SALMON SPAWNER SURVEYS IN THE UPPER TRINITY RIVER BASIN (continued)
We observed Program-marks (spaghetti tags and/or operculum punches) on 36 spring and 21 fall chinook carcasses in the mainstem Trinity River spawner survey. Program-marked spring and fall chinook were recovered from both JCW and WCW (Table 8). Of the 57 Program-marked chinook salmon we observed, 33 were condition-one carcasses and 24 were condition-two carcasses.
We used only condition-one chinook salmon carcasses observed to determine the proportion of Program-marked chinook salmon in the spawner survey. This is because we were more likely to correctly identify a Program-mark on a fresh (i.e. condition-one) fish than one in an advanced state of decomposition (Table 8).
Recovery of spring-run condition-one Program-marked chinook was over 2½ times (9.4%) that of similar fall-run fish. Spring chinook Program-marked at JCW made up a larger percentage (7.8%) of observed carcasses than those from WCW. Program-marked fall chinook from WCW (2.5%) were recovered at twice the rate of those from JCW.
We did not record the condition of coho during the survey so we could not separate out the proportion of Program-marked condition-one fish. Eleven Program-marked coho, ten from WCW and one from JCW, were recovered in the mainstem Trinity River, constituting 21.6% of all adult coho carcasses observed (Table 8).
TABLE 8. Proportions of recovered Program-marked (spaghetti-tagged & operculum-punched) adult salmon carcasses in the 1992-93 mainstem Trinity River spawner survey.
|
Spring-run chinook |
Fall-run chinook |
Coho salmon | |||||||
|
Tag site |
Program marks a/b/ |
Total observed b/ |
% Program marks |
Program marks a/b/ |
Total observed b/ |
% Program marks |
Program marks |
Total observed c/ |
% Program marks |
|
Willow Creek Weir |
4 |
256 |
1.6 |
6 |
243 |
2.5 |
10 |
51 |
19.6 |
|
Junction City Weir |
20 |
256 |
7.8 |
3 |
243 |
1.2 |
1 |
51 |
2.0 |
|
Totals: |
24 |
256 |
9.4 |
9 |
243 |
3.7 |
11 |
51 |
21.6 |
|
a/ Program marks include spaghetti tags and operculum punches. b/ Only condition-one chinook salmon were used for this count. c/ Both condition-one and condition-two coho salmon were used for this count. |
We recovered 11 chinook salmon carcasses and only one coho salmon carcass in the mainstem spawner survey which appeared to be Ad-clipped. Based on CWTs recovered from the chinook carcasses, three were spring-run, and three were fall-run of TRH origin (Appendix 8). One CWT was from a naturally produced chinook, more than likely a spring-run. There were four carcasses which were Ad-clipped but whose CWTs were either unreadable or shed.
The proportion of Ad-clipped chinook salmon in the spawner survey was estimated by analyzing only those Ad-clipped fish that had CWTs (Ad+CWT) and were condition-one carcasses. Carcasses in advanced decomposition (i.e. condition-two fish) were more likely to have shed their CWT. The percentage of Ad+CWTs observed in fall chinook condition-two carcasses was only 0.3% (1/337), while for condition-one carcasses, it was 1.2% (3/243). Our estimates of the Ad-clipped proportion in the spawner survey, however, were not comparable to the proportions of Ad-clipped fish observed returning to JCW, WCW, and TRH. This was because in the spawner survey we considered as Ad-clipped only those carcasses that had CWTs, while at the other sites all Ad-clipped fish even without CWTs were counted. To make our estimated proportions more comparable, we expanded the numbers of condition-one Ad+CWT carcasses observed in the spawner survey by a CWT shedding rate for Ad-clipped chinook salmon observed at TRH. During this season, 26.1% (57/218) of the Ad-clipped spring chinook, and 11.3% (39/344) of the Ad-clipped fall chinook at TRH had shed their CWTs. Expanding our counts of condition-one Ad+CWT carcasses in the spawner survey by the aforementioned CWT shedding rates, 1.9% of the spring, and 1.2% of the fall chinook observed in the spawner survey were Ad-clipped.
We determined the incidence of hatchery-produced chinook salmon among the carcasses seen in the spawner survey by comparing the ratios of Ad-clipped (hatchery-marked) chinook salmon at various locations within the river.
