The salmon described in the paragraph above are spring chinook, also called "summer salmon" by local residents. They may have been the most abundant salmonid in the South Fork Trinity River before the 1964 flood. Other anadromous fish species that are native to the river include fall chinook salmon, coho salmon, summer steelhead, winter steelhead, and Pacific lamprey. There are occasional chum salmon that return to the South Fork (Jong and Mills in press), but whether or not a viable run of these fish existed in the past is unknown.
Changes that occurred in the South Fork Trinity River channel after the 1964 flood, and other factors, have contributed to drastic reductions in salmon and steelhead runs. Runs have fallen to such low levels that there is concern that some stocks present in the river may become extinct (Higgins et al., 1992). Recent population levels have caused concern among management agencies (Tyrrel, 1989) and one conservation group called for an official review of whether or not the basin's spring chinook and summer steelhead should be afforded protection under California's Endangered Species Act (Baiocchi, 1990).
Fisheries scientists have discovered that salmon and steelhead develop distinct sub-populations because they spawn separately (Berst and Simon, 1981). Populations of these fish that spawn at different times and in different locations are known as stocks (Ricker, 1972). The homing instinct has guided local stocks of salmon and steelhead back to the South Fork Trinity River for thousands of generations. During this time, these fish stocks have developed many adaptations that allow the population to best survive the unique conditions of this river basin.
Genetic analysis can be used to identify stocks (Utter, 1981) but genetic tests are not always conclusive (McIntyre, 1984). Other traits used for stock identification are resistance to disease, early life history patterns, timing of migrations and spawning, number and size of eggs, ocean range, or other physiological traits (Nicholas and Hankin, 1988). Below are stock characteristics for all anadromous fish returning to the South Fork Trinity River based on scientific information gathered, and observations of residents and anglers. The stocks defined below are actually broad stock groups, adapted to the entire South Fork Trinity basin, which are called "management units" (McIntyre, 1984). Distinct sub-populations may exist or once have existed within the basin, such as the Hayfork "summer salmon" described by local residents. While it may not be practical to manage for all small sub-populations within the basin, preserving whatever genetic diversity that remains is certainly desirable (Baker, 1988).
Spring Chinook
Chinook salmon are also known as king salmon because they can attain great size by spending up to four years feeding in the ocean. Spring chinook often return to rivers that are fed by snow melt. They hold in deep pools during summer, then spawn in early fall. Spring chinook enter the South Fork Trinity River from April through July, with the run peak occurring in mid-June (Dean, in press). Until the early 1960's, Hayfork Creek had a run of spring chinook that migrated upstream during a similar time frame (Irl Everest, personal communication). Exact time of entry from the ocean into the Klamath River is unknown, but the U.S. Fish and Wildlife Service (1990) found that some spring chinook come in as early as February.
Recent studies of South Fork Trinity adult spring chinook behavior during summer showed that from July to spawning time, the fish exhibited little movement from their chosen holding pools (Barnhardt and Hillemeier, 1993). However, Dean (personal communication) noted that a few fish migrated to different pools when water temperatures reached 75° F (24° C), a temperature often thought to be lethal for salmon and steelhead (Reiser and Bjornn, 1979). In the late 1950's, spring chinook were observed holding below the mouths of cold water tributaries, such as Rusch Creek, during summer (Roger Jaegel, personal communication).
Studies conducted before the 1964 flood found that spring chinook spawning began near the East Fork of the South Fork around September 20 and progressed downstream (LaFaunce, 1967). The peak of spawning activity was in the second week of October. The lower extent of spawning activity on the South Fork was at Hyampom, but also extended from 2-7 miles up Hayfork Creek. Dean (personal communication) has noted spring chinook spawning below Hyampom in the South Fork Trinity River in all years of his surveys. In 1990-1992, Dean (in press) did not find any spawning activity in the vicinity of the East Fork of the South Fork. In those years, spawning began in the area of Silver Creek on October 3 and was completed by the third week of October in lower sections. In 1993, however, 25 spring chinook redds were found between Silver Creek and the East Fork of the South Fork (Dean personal communication). Sustained high flows during migration periods in 1993 seem to have allowed distribution further upstream than in previous years.
