Previously uninvestigated tributaries were initially sampled at a convenient location within the reach expected from experience with similar streams to contain rearing chinook. When juveniles were not found, additional downstream sites were sampled until the mouth was reached or rearing juveniles were found. When juveniles were found at the first sample site, additional upstream sites were sampled until a point was found at which they no longer occurred. In all cases, an effort was made to find any physical feature which might limit further upstream movement. In streams previously documented to contain rearing juveniles, a series of sites were sampled to document the upstream limits of use this year.
Selected sites in the tributaries were sampled at approximately monthly intervals throughout the potential salmonid-use period. At each sample site a suitable habitat area (usually a pool or run) was chosen for sampling. The downstream end of the sample area was blocked with a 1/4 inch mesh seine, then fish were captured in repeated hauls of a 40 ft by 6 ft by 1/4 inch mesh knotless nylon seine fished from upstream to downstream. Rocks and other heavy objects, which might crush fish, were removed from the seine before the haul was completed. Juvenile salmon and small minnows were transferred by dipnet to 5-gal buckets of clean water for immediate processing. Large Fish (>150 mm), which might injure smaller ones, were placed into separate buckets. Chinook captured in each haul were kept in separate container and processed separately. Repeated hauls (from two to five) were taken until the number of chinook captured per haul decreased substantially. Counts were made of chinook juveniles in each haul and population density was estimated with a depletion analysis (Brower et al. 1990, Zippin, 1958).
When substantially more than 50 juvenile chinook were captured at a site, a subsample of 50+ was retained for processing and the rest were counted and released. Large catches of other species were also counted and subsampled. Small fish were anesthetized to reduce trauma and facilitate measuring and weighing. Small numbers of juvenile chinook, (10-12 at a time), were transferred into a bucket containing dilute 50 - 80 ppm tricane methanesulfonate (TMS 222, brand name Finquel from Argent Chemical Company). After fish lost equilibrium, they were examined for adipose fin clips, measured to the nearest mm on a fish board, blotted gently with a chamois cloth, weighed to the nearest 0.1 g, then transferred to a bucket of fresh stream water for recovery (Anderson and Gutreuder, 1983). As soon as fish recovered from anesthesia, they were released into the habitat from which they were captured.
The daily length table generated by the California Department of Water Resources Environmental Services Office (Johnson, et al., 1992) was used to classify juvenile chinook as to run membership. Condition factors (K) were calculated from the formula:
| K = 100,000 x weight in grams /(fork length in mm)3. |
Fish other than juvenile salmon were measured, but not weighed. Fish larger than 150 mm, since they had potential for immediate catch and consumption by anglers and MS 222 is not approved for use in fish destined for immediate consumption, were measured without anesthesia and released.
Notes were made as to the physical and biological conditions present at each site. Water temperature was measured with a mercury thermometer during each sampling period. Onset "Datalogger" thermographs were established in representative habitat sites in several creeks. Turbidity and water velocity were measured with portable meters at most sites during each sampling period. All sites were referenced as measured distance upstream or downstream from a prominent landmark such as a bridge or tributary confluence. Sites were then located on a GIS projection of 1994 Census TIGER Files and stream distance from the Sacramento River to the sample site measured in kilometers. Study tributaries were examined on a GIS riparian map (Geographical Information Center, 1997) and reaches deficient in riparian vegetation catalogued.
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