The proportions of Ad-clipped spring and fall chinook varied at the different recovery sites, probably partly as the result of hatchery-produced fish homing to the hatchery. Since naturally produced chinook salmon would become less abundant in upstream areas as they spawned in the lower mainstem or its tributaries, we would expect that the percentage of hatchery-produced chinook in the population would increase progressively at each upstream sampling site, and would be highest at the hatchery. Ad-clipped chinook salmon relative occurrence was highest at the hatchery, intermediate at the weirs, and lowest in the mainstem Trinity River spawner survey (Table 9). The Ad-clip ratio seen in the spawner survey may have been less than at the weirs, since the weirs captured both hatchery and natural upstream migrants, while the spawner survey emphasized in-river spawners which would be more likely to be naturally produced fish.
TABLE 9. Comparison of the estimated proportions of adipose fin-clipped chinook salmon in the mainstem spawner survey to those observed at three locations on the Trinity River during the 1992-93 season.
|
Site |
Ad-clips a/ |
Total b/ |
% Ad-clips |
Ad-clips a/ |
Total b/ |
% Ad-clips |
|
|
Willow Creek Weir c/ |
2 |
33 |
6.1 |
15 |
386 |
3.9 |
|
|
Junction City Weir |
45 |
656 |
6.9 |
42 |
738 |
5.7 |
|
|
Trinity River Hatchery |
218 |
1,846 |
11.8 |
344 |
3,990 |
8.6 |
|
|
Mainstem Trinity River survey |
5 |
256 |
1.9 |
3 |
243 |
1.2 |
|
|
a/ All adipose fin-clipped fish were counted at the weirs and hatchery. Only condition-one carcasses with coded-wire tags were considered Ad-clipped for the spawner survey. The spawner survey recovered four spring and three fall chinook which had both Ad-clips and coded-wire tags. These numbers were expanded to account for Ad-clipped fish which may have shed their tags. Coded-wire tag shedding rates were from this year's Trinity River Hatchery coded-wire tag recovery records. b/ Trinity River Hatchery total is an estimate based on coded-wire tag recoveries. c/ Only a small portion of the late spring-run chinook salmon population was sampled at this site. | |||||||
The percentage of Ad-clipped spring chinook observed at the three locations in the Trinity River basin below Lewiston Dam ranged from 1.9% to 11.8% (Table 9), and were significantly different from each other (X2= 17.42, df=2, P=0.0006).
During 1988 through 1990, based on expansions of CWT recoveries, approximately 97% of the spring chinook recovered at TRH were of hatchery origin. But in 1991, the proportion was 65.4% (Zuspan 1994). This year, using the same methodology, an estimated 72.1% of the spring chinook at TRH were of TRH origin. The apparent lower proportions during the last two seasons were artifacts of the high CWT shedding rates, which would have had the effect of decreasing the estimates of TRH-produced fish returning to the hatchery. We believed the actual percentage of hatchery-produced chinook salmon returning to TRH was similar to the higher proportions seen in previous years. Therefore, we assumed that the 11.8% Ad-clip ratio for spring-run fish observed at TRH represented a population of 100% TRH-origin chinook salmon. Since only 1.9% of the spring-run chinook salmon carcasses in the spawner survey were Ad-clipped, we estimated that 16.1% (1.9/11.8) were of hatchery origin, while the remaining 83.9% were naturally produced.
The Ad-clip percentage of fall-run chinook salmon ranged from 1.2% to 8.6% at the four sampling sites this season (Table 9). The differences in chinook salmon Ad-clip proportions among the four sites was statistically significant (X2=38.86, df=3, P=0).
Since most of the fall-run chinook recovered at TRH were estimated to be of hatchery origin (based on expansions of CWT recoveries), we assumed that the 8.6% Ad-clip ratio for fall-run fish observed at TRH represented a population of 100% hatchery-produced chinook salmon. Since only 1.2% of the fall-run chinook salmon in the spawner survey were Ad-clipped, we estimated that 14.0% (1.2/8.6) were of hatchery origin, while the remaining 86.0% were naturally produced.
