WSP01392 - Laserfiche WebLink

Home Browse Search

Species composition was found to shift when all fish (including < 15 cm) are used. Small fish are more typically associated with shoreline habitats and comprise a small percent of the main channel population. Also the effort to sample small fish from the e1ectrofishing boat varied between years. At the Sevens station in 1998 a 30 m section in the lower part of the study area was walked electrofished and several hundred speckled dace, sand shiner and a few redside shiner were taken from along the bank under an overhanging tree. Inclusion of these fish resulted in a shift in species composition with dace becoming the third most common fish (Appendix Table A.1). That shoreline electrofishing special effort was not made at Sevens in 1999. At the Duffy station, the small mouth bass YOY count was 774 in 1998 and 698 in 1999. YOY small mouth bass were dispersed and ubiquitous in the main channel and were easy to capture or count from the boat without any special effort. When fish less than 15 cm are included, small mouth bass had the highest percent composition in 1998 at 27% and white sucker were second at 22% (Appendix Table A.2). In 1999 at Duffy YOY white suckers increased and white sucker was still the most common species but dropped to 27% of the total and small mouth bass increased to 23% overall (Appendix Table A.2). Fish collected by seining include: speckled dace Rhinichthys osculus, mottled sculpin Coitus hairdi, sand shiners Notropis stramineus, fathead minnows Pimephales promelas, brook stickleback Culaea inconstans, redside shiner Richardsonius halteatus and green sunfish Lepomis cyanellus) (Appendix Table A2.3). COLORADO RIVER Percentages of fish over 15 cm captured by electrofishing in the IS-mile reach varied in the three sections sampled. Flannelmouth sucker were the most common fish caught at all three main channel sites and their percent composition was 41 % in the study area, 55% in the 30 I I I I I I I I I I I I I 1