Staff of the California Department of Fish and Game's Trinity Fisheries Investigations Project conducted a steelhead (Oncorhynchus mykiss) marking program at Trinity River Hatchery from 5 October to 31 December 1990. Unique combinations of fin clips were given to each group of fish to permit identification of brood year upon recapture. This season, we marked 970,617 fish from brood year 1990 with an adipose and left ventral fin clip, to be released as yearlings, and 102,316 fish from brood year 1989 with an adipose and right ventral fin clip, to be released as two-year-olds.
We checked 1,500 steelhead from brood year 1990 and 1,000 from brood year 1989 for fin clip accuracy prior to release. We found that 2.1% of the fish from brood year 1989 and 0.7% of those from brood year 1990 were poorly fin-clipped. We monitored adult steelhead returning to Trinity River Hatchery from 5 September 1990 through 27 March 1991, when migration was determined to have been complete. During that time, six steelhead from brood year 1988 returned to Trinity River Hatchery.
To determine relative return rates and contributions to spawning escapements and the fisheries made by steelhead produced at Trinity River Hatchery, and to evaluate experimental hatchery management practices aimed at increasing adult returns.
The completion of the Trinity River Division of the Central Valley Project (15 May 1963) blocked access to a significant part of the historic steelhead spawning and rearing habitat in the Trinity River basin, and resulted in significant downstream flow reductions. This project-induced reduction in fishery habitat is the major factor contributing to the decline of annual runs of steelhead in the Trinity River system.
In October 1984, U.S. Public Law 98-541 was signed into law to mitigate for fish and wildlife losses. This act, commonly referred to as the Trinity River Basin Fish and Wildlife Restoration Act, authorized the expenditure of $57 million over a 10-year period to implement a program to restore fish and wildlife populations to pre-dam conditions.
One of the major goals of the California Department of Fish and Game's (CDFG) Klamath-Trinity Program is to develop fishery harvest management recommendations which are compatible with the goal of restoring full, natural salmon and steelhead production in the Trinity River and its tributaries downstream from Lewiston Dam. Knowledge of hatchery- and naturally produced steelhead escapements into the Trinity River is needed to develop management recommendations and determine the effectiveness of those recommendations. To differentiate between naturally produced and hatchery-produced steelhead, all steelhead reared at Trinity River Hatchery from 1978 through 1981 were systematically fin clipped before being released. Run size and escapement estimates of hatchery-produced and naturally produced steelhead were made during the 1978-79, 1980-81, and 1982-83 seasons. (Heubach and Hubbell 1980, Heubach 1984, Zuspan et al. 1985).
This year, staff of CDFG's Trinity Fisheries Investigations Project (TFIP) continued to mark steelhead produced at Trinity River Hatchery (TRH) as part of the first half of our Project's efforts to meet the Job Objectives. The second half, which began this season, includes the monitoring of adults returning to TRH.
The amount of feed given to fish reared at TRH is determined by taking weekly standard weight counts (number of fish per pound), and then fish are fed according to suggested manufacturers requirements (Gary Ramsden, Manager, Trinity River Hatchery, CDFG, pers. comm.). The average weight of fish was determined by dividing one lb by the number of fish per pound, based on data from TRH feeding schedules which record the number of fish per pound.
Marking Operations
Staff of CDFG's TFIP marked steelhead at TRH inside two wooden sheds measuring 3 m X 3 m, and positioned directly over the hatchery ponds. Positioning the sheds over the ponds allowed access for two crews of four markers, each, to effectively net fish into each shed. Each shed contained a four-station marking table and was equipped with a circulating, holding tank (approximately 284 liters) through which fresh hatchery pond water was pumped. Fish were netted directly from the hatchery ponds and placed into the holding tank located inside the shed. Another smaller holding sink, also with circulating fresh, pond water, was located in the center of each marking table. One shed was equipped with a recirculating tricaine methanesulfonate (MS-222) system (approximately 76 liters), which was changed once per day with fresh aqueous MS-222 solution. This system used 1.5 cups of MS-222 per week. The recirculating MS-222 system was installed to minimize fish mortality caused by overdoses of anaesthetic. The other shed had a separate, non-circulating MS-222 sink at each of the four work stations, with each marker responsible for controlling their own MS-222 concentrations. Comparisons of MS-222 usage between the two sheds are not conclusive at this time. The temperatures of the fresh water and MS-222 solutions from both sheds were monitored regularly throughout the day.
