Staff of the California Department of Fish and Game's Trinity Fisheries Investigations Project conducted a trapping and coded-wire tagging operation for naturally produced, juvenile chinook salmon (Oncorhynchus tshawytscha) on the mainstem Trinity River below Lewiston Dam from 16 January through 26 May 1991.
We trapped 89,208 juvenile chinook salmon, 903 juvenile coho salmon (O. kisutch), and 7,275 juvenile steelhead (O. mykiss) at four locations during the study. Peak catch-per-unit-effort for juvenile chinook salmon was at the most downstream site, occurring early May. Weekly average fork lengths of trapped juvenile chinook salmon tended to increase throughout the trapping period.
We adipose fin-clipped and implanted coded-wire tags into 80,087 juvenile chinook salmon, a sub-sample of which ranged in size from 36 to 95 mm fork length. After adjusting for tagging mortality, tag shedding, and poor fin clips, we effectively coded-wire tagged and released 72,865 juvenile chinook salmon.
One two-year-old chinook salmon that had been coded-wire tagged near Junction City in 1988 was recovered this year during spawner surveys in the North Fork Trinity River.
To capture, mark (adipose fin-clip), tag (binary-coded wire), and release representative groups (up to 100,000 fish/group) of naturally produced chinook salmon fry/fingerlings in the mainstem Trinity River and/or selected Trinity River tributary streams, for use in subsequent determinations of their survival and contributions as adults to the ocean and river fisheries and spawning escapements.
The Trinity River system in Northern California is a major producer of chinook salmon (hereafter called chinook) for the Klamath River basin. Knowledge of fry- or fingerling-to-adult survival, harvest, and spawning escapement of these stocks is crucial to wise management of chinook in the basin.
Federal legislation (U. S. Public Law 98-541, enacted in 1984) has resulted in a major effort to restore the fishery resources in the Trinity River basin to pre-Trinity Project conditions. Emphasis for this effort is placed on naturally produced chinook. Survival, catch, and escapement data for these fish will help to evaluate the effectiveness of these restoration efforts.
Previous coded-wire-tagging studies of juvenile chinook in the Trinity River basin have focused on hatchery-produced chinook and made references to naturally produced chinook based on those results (Heubach and Hubbell 1979, Heubach 1980, Maria and Heubach 1981, 1984a, 1984b, 1984c).
In this study, the California Department of Fish and Game's (CDFG) Trinity Fisheries Investigations Project (TFIP) personnel trapped, adipose fin-clipped and coded-wire tagged (Ad+CWT), and released naturally produced juvenile chinook. Subsequent studies of these fish as adults, by TFIP and other projects of the CDFG's Klamath-Trinity Program, will be used to determine survival, harvest, and spawning escapement for this important component of the Trinity River basin's chinook stocks.
This is the third year of the study. Previous years (Zuspan 1991b and 1992b) dealt only with the tagging aspect of the study. This report, and those to follow, will also address the recovery of tagged fish as adults.
Weekly sampling data collected by Project personnel at the trapping sites are presented in Julian week (JW) format. Each JW is one of a consecutive set of 52 weekly periods, beginning 1 January, regardless of the day of the week on which 1 January falls. The extra day in leap years is added to the ninth week, and the last day of the year is included in the 52nd week (Appendix 1). This procedure allows between-year comparisons of identical weekly periods.
We trapped at four primary sites in the mainstem Trinity River this season. Site names and river km (RKM) locations were: 1) Lewiston at RKM 175, 2) Steel Bridge at RKM 159, 3) Indian Creek at RKM 153, and 4) Sky Ranch at RKM 136 (Figure 1).
FIGURE 1. Map of the Trinity River below Lewiston Dam showing the four trapping sites used in 1991.
Trapping began 16 January and was concluded 26 May 1991. Our primary objective was to capture up to 100,000 juvenile chinook for coded-wire tagging. To that end, we trapped sporadically at each of the four sites to locate the site that would produce the highest numbers of fish at a given time.
Our trapping apparatus consisted of from one to nine fyke nets measuring 3.1 m wide by 1.2 m high at the mouth, by 7.6 m long, tapering to a 0.33-m by 0.33-m exit leading into dual live boxes. Fyke nets were attached, at their mouth, to a 2.5-cm (1-in) diameter galvanized pipe frame of the same dimensions as the net opening, which was connected by ropes to metal posts driven into the stream bed. The nets were normally set in the late afternoon and recovered mid-morning the next day.
All fish trapped were counted and a sub-sample of each species was measured to the nearest mm of fork length (FL).