Although Dean (in press) found no spring chinook spawning activity in lower Hayfork Creek in 1990-92, six redds were found within the lower two miles upstream from the mouth in 1993 (Dean, personal communication). According to local residents, in the 1950's, spring chinook spawned during fall in the main stem of Hayfork Creek and in the lower end of tributaries such as Salt Creek, Tule Creek, Big Creek, and the East Fork of Hayfork Creek. Chinook salmon juveniles were found in 1989 above the East Fork of Hayfork Creek (USFS, 1990). Since no fall chinook salmon were ever known to spawn in upper Hayfork Creek, it seems likely that the juveniles were of spring chinook stock.
Average length of returning South Fork Trinity spring chinook
in 1990-1992 was about 24 inches in length (60.4 cm) while the
range of lengths was from 14 to 30 inches (34-76 cm) (Dean, in
press). Dean (in press) studied scales of adult spring chinook
to determine their life history. Age at maturity of returning
spring chinook adults varied between 1991 and 1992 (Table 2-1).
Over the two years 38-54% of spring chinook returning were four
and five year old fish. Frissell and Harai (1988) suggested that
salmon that mature at an older age may have a selective advantage
if a stock is spawning in an unstable stream bed. It is possible
that these larger fish may have an advantage in the South Fork
because they are able to bury their eggs deeper, which protects
their eggs from scour during high flows.
Table 2-1. Age at maturity of spring chinook salmon trapped on
South Fork Trinity River in 1991 and 1992 (Dean in press).
Age at Maturity 1991 1992
2 yr. olds 17% 22%
3 yr. olds 29% 40%
4 yr. olds 45% 32%
5 yr. olds 9% 6%
Dean (in press) found that the downstream migration of spring chinook juveniles began in April and ended around June 10. Trapping at Forest Glen showed that juvenile migration peaked on May 10, whereas downstream at Hyampom, the peak migration occurred on May 21. Scale analysis indicated that 88% of returning adults had spent less than one year in fresh water as a juvenile, and that the remaining 12% had spent more than one full year (Dean, in press). A 1989 habitat typing survey in Plummer Creek found several hundred chinook juveniles, of which about 15% were yearlings (Gilroy and Arey, 1993b). This type of early life history is thought to be somewhat rare in the Klamath basin (USFWS, 1991).
Interestingly, three of the five scales taken from five year old fish in 1991 showed they had spent a full year in fresh water. There may be some linkage between a larger fish size at ocean entry and the later age at maturity. While recent studies by the California Department of Fish and Game have provided some good information regarding spring chinook (Dean in press), it will take several years of data collection before it can be determined if South Fork spring chinook salmon have distinctive life history traits. Some adaptations, such as their ability to migrate even during periods of high stream temperature, might be difficult to duplicate with chinook stocks of other origins if South Fork stocks were lost.
Fall Chinook
Fall chinook in the South Fork Trinity River were called "dog salmon" by local residents and were never a popular sport fish because they were already in a spawning condition when they arrived at Hyampom. The fall chinook run has been reported to begin in September and peak in late October (LaFaunce, 1967, Jong and Mills, in press). However, in 1990, when the California Department of Fish and Game weir remained in place, fish were counted as late as mid-December. Lengths of fall chinook adults measured at the counting weir ranged from 15-41 inches (40-102 cm).
LaFaunce (1967) found fall chinook spawning in the main river downstream from Hyampom, and in the lowest three miles of Hayfork Creek, from about October 15 through November 20. Jong and Mills (in press) found distribution of spawning was similar to that described by LaFaunce, but that spawning continued into December. Cedarholm (1984) hypothesized that run timing of steelhead had shifted to a later peak due to unstable spawning gravel conditions. Those fish spawning after the peak of the last storm had the best chance of having eggs survive. Unstable spawning conditions that have existed in the South Fork Trinity below Hyampom since 1964 may be causing a shift toward later run timing. Alternatively, later spawning may have been occurring in earlier years, but not detected simply because no survey was conducted.
