SURVIVAL, AND CONTRIBUTIONS TO THE FISHERIES AND SPAWNER ESCAPEMENTS MADE BY STEELHEAD PRODUCED AT TRINITY RIVER HATCHERY (continued)
Brood Year 1991 (Two-year-olds). Approximately 15,000 fish were held over from the 1992 marking season because they did not meet the minimum release size. Fish from the 1991 BY were reared at TRH, marked this season, and released as two-year-olds.
According to TRH feeding schedule records, progressive growth occurred throughout the rearing period. During April 1992, the average weight of each fish was 30.2 g, and increased to 378 g by the release date (Figure 1).
Brood Year 1992 (Yearlings). According to TRH feeding schedule records, the 1992 BY fish also grew progressively throughout the rearing cycle. Smaller grade fish were constantly culled and kept in separate hatchery ponds throughout rearing. Smaller fish were probably from eggs that were spawned out last (Laird Marshal, Assistant Manager, TRH, CDFG, pers. comm.). We identified four different size-classes in this BY from TRH feeding schedules. After 24 December 1992, we combined the three larger classes into two, and then into one size-class after 28 January 1993, when average individual weight of fish converged at 65 g. Smaller grade fish were recorded as a separate size-class throughout rearing. The average weight of fish from this BY on the date of release was 103.8 g for the larger steelhead, and 63.9 g for the smaller steelhead. Fluctuations seen in recorded size are probably the result of constant grading by TRH personnel (Figure 2).
FIGURE 2. The average weights of yearling steelhead from the 1992BY reared at TRH.
This is the fourth consecutive season that Project personnel completed marking and release operations at TRH. To date, we have marked five BYs with a combination of various fin clips (Appendix 1).
Brood Year 1991 (Two-year-olds). We completed marking a total of 15,665 fish from the 1991 BY this season with an Ad+RV fin-clip combination on 5 January 1993, and released them as two-year-olds. Releases were made into the mainstem Trinity River at TRH, the old weir site (RKM 178.6), and at Old Lewiston Bridge (RKM 176.9). Three release locations were chosen to allow increased angling opportunities over a wider area, and minimize residualism (Laird Marshal, Assistant Manager, TRH, CDFG, pers. comm.). The average size of these fish upon release was 2.6 fish/kg (Table 1).
TABLE 1. Summary of TRH steelhead marking and release for the 1992-93 season.
During the hatchery mark evaluation procedure, we checked 1,000 steelhead from this BY and found some dorsal and caudal fin erosion, and scale loss; an organosomatic analysis was not done because of the limited number of fish. Of the 1,000 fish examined, we found 0.5% (5/1000) were poorly fin-clipped. Six hundred of the 1,000 fish were measured. According to TRH fish planting estimates, they released a total of 13,650 fish from this BY; thus we estimated 2,015 mortalities occurred during the rearing period. Altogether, 13,582 steelhead from this BY were considered effectively marked (Table 2). At release, FLs ranged from 184 mm (7.2 in) to 421 mm (16.6 in), and averaged 322.1 mm (12.7 in) with a sample SD of 4.02 (Figure 3).
FIGURE 3. Length frequency distribution of fin-clipped two year old steelhead from the TRH 1991 BY.
Brood Year 1992 (Yearlings). We marked steelhead from this BY with an Ad+LV fin-clip combination from 14 January through 2 April 1993. Throughout this period TRH personnel continually graded fish according to size. Between 14 January and 5 March, we marked a total of 320,192 steelhead. The approximately 5,000 fish remaining were considered too small to fin clip, so marking was temporarily halted. We marked the remaining 4,683 fish from this BY on 2 April, giving us a total of 324,875 fin-clipped yearling steelhead for the season. The average size of these fish was 9.7 fish/kg for the larger fish, and 15.7 fish/kg for the smaller grade fish (Table 1).
We examined a subsample of 6,470 steelhead from the 1992 BY to see how well they were marked, and found 0.11% (7/6470) with poor fin clips. Comparing TRH fish planting estimates with the total number of fish marked, we estimate 936 mortalities occurred during the rearing process. An estimated 323,583 steelhead from this BY were effectively marked and released into the Trinity River at TRH. (Table 2).
TABLE 2. Summary of hatchery mark evaluations for steelhead fin-clipped between 01/05 and 04/02/93.
Of the 6,470 fish examined, we measured 2,870 (44.4%). Average FLs for the two size groups were determined separately. Smaller- sized fish made up 18.4% (527/2870) of our measured sample. Fork lengths of this size group ranged from 76 mm (3.0 in) to 151 mm (5.9 in), and averaged 124.8 mm (4.9 in) with a sample SD of 1.41. Larger sized fish ranged from 152 mm (6.0 in) to 291 mm (11.5 in), and averaged 198.1 mm (7.8 in) with a sample SD of 1.96 (Figure 4).
A subsample of 20 fish was collected at TRH prior to release by the CDFG pathologist. An organosomatic analysis was done and results were determined by autopsy. Results showed some dorsal and caudal fin wear and scale loss; however, their overall general condition upon release, determined by both the pathologist and Project personnel, appeared to be excellent.
FIGURE 4. Length frequency distribution of fin-clipped yearling steelhead from the 1992 TRH BY.
