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 13 January through 26 May 1992.
We trapped 81,851 juvenile chinook salmon, 500 juvenile coho salmon (O. kisutch), and 5,542 juvenile steelhead (O. mykiss) at four locations during the study. Peak catch-per-unit-effort for juvenile chinook salmon measured at the trapping site where we had the most consistent effort occurred in late April. 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 59,971 juvenile chinook salmon, a sub-sample of which ranged in size from 29 to 110 mm, averaging 57.7 mm fork length. After adjusting for tagging mortality, tag shedding, and poor fin clips, we effectively coded-wire tagged and released 56,610 juvenile chinook salmon.
We estimate six chinook salmon from the 1988 brood year, coded-wire tagged by this Project, were harvested in the ocean as three-year-olds this season. Additionally, one chinook salmon from this group was recovered at Trinity River Hatchery.
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 spawner escapement of these stocks is crucial to wise management of chinook in the basin.
Recent 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 inferences 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, coded-wire tagged (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.
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 conducted trapping at four primary sites in the mainstem Trinity River this season. Site names and river km (RKM) locations were: 1) Lewiston at RKM 177, 2) Ambrose at RKM 172, 3) Hard Hat at RKM 148, and 4) Sky Ranch at RKM 134 (Figure 1).
FIGURE 1. Map of the Trinity River below Lewiston Dam showing the four trapping sites used in 1992.
We began trapping on 13 January 1992 and finished on 26 May 1992. 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 seven 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 mouth, 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 Ambrose, Hard Hat, 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 Technology (use of brand names is for identification only and does not imply the endorsement of any product by the CDFG). 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 an 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 on 13 January 1992 and continued at varying locations and intensity through 26 May 1992 (Table 1). We discontinued trapping in late May because of decreasing catches and rising river temperatures. Also, the release of 210,188 spring-run chinook from Trinity River Hatchery (TRH) on 5 June 1992 precluded further trapping of only naturally produced fish for the remainder of the season.
We captured 81,851 juvenile chinook this season. Totals by site were: 1) 1,832 at the Lewiston Site, 2) 16,102 at the Ambrose Site, 3) 38,817 at the Hard Hat Site and, 4) 25,100 at the Sky Ranch Site (Appendices 2, 3, 4, 5).
Catch-per-unit-effort (CPUE), measured as the 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 (487) was at the Ambrose Site followed by the Sky Ranch Site (450), the Hard Hat Site (434), and the Lewiston Site (356).
We measured the FLs of 11,102 chinook during the trapping season. These fish ranged in FL from 29 to 142 mm. Weekly average FLs of fish at the four trapping sites generally increased though time (Figure 3, Appendices 2, 3, 4, 5). At the Sky Ranch Site, where we trapped every JW through the season, the average FL of juvenile chinook was 36.7 mm in mid-January and increased to 65.1 mm by late May (Figure 3).
We caught 5,542 steelhead this season. Steelhead were caught at all sites throughout the trapping season (Appendices 2, 3, 4, 5). Catches were relatively low until mid-March when large numbers of hatchery-produced steelhead were captured, coincident with hatchery releases. We found that 36.6% of the steelhead captured this season were fin-clipped, indicating they were from TRH. Beginning with the 1989 brood year, all steelhead produced at TRH have been fin-clipped prior to release (Aguilar 1992).
We caught 500 coho salmon this season. Only yearlings were captured prior to 12 February, afterward, both yearlings and young-of-the-year were caught. The highest catch for coho was at the Hard Hat site (14 fish/trap/night) and occurred during mid-February (Appendix 3).
Tagging operations began 13 March and continued through 18 May 1992. During this period, we marked (Ad+CWT) and released 59,971 juvenile chinook. Tagging took place at the Ambrose, Hard Hat, and Sky Ranch sites.