Adult fall chinook salmon return predominantly as 3 year olds with few 4 year olds and only a very rare 5 year old. The number of chinook salmon returning as 2 year olds (jacks) varies greatly from year to year (Jong and Mills, in press).
Most information on juvenile life history of South Fork Trinity River fall chinook salmon comes from scale analysis of returning adults. Juvenile fall chinook from the basin enter the ocean at the smallest size of any natural stock in the Klamath Basin (Sullivan, 1989). Sullivan (1989) found that 92% of South Fork Trinity fall chinook juveniles enter the ocean in their first year of life while the remaining 8% spend more than a full year in freshwater. Of fish that entered the ocean in their first year of life, those that lived for 8-10 months in the river or estuary attained a length of 2.25 to 3 inches (90-120 mm) and had the highest survival rate (Mills, unpublished report).
Coho Salmon
Coho salmon, also known as silver salmon, mature after spending just two years in the ocean. For this reason, they do not attain the great size of chinook salmon. The coho species is better adapted to smaller river systems, so may never have been the dominant salmon species of the Klamath basin (USFWS, 1991). Little information on abundance of coho salmon in the Klamath basin is available except for Snyder (1931), who noted that 11,162 coho salmon were landed incidentally in chinook salmon fisheries between September 20 and October 22, 1919. The spawning destination of these fish within the Klamath basin is unknown. No population estimate for this species in the South Fork Trinity was ever calculated.
Scientific reports note that coho salmon spawned in tributaries below the South Fork Trinity River prior to the 1964 flood (USFWS, 1979), but no surveys were conducted in the South Fork basin. Milt and Gene Mortenson (personal communication) described what were most certainly coho salmon spawning in small tributaries such as Pelletreau Creek, Mill Creek and Kerlin Creek prior to the 1964 flood. Males were described as having red sides, hump backs, and pronounced snouts, while females looked more like a steelhead except darker in color. Stream surveys conducted by Coots (1952) in Butter, Olsen, and Eltapom Creeks found juvenile coho salmon confirming these accounts of local residents.
Coho salmon are still known to occur on the South Fork Trinity River, although their numbers seem to be extremely low and run timing has been variable (Jong and Mills, in press). Typical spawn timing for Klamath basin native coho stocks is from November to January (Leidy and Leidy, 1984). In 1985, a small coho salmon run entered the South Fork during the week ending November 11, while in 1990 the coho run peaked during the week ending on January 14 (Jong and Mills, in press). Nearly 40% of the coho returning in 1985 had adipose fin clips which signifies they were of hatchery origin. Prespawning mortality of female coho salmon was estimated to be nearly 100%. It is quite possible that the 1985 run was completely of hatchery origin. Coho salmon measured at the CDFG counting weir ranged from 16 to 34 inches in length (41-85 cm), with an average length of 25 inches (61.9 cm).
Coho juveniles usually spend one year in fresh water, favoring pools formed by large woody elements (Reeves et al., 1988), before entering the ocean. Very little is known about the life history of juvenile coho salmon in the South Fork Trinity basin. Downstream migration of coho peaks in April and May in the Klamath basin (Leidy and Leidy, 1984). In 1985, several hundred coho salmon juveniles were trapped in the South Fork Trinity River below the mouth of Madden Creek (CDFG 1993). Two juvenile coho were also trapped in a fyke net operated for one evening at Sandy Bar in May 1992.
Winter Steelhead
Baker (1988) found substantial genetic differences between Trinity River Hatchery steelhead and those of the South Fork Trinity. While there was similarity among samples from various sub-basins within the South Fork Trinity watershed, Baker (1988) noted numerous rare genetic traits that he suggested were important to preserve. Hodges et al. (1989) conducted similar studies and suggested that sub-basins did not have distinct races of steelhead according to the genetic tests conducted.
