Salmon Spawner Surveys in the Upper Trinity River Basin (Continued)
Salmon spawner distribution in the mainstem Trinity River is presented based on the seven-zone system first used in 1987 (Stempel 1988). The results of Zones 6 and 7 were combined this year because too few flagged chinook were recovered in these individual zones to make reliable estimates. Distribution estimates are for adult fish only. This is because grilse and adult salmon are recovered in the survey at different rates; a fact that would force us to stratify the distribution estimate. Also grilse are relatively unimportant to the spawner escapement as they are predominantly unimportant to the spawner escapement as they are predominantly males and frequently do not spawn because of competition from larger, older males.
Chinook Salmon
Mainstem Trinity River. We examined 716 adult chinook this season, excluding flag recoveries. The numbers of chinook salmon spawners were greatest in upstream zones, decreasing from a high of 314 fish in Zone 1 to 38 fish in Zone 5
We recognize that carcass counts alone cannot be used to accurately describe distribution because recovery efficiency can vary from zone to zone, due to differences in stream morphology. Therefore, the percentage of flags recovered for each zone was used to determine the recovery efficiency of that zone (Table 5). Even based on the total number of chinook salmon recovered divided by the different recovery efficiency rates for each zone, the percent of chinook salmon spawners decreased downstream in successive zones below Zone 1 (Table 5). Spawner density, in terms of spawners per river km, was also highest in the uppermost section (198 spawners/km), and decreased steadily in a downstream direction
As noted in previous years (Zuspan 1991a, 1992a), a potential source of error in this estimate is the assumption that flagged chinook salmon carcasses are recovered only in the zone that they were originally flagged. If flagged fish are recovered in downstream zones, it would tend to increase the efficiency estimate in the recovery zone while decreasing the estimate in the flagging zone.
To determine the extent that carcasses drifted from one zone to another, fish flagged in each zone were given a distinct hog ring color. Recoveries that were originally flagged in another zone were recorded as such. This season, all of the 143 flags recovered were found in the same zone in which they were originally flagged. This indicates that carcass drifting had no effect on chinook salmon distribution estimates.
Tributaries. Spawning adult chinook salmon made very limited use of tributaries this year. Since so few chinook salmon were examined (seven, excluding flag recoveries), redd counts were used to describe spawner distribution.
We located 21 chinook salmon redds during the tributary survey. Redds were observed in only four of the nine tributaries surveyed. The mainstem of the North Fork Trinity River had 10 redds, followed by the East Fork of the North Fork with eight, Canyon Creek with two, and Browns Creek with one (Appendix 4).
Coho salmon
Mainstem Trinity River. We observed only 61 adult coho salmon in the mainstem spawner survey this year, most of which were seen in Zones 1 and 2 (Table 6). We estimated the total number of coho salmon which spawned in each zone by dividing the actual number of carcasses observed by the recovery efficiencies for that zone developed from chinook salmon flag recoveries. Like chinook salmon, coho spawning density was highest in the uppermost zone (11 spawners/km). Downstream of Zone 1, coho spawner density ranged form 6 to 2 spawners per km
Tributaries. We recovered only one coho salmon during the tributary surveys. It was recovered in the East Fork of the North Fork Trinity River (Appendix 4).
Program Marks
We observed Program marks (spaghetti tags or operculum punches) on 37 spring-run and 38 fall-run chinook salmon in the mainstem Trinity River spawner survey. All of the spring-run chinook salmon were tagged at Junction City Weir. Of the fall-run chinook salmon recovered, 27 were from Junction City Weir, 8 from Willow Creek, 2 from both Junction City and Willow Creek weirs, and 1 from the Klamath River mouth. Of the 75 Program-marked chinook observed, 62 were condition-one fish, while the remainder were condition-two fish. The single weir-marked coho observed in the survey was from Junction City weir.