Tagging took place only at the Steel Bridge and Sky Ranch sites. The tagging sites were located adjacent to the trapping sites. Tagging was conducted inside a 5.5 m (18 ft) long office trailer converted for that purpose. A 3.5 KW generator was used to supply the electrical needs of the operation (tagging machines, pumps, lights).
Captured juvenile chinook were anesthetized with tricaine methanesulfonate (MS222 ), their adipose fin removed, and a coded-wire tag implanted. Tag injectors and quality control devices were purchased from Northwest Marine Technology1/. Because of the small size of the fish captured, 1/2-length tags were used. Between two and four tagging machines were employed, depending on availability of fish for tagging.
A sample of 100 fish from each day's tagging was held for quality control, and the remainder were released back into the river at the tagging site throughout the day. Fish in the quality control sample were put into holding cages kept in the river and, after a minimum of 24 hours, checked for mortality, tag retention, and adipose fin-clip (Ad-clip) effectiveness. Tag retention was determined by passing fish through the electronic tag (metal) detector and Ad-clip effectiveness was determined by direct examination.
As part of ongoing studies, the CDFG recovers Ad-clipped and CWT fish from among ocean- and inland-harvested fish, and hatchery and natural spawner returns. Heads from Ad-clipped fish are collected and their coded-wire tags removed and decoded.
We began trapping 16 January, and continued at varying locations and intensities through 26 May 1991 (Table 1). In late May, high flows (914 m/sec) from experimental dam releases and the coincident release of approximately 1.9 million juvenile chinook from Trinity River Hatchery (TRH) precluded further trapping of naturally produced fish for the season.
Chinook Salmon
We captured 89,208 juvenile chinook this season. Totals by site were, 1) 848 at the Lewiston Site, 2) 20,458 at the Steel Bridge Site, 3) 554 at the Indian Creek Site and, 4) 67,348 at the Sky Ranch Site (Appendices 2, 3, 4, 5).
Catch-per-unit-effort (CPUE), measured as weekly average number of fish caught per-night per-net fished, varied considerably between trapping sites (Figure 2, and Appendices 2, 3, 4, 5). The highest CPUE (485) was at the Sky Ranch Site followed by the Steel Bridge Site (438), Indian Creek Site (192), and the Lewiston Site (84).
We measured the FLs of 2,151 chinook during the trapping season. These fish ranged in FL from 24 to 97 mm. Weekly average FLs of fish at the four trapping sites generally increased though time (Figure 3, Appendices 2, 3, 4, 5). Average FL of juvenile chinook was 37.0 mm in late January and increased to 68.7 mm by late May.
FIGURE 2. Weekly average catch of juvenile chinook salmon per-trap per-night at the four trapping sites in the mainstem Trinity River during 1991.
Other Salmonids
We captured 7,275 steelhead this season. Steelhead were caught at all the sites throughout the trapping season (Appendices 2, 3, 4, 5). Catches were relatively low until mid-March, when we began catching large numbers of hatchery-produced steelhead. About 85% of the steelhead captured this season were fin-clipped, indicating they were from TRH .
We captured 903 coho salmon this season, both yearlings and young-of-the-year (YOY). YOY were first noted during the Julian week beginning 12 March 1991. Previously, we trapped only yearlings (Appendices 2, 3, 4, 5).
Tagging operations began 18 April and continued through 27 May 1991. During this period, we marked (Ad+CWT) and released 80,087 juvenile chinook. Tagging took place at both the Steel Bridge and Sky Ranch sites.
Steel Bridge Site
At the Steel Bridge Site, we tagged 19,777 juvenile chinook with coded-wire tag number 6-1-8-1-12. Tagging at this site began 18 April and continued through 2 May 1991. The independent, non-overlapping estimates, based on quality control groups, of tagging mortality, poor fin clips, and the numbers of coded-wire tags that were shed are shown in Table 2. After subtracting these estimates from the total tagged, we effectively CWT and released 19,090 juvenile chinook (Table 2).
Sky Ranch Site
Tagging began 3 May and continued through 27 May 1991 at the Sky Ranch Site. During this period, we tagged 29,550 fish with coded-wire tag number 6-1-8-1-13, and 30,760 fish with coded-wire tag number 6-1-8-1-14. The independent, non-overlapping estimates, based on quality control groups, of tagging mortality, poor fin clips, and the numbers of coded-wire tags that were shed are shown in Table 2. After subtracting these estimates from the total tagged, we effectively CWT and released 26,741 juvenile chinook with coded-wire tag number 6-1-8-1-13 and 27,034 with coded-wire tag number 6-1-8-1-14 (Table 2).