Winter steelhead return to the South Fork Trinity River beginning in September and continuing through May (Mills and Wilson, 1991; Wilson and Mills 1992, Wilson and Collins 1992, Dean, in press). As more information is gathered, a distinction may be able to be drawn between fall steelhead and winter steelhead but these groups are aggregated for the purpose of this report. Adult steelhead trapped at Sandy Bar weir spent an average of 37 days migrating upstream from the Willow Creek weir but some spent as long as 84 days or as few as two in transit (Wilson and Collins 1992). Adults often move upstream in response to increased flows during storms. As a result, trapping or counting these fish is often difficult due to high flows and turbidity.
Adult steelhead and half-pounders trapped by the California Department of Fish and Game at the Sandy Bar weir from 1989 to 1991 have ranged in size from 14 to 31 inches in length (35-77 cm) (Wilson and Mills, 1992; Wilson and Collins 1992). Larger fish, exceeding 18 pounds, have been reported by long-time fishermen (Milt Mortenson, personal communication; Albert Bramlet, personal communication), and steelhead of this size would approach 40 inches in length. South Fork Trinity steelhead scale samples from 1988-1989 showed that 72% were first time spawners, 22% had spawned once before, and 6% had spawned twice (Mills and Wilson 1991).
According to scale samples taken from South Fork Trinity adult steelhead in 1988-1989: 9% were half-pounders (less than one year in the ocean), 56% of the fish spent one year in the ocean, 28% two years and only 6% three years (Mills and Wilson 1991). Klamath basin steelhead often return to freshwater as half-pounders after less than a full year in the ocean (Kesner and Barnhardt, 1972) and are not sexually mature. About 40% of South Fork Trinity steelhead had scale checks to indicate that they had exhibited this behavior (Mills and Wilson 1991, Wilson and Mills, 1992).
Satterthwaite (1988) noted that there is considerable straying of half-pounders between the Klamath and the Rogue Rivers, although the rate varies between years. This phenomenon suggests that Klamath basin steelhead feed along the continental shelf between the two rivers. The fact that most South Fork Trinity steelhead spend just one year in the ocean as adults and often return as half pounders may indicate that they do not migrate for long distances in the ocean. Light et al. (1988) found that some adult steelhead from California migrated a considerable distance to the northwest, toward the mid-Pacific. Although we have no tangible evidence, those few fish that do remain in the ocean longer than one year could be a sub-group that has a more extended ocean migrations.
Scale samples also give particular insight into which early life history strategy leads to the best chance of survival. Approximately 75% of returning adult steelhead sampled in 1988-89 and 1989-90 spent two years in freshwater and approximately 25% spent three years in freshwater (Mills and Wilson, 1991; Wilson and Mills 1992). No scales have been found that indicate any one year old steelhead or young of the year survive ocean entry. This suggests that larger sized juvenile steelhead entering the ocean have a greatly increased chance of survival. Alternatively, it is possible that there are no adult steelhead exhibiting 0+ or 1+ life histories simply because they do not smolt prior to two years of age (CDFG 1993). Older age steelhead juveniles migrate downstream from fall through early April, with a peak outmigration in March.
Young of the year steelhead (0+) show peak out-migration in the last week in May but continue to migrate downstream through June as stream temperatures rise. Since young of the year steelhead were not found in USFS habitat typing surveys in the main South Fork Trinity River below Hyampom (USFS 1990b, Dale 1990) and thermal problems exist in the main stem of the Trinity and Klamath Rivers in late summer (USFWS 1991), likelihood of survival of downstream migrating 0+ steelhead seems low.
Summer Steelhead
Summer steelhead have a life history somewhat similar to spring chinook in that they enter the Klamath River in spring, and enter the South Fork Trinity in early spring and early summer. It was assumed by Roelofs (1984) that Klamath River basin summer steelhead stocks spawn in fall before the winter steelhead. Everest (1973) found that Rogue River summer steelhead spawned after the first rains in late fall. No summer steelhead spawning has been observed in the main stem South Fork Trinity River during spring chinook spawning surveys (Dean, personal communication).
