Between 1 July 1990 and 30 June 1991, the California Department of Fish and Game's Trinity River Project marked (adipose fin-clipped and binary coded-wire tagged) three 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 at the hatchery. We marked 299,463 spring-run and 97,810 fall-run chinook salmon, and 51,088 coho salmon. In addition, Trinity River Hatchery personnel marked and released two lots of fall-run chinook salmon, totaling 46,168 fish, as part of a hatchery feed experiment.
Recovery operations at Trinity River Hatchery captured 602 adipose fin-clipped chinook and coho salmon. Coded-wire tags were recovered from 345 spring-run and 211 fall-run chinook salmon. None were recovered from coho salmon.
Run-size, angler harvest, and spawner escapements of marked spring- and fall-run chinook salmon of the 1985 through 1989 brood years are presented. Complete returns were only available for fish from the 1985 brood year, returning as two- through five-year-olds. Based on coded-wire tags collected from 1987 through 1990, we estimate that 7,929 spring-run and 7,239 fall-run chinook salmon from the 1985 brood year produced at Trinity River Hatchery returned to the Trinity River basin upstream of the Willow Creek Weir.
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 of 1 July 1990 through 30 June 1991, the California Department of Fish and Game's (CDFG) Trinity River Project marked (adipose fin-clipped and coded-wire tagged [Ad+CWT]) and released chinook salmon smolts and yearlings, and 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 released 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 spawning escapements in the Trinity basin, in order to properly manage hatchery production and fishery harvest.
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 (MS 222). Once anesthetized, we marked the fish by removing their adipose (Ad) fin and injecting a coded-wire tag (CWT) into their rostrum. A NMT MK 41/ tagging unit was used to tag smolt spring chinook with half-length CWTs, and yearling chinook and coho with full-length tags.
After marking, fish were dropped into a funnel supplied with running water that lead to a quality control device. The quality control device magnetized the CWT, detected the tag, and tallied the marked fish. Marked fish continued through the funnel and dropped into a rearing pond situated next to the pond containing the unmarked fish. If a fish had not received a CWT, the quality control device gave a warning signal and diverted the fish into a funnel leading to a rejection bucket. Periodically, fish in the rejection bucket were re-anesthetized, re-tagged, and dropped into the funnel leading to the quality control device. Periodically during the marking period, we inspected samples of fish for the depth of CWT insertion and quality of the fin clip.
All fish from a particular mark group were held in separate rearing ponds until release. Immediately before the marked salmon were released, a systematic sample of 300 to 400 fish from each group was examined for CWT retention and the quality of the adipose fin clip, and measured to the nearest mm fork length (FL).
The total number of "effectively-marked" (properly tagged and fin-clipped) fish released was calculated by subtracting mortalities, 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 fish of a particular CWT group were released concurrently with unmarked fish of the same strain, BY, and size in the Trinity River immediately below TRH.
Coded-wire Tag Recovery
The TRH fish ladder was open from 1 September 1990 through 27 March 1991. 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 Project tags and fin clips, and its sex and FL (in cm) were recorded. Marked fish which were not ready to spawn were given a distinguishing fin clip and placed in ponds to ripen. Later, when the 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 heads of all marked salmon and placed each in a zip-lock 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 recovery and decoding (Ocean Salmon Project personnel provided us with a computer file of the CWT recovery data for editing and analysis).
Run-size, Contribution to Fisheries and Spawner Escapement of Coded-wire Tagged Salmon
The information needed to estimate the numbers of 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 used to determine the run-size and harvest estimates are presented as a part of Task IV (p x - x). To estimate the numbers of the salmon above a specific weir site with a CWT, we used the equation:
NWADclip NHAD+CWT
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; NHAD+CWT = 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 = ________
NHAD+CWT
where, FCWT group = fraction of the salmon population with a specific tag code; and NHCWT group = number of salmon observed at TRH with a specific tag code.
We estimated the total number of chinook salmon upstream of the weir with a specific tag code with the equation:
NCWT group = NCWT X FCWT group
where, NCWT group = estimated total number of salmon of a specific CWT code group.
The estimated number of fish from each tag-code 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 tag-code group caught in the Trinity River sport fishery; and Nharvest rate estimate = harvest rate estimate.
We estimated the total number of fish 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 tag group available to the spawner escapement.