One two-year-old fish, which had been tagged in 1989, was recovered this season by TFIP personnel during spawner surveys in the North Fork Trinity River (Zuspan 1992c). That fish was one of 15,704 juvenile chinook CWT and released near Junction City in 1989 (Zuspan 1991b). It is of interest to note that, while this fish had been trapped and tagged in the mainstem Trinity River upstream of the North Fork Trinity River, it apparently strayed into the North Fork Trinity River to spawn. No other recoveries of Project-tagged fish were reported this year.
We were unable to capture enough juvenile chinook to reach our goal of tagging 100,000 naturally produced fish this year. This was the direct result of poor escapement of the progenitors of this year's juvenile chinook. Natural spawner escapement for chinook salmon (spring- plus fall-run) above Junction City was the lowest ever recorded.
Because of the low catches, we instigated an intensive trapping program, trapping up to 80% of the river's cross section on a seven-day-a-week basis. Trapping effort this year was 2.6 times that of last year (374 vs. 143 trap nights), while the total juvenile chinook catch was only 55.2% (89,208 vs. 161,730) of last year's (Zuspan 1992b). Both the overall juvenile chinook CPUE and adult escapement of their progenitors were down a similar amount when compared to the previous year. The 1990 adult chinook escapement was 16.8% of the 1989 escapement (5,811 vs. 14,587 [Bill Heubach, CDFG, pers. comm.]), while the CPUE for 1991 juvenile chinook was 23.1% of that in 1990.
While it seems unlikely there is a linear relationship between adult escapement and production, trapping this year does suggest an important correlation.
1. Job 2 activities should be continued in FY 1991-92.
2. In the event of a low chinook escapement in 1991, the Project should be prepared to increase our trapping efforts. This will require the purchase and construction of additional trapping equipment.
3. We should continue our efforts to recover coded-wire tagged chinook that are harvested by anglers or that return to TRH. Efforts to recover code-wire tagged fish spawning naturally should be increased.
Aguilar, B. 1992. Survival and Contributions to the Fisheries and Spawner Escapements Made by Steelhead Produced at Trinity River Hatchery. Chapter VI. Job VI. p. 136-140. In: Kevan Urquhart (ed.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1989-1990 Season. June 1992. 140 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Heubach, B., and P. Hubbell. 1979. FY 1978 Progress Report. Task V. Salmon Tagging and Release Monitoring. p. 1-5. In: Paul M. Hubbell (ed.), Evaluation Report--FY 1978. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. January 1979. 65 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Heubach, B. 1980. FY 1979 Progress Report. Task V. Salmon Tagging and Release Monitoring. p. 75-79. In: Paul M. Hubbell (ed.), Progress Report. Fishery Investigations - Trinity River. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. September 1980. 141 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Maria, D., and B. Heubach. 1981. FY 1980 Progress Report. Task V. Salmon Tagging and Release Monitoring. p. 7-12. In: Paul M. Hubbell (ed.), Progress Report. Fishery Investigations - Trinity River. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. Tasks II, V and VII. December 1981. 23 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Maria, D., and B. Heubach. 1984a. FY 1981 Progress Report. Task V. Salmon Tagging and Release Monitoring. p. 6-15. In: Paul M. Hubbell (ed.), Progress Report. Fishery Investigations - Trinity River. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. Tasks II, V, VII. October 1984. 24 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Maria, D., and B. Heubach. 1984b. FY 1982 Progress Report. Task V. Salmon Tagging and Release Monitoring. p. 5-13. In: Paul M. Hubbell (ed.), Progress Report. Fishery Investigations - Trinity River. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. Tasks II, V. November 1984. 13 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Maria, D., and B. Heubach. 1984c. FY 1983 Progress Report. Task V. Salmon Tagging and Release Monitoring. p. 1-11 In: Paul M. Hubbell (ed.), Progress Report. Fishery Investigations - Trinity River. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. Task V. November 1984. 11 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA. 95814.
Zuspan, M. 1991b. Capture and Coded-wire Tagging of Naturally Produced Chinook in the Trinity River Basin. Chapter II. Job II. p. 24-33. In: Carpenter, R., and K. Urquhart (eds.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1988-1989 Season. August 1991. 51 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, Ca. 95814.
Zuspan, M. 1992b. Capture and Coded-wire Tagging of Naturally Produced Chinook in the Trinity River Basin. Chapter II. Job II. p. 30-43. In: Kevan Urquhart (ed.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1989-1990 Season. June 1992. 140 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, Ca. 95814.
Zuspan, M. 1992c. Salmon Spawner Surveys in the Upper Trinity River Basin. Chapter I. Job I. p. 1-31. In: Urquhart, K., and R. Carpenter (eds.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1990-1991 Season. October 1992. 184 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, Ca. 95814.
APPENDIX 1. List of Julian weeks and their calendar date equivalents.
