Between 1 July 1992 and 30 June 1993, the California Department of Fish and Game's Trinity River Project marked (adipose fin-clipped and binary coded-wire tagged) five groups of chinook salmon (Oncorhynchus tshawytscha) and one group of coho salmon (O. kisutch) at Trinity River Hatchery. The fish were released into the Trinity River through the hatchery release facility. We effectively marked 325,835 spring-run and 307,332 fall-run chinook salmon, and 53,058 coho salmon.
Recovery operations at Trinity River Hatchery captured 921 adipose fin-clipped chinook and coho salmon. Coded-wire tags were recovered from 161 spring-run and 305 fall-run chinook salmon, and 321 coho salmon.
Run-size, in-river angler harvest, and spawner escapements of marked spring- and fall-run chinook, and coho salmon of the 1987 through 1990 brood years are presented. Complete returns are only available for both runs of chinook from the 1987 brood year, returning as two- through five-year-olds, and for coho from the 1989 brood year, returning as two- and three-year-olds.
We estimated that 210 spring-run and 547 fall-run chinook salmon from the 1987 brood year returned to the Trinity River basin upstream of Junction City Weir and Willow Creek Weir, respectively, as two- through five-year-olds during the years 1989 through 1992. We also estimated that 461 marked coho salmon from the 1989 brood year entered the Trinity River basin upstream of the Willow Creek Weir during the 1991 and 1992 seasons.
To determine relative return rates and the contribution to spawning escapement and the fisheries made by chinook and coho salmon produced at Trinity River Hatchery, and to evaluate experimental hatchery management practices aimed at increasing adult returns.
During the period 1 July 1992 through 30 June 1993, the California Department of Fish and Game's (CDFG) Trinity River Project marked and released chinook salmon smolts and yearlings, and one-year-old-plus (yearling+) coho salmon produced at Trinity River Hatchery (TRH), and recaptured fish from previously marked brood years (BY) returning to TRH. Similar marking studies began at TRH in 1977 with the marking and release of fall-run chinook salmon (fall chinook) from the 1976 BY. Beginning with the 1977 BY, representative, marked subsets of TRH-produced fish have been included in all releases of smolt, yearling, and yearling+ spring-run (spring chinook) and fall chinook from TRH and its associated off-site rearing locations. Beginning in 1978, representative samples of coho salmon (coho) were marked and released from TRH in most years, except BY's 1987 and 1988.
These earlier studies were funded by the U.S. Bureau of Reclamation (USBR), and with Anadromous Fish Act funds administered by the U.S. Fish and Wildlife Service. The current program has been funded by the USBR since 1 October 1989.
These marking studies are designed to provide survival rates and catch-to-escapement ratios for spring and fall chinook and coho salmon reared at TRH. State and Federal management agencies need to evaluate the contributions of salmon produced at TRH to the various fisheries and spawner escapements in the Trinity River basin, in order to properly manage hatchery production and fishery harvest.
Marking and release methods were similar to those used in the 1991-92 season (Heubach and Miller 1994). Salmon selected for marking at TRH were crowded into a small area beneath a marking shed situated over their rearing pond. After crowding, fish were dip-netted into a 152.4 x 61.0 x 76.2-cm wooden holding tank in the tagging shed through which water from the pond was circulated. We dip-netted approximately 25 fish at a time from the holding tank into pans containing an anesthetic solution of tricaine methanesulfonate. Once anesthetized, we marked the fish by removing their adipose (Ad) fin, and injected a coded-wire tag (CWT) into their rostrum with a Northwest Marine Technologies Mark IV tagging unit. Spring chinook smolts received half-length tags, while all other salmon groups received full-length tags.
After marking, fish were dropped into a funnel supplied with running water that led to a quality control device. If the fish had a CWT, the quality control device tallied it and diverted the fish into a separate rearing pond. If a fish had not received a CWT, the quality control device gave a warning signal and diverted the fish into a rejection bucket. Fish in the rejection bucket were re-tagged later that day. Periodically during the marking period, we inspected samples of fish for the placement and retention of the CWT and quality of the Ad-clip.
Salmon from a particular tag group were held together in separate rearing ponds until release. Immediately before release, a systematic sample of 300-to-500 fish from each tag group was examined for CWT retention and the quality of the Ad-clip, and measured to the nearest mm fork length (FL).
We determined the number of properly tagged and fin-clipped (effectively marked) fish released by subtracting mortalities, which occurred during and after tagging operations, and the estimated number of fish that had shed CWTs or were improperly fin-clipped, from the total fish marked.
All tagged fish of a particular CWT group were released concurrently with unmarked fish of the same strain, BY, and size into the Trinity River through the hatchery release facility.
The TRH fish ladder was open from 11 September 1992 through 28 March 1993. Hatchery personnel conducted fish sorting and spawning operations two days per week.
