7056 - Laserfiche WebLink

Home Browse Search

1. Fish to be studied were selected by tag number from a table of random digits. 2. The day was divided into three eight-hour periods and one selected at random. A fish was then observed during this period. If a fish remained stationary for 30 minutes, then water depth, water velocity and substrate determinations were made at 15 min intervals. 3. After a fish had been monitored for three, eight-hour periods, the fish with the next tag number was then selected for study. The location of each radiotelemetered fish was carefully fixed and recorded. General location was recorded in river miles (RM) upstream of the mouth of each river, as given in Belknap and Belknap (1974) and Evans and Belknap (1973), and converted into river kilometers (RK) later. If the fish remained in one location for 30 min it was assumed this habitat was preferred and microhabitat information was recorded, including the general habitat, substrate type, water depth and water velocity. Water depth, average velocity and substrate measurements at that point in the stream were taken only when the fish moved to another location or at the end of the study perioq in order to minimize distur- bance to the fish. Water depth was recorded by direct measurement with a wading rod and average water velocity was measured 0.6 of the distance from the water surface with a Marsh-McBirney current meter. Substrate type was obtained by direct observation and by probing with a wading rod. For additional information on radiotelemetry methods see Tyus, et a 1. (1 984) . Larval Colorado squawfish were collected at least weekly during the spawning season in 1983 by seining backwater areas with 1 m ichthyoplankton seines. In addition, larval samples were taken from the two primary spawning locations in the Yampa River in 1983. These samples were preserved in 5% formalin (40% formaldehyde) solution and shipped to Colorado State University where the fish were sorted and identified. A special Colorado squawfish young-of-the-year (YOY) survey has been conducted each fall in the Green River mainstem since 1979 and the Yampa River was included in this survey in 1981. The objectives of this survey included the identification of nursery areas in river regions occupied by YOY Colorado squawfish of fingerling s'ize (25-60 mm). Colorado squawfish of fingerling size (25-60 mm) were sampled with seines (3X5 mm mesh) from mid-September through October. These YOY surveys were quantitative; the areal extent of each seining effort was recorded, as were the water depth, water velocity, and substrate charac- teristics of the areas sampled (Archer et al. 1980). Sampling sites were river backwaters selected at about 5 mi (8 km) intervals. At least two seine hauls were made in each backwater, and one similar haul was made along the adjacent river shoreline. 5