Marking steelhead involved anaesthetizing them with MS-222, removing one or more of their fins by clipping, and releasing them into a pond reserved for marked fish. To keep count of fish marked, each marking station was equipped with a manual counter. A combination of right ventral (RV) or left ventral (LV) and adipose (Ad) fin clips was used to differentiate each fish's brood year (BY) and age at release. Fish marked during this season were from the 1989 BY, given a Ad+RV fin clip to be released as two year-olds, and from the 1990 BY, given a Ad+LV fin clip to be released as yearlings.
We had previously marked 144,800 steelhead from the 1989 BY with an Ad+RV fin clip during the spring of 1990 (Aguilar 1992). These fish were moved off-site to the Old Sawmill Site at Lewiston (river km 175.4) for rearing because of lack of space at TRH. As of 3 April 1990, an estimated 110,000 fish from this BY remained to be marked, but operations were halted because of rising water temperatures which could have lead to increased mortalities. The remaining fish from this BY were reared at TRH, and marked this season when water temperatures cooled.
Numbers of fish released from TRH were estimated by TRH personnel, using the standard weight count method on a subsample of marked fish at time of release. Numbers of fish released from the Old Sawmill Site were estimated by TRH personnel, using a Peterson estimate on marked fish only.
Hatchery Mark Evaluations
To determine fin-clip accuracy, we examined a sample of the marked steelhead just prior to release. These fish were anaesthetized with MS-222, measured to nearest cm fork length (FL), and checked for how well the fin was removed during the marking process. Fin clipping is considered a permanent mark if the rays are removed to the point of attachment to the bone (Stuart 1958, Eipper and Forney 1965, Jones 1979). Fins which were less than 1/2 removed are likely to regenerate. In this situation, fin rays appear distorted at the location of the clip. Unless those persons checking for fin clips on returning adults specifically look for distorted rays, fish that were actually marked, may be unrecognizable. We determined the number of effectively marked fish by multiplying the percent of fish with poor fin clips by the total number of fish released, and subtracting this product from the total.
Prior to release, a sample of marked fish was autopsied for signs of health and general condition by a CDFG pathologist. Project personnel also checked the fish for general condition, by sight examination during the hatchery mark-evaluation procedure.
Recovery Operations
Project personnel monitored steelhead returning to TRH from 13 September 1990 through 27 March 1991. We examined the fish for fin clips, measured them to the nearest cm FL, and recorded their sex. Steelhead were also checked for fin clips by Trinity River Project (TRP) personnel during their operation of the Willow Creek Weir, located 132.0 km downstream of TRH, and at the Junction City Weir, located 42.4 km downstream of TRH.
Brood Year 1989 (2-year-olds)
These fish were not marked and released in 1990 as yearlings, because TRH management determined they would not reach the minimum release size of 15.2 cm (6 in.) by March 1991. At the beginning of TRH's 1990-91 feeding schedule, the average weight of these fish was 36 gm (12 - 13 fish per pound). Hatchery records show there was progressive growth from 23 May to 19 September 1990. From 19 September 1990 to 9 January 1991 there was no recorded growth. This frequently occurs because of water temperatures, and culling and grading of the fish (Gary Ramsden, Manager, Trinity River Hatchery, CDFG pers. comm.). From 9 January to 6 February 1991, average weight increased from 65 gm to 110 gm. At release in March 1991, average weight was 115 gm (Figure 1).