Fish were sorted by species and spawning condition. Each fish was examined for external tags and fin-clips, and its sex and FL (cm) were recorded. Ad-clipped fish which were not ready to spawn were given an additional distinguishing fin-clip and placed in ponds to ripen. Later, when these fish were killed and spawned, we determined the initial day the fish was sorted from its unique fin-clip. These dates were used in Chapter IV to document the timing of the returns of hatchery fish to TRH. We removed the heads of all Ad-clipped salmon and placed each in a sealable plastic bag with a serially numbered tab noting the date, location recovered, species, sex, and FL. Salmon heads were frozen and given to the CDFG/Ocean Salmon Project for tag extraction and decoding. We were provided with a computer file of the CWT data for editing and analysis.
The information needed to estimate the numbers of the salmon of a specific CWT group that returned to the Trinity River basin, and contributed to the fisheries and spawner escapement are: 1) run size; 2) the proportion of the run comprised by the various CWT groups; and 3) the harvest rate. Methods to determine the run-size and harvest estimates are presented in Chapter IV (p. 102). The same sets of equations employed during the 1991-1992 season were used to determine run-size, harvest, and spawner escapement (Heubach and Miller 1994).
To estimate the numbers of the salmon above a specific weir site with a CWT, we used the equation:
NWADclip NHADCWT
NCWT = ________ X _____ X Nrun-size estimate
NW NHADclip
where, NCWT = estimated number of the specific species of salmon above the weir with a CWT; NWADclip = number of salmon observed at the weir with an Ad-clip; NW = total number of salmon observed at the respective weir; NHADCWT = number of salmon observed at TRH with an Ad-clip and a CWT; NHADclip = total number of Ad-clipped salmon observed at TRH; and Nrun-size estimate = run-size estimate.
Using the various CWT groups recovered at TRH, we estimated the fraction of the population upstream of the weir with a specific CWT with the equation:
NHCWT group
FCWT group = ________
NHADCWT
where, FCWT group = fraction of the salmon population with a specific CWT code; and NHCWT group = number of salmon observed at TRH with a specific CWT code.
We estimated the total number of chinook salmon upstream of the weir with a specific CWT code with the equation:
NCWT group = NCWT X FCWT group
where, NCWT group = estimated total number of salmon of a specific CWT group.
The estimated number of fish from each CWT group caught in the Trinity River sport fishery upstream of the weir was then estimated by the equation:
SFCWT group = NCWT group X Nharvest rate estimate
where, SFCWT group = number of salmon of a specific CWT group caught in the Trinity River sport fishery; and Nharvest rate estimate = harvest rate estimate.
We estimated the total number of fish of a specific CWT group available to the spawner escapement by the equation:
NCWT escapement = NCWT group - SFCWT group
where, NCWT escapement = the total number of salmon of a specific CWT group available to the spawner escapement.
The estimated number of salmon of a specific CWT group available to the natural spawner escapement was:
NCWT natural escapement = NCWT escapement - NHCWT group
where, NCWT natural escapement = the estimated number of a specific CWT group contributing to natural spawning escapement.
All estimates for spring and fall chinook are for the Trinity River upstream of Junction City Weir (JCW) (river km [RKM] 136.5) and Willow Creek Weir (WCW) (RKM 47.0), respectively.
Five groups of chinook salmon reared at TRH, totaling 633,167 fish, were effectively marked (Ad-clipped and CWTed), and released into the Trinity River from the hatchery during October 1992 and June 1993 (Table 1). One group of spring chinook yearlings and two groups of fall chinook yearlings were released in October 1992. All three groups were from the 1991 BY. The two groups of yearling fall chinook were released as a replicate tag-experiment to determine variability in the numbers of CWTed fish caught in the fisheries and returning to the hatchery. Spring and fall chinook smolts of the 1992 BY were released in June 1993. We also marked coho from the 1991 BY at TRH. The coho were released into the Trinity River in March 1993(Table 1).
All chinook and coho tag groups were released concurrently with unmarked fish of the same BY, strain, and size.
TABLE 1. Coded-wire-taggeing and release of spring- and fall-run chinook and coho salmon from TRH
We recaptured 921 TRH-produced, Ad-clipped chinook and coho during the 1992-93 season. These consisted of 140 male and 78 female spring chinook, 184 male and 160 female fall chinook, and 262 male and 97 female coho (Table 2).
CWTs were extracted from 787 of the 921 Ad-clipped salmon recaptured. These were from 161 spring chinook, 305 fall chinook, and 321 coho.
In addition to the CWTs from TRH-produced fish, we also recovered four CWTs from fish tagged by the Trinity Fisheries Investigations Project (another element of CDFG's Klamath-Trinity Program). These were naturally produced chinook captured and tagged in the mainstem Trinity River from the BYs 1988 and 1989 (one fish each), and 1990 (two fish) (see Chapter II).
