7615 - Laserfiche WebLink

Home Browse Search

Electrofishing a large river can be affected by a variety of factors such as experience of the collectors, streamflow, turbidity, water temperature, etc. Therefore, in order for data to be truly comparable, every effort should be made to reduce and/or account for the many factors that could affect electrofishing efficiency. Because of the large number of investigators and sampling designs used to collect the data discussed here, many of these factors can not be accounted for. Thus direct comparisons among years in an attempt to detect changes in the adult population will not be meaningful. However, general comparisons among years and or reaches may be useful to compare the relative importance of the reaches or to examine changes in the size structure of the population. Post-Larval Colorado Squawfish Monitoring A total of 17 files contained data that met the criteria for post-larval Colorado squawfish monitoring (Table 3). Sampling programs very similar to the current post-larval Colorado squawfish monitoring program were initiated by the Fish and Wildlife Service in the Green River in 1979 and in the Colorado River in 1982. The 1979 effort was relatively unstructured, with investigators simply proceeding downstream and sampling backwaters as they came to them. However, in 1980 the design included sampling one backwater with two seine hauls in each 5-mi reach of river. This design forms the basis of the monitoring program. The early sampling included the entire length of the river, so each of the designated reaches was sampled completely in the earlier collections. Because the sampling design was basically similar and the designated reaches were completely sampled in the earlier collections, the earlier data should be reasonably comparable with 11