Between 1 July 1988 and 30 June 1990, staff of the California Department of Fish and Game's Trinity River Project marked and released four groups of chinook salmon (Oncorhynchus tshawytscha) totaling 584,424 fish. The total included 285,233 spring-run and 299,191 fall-run chinook salmon. Each fish had its adipose fin clipped, was binary coded-wire tagged, and then released into the Trinity River below the Trinity River Hatchery. In addition to these efforts, Trinity River Hatchery personnel tagged and released two lots of fall-run chinook salmon totaling 46,365 fish.
Recovery operations at Trinity River Hatchery recaptured 2,385 adipose fin-clipped chinook and coho salmon (O. kisutch), and 2,211 coded-wire tags were recovered from 671 spring-run chinook, 1,120 fall-run chinook, and 421 coho salmon.
To determine relative return rates and contribution to spawning escapement and the fisheries made by chinook salmon produced at Trinity River Hatchery, and to evaluate experimental hatchery management practices aimed at increasing adult returns.
During the period 1 July 1989 through 30 June 1990, 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 produced at Trinity River Hatchery, and recaptured fish from previously marked brood years (BY) returning to the hatchery. Similar marking studies began at Trinity River Hatchery (TRH) in 1978, with the marking of fall-run chinook salmon from the 1976 BY. Beginning with the 1977 BY, representative marked subsets of TRH-produced fish have been included in all releases of smolt and yearling chinook salmon released from TRH and at other, off-site locations.
These earlier studies were funded by the U.S. Bureau of Reclamation (USBR) and Anadromous Fish Act funds administered by the U.S. Fish and Wildlife Service. The current program was funded by Anadromous Fish Act Funds from 1 July through 30 September 1989, and by the USBR from 1 October 1989 through 30 June 1990.
These marking studies are directed at providing survival rates and catch-to-escapement ratios for spring- and fall-run chinook salmon reared at TRH. State and Federal management agencies need to evaluate the contributions of chinook salmon produced at TRH to the various fisheries, and spawning escapements in the Trinity River basin, in order to properly manage hatchery production and fishery harvest.
Chinook salmon selected for marking at TRH were crowded into a small area beneath a marking shed situated over their rearing pond. After crowding, the fish were dip-netted into a 152.4 X 61.0 X 76.2-cm wooden holding tank in the tagging shed, through which pond water 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 fin and injecting a coded-wire tag (CWT) into their rostrum.
In September and October 1989, we tagged yearling chinook salmon with a NMT MK2A1/ tagging unit, using whole CWTs, whereas we tagged chinook salmon smolts in March and April 1990 with a NMT MK41/ tagging unit, using half-length CWTs.
After tagging, we dropped the fish into a funnel supplied with running water that lead to a quality control device. The quality control device magnetized the CWT and tallied the tagged fish. Tagged fish continued through the funnel and dropped into a rearing pond situated next to the pond containing the untagged fish. If a fish did not receive 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, 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 tagged fish from a particular tagging group were held in separate rearing ponds until release. Immediately before the marked chinook salmon were released, a systematic sample of 200 to 800 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 based on the total number of fish in each group released minus dead fish recovered during and after tagging operations, and the number of fish we estimated had shed CWTs or were improperly fin-clipped.
All tagged fish of a particular CWT group were released concurrently with unmarked fish of the same strain, BY, and size in the river below TRH.
The TRH fish ladder was open from 8 September 1989 through 17 March 1990. Hatchery personnel conducted fish sorting and spawning operations two to three days per week, depending on the numbers of fish available each day.
We examined all salmon entering TRH for an adipose fin clip, determined their species and sex, measured them to the nearest cm FL, and removed the heads of all salmon bearing an adipose fin clip. Each salmon head was frozen in a plastic bag with a serially numbered tab noting the date and location captured, species, sex, and FL of the fish. The salmon heads and data were given to the CDFG's Ocean Salmon Project for CWT retrieval, decoding, and data entry. Ocean Salmon Project personnel provided us a computer file of the CWT recovery data for editing and data analysis.
Four groups of chinook salmon reared at TRH, totaling 584,424 fish, were marked (Ad+CWT) and released into the Trinity River below the hatchery during October 1989 and May 1990 (Table 1). The yearling chinook salmon released in October 1989 consisted of one group each of spring- and fall-run fish from the 1988 BY. The chinook salmon smolts released in May 1990 consisted of one group each of spring- and fall-run fish from the 1989 BY. All groups of Ad+CWT chinook salmon were released concurrently with unmarked fish of the same BY, strain and size. These releases were made as part of an ongoing program to monitor relative return rates, and contributions to the spawning escapements and the fisheries made by salmon produced at TRH.
In addition to this study's marked salmon releases, TRH personnel marked (Ad+CWT) and released two groups of fall-run chinook salmon yearlings from the 1988 BY (46,365 fish) as part of a feed experiment (Table 1).
We recaptured 2,385 marked (Ad+CWT) chinook and coho salmon at TRH during the 1989-90 season and recovered CWTs from 671 spring-run and 1,120 fall-run chinook salmon, and 421 coho salmon. Yearlings from the 1985 and 1986 BYs comprised 88% and 84%, respectively, of the CWT spring- and fall-run chinook salmon we recovered this season (Appendix 1). All of the CWT coho salmon recovered, and probably all of the marked coho that had shed their CWTs, represented fish of the 1986 BY released in March 1988. No stray CWT chinook or coho salmon were recovered at TRH during the 1989-90 season.
Yearling fish released this season (1988-89) are expected to begin returning to TRH during the 1990-91 season, whereas smolts released this season should begin returning to TRH during the 1991-92 season. Thus, we will be reporting on the return to TRH, survival, and contributions to spawner escapements and the fisheries of fish released this year in the 1990-91 and later year's annual reports.
1. Marking (Ad+CWT) of smolt and yearling chinook salmon should be continued during the 1990-91 season.
2. Marking (Ad+CWT) of yearling+ coho salmon should be added to the program, beginning in the 1990-91 season.