Brood Year 1990 (yearlings)
According to hatchery feeding schedules, there was progressive growth throughout the time these fish were reared at TRH. On 23 May, the average fish weighed 3 gm. At release, average weight was 65 gm (Figure 1).
Marking Operations
This season we marked 102,316 fish held over from the 1989 BY to be released as two-year-olds, and 970,617 fish from the 1990 BY to be released as yearlings. Both groups were released in March 1991 (Table 1).
TABLE 1. Summary of steelhead fin-clipping operations at TRH …….
Brood Year 1989 (2-year-olds)
We previously marked 144,800 steelhead from this BY with an Ad+RV fin clip during the spring of 1990 (Aguilar 1992). These fish were moved off-site to the Old Sawmill Site for rearing because of lack of space at TRH. On 18 March 1991, pond screens at the Old Sawmill Site were pulled and fish were allowed to enter the mainstem Trinity River of their own volition. At release, the mean size of fish from these ponds was 2.0 fish/kg (Table 1).
We completed marking the remaining fish from the 1989 BY from 5 through 17 October 1990. We marked a total of 102,316 fish. These fish were reared at TRH until 18 March 1991, when pond screens were removed and fish were allowed to leave of their own volition. Mean fish size at release was 1.6 fish/kg (Table 1).
Brood Year 1990 (yearlings)
We marked 970,617 yearlings from the 1990 BY from 17 October through 31 December 1990 with a Ad+LV fin clip. These fish were reared at TRH until 18 March 1991, when pond screens were removed and fish were allowed to leave of their own volition. Mean fish size at release was 3.2 fish/kg (Table 1).
Hatchery Mark Evaluations
Brood Year 1989 (2-year-olds)
On 15 March 1991, we examined a subsample of 1,000 steelhead reared and released from the Old Sawmill Site. It appeared that 2.8% of them (28/1000) were unmarked fish, indicating a large number with poor fin clips. We later discovered that naturally produced (unmarked) steelhead were able to enter ponds at this site and mix with the marked fish. Because of this, we were unable to determine the number of fish with poor fin clips and make an adjustment for the number of effectively marked fish released from this location. The number of effectively marked fish was determined from fish of the same BY reared at TRH. TRH personnel estimated that 83,551 marked steelhead were released from the Old Sawmill Site. Based on their estimate, there were approximately 61,249 holding mortalities. Adjusting for the proportion of poor fin-clips seen at TRH, we estimate 81,796 effectively-marked, two-year-old fish were released from this location in 1991 (Table 2).
TABLE 2. Summary of steelhead hatchery mark evaluations from 5 October 1990 through 18 March 1991.
On 14 and 15 March 1991, we examined a sub-sample of 1,000 of the steelhead which were reared at TRH. Lengths ranged from 11.0 to 32.0 cm FL, and averaged 21.7 cm FL with a sample standard deviation (SD) of 3.52 (Figure 2).
We found 2.1% (21/1000) of these fish had poor fin clips. TRH personnel determined 101,299 steelhead were released, with approximately 1,017 holding mortalities. Based on their estimate, we determined 99,171 two-year-old steelhead were effectively marked and released from TRH (Table 2).
Based only on the rate of poor fin clips observed for 1989 BY fish reared and released from TRH (2.1%), we estimate 180,967 two-year-old fish from the 1989 BY were effectively marked and released from the two sites combined (Table 2). Overall condition and health of fish from both locations at time of release were good, with the exception of some fin erosion.
Brood Year 1990 (yearlings)
On 18 March 1991, we examined a subsample of 1,500 fish from the 1990 BY which we marked with Ad+LV fin clips. We found 0.7% (11/1500) of the fish had poor fin clips. Personnel from TRH counted 1,017 mortalities, thus we estimate 962,812 yearling steelhead were effectively marked and released from the 1990 BY. Lengths ranged from 10.0 to 24.0 cm FL, averaged 18.0 cm FL, with a sample SD of 1.99 (Figure 3). Overall, general condition and health were good, with the exception of some fin erosion.
