Between 1 July 1991 and 30 June 1992, 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 below the hatchery. We marked 292,916 spring-run and 309,456 fall-run chinook salmon, and 52,233 coho salmon.
Recovery operations at Trinity River Hatchery captured 385 adipose fin-clipped chinook and coho salmon. Coded-wire tags were recovered from 45 spring-run and 301 fall-run chinook salmon, and five coho salmon.
Run-size, angler harvest, and spawner escapements of marked spring- and fall-run chinook of the 1986 through 1990 brood years are presented. Complete returns were only available for fish from the 1986 brood year, returning as two- through five-year-olds. Based on coded-wire tags collected from 1988 through 1991, we estimate that 2,063 spring-run and 5,191 fall-run chinook salmon from the 1986 brood year returned to the Trinity River basin upstream of Junction City Weir and Willow Creek Weir, respectively, as two- through five-year-olds. An estimated 12 coho salmon of the 1989 brood year also entered the Trinity River basin upstream of the Willow Creek Weir this season.
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 1991 through 30 June 1992, 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 variously 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 1990-91 season. 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 Ad fin and injecting a 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 led to a quality control device. The quality control device magnetized the CWT, detected the tag, and tallied the tagged fish. Tagged 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, tag retention, and quality of the fin clip.
All tagged 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 tag group was examined for CWT retention and the quality of the Ad 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 numbers 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 in the Trinity River immediately below TRH.
The TRH fish ladder was open from 16 September 1991 through 27 March 1992. 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 (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. At this time, we removed heads of all Ad-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).
The data 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 proportions 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 as a part of Task IV (pp 103 - 167). The same sets of equations employed during the 1990-91 season were used to determine run-size, harvest, and spawner escapement (Heubach, et al. 1992). To estimate numbers of the salmon with a CWT above a specific weir site , 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 code group.
The estimated number of fish from each CWT 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 of a specific CWT code 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 specific CWT code group available to natural spawner escapement is:
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] 136.4) and Willow Creek Weir (WCW) (RKM 46.8), respectively.
Five groups of chinook salmon reared at TRH, totaling 602,372 fish, were marked (Ad+CWT), and released into the Trinity River below the hatchery during October 1991 and June 1992 (Table 1). Two groups of spring chinook yearlings and one group of fall chinook yearlings were released in October 1991. All three groups were from the 1990 BY. The two groups of yearling spring chinook were released as a replicate tag experiment to determine variability in the numbers of CWT fish caught in the fisheries and returning to the hatchery. Spring and fall chinook smolts of the 1991 BY were released in June 1992. We also marked (Ad+CWT) coho from the 1990 BY at TRH. The coho were released into the Trinity River below TRH in April 1992 (Table 1).
Fall chinook from the 1990 BY which were released as yearlings were the survivors of a pandemic of Infectious Hematopoietic Necrosis (IHN) that occurred during the spring of 1991 (Heubach, et al. 1992). The 1990 BY spring chinook were also exposed to the disease but suffered little mortality. There was very little mortality of these spring and fall chinook during marking, suggesting they were in good condition (Table 1). Hatchery personnel considered the fish to be in excellent condition when released.
Spring and fall chinook of the 1991 BY released as smolts were not exposed to any pathogens, so far as we know, and mortality during and following marking was very low (Table 1). They were also considered to be in excellent condition when released.
The 1990 BY coho released in April 1992 were infected with Bacterial Kidney Disease (BKD), Corynebacterium spp., at various times while being reared at TRH, but there was no apparent mortality due to the disease. Also, there was very little mortality while they were being marked (Table 1). Hatchery personnel considered them to be in fair condition when released because they still tested positive for BKD.
All chinook and coho tag groups were released concurrently with unmarked fish of the same BY, strain, and size.
We recaptured 385 marked (Ad+CWT) chinook and coho at TRH during the 1991-92 season. CWTs were recovered from 45 spring chinook, 301 fall chinook, and five coho (Table 2). Spring chinook from the 1987 and 1988 BYs, released as smolts, comprised 58% of the CWTed spring chinook we recovered, while the remainder were 1986, 1988 and 1989 BY fish released as yearlings. Fall chinook of the 1987 and 1988 BYs, released as yearlings, comprised 77% of the CWTed fall chinook we recovered.
TABLE 1. Coded-wire-tagged (CWT) and unmarked chinoo and coho salmon releases from TRH…
The five CWTed coho recovered were grilse from the 1989 BY. We did not expect to see any marked adult coho from TRH during the 1991-92 season, because none of the 1988 BY coho produced at the hatchery were marked.
In addition to the CWTs from TRH-produced fish recovered this year at TRH, we recovered a CWT chinook that had been tagged and released by the Trinity River Fisheries Investigation Project (another element of CDFG's Klamath-Trinity Program). This naturally produced fish had been captured, tagged and released as a juvenile between 29 March and 12 May 1989 in the Trinity River near Junction City. We also recaptured a CWT chinook that had been tagged and released by U. S. Forest Service personnel on 13 November 1990 in Horse Linto Creek, a tributary to the Trinity River.
We estimate that 0.05% of the 1986 BY spring chinook released from TRH in May 1987 as smolts (CWT code 061412), and 1.9% of the fish released as yearlings (CWT code 065639), returned to the Trinity River basin upstream of JCW. Yearlings from the 1986 BY returned as two- through five-year-olds, but fish released as smolts returned only as two- through four-year-olds. An estimated 225 of the returning marked 1986 BY spring chinook were caught above JCW by anglers, leaving 1,828 available for spawner escapement (Table 3).
We estimate only 0.21% of the 1986 BY fall chinook released as yearling+ (CWT code 066310) returned to the Trinity River basin upstream of WCW as three- and four-year-olds. None of these fish returned as two-year-olds. Only 0.07% of the three groups of 1986 BY released as smolts returned to the Trinity River basin upstream of WCW as two- through four-year-olds (Table 3).
Conversely, nearly 4.5% of the 1986 BY fall chinook released as yearlings returned to the Trinity River basin upstream of WCW. Another 1.4% of a group of yearlings released as part of a TRH feed experiment also returned. None of the fish from the six tag groups of the 1986 BY fall chinook returned as five-year-olds.
The poor survival and return of the 1986 BY may be due to mortality from IHN after being released from the hatchery or the off-site rearing ponds. The fish showed the symptoms of IHN while being reared but mortality was difficult to assess at the off-site rearing ponds.
We estimate 12 marked coho grilse from the 1989 BY returned to the Trinity River basin upstream of WCW, five of which entered TRH.
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 1992-93.
Heubach B., M. Lau, and E. Miller. 1992. Survival and contribution to the fisheries and spawner escapement made by chinook and coho salmon produced at Trinity River Hatchery. Chapter V. Job V. p 147-157.In: K. Urquhart (ed.). 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.