We estimated the run-size, angler harvest, and spawning escapement of the eight spring chinook CWT groups returning to the Trinity River upstream of Junction City Weir this season (Table 3). CWT group 066147 was the only spring chinook group (1987 BY smolt release) returning to TRH with a completed life cycle (ages two- through five-years-old). These fish were raised at an off-site facility while Trinity River Hatchery was being modernized. There were no 1987 BY yearling spring chinook raised. The overall return rate of CWT group 066147 was 0.113 percent, with three- through five-year-olds comprising 0.080 percent of overall returns (Table 3, Figure 1).
The other CWT groups have not yet completed their life cycles, but in general, the yearling release groups are returning as adults at rates at least three-times greater than their smolt release counterparts (Table 3, Figure 1). The 1989 BY smolt release group (CWT 0601040102) has, so far, had very poor return rates with 0.003 percent returning as three-year-olds. The comparable yearling release group (CWT 065639) returned as three-year-olds at almost 30 times that rate (0.087 percent).
It should be noted that CWT group 065639 may be composed of both fall and spring chinook. This group, from the 1989 BY, was tagged and released as yearling spring chinook (Heubach, et al. 1992). However, based on their entry dates at TRH, it appears likely that over 50% of the returning fish from this group were actually fall chinook (see Chapter IV, p. 123).
All fall chinook estimates were for the Trinity River basin upstream of the Willow Creek Weir.
Two CWT groups (065633 and 065631) completed their life cycles this season. Both of these groups, from the 1987 BY, were reared off-site at the Ambrose Ponds during hatchery modernization. The overall return of three- through five-year-olds for the yearling release group was about 10 times that of the smolt release group (0.385 vs. 0.040 percent, respectively) (Table 4, Figure 1).
The CWT group of 1988 BY yearlings (CWT 065632) returned at a rate of about 15 times greater than its smolt release counterpart (CWT code 065635) (Table 4, Figure 1). This was for overall returns of three- and four-year-old fish. Some returns can be expected during the fifth year.
Two 1988 BY fall chinook CWT groups (CWT 065522 and CWT 065523) were used in a feed-experiment conducted by Trinity River Hatchery personnel. The experiment was designed to determine if there was a difference in the adult returns of chinook raised on diets supplied by two different vendors. The adult return rates for these two groups are essentially identical (0.186 and 0.188 percent), although there appeared to be a difference in the age-at-return of the adults (Table 4, Figure 1). No two-year-old fish of either group were recovered.
TRH personnel repeated the feed-experiments with the 1989 BY, CWT groups 065637 and 065641. The return rates for both two- and three-year-old fish were higher for the CWT group 065641 (Table 4, Figure 1).
Only two CWTed coho groups returned to the Trinity River upstream of Willow Creek Weir this season. The overall return of the 1989 BY CWT group 065660 was 0.902 percent. This was composed of 0.893 percent three-year-olds and 0.010 percent two-year-olds (Table 5).
Two-year-olds from the 1990 BY (CWT 065657) returned at a relatively high rate of 0.971 percent (Table 5). It is unknown if the high return rate of these fish as two-year-olds will also be seen in high returns of this group as three-year-olds.
TABLE 5. Run-size, percent return, sport catch and spawner escapement estimates for Trinity River Hatchery-produced, coded-wire-tagged coho salmon returning to the Trinity River upstream of Willow Creek Weir during the 1992 and 1993 seasons.
|
Estimated returns | ||||||||||||
|
Release Data |
Spawning escapement | |||||||||||
|
CWT a/ code |
Brood year |
Date |
Number |
Site |
Age |
Run-size |
% of release |
River harvest |
Hatchery |
Natural |
Total |
|
|
065660 |
1989 |
03/18/91 |
51,088 |
TRH |
2 |
5 |
.010 |
0 |
5 |
0 |
5 |
|
|
3 |
456 |
893. |
58 |
152 |
246 |
398 |
||||||
|
Totals: b/ |
461 |
.902 |
58 |
157 |
246 |
403 |
||||||
|
065657 |
1990 |
04/03/92 |
52,233 |
TRH |
2 |
507 |
.971 |
0 |
169 |
338 |
507 |
|
|
a/ CWT = coded-wire tag b/ Totals are presented only for brood year 1989. These fish have reached three years of age and are considered to have completed their life cycle. | ||||||||||||
Coded-wire tagging and release of smolt and yearling chinook and coho, and the monitoring of adult salmon returns at Trinity River Hatchery should be continued in 1993-94.
Heubach, B., M. Lau, and E. Miller. 1992. Survival and contribution to the fisheries and spawner escapements made by chinook and coho salmon produced at Trinity River Hatchery. Chapter V, Job V. pp. 146-157. In: K. Urquhart 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 Ninth St., Sacramento, CA 95814.
Heubach, B., and E. Miller. 1994. Survival and contribution to the fisheries and spawner escapements made by chinook and coho salmon produced at Trinity River Hatchery. Chapter V, Job V. pp. 168-179. In: K. Urquhart and R. M. Kano (eds.). Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1991-1992 Season. February, 1994. 235 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div., 1416 Ninth St., Sacramento, CA 95814.
