Laserfiche WebLink
<br />558 <br /> <br />Methods: <br /> <br />1. Collect daily drift samples at two predetermine localities (Four Corners and Mexican Hat) <br />starting in June and continuing until the end of August. Nets will be set each day at dawn and <br />dusk and left in the water for about two-hours. The amount of water filtered by each net (m3) <br />will be measured by General Oceanic Flow-meters (Model 203 OR) suspended in the center of <br />the nets. This information (m3) will allow us to determine catch per unit effort based on <br />volume of water sampled versus time sampling. <br /> <br />2. At the end of each two-hour net-set period, the contents of each net will be rinsed into <br />separate one-gallon plastic bags, labeled with unique field numbers, and preserved in 10% <br />formalin. Drift material will be allowed to cure for at least two days before samples are <br />processed and fishes separated from the debris. Cleaned samples were returned to the _ <br />laboratory for analysis. All fish specimens will be identified and counted. In addition, <br />specimens will be assigned to more coarse categories such as "drift" and "incidental". The <br />former category refers to individuals with minimal or no control over their longitudinal <br />movement. The latter classification refers to individuals whose developmental stage should <br />have allowed them to avoid capture in drift nets. <br /> <br />3. Light-traps will be set at two sites on the San Juan River. Sampling with this passive <br />collecting device will begin in early April and continue into May. Traps will be set after dusk <br />in a low-velocity non-mainstream habitat and remain there for about four hours. Traps will be <br />set every other night. Catch rate will be determined as the number of fish collected per time <br />sampled. Selection of collection sites will be based, in part, on the spring 1997 distribution of <br />radio-tagged razorback sucker. We will attempt to locate the sampling stations in close <br />proximity (downstream) to concentrations of razorback sucker. <br /> <br />4. Data will be converted to catch rate and compared across and within sites by species. In <br />addition, catch rate between and within sites will be compared across time (1996 samples). <br />Specimens will be distinguished and compared by residence status (native versus non-native) <br />and catch rate over-laid with the annual hydro graph. <br /> <br />5. Prepare a comprehensive synthesis and comparison of 1991--1996 drift net sampling. <br />Minimally, this integration report will include analysis of catch by species across years and <br />differing flow regimes. <br /> <br />6. Coordinate with San Juan River researchers who are tracking the movements of Colorado <br />squawfish and identify the putative spawning area for that species. Examine reaches in close <br />proximity of the spawning area for their potential to become drift-net sampling stations in <br />1997. <br /> <br />18 <br />