Only condition-one fish were used to determine the actual percentage of Program marks 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 advanced decay. The percentage of condition-one chinook salmon recovered in the survey which had been marked at the three tagging sites ranged from 10.5% to 0.4%
Adipose Fin Clips and Coded-wire Tags
We recovered 53 chinook salmon and one coho salmon in the spawner survey which appeared to be Ad-clipped. Based on their CWTs, 9 were spring-run chinook salmon, 11 were fall-run chinook salmon, and 34 fish did not have CWT's (Appendix 7). Nineteen of the CWT recoveries were from chinook salmon produced at Trinity River Hatchery, while one was from a naturally produced chinook salmon originally trapped and tagged in the mainstem Trinity River under other Program activities (Zuspan 1991b).
The high percentage of apparently Ad-clipped chinook salmon without CWTs (63%) was probably the result of misidentifying Ad-clips. To minimize the number of Ad-clipped fish missed during the spawner survey, as noted last year (Zuspan 1992a), surveyors were instructed to consider any fish that had a missing or deformed adipose fin an Ad-clipped fish. While this procedure apparently resulted in misidentifying non-Ad-clipped fish as Ad-clipped, it probably allowed for the collection of nearly all the actual Ad-clipped fish.
The percentage of Ad-clipped fish in the spawner survey is best estimated by considering only those Ad-clipped fish that had CWTs (Ad+CWT) and were condition-one fish, as Ad-clips could not be reliably determined on fish in advanced decay (i.e. condition-two fish). However, this method does not produce an estimate of Ad-clipped fish that can be directly compared with the estimate of Ad-clipped fish returning to the weirs or TRH. This is because we consider Ad-clipped fish in the spawner survey to be only those fish that have CWTs, while at the other sites they count fish with Ad-clips irrespective of their having a CWT. To make the two estimates comparable, the number of Ad+CWT observed in the spawner survey was expanded by the CWT shedding rate for chinook salmon observed at TRH. For example, of the 379 Ad-clipped spring-run chinook salmon observed at TRH, 345 (91.1%) had CWTs, indicating a 8.9% CWT shedding rate for these fish. The CWT shedding rate for fall-run chinook salmon at TRH was 4.1%. Expanding our counts of Ad+CWT fish in the spawner survey by the aforementioned CWT shedding rates, 4.5% and 4.7% of the spring- and fall-run chinook salmon observed in the spawner survey were Ad-clipped. The percentage of Ad-clipped spring- and fall-run chinook salmon varied at the different recovery sites, probably as the result of hatchery-produced fish homing to the hatchery
Since naturally produced chinook salmon also spawn in the lower mainstem or its tributaries, we would expect the percentage of hatchery-produced, Ad-clipped chinook salmon in the population to increase at each sampling site proceeding upstream, and to be highest at the hatchery. This is the case for both chinook salmon runs at the weir sites and the hatchery (Table 8). However, the percentage of Ad-clipped salmon was lower in the mainstem Trinity River spawner survey than at any other sample site (Table 8). Ad-clip rates in the spawner survey may have been less than at weirs downstream, as the weirs captured a fraction of all upstream migrants, both hatchery and natural fish, while the spawner survey emphasized in-river spawners which would be more likely to be naturally produced fish.
We determined the incidence of hatchery-produced chinook salmon among the carcasses seen in the spawner survey by comparing the rate of Ad-clipped (hatchery-marked) chinook salmon at various locations within the river.
Spring-run Chinook Salmon
The percentage of Ad-clipped spring-run chinook salmon observed at the three locations in the Trinity River basin below Lewiston Dam ranged from 4.5% to 14.9% (Table 8), and are significantly different (X2=17.76, df=2, p=0.0001) from each other.
Since most (97%) of the spring-run chinook salmon recovered at TRH are estimated to be of hatchery origin (Bill Heubach, Calif. Dept. of Fish and Game pers. comm., based on expansions of CWT recoveries), we assume that the 14.9% Ad-clip rate for spring-run fish observed there can be used to represent the ad-clip rate for a population of 100% TRH-origin chinook salmon. It is not possible to use the original hatchery Ad-clip rates to determine the proportion of hatchery vs. wild fish returning to TRH, because the proportion of hatchery-produced chinook salmon groups that are Ad-clipped varies annually, and returns to TRH are a varying mix of brood years. In addition, different brood years may have experienced different rates of mortality among marked vs. unmarked fish. Since our survey recovered Ad-clipped spring-run chinook salmon at only 30.2% (4.5/14.9) of the Ad-clip rate observed at TRH, we estimated that 30.2% of the spring-run chinook salmon observed in the survey were of TRH origin while the remaining 69.8% were naturally produced.