The estimated number of salmon available to natural spawner escapement is:
NCWT natural escapement = NCWT escapement - NHCWT group
where, NCWT natural escapement = the estimated number of a specific coded-wire-tag group contributing to natural spawning escapement.
All estimates for spring and fall chinook are for the Trinity River system upstream of Junction City Weir (JCW) (river km [RKM] 136.4) and Willow Creek Weir (WCW) (RKM 46.8), respectively.
Three groups of chinook salmon reared at TRH, totaling 397,273 fish, were marked (Ad+CWT), and released into the Trinity River below the hatchery during October 1990 and May 1991 (Table 1). The spring and fall chinook yearlings were released in October 1990. Both releases were from the 1989 BY. Spring chinook smolts of the 1990 BY were released in May 1991. We marked (Ad+CWT) 51,088 coho from the 1989 BY at TRH. The coho were released into the Trinity River below TRH in March 1991.
Fingerling spring and fall chinook from the 1989 BY reared at TRH showed symptoms of Enteric Redmouth Disease (Pseudomonas hydrophila) so all were treated. The 1989 BY spring and fall chinook released as yearlings appeared free of the disease. The fall chinook suffered virtually no mortality, and the spring chinook had insignificant mortality between marking and release (Table 1). Hatchery personnel considered the fish to be in excellent condition when released.
TABLE 1. Coded-wire-tagged (CWT) and unmarked chinook and coho salmon releases from TRH…
Fall chinook smolts from the 1990 BY were not marked in the spring of 1991 because of a pandemic of Infectious HematopoieticNecrosis (IHN). All survivors will be released during fall 1991, as yearlings. The outbreak of IHN also infected the spring chinook, and 11% of the smolts that were marked died during and after marking, due to a combination of the disease and handling stress (Table 1). The fish were still infected when released and were considered by hatchery personnel to be in fair condition.
The 1989 BY coho released in March 1991 were infected with Bacterial Kidney Disease (Corynebacterium sp.) and were considered to be in poor-to-fair condition when released. The mortality during and following marking was moderately high (Table 1).
In addition to the salmon marked by Project Personnel, TRH personnel marked (Ad+CWT) and released two groups (46,168 fish) of fall chinook yearlings from the 1989 BY as part of a feed experiment (Table 1). The experiment's results will be reported in a forthcoming TRH annual report.
All chinook and coho mark groups were released concurrently with unmarked fish of the same BY, strain, and size.
Coded-wire Tag Recovery
We recaptured 602 marked (Ad+CWT) chinook and coho at TRH during the 1990-91 season. Tags were recovered from 345 spring chinook and 211 fall chinook. None were recovered from coho (Table 2). Spring chinook from the 1986 BY, released as yearlings, comprised 77% of the CWTed spring chinook we recovered, while 75% of the CWTed fall chinook recovered were from the 1986 and 1987 BYs that had been released as yearlings.
The three marked coho that entered TRH probably had natural marks, as no tags were recovered from them. No marked coho from TRH should have been returning during the 1990-91 season, because none of the 1987 or 1988 BY coho produced at TRH were marked. No chinook or coho salmon were recovered at TRH during the 1990-91 season that were released from other facilities.
Run-size and Contribution to Fisheries and Spawner Escapement of Coded-wire Tagged Salmon
In this report period, complete returns were only available for spring and fall chinook from the 1985 BY, and they were the only groups used for the following analyses. We estimate that 5.7% of the 1985 BY spring chinook released from TRH in October 1986 as yearlings (CWT code 066144) returned to the Trinity River basin upstream of JCW as two- through five-year-olds. An estimated 771 of the 5,808 returning fish were caught by anglers, thus 5,037 were available for spawner escapement. The total return rate of spring chinook released as yearlings was approximately five times the return rate of spring chinook from the 1985 BY released as smolts (CWT code 066142) (Table 3).
TABLE 2. Release and recovery data of CWT chinook salmon produced at TRH, some years……..
We estimate that 4,164 1985 BY fall chinook released as yearlings (CWT code 065625) returned to the Trinity River basin above WCW and that 489 were caught by anglers, thus the remaining 3,675 were available for spawner escapement. The total return rates of fall chinook of the 1985 BY released as yearlings was approximately three times the return rate of fall chinook from the same BY released as smolts (CWT code 065623) (Table 3).
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 1991-92.