At the Ambrose Site, we tagged 8,348 juvenile chinook with coded-wire tag number 6-1-8-3-1. Tagging at this site began 13 March and continued through 30 March 1992. Independent, non-overlapping estimates, based on quality control groups, of tagging mortality, poor fin clips, and the number 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 8,070 juvenile chinook from this site (Table 2).
At the Hard Hat Site, we tagged 35,043 juvenile chinook with coded-wire tag numbers 6-1-8-3-3, 6-1-8-3-6, 6-1-8-3-7, and 6-1-8-3-8 (Table 2). Tagging at this site began 9 April and continued through 7 May 1992. Independent, non-overlapping estimates, based on quality control groups, of tagging mortality, poor fin clips, and the number 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 33,195 juvenile chinook from this site (Table 2).
Tagging began 10 April and continued through 18 May 1992 at the Sky Ranch Site. During this period, we tagged 16,580 fish with coded-wire tag numbers 6-1-8-3-4, 6-1-8-3-9, and 6-1-8-3-10 (Table 2). Independent, non-overlapping estimates, based on quality control groups, of tagging mortality, poor fin clips, and the number 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 15,345 juvenile from this site (Table 2).
The CDFG's Ocean Salmon Project estimates that seven chinook from the 1988 brood year, coded-wire tagged by this Project in 1989 (Zuspan 1991), were recovered as three-year-olds this year. These included three each from the Oregon and California ocean fishery, and one from Trinity River Hatchery (Richard Dixon, Calif. Dept. Fish and Game, pers. comm.). One two-year-old fish from this coded-wire tag group was recovered during spawner surveys last year in the North Fork Trinity River (Zuspan 1992b). 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 (non-hatchery) spawner escapement for chinook salmon (spring- plus fall-run) above Junction City was the lowest on record, only 15.4% of the 1989 run (5,453 vs 34,587) and 92.1% of last year's run (5,453 vs. 5,811) (spawner escapement estimates from Bill Heubach, CDFG, pers. comm).
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 1.2 times that of last year (442 vs. 374 trap nights), and 3.9 times that of 1990 (442 vs. 143). Total juvenile chinook catch this year was 91.8% (81,851 vs. 89,208) of last year's and only 50.6% (81,851 vs. 161,730) of that in 1990 (Zuspan 1992a, 1992b). (We trapped both naturally and hatchery-produced chinook salmon in 1990. This anlysis considers only the effort expended and fish trapped prior 18 May 1990, the date TRH chinook were released.) In a pattern noted last year (Zuspan 1992b), both the overall juvenile chinook CPUE and adult escapement of their progenitors were down similar amounts. The 1991 adult chinook escapement (spring- plus fall-run) was 92.1% of the 1990 escapement and 15.4% of the 1989 escapement, while the CPUE for 1992 juvenile chinook was 77.6% of that in 1991 and 16.4% of that in 1990.
While it seems unlikely that there is a linear relationship between adult escapement and production, trapping during the last three years suggest an important correlation.
1. Job 2 activities should be continued in FY 1992-93.
2. In the event of a low chinook salmon escapement in 1992, the Project should be prepared to increase our trapping effort. 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: K. Urquart (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., 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: P. 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., 1416 9th St., Sacramento, CA. 95814.
Heubach, B. 1980. FY 1979 progress report. Task V. Salmon tagging and release monitoring. p. 75-79. In: P. 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., 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: P. 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., 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: P. 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., 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: P. 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., 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: P. 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., 1416 9th St., Sacramento, CA. 95814.
Zuspan, M. 1991. 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., 1416 9th St., Sacramento, Ca. 95814.
Zuspan, M. 1992a. Capture and coded-wire tagging of naturally produced chinook in the Trinity River Basin. Chapter II. Job II. p. 30-43. In: K. 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., 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. 32-49. In: Urquhart, K., and R. Carpenter (eds.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1990-1991 Season. December 1992. 186 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div., 1416 9th St., Sacramento, Ca. 95814.
APPENDIX 1. List of Julian weeks and their calendar date equivilants.
