats, <br /> <br />i.*_ <br />f}: <br />., <br />~~ <br />;;:'1': <br />r~~ <br />~~i <br />"., ~ <br />~ <br />:.t1l <br />.~ <br />;-~~ <br /> <br />~~'>'j <br />,-~');,,: <br /> <br />Rl\Production <br /> <br />Certain aspects of the reproductive biology and spawning preferences of razorback suckers are <br />relatively wen known (Maddux 1993), Available infonnation has been derived primarily from <br />visual observations in lower basin reservoirs, especially Lake MOhave and radio telemetry studies <br />in riverine environments in the upper basin. <br /> <br />12 <br />