Fall-run chinook Salmon
The Ad-clip percentage of fall-run chinook salmon was lowest in the spawner survey (4.7%) followed by Willow Creek Weir (6.0%), Junction City Weir (6.6%), and TRH (12.8%) (Table 8). The differences in chinook salmon Ad-clip rates among the four sites is statically significant (X2=32.3, df=3, p<0.001).
Since most (92%) of the fall-run chinook recovered at TRH are estimated to be of hatchery origin (Bill Heubach, Calif. Dept. of Fish and Game, pers. comm., based on expansions of CWT recoveries), we assumed that the 12.8% Ad-clip rate for fall-run fish observed at TRH could be used to represent the ad-clip rate for a population of 100% hatchery-produced chinook salmon. Since only 4.7% of the fall-run chinook salmon in the spawner survey were Ad-clipped, we estimated that 36.7% (4.7/12.8) were of hatchery origin, while the remaining 63.3% were naturally produced.
Computational Assumptions
There are several assumptions which could be potential sources of error in using the aforementioned method to determine the incidence of hatchery fish spawning in the river. We assume that field personnel actually observed all possible Ad-clips in the survey. The recognition of an Ad-clip, even on fish in relatively good condition, can be difficult. We are also assuming that the probability of observing and recovering an Ad-clipped fish is the same in the survey as at the hatchery, and, most importantly, that ratios of Ad-clip to unmarked hatchery fish are the sane in the spawner survey as at TRH. Since different chinook salmon release groups are Ad-clipped at different rates, this last assumption is only valid if the various CWT groups occur in the spawner survey in the same proportions as among the fish recovered at TRH.
1. Annual spawner survey activities should be continued, with current objectives, in FY 1991-92 and beyond.
2. To increase the number and accuracy of our Ad-clip fish recoveries, all chinook salmon with questionable Ad-clips should be passed through a tag detector. This should allow us to more reliable estimate the proportion of hatchery and naturally produced fish spawning in the wild. Additionally, the increased effort will insure better recovery of naturally produced Ad-clipped chinook which will be returning as adults beginning in 1991.
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.
Miller, E. 1972. (Untitled file report) Summary of the 1972 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1973. (Untitled file report) Summary of the 1973 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1974. (Untitled file report) Summary of the 1974 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1976. (Untitled file report) Summary of the 1976 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1978. (Untitled file report) Summary of the 1978 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1979. (Untitled file report) Summary of the 1979 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1980. (Untitled file report) Summary of the 1980 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1981. (Untitled file report) Summary of the 1981 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1982. (Untitled file report) Summary of the 1982 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1984. (Untitled file report) Summary of the 1984 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
Miller, E. 1985. (Untitled file report) Summary of the 1985 spawner survey in the upper Trinity River basin. Available from Calif. Dept. Fish and Game - Region I, 601 Locust St., Redding, CA. 96001.
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.
Pacific Southwest Inter-Agency Committee 1973. River Mile Index, Klamath River, Pacific Slope Basin, California-Oregon. Report of the Water Management Technical Subcommittee. July 1973. 56 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.
Stempel, M. 1988. Chinook salmon spawning survey in the upper Trinity River during the fall of 1987. USFWS file report. Available from USFWS F.A.O., P.O. Box 1450, Weaverville, Ca 96093.
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. 1991a. Salmon spawner surveys in the upper Trinity River Basin. Chapter I. Job I. p. 1-23. In: Carpenter, R., 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.-Room 1251, 1416 9th St., Sacramento, Ca. 95814.
Zuspan, M. 1991b. Capture and Coded-wire Tagging of Naturally Produced Chinook in the Trinity River Basin. Chapter II. Job II. p. 24-33. In: Carpenter R., 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.-Room 1251, 1416 9th St., Sacramento, Ca. 95814.
Zuspan, M. 1992a. Salmon Spawner Surveys in the Upper Trinity River Basin. Chapter I. Job I. p. 1-29. In: Kevan 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.-Room 1251, 1416 9th St., Sacramento, Ca. 95814.