There were several assumptions which could be potential sources of error in using the above methods to determine the incidence of hatchery fish spawning in the river. We assumed that field personnel actually observed all possible Ad-clips (according to our criteria). Using the strict protocol similar to last year (i.e. using a CWT detector on all carcasses, and by considering only condition-one carcasses), we presumed we were successful at accounting for essentially all Ad+CWT fish during our survey. We also assumed that the probability of observing and recovering an Ad-clipped fish was the same in the survey as at the hatchery, and, most importantly, that the ratios of Ad-clipped to unmarked hatchery fish were the same in the spawner survey as at TRH. Since different chinook salmon release groups were Ad-clipped at different ratios, this last assumption is only valid if the various CWT groups occurred in the spawner survey in the same proportions as among the fish recovered at TRH.
This is the fifth year of a multi-year effort of spawner surveys in the Trinity River basin. The following recommendations should be considered:
1. Spawner survey activities should be continued, with current objectives, in FY 1993-94 and beyond.
2. To increase the number and accuracy of our Ad-clip salmon recoveries, we should continue to pass all salmon through a tag detector. This should allow us to more reliably estimate the proportion of hatchery- and naturally produced fish spawning in the wild.
3. Flows from Lewiston Dam should be increased during the late summer to mid-fall period from the base 300 CFS to approximately 450 CFS. The purpose of the higher flows would be to distribute chinook salmon spawners more evenly in the mainstem Trinity River. A more even distribution of spawners should also lead to a decrease in prespawning mortality. The increased flows could be especially important during years of high escapement when chinook salmon in the Trinity River have historically suffered unusually high prespawning mortality.
Gibbs, E. D. 1956. A report on king salmon, Oncorhynchus tshawytscha, in the upper Trinity River, 1955. Calif. Dept. Fish and Game, Inland Fish. Admin. Rep. No. 56-10. 14 p.
La Faunce, D. A. 1965. King (chinook) salmon spawning escapement in the upper Trinity River, 1963. Calif. Dept. Fish and Game, Mar. Res. Admin. Rep. No. 65-3. 10 p.
Moffett, J. W., and S. H. Smith. 1950. Biological investigations of the fishery resources of the Trinity River, Calif. USFWS Spec. Sci. Rep., Fish. Bull. No. 12. 71 p.
Rogers, D. W. 1970. A king salmon spawning escapement and spawning habitat survey in the upper Trinity River and its tributaries, 1968. Calif. Dept. Fish and Game, Anad. Fish. Admin. Rep. No. 70-16. 13 p.
Rogers, D. W. 1973. King salmon, Oncorhynchus tshawytscha, and silver salmon, Oncorhynchus kisutch, spawning escapement and spawning habitat in the upper Trinity River, 1970. Calif. Dept. Fish and Game, Anad. Fish. Admin. Rep. No. 73-10. 14 p.
Rogers, D. W. 1982. A spawning escapement survey of anadromous salmonids in the upper Trinity River, 1971. Calif. Dept. Fish and Game, Anad. Fish. Admin. Rep. No. 82-2. 11 p.
Smith, G. E. 1975. Anadromous salmonid spawning escapements in the upper Trinity River, 1969. Calif. Dept. Fish and Game, Anad. Fish. Admin. Rep. No. 75-7. 17 p.
Weber, G. 1965. North coast king salmon spawning stock survey 1956-57 season. Calif. Dept. Fish and Game, Mar. Res. Admin. Rep. No. 65-1. 34 p.
Zuspan, M. 1991. Salmon spawner surveys in the upper Trinity River Basin. Chapter I. Job I. pp. 1-23. In: R. Carpenter, and K. Urquhart (eds.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1988-1989 Season. August 1991. 51 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div., 1416 9th St., Sacramento, CA 95814.
Zuspan, M. 1992a. Salmon spawner surveys in the upper Trinity River basin. Chapter I. Job I. pp. 1-29. 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. Fish and Game, Inland Fish. Div., 1416 9th St., Sacramento, CA 95814.
Zuspan, M. 1992b. Salmon spawner surveys in the upper Trinity River basin. Chapter I. Job I. pp. 1-31. 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 9th St., Sacramento, CA 95814.
Zuspan, M. 1994. Salmon spawner surveys in the upper Trinity River basin. Chapter I. Job I. pp. 1-37. In: K. Urquhart, and R. M. Kano (eds.), Annual Report of the Trinity River Basin Salmon and Steelhead Monitoring Project, 1991-1992 Season. February 1994. 235 p. Available from Calif. Dept. Fish and Game, Inland Fish. Div., 1416 9th St., Sacramento, CA 95814.
APPENDIX 1. Other sources of data.
