Sampling was especially difficult near the mouths of the tributaries. It proved impossible to sample all sites in a comparable manner, despite efforts to do so. The lower ends of most tributaries simply did not provide open, unobstructed sampling sites. Since we were usually working around snags or seining only a portion of the habitat, fish had a variable chance of escaping. At most sites our 40 foot seines were not long enough to reach across the stream but the ubiquitous presence of snags precluded effective use of longer seines. Since stream segments could not be blocked off as we did in former years in upstream reaches, we had no way of checking efficiency of sampling.
We accessed the lower reaches of the tributaries by canoe, which provided a much better perspective than previous years sampling from vehicles. Traveling by canoe, one sees the continuity of habitat within the creek and is able to find many more suitable sites for sampling. This improved perspective, however, only emphasizes the problems inherent in even semi-quantitative sampling. Samples can only be taken where conditions permit and do not represent a random selection from the creek’s potential habitat, most of which is impossible to sample due to cover, depth, or velocity. Sampling efficiency also varies from site to site and from stream stage to stream stage even for samples taken at identical sites. Even size comparisons between sites may be invalidated if in one site only a limited section of relatively shallow habitat (favored by smaller fish) could be sampled and in the other site, all habitat types present could be sampled.
Table 1 provides a summary of sampling results from each site and date.
An overview of the number of juvenile chinook captured broken down to race by the Upper Sacramento River Daily Length Chart is given in Table 2.
Table 2. Numbers of each race captured in the 1999 sampling season.
|
Race |
Number Captured |
|
Fall |
3075 |
|
Winter |
183 |
|
Spring |
177 |
|
Late Fall |
4 |
|
TOTAL |
3439 |