All scientific and personal observations indicate that summer steelhead runs in the South Fork Trinity have never been substantial. LaFaunce (personal communication) indicated that he had seen only incidental summer steelhead in all the years that he studied the river and that no summer steelhead were netted during tagging studies that captured several hundred spring chinook in 1964. Occasional summer steelhead have been sighted in Hayfork Creek in recent years (McCaslin et al., 1988), but their former abundance in that stream is unknown.Studies by Kesner and Barnhardt (1972) showed that 27% of Klamath basin summer steelhead migrated to the ocean after 1 year in fresh water, 65% after 2 years, and 8% after 3 years. Everest (1973) found that 97% of Rogue River summer steelhead returned as half pounders. No specific information on other early life history traits or adult behavior of summer steelhead of the South Fork Trinity basin is available.
Everest (1973) found that many Rogue River summer steelhead spawned in low gradient, intermittent headwater tributaries. It is possible that lack of suitable tributaries for spawning put these fish in direct competition with spring chinook for main stem spawning habitat. Alternatively, "deficiencies in juvenile rearing habitat for older (1+) parr" may be limiting summer steelhead production (CDFG 1993). This would not explain, however, why these fish do not seem to have been abundant before the South Fork Trinity River watershed was disturbed.
Chum Salmon
No information is available on chum salmon stock identification for the South Fork Trinity River. There may or may not have been a viable, genetically distinguishable run of chum in the basin.
Pacific Lamprey
Local residents of Hyampom describe runs of Pacific lamprey that move upstream to spawn in spring and die in early summer. Many who were raised in Hayfork recall great masses of wriggling lamprey adults working their way up over the large waterfall on Hayfork Creek above the East Fork during the spring months (Irl Everest personal communication). Dean (personal communication) remembered some lamprey moving upstream during the fall in the early 1970's. This latter observation is consistent with some upstream movement of adult lampreys throughout summer and early fall in the main Trinity River before construction of the dam (Moffett and Smith, 1950). These pre-dam studies recognized, however, that the majority of Pacific lamprey moved upstream in spring and spawned from April through early June.
Adult lamprey parasitize large fish or even whales during their typical two year stay in the ocean. Adults may take several months migrating upstream to spawn. They can use their sucking disc to move up over water falls and other obstacles. The female lamprey will lock her sucking disc on a rock and thrash her tail to dig a nest in pea-size gravels. The male will often join in nest building. Both male and female can move larger rocks downstream out of the nest pocket by attaching themselves to the rock and swimming in a reverse direction. When spawning, the female locks onto a rock above the nest with her sucking disc and the male attaches to the head of the female. Their bodies intertwine as the male fertilizes the 20,000 to 200,000 eggs that the female lays (Moyle, 1976). Both lamprey then move upstream, create a disturbance that buries the eggs, and then repeat the spawning activity.
Young lamprey larvae are known as ammocetes and have no eyes. They burrow into fine sediment and detritus where they filter feed for 3-7 years. Juveniles may move down stream annually to find other suitable habitat. This downstream movement may be caused by high flushing flows in winter (Moffett and Smith, 1950). Numerous lampreys have been electroshocked during fisheries surveys in cold water tributaries such as Big Creek, Salt Creek and Rusch Creek (Irizarry, personal communication). Thousands have also been trapped by Dean (in press) in downstream migrant traps at Forest Glen.
Fisheries managers, scientists and the public concur that there has been a substantial decline in abundance of fish returning to the South Fork Trinity River, although little data on long-term population trends is available. Prior to 1960, no formal scientific information was gathered to calculate abundance of any anadromous or resident fish populations. Both steelhead and salmon have received more management attention during the Trinity River Restoration Program, so information on run strengths has become available in recent years. Studies on fall chinook, spring chinook and winter steelhead have been conducted by the California Department of Fish and Game under the Natural Stocks Assessment Program which is funded by the Sport Fish Restoration Act.
