Laserfiche WebLink
<br />:~ <br />r- <br />t'- <br />~ummary <br />i,;Jnitial modeling of flow-habitat relationships has been conducted and additional studies are <br />1C::continuing. This objective will be completed in 1997 as habitat studies are completed. <br /> <br />5.2.5. Determine and Monitor Habitat Use of Endangered and Other Native <br />Fishes. <br /> <br />. 5.2.5.1. <br /> <br />Determine Habitat Requirements for Different Life Stages <br /> <br />A number of SJRRIP studies have focused on habitat use by the fishes of the river, including Buntjer <br />et al. (1993, 1994), Ryden and Pfeifer (1993, 1994, 1995a, 1995b, 1996a, 1996b), and Miller <br />(1994a, 1995). <br /> <br />Colorado Sauawfish <br />Habitat requirements of Colorado squawfish are relatively well known from studies conducted in <br />the upper Colorado River Basin (USFWS 1990). Spawning occurs in cobble/gravel areas typically <br />found in canyons. Larvae emerge from the cobble and drift downstream, apparently until they find <br />suitable habitat (Tyus 1991). Larvae seek out warm, still, backwater areas along shorelines. <br />Backwaters (areas surrounded by land on three sides and having an outlet to the main river) are the <br />primary habitat for young until they reach 120-200 nun total length, usually in their second or third <br />year oflife. Subadults (200-400 millimeters (mm)) tend to move about the river more but still prefer <br />backwater habitats. Relatively deep backwaters (3 feet or more at the mouth) are preferred by young <br />, and sub adults (Holden 1977). <br /> <br />Adult Colorado squawfish (400 nun plus) usea variety of habitats. During spring runoff, adults are <br />typically found in backwaters or flooded riparian areas where temperature is higher than in the main <br />river (Wick et al. 1983). As high flows recede, adults move toward spawning areas, often migrating <br />over 100 miles. Spawning areas are typically riffle-run areas with cobble substrates. Following <br />spawning (typically in July), the adults often move back to the areas they migrated from. In the <br />Green River, some adults spend most of their time in tributaries, such as the White River or upper <br />Yampa River. ,They move down the tributaries to spawning sites and:then back up the tributaries . <br />following spawning. Other adults live in the main rivers, such as the Green and Colorado, year- <br />round, migrating up or down the river to their spawning sites. Adults are typically found in runs <br />along shorelines during the summer and fall, probably using low velocity pockets alongside the main <br />current. During winter, adults move relatively little and prefer slow velocity habitats (Valdez and <br />Masslich 1989) such as slow runs, slackwaters, eddies, and backwaters. <br /> <br />As illustrated by this information, Colorado squawfish require a diverse river system with a variety <br />of habitats. Colorado squawfish populations (i.e., a reproducing group offish) in the Green River <br />System utilize several hundred miles of rivers, including portions of the main Green River, and <br />tributaries such as the Yampa and White rivers. Key habitat components include only a few <br />spawning areas (one in the Green River and one in Yampa River) characterized by clean, cobble <br />substrate and a long nursery area reach downstream of spawning sites with abundant backwater <br />habitats. <br /> <br />San Juan River Recovery Implementation Program <br />Summary Report <br /> <br />22 <br /> <br />17 January 1997 <br />PR-576-2 <br />