Annual Run-size, Harvest, and Spawner Escapement Estimates for Trinity River Basin Chinook and Coho Salmon and Steelhead (continued)
We tagged and recovered too few grilse salmon to stratify our estimates by adults and grilse this year. Instead, we combined the numbers of adults and grilse tagged and recovered in order to calculate the population estimate, and then proportioned the estimate based on the ratio of adults and grilse observed at each of the weirs.
We estimated that 4,030 (2,359 adults and 1,671 grilse) spring chinook (including those harvested) migrated into the Trinity River basin upstream of JCW during the 1992-93 season (Table 13). Anglers caught and kept an estimated 104 (4.4%) of the adults and 194 (11.6%) of the grilse from the spring run. The spawning escapement upstream of JCW during the 1992-93 season was estimated to be 3,732 fish, including 1,846 spring chinook that entered TRH (Table 14).
Based on the Normal Approximation, the 95% confidence interval for the run-size was 3,609-4,479 fish (Table 13).
This is the third-lowest run-size estimate for spring chinook since we began operations in 1977. Run-size has ranged from 62,692 fish in 1988 to 2,381 fish in 1991 (Appendix 11).
We estimated that 14,164 (11,232 adults and 2,932 grilse) fall chinook (including those harvested) migrated into the Trinity River basin upstream of WCW during the 1992-93 season, and 9,584 (7,054 adults and 2,530 grilse) of these fish continued their migration upstream of JCW (Table 13). We estimated that anglers harvested 314 adults (2.8%) and 158 (5.4%) grilse from the 1992-93 fall chinook run, including 15 grilse and 127 adults caught upstream of JCW. Therefore, we estimated the Trinity River fall chinook escapement at 13,692 fish upstream of WCW and 9,442 fish upstream of JCW, including the 3,990 fall chinook that entered TRH (Table 14).
Based on the Normal Approximation, the 95% confidence interval for the fall chinook run-size upstream of WCW was 11,578-17,006 fish (Table 13).
The fall chinook run-size this year is the fourth-lowest since the current program began in 1977. The estimated run-size upstream of WCW has ranged from 147,888 fish in 1986 to 9,207 fish in 1991 (Appendix 12), while the run-size upstream of JCW has ranged between 121,033 and 4,787 fish (Appendix 13).
We estimated that 10,339 coho (including those harvested) migrated into the Trinity River basin upstream of WCW during the 1992-93 season, and 5,683 continued their migration upstream of JCW (Table 13). An estimated 0.23% (24) of the coho were harvested upstream of WCW, but none were caught upstream of JCW. The spawning escapement estimate for coho upstream of WCW was 10,315 fish, 5,683 of which continued upstream of JCW and included 3,582 fish that entered TRH (Table 14).
The 95% confidence interval, based on the Poisson Approximation, ranged between 8,801 and 12,269 coho salmon upstream of WCW (Table 13).
Estimated coho salmon run-size upstream of WCW has ranged from 1,971 fish in 1983 to 59,079 fish in 1987 (Appendix 14), and between 2,177 and 26,370 fish for the Trinity River upstream of JCW (Appendix 15).
We estimated that 3,046 adult fall-run steelhead, comprised of 1,731 naturally produced and 1,315 hatchery-produced fish, migrated upstream of WCW (Table 13). From these, anglers harvested an estimated 166 and 126 naturally and hatchery-produced steelhead, respectively. Twenty-five naturally produced and 430 hatchery produced steelhead entered the hatchery, leaving 1,540 naturally produced and 759 hatchery-produced steelhead for the natural spawner escapement upstream of WCW (Table 14).
The 95% confidence interval, based on the Poisson Approximation, ranged between 2,120 and 4,706 fall-run steelhead upstream of WCW (Table 13).
The fall-run steelhead run-size above WCW this year was the lowest recorded since 1980. Intermittent estimates made since that year have ranged from 37,276 in 1989 to this year's low estimate (Appendix 16).
Too few steelhead were trapped at JCW to develop a run-size estimate for the basin upstream of that site this year. Previous run-size estimates upstream of JCW have ranged from 2,285 in 1991 to 13,574 in 1989 (Appendix 17).
1. Tagging and recapture operations for adult spring-run and fall-run chinook and coho salmon, and adult fall-run steelhead conducted in the Trinity River basin should be continued during the 1993-94 migration season, using the capture sites near Willow Creek and Junction City.
2. More detailed information should be requested from anglers returning tags, including: 1) if the fish was kept or released, and 2) if the tag was recovered from a fish found dead (carcass recovery).
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APPENDIX 1. List of Julian weeks....
APPENDIX 2. Fork length distribution of coded-wire-tagged, TRH-produced, spring-run chinook salmon...
APPENDIX 3. Fork length distribution of coded-wire-tagged, TRH-produced, fall-run chinook salmon..
APPENDIX 4. Fork length distribution of spring-run chinook salmon trapped and tagged in the Trinity...
APPENDIX 5. Fork length distribution of fall-run chinook salmon trapped and tagged in the Trinity...
APPENDIX 6. Fork length distribution of coho salmon trapped and tagged in the Trinity...
APPENDIX 7. Fork length distribution of fall-run steelhead trapped and tagged in the Trinity...
APPENDIX 8. Release and recovery data for TRH-produced, fin-clipped and non-fin-clipped fall-run SH...
APPENDIX 9. CDFG Commission regulations that affected salmonid harvest in the Trinity upstream of WCW...
APPENDIX 10. Fork length distribution of TRH-produced, fin-clipped fall-run steelhead trapped in the Trinity...
APPENDIX 11. Spring-run chinook run-size, spawner escapement and angler harvest estimates for the Trinity...
APPENDIX 12. Fall-run chinook run-size, spawner escapement and angler harvest estimates for the Trinity upstream of WCW from 1977 through 1992...
APPENDIX 13. Fall-run chinook run-size, spawner escapement and angler harvest estimates for the Trinity upstream of JCW from 1977 through 1992...
APPENDIX 14. Coho run-size, spawner escapement and angler harvest estimates for the Trinity upstream of WCW from 1977 through 1992...
APPENDIX 15. Coho run-size, spawner escapement and angler harvest estimates for the Trinity River upstream of JCW from 1977 through 1992... ...
APPENDIX 16. Fall-run steelhead run-size, spawner escapement and angler harvest estimates for the Trinity upstream of WCW from 1977 through 1992......
APPENDIX 17. Fall-run steelhead run-size, spawner escapement and angler harvest estimates for the Trinity upstream of JCW from 1977 through 1992.