Spring Chinook Remain At Low Levels
When a major dam was proposed for the South Fork Trinity near Eltapom Creek in the 1960's, chinook salmon population estimates were made to help calculate mitigation requirements. Healy (1963) estimated that 7,000 to 10,000 spring chinook spawned in the South Fork Trinity River and its tributaries. In 1964, LaFaunce (1967) tagged salmon to more precisely estimate the spring run at 11,600. The number of spring chinook returning after the 1964 flood has ranged from a few dozen to around 300, although comprehensive surveys of the river have only been done during the past few years (Table 2-2). Dive sweeps of the entire South Fork in 1991 and 1992 yielded estimates of about 220 and 330, respectively, adult spring chinook returning to the river (Dean, in press). The adult population rose to over 500 fish in 1993 (Dean personal communication).
In 1991-1992, only an estimated 50% of these returning adults survived to spawn (Dean, in press). This pre-spawn mortality rate is comparable to the 44% level found in the Deschutes River in Oregon but much higher than the 12% mortality estimated for Rogue River spring chinook (Lindsey et al., 1989 as cited by Dean, in press). The mortality in the South Fork Trinity River was only marginally lower than the 62.8% mortality found for main stem Trinity River spring chinook in 1990 (Zuspan, 1991). Warm water conditions, predation, and poaching, to a lesser extent, may all be contributing to mortality of South Fork Trinity River spring chinook.
Fall Chinook Show Declining Trend
LaFaunce (1967) was able to distinguish between fall and spring chinook, even though there was some overlap in their spawning range. He did carcass surveys and redd counts to arrive at the estimate that 3,337 fall chinook spawned in the lower 2.5 miles of Hayfork Creek and downstream from Hyampom in the main South Fork.
Between 1984 and 1990, the California Department of Fish and Game set up a weir at Sandy Bar, on the lower main stem of the South Fork Trinity River, to tag fall chinook and help estimate recent population trends (Jong and Mills, in press). Estimates of returns to the South Fork Trinity River have ranged from 345 to 2,640 (Figure 2-1). It is the convention of the Pacific Fisheries Management Council and the Klamath Fisheries Management Council to exclude two year old male chinook salmon (jacks) from spawner counts; therefore, jack salmon are shown separately in Figure 2-1.
In 1991, CDFG ceased fall chinook salmon population estimates in the South Fork Trinity River (Barry Collins, personal communication) but the Natural Stocks Assessment Program plans to periodically assess this stock in the future (CDFG 1993). While population estimates were not conducted in 1991 and 1992 some information on relative abundance of South Fork Trinity River fall chinook salmon is available. In 1990, when the population was estimated to be 345, 223 adult fall chinook were captured in 169 days of weir operation (CDFG 1993). By contrast, in 1991 there were 202 counted in 160 days and in 1992 351 were counted in just 69 days of weir operation (CDFG 1993). One might infer from this information that runs in 1991 were similar to 1990 but that 1992 represented a rebound in the population. In 1993, there were 736 chinook salmon counted at Sandy Bar weir so it may represent an even stronger spawning return (Larry Hansen, personal communication).
Two factors have affected South Fork fall chinook in the recent past: 1) they is a high incidence of straying from hatcheries into the South Fork, and 2) they suffer high rates of pre-spawning mortality in some years. The Sandy Bar weir has captured fall chinook salmon that have come from Trinity River Hatchery and Iron Gate Hatchery, as well as from small scale rearing projects at Horse Linto Creek, the Hoopa Reservation, and Cappell Creek in the lower Klamath River. Stray rates have ranged from as high as 29% in 1984 to a low of 4% in 1990. The total number of wild fish escaping to spawn in the South Fork Trinity River must be adjusted downward to account for high hatchery stray rates. Straying can also have a detrimental effect on the native chinook population in the basin (for full discussion see Chapter VIII).
Female fall chinook salmon pre-spawn mortality has ranged from a high of 71% in 1985 to zero in 1988 (Table 2-3). The actual number of spawning female fall chinook salmon is therefore, significantly less than estimated escapement. The sex ratio of adult fall chinook salmon returning to the South Fork Trinity River basin has been dominated by males, with an average male:female ratio of nearly 75:25 (Jong and Mills, in press). The combination of high pre-spawning mortality and the low number of females related to the skewed sex ratio led to an extremely low number of female chinook spawners in 1990 (Table 2-3).