Naturally produced 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 fresh water to spawn when they are 38 to 69 cm in total length. Life-history patterns of steelhead are variable, 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. These fish are referred to as half-pounders.
In relation to life-history patterns, this was the second and third years we expected to see returns of fish which were released in 1990 and 1991 (1988, 1989 and 1990 BYs). Experimental hatchery management practices aimed at increasing adult returns were not conducted with any of these steelhead release groups.
There was a significant loss of returning steelhead at TRH this year due to otter predation before recoveries could be made. Otters took fish directly from the holding tanks and fish trap, where only fish body parts were occasionally found. In addition to reducing the possible recovery of marked steelhead, fewer spawners were obtained and fewer eggs taken, which will result in a lower number of juvenile steelhead available for marking next season. Plans to trap and relocate some otters are being made and will be discussed in future reports.
Project personnel monitored steelhead returning to TRH from 14 September 1992 through 28 March 1993, when migration was completed. During that period 586 steelhead returned, of which 568 (96.9%) were fin-clipped, making up the greater proportion of returns to the hatchery. Of those marked fish, 119 (20.9%) had LV fin-clips, from the 1989 BY released as yearlings or from the 1991 BY yearling release; and 130 (22.2%) had RV fin-clips, from the 1989 BY or the 1990 BY two-year-old releases. Ad+RV fin-clips were seen on 76 (13.0%) of the marked steelhead, indicating they were from the 1989 BY yearling release; and 234 (39.9%) fish had Ad+LV fin-clips, indicating they were from the 1990 BY yearling release (Appendix 1). Nine steelhead were marked with an Ad fin-clip only, origin unknown, and 18 were unmarked. Ad-clipped-only fish may have at one time been marked in conjunction with a ventral fin clip, and were probably the result of poor fin clipping and regeneration.
During the 1990-91 and 1991-92 seasons, totals of 927 and 295 steelhead, respectively, were observed at TRH. Marked fish constituted 2.4% of the 1990-91 returning fish, and 62.0% of the 1991/92 returns. Three- and four-year-old adults of the 1988 BY, released as two-year-olds, composed the largest proportions of the marked fish recovered at TRH for both those seasons(Appendix 2).
TRP personnel monitored steelhead at Junction City Weir from 21 May through 8 December 1992, when migration was complete. During that period 29 steelhead were recorded, of which 17 (58.6%) were fin-clipped. Of those marked fish, 12 (70.6%) had Ad+LV fin-clips, indicating they were from the 1990 BY; three (17.6%) had Ad+RV fin-clips, indicating they were from the 1989 BY; and one (5.9%) had a LV fin-clip, from the 1991 BY. One recovery was marked with an Ad fin-clip only, and 12 were unmarked. No RV fin-clipped steelhead were recovered at the Junction City Weir this season.
During each of the past three seasons, the total number of steelhead caught at Junction City Weir was lower than at either of the other two recovery sites. The percentage of fin-clipped fish seen at Junction City, however, was intermediate to the percentages seen at TRH and Willow Creek Weir. The marked fish recovered during the 1990-91 season could not be assigned to a BY release group because of a questionable fin clip. Four-year-olds from the 1988 BY made up the largest proportion of marked fish recovered at Junction City Weir during the 1991-92 season (Appendix 2).
TRP personnel monitored steelhead at Willow Creek Weir from 20 August through 2 December 1992, when migration was complete. During that period 190 steelhead were observed, of which 85 (44.7%) were fin-clipped. Of those marked fish, one (1.2%) had a RV fin-clip, from the 1988 BY; 12 (14.1%) had LV fin-clips, from the 1989 BY or from the 1991 BY. Ad+RV fin-clips were seen on 17 (20.0%) of the marked steelhead, indicating they were from the 1989 BY; and 47 (55.3%) had Ad+LV fin-clips, indicating they were from the 1990 BY. Eight recoveries had an Ad fin-clip only, and 105 were unmarked.
No marked steelhead were seen at Willow Creek Weir during the 1990-91 season. During the 1991-92 season, four-year-olds from the 1988 BY again made up the largest proportion of marked fish recoveries.
1. Marking should continue, starting at the latest possible date to allow the maximum time for fish growth. This would eliminate unnecessary delays during marking.
2. Only one marking shed should be used next season because of the low number of steelhead expected to be available.
3. Steps should be taken to reduce or eliminate otter predation upon steelhead returning to TRH.
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.
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.
Heubach, B. 1984. Progress Report, 1981-82 Season. Task VI. Trinity River salmon and steelhead tagging program. pp. 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. Calif. Dept. of Fish and Game, Inland Fish. Div., 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. pp. 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. Calif. Dept. of Fish and Game, Inland Fish. Div., 1416 9th St., Sacramento, CA 95814.
Moyle, P. B. 1976. Inland Fishes of California. pp. 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. pp. 215-237. (Tagging and Marking). In: L.A. Nielson and D. L. Johnson, (eds.), Fisheries Techniques. American Fisheries Society. Virginia: Southern Printing Co. 1983.
Zuspan, M., D. Maria, and B. Heubach. 1985. Progress Report, 1982-83 Season. Task IV. Trinity River salmon and steelhead tagging program. pp. 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. 146 p. Calif. Dept. of Fish and Game, Inland Fish. Div., 1416 9th St., Sacramento, CA 95814.
