7079 - Laserfiche WebLink

Home Browse Search

be used during most of the summer months. Conductivity over 1400 umho/cm3 actuated a protective circuit in the VUP box to stop current. Hand-held electrodes with long cords were occasionally used to sample areas inaccessible by boat during low flow. Small fish were occasionally collected with finer-mesh dipnets during electrofishing; these specimens were usually included and pro- cessed with seine collections. A commercial gill net (9.14 m x 3.1 m x 50.8-mm mesh) and an experi- mental gill net (45.7 m x 1.8 m with 3.2-mm to 38.1-mm mesh) were used in 1975 and March 1976. Nets were set at dusk and picked the following morning before daybreak. Gill net data are reported herein as part of the electro- fishing results. Various seines were used depending on their availability and specific conditions at each station in 1976 and 1977 (and minimally in 1975 to determine species present). The most effective seines for small fish had a mesh of about 3.2 mm. Fine-mesh (0.5-1.0 mm) dipnets were used in 1976 and 1977 to collect larvae and supplement seine collections in shallow shoal, backwater and shorelines areas. Seine and dipnet collections were combined for analysis. A conical 0.5-m plankton net (0.5-mm mesh) was used experimentally in 1976. It was held in a stationary mid-stream position for 5 min at each site sampled. Commercial cylindrical minnow traps were used briefly in 1976; captures were processed as part of the seine collections. Sample Processing Most larger fish were field-processed and released; many smaller fish, especially larvae and early juveniles, were preserved for processing in the laboratory. The latter specimens were initially fixed in 5-10% forma- lin and later stored in 3% buffered formalin. Large specimens were stored in 70% ethanol. A11 fish were identified, enumerated, and measured to the near- est millimeter total length (TL). Large, field-processed collections of 36