Recovery Operations
Juvenile steelhead migrate to sea after spending one to three years in fresh water. They usually stay one to two years in salt water, then return to freshwater to spawn when they are 38 to 69 cm in total length. Life history patterns of steelhead are variable, however, and growth rates may vary (Moyle 1976).
A fraction of the Trinity River steelhead run have a unique life history pattern in that they will stay less than one year in salt water, and return to fresh water after several months (Hopelain 1987). These fish are referred to as half-pounders.
Project personnel monitored steelhead returning to TRH from 13 September 1990 through 27 March 1991, when migration was complete. During that time, 927 steelhead returned to TRH, 22 of which were marked. Fifteen were marked with a RV fin clip, indicating they were from the 1988 BY released as two-year-olds. One was marked with a LV fin clip, indicating it was from the 1989 BY released as a yearling. One was marked with a Ad+RV fin clip indicating it was from the 1989 BY released as a two-year-old. Five were marked with an Ad fin clip of unknown origin.
Personnel from the TRP caught 138 steelhead at the Junction City Weir during the 1990-91 season. One was marked with a right pectoral fin clip of unknown origin. Three hundred twenty five unmarked steelhead were recovered at the Willow Creek Weir.
Although Project and TRH personnel were monitored adult returns this season, we did not expect to see many fin-clipped fish until next year, when most fish released in 1990 (1988 and 1989 BY's) are expected to return. Because of the small number of returns this season, we were unable to determine relative return rates and contributions to the spawner escapement and the fisheries made by steelhead produced at TRH.
1. To minimize possibilities of an overdose of anaesthetic, both marking sheds should be equipped with a recirculating MS-222 system.
2. To minimize the number of poor fin clips, fin clip accuracy should be checked on a daily basis.
3. To increase measurement accuracy, all fish taken during the hatchery mark-evaluation process should be measured to the nearest mm of fork length.
Aguilar, B. 1992. Survival, and contribution to the fisheries and spawner escapement made by chinook salmon produced at Trinity River Hatchery. p. 128-135 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. of Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA 95814.
Eipper, A., and J. Forney. 1965. Evaluation of partial fin-clips for marking largemouth bass, walleyes, and rainbow trout. New York Fish and Game Journal, 12:233-240.
Heubach, B. 1984. Progress Report, 1981-82 Season. Task VI. Trinity River salmon and steelhead tagging program. p. 49-106. 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 I and VI. December 1984. 106 p. Available From Calif. Dept. of Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA 95814.
Heubach, B. and P. M. Hubbell. 1980. FY 1979 Progress Report. Task VI. Lower Trinity River salmon and steelhead tagging program. p. 80-132. 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. of Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA 95814
Hopelain, J. S. 1987. Age, growth, and life history of Klamath River basin steelhead (Salmo gairdneri), as determined from scale analysis. 33 p. Available from Calif. Dept. of Fish and Game, Inland Fisheries Div.-Room 1251, 1416 9th St., Sacramento, CA 95814.
Jones, R. 1979. Materials and methods used in marking experiments in fishery research. Food and Agriculture Organization of the United Nations, Fisheries Technical Paper Number 190 (FIRM/T190). Rome, Italy.
Moyle, P. B. 1976. Inland Fishes of California. p. 131-132. Univ. of Calif. Press, Berkeley, CA. 405 p.
Stuart, T. A. 1958. Marking and regeneration of fins. Freshwater Salmon Fisheries Research, Edinburgh, Scotland 22.
Zuspan, M., D. Maria, and B. Heubach. 1985. Progress Report, 1982-83 Season. Task IV. Trinity River salmon and steelhead tagging program. p. 62-146. In: P. M. Hubbell (ed.), Progress Report. Fishery Investigations--Trinity River. Trinity River Basin Fish and Wildlife Task Force Priority Work Item No. 5. January 1985. 84 p. Available from Calif. Dept. of Fish and Game, Inland Fish. Div.-Room 1251, 1416 9th St., Sacramento, CA 95814.
