3. Ecological Conditions of Streams as a Factor Limiting Production of Salmon and Steelhead
Land management and regulatory agencies have completed habitat typing inventories and stream surveys for most major tributaries in the South Fork Trinity River basin. These inventories include information on stream conditions, as well as the abundance of juvenile salmonids and their observed habitat preferences. Findings of the habitat typing reports suggest that freshwater habitat in the basin is one factor that is limiting salmonid production. Densities of juvenile salmon and steelhead in the South Fork Trinity River and a number of its tributaries are extremely low relative to streams in other areas of the Pacific Northwest and elsewhere in the Klamath/Trinity basin. Of the streams surveyed, only Eltapom Creek, Butter Creek, Plummer Creek, Rusch Creek and upper Salt Creek have relatively high densities of juvenile salmonids.
There appears to be an inverse relationship in many sub-basins in the South Fork Trinity River between the amount of fine sediment and sand in pools, and the density of juvenile salmonids. Stream channels with the greatest fine sediment accumulations in pools, and with low juvenile fish densities include lower Salt Creek, Hayfork Creek above 9-mile bridge, the entire main stem of the South Fork, East Fork South Fork and Grouse Creek. Long-term sediment control is expected to be an important component of habitat restoration and fisheries recovery. Recommendations for improvement of habitat conditions are offered in association with a chapter specifically on that topic, as well as in sections on needed changes in land management and the implementation of watershed restoration measures.
A similar inverse relationship exists between fish abundance and stream temperature in many areas of the South Fork. For example, summer stream temperatures in Hayfork Creek at Hyampom have risen as high as 85°F in recent years and as high as 81°F in main stem South Fork Trinity River. Green sunfish and other exotic species have established breeding populations in drought years, signifying a major ecological shift. Recommendations for moderating water temperatures are include in a chapter dealing directly with water quality and water quantity issues and needs.
4. Landscape Stability and Erodibility
Erosion and sedimentation processes in the South Fork Trinity River watershed have long been thought to be a significant factor contributing to the historic declines of salmonid stocks in the basin. Extensive unstable areas still exist within the watershed and the combined effect of floods and land use can be expected to cause additional habitat degradation in future floods unless widespread corrective work is undertaken soon (see Chapter 11).
The South Fork is a large and diverse watershed with significant portions underlain by stable bedrock and other substantial regions of highly unstable terrain. For this reason, different sub-watersheds are naturally characterized by widely variable erosion rates, and the imprint of forest land management and agriculture has been locally severe. Eastside watersheds (tributary to Hayfork Creek) generally display low erosion rates and sediment yields compared to slopes and basins draining directly into the South Fork. These westside lands are particularly susceptible to erosion and landsliding following land disturbance.
Floods in the South Fork Trinity River basin, such as in 1964, have served as the chief triggering mechanism for widespread erosion and cumulative effects in many sub-watersheds. However, without the extensive harvesting of steep inner gorge slopes and the widespread land disturbance that preceded these storms, damage to aquatic habitat in the main stem and tributaries would probably have been significantly less severe and shorter lived than it has been. While some watersheds have largely recovered their physical character following the 1964 event, many basins still suffer from continued erosion and sedimentation as well as the legacy of thick deposits of stored sediment and resultant wide, shallow streambeds.
Recent wildfires and associated salvage logging on federal lands, combined with road building and heavy timber harvesting on private lands, is setting the stage for continued high levels of stream channel sedimentation for the near future. Recommendations for 1) watershed assessments of potential erosion on both USFS and private lands, 2) implementation of watershed restoration projects, and 3) changes in land use practices, are included in chapters specifically addressing these topics. Above all, land management practices need to be sensitive to the high variability in erodibility and, especially, slope stability found in the South Fork Trinity River watershed. It should be recognized, both in practice and in regulation, that a land management practice which is acceptable in one terrain type may cause entirely unacceptable impacts and damage in another, nearby location.
5. Forest Land Management as a Limiting Factor in Restoration of South Fork Trinity River Fisheries
Past land use on public and private forest lands has had a profound effect on fisheries habitat and stream conditions in the South Fork Trinity River and its tributaries. Although 80% of the basin is managed by the U.S. Forest Service, impacts from remaining private forest lands have been profound and had severe effects on streams and fish habitat. The impacts of land use and past floods has severely degraded the basin's streams. Without changes in private land forest practices and concurrent watershed restoration, future floods are likely to cause additional watershed damage and threaten depleted fisheries populations.
By 1977, the date of the last assessment of watershed conditions, 52% of the South Fork watershed had already been logged and over 3,400 miles of road had been built. The most sensitive, unstable areas in the watershed occur on private forest lands on South Fork Mountain and along the oversteepened inner gorge slopes of the South Fork and its tributaries. The risk of initiating landsliding and downstream sedimentation by continued, unabated management in and near these inner gorge areas is high. USFS cumulative effects analysis and restricted operating procedures on sensitive lands in the South Fork have provided substantially improved protection against future erosion and watershed degradation. No comparable practices are in place for private forest lands. Future mass movement associated with private timber and roading operations threatens to delay recovery of the lower South Fork Trinity River and its fisheries resources.
According to the USFS, federally managed watersheds in which cumulative erosion and sedimentation effects are likely to be a near-term problems include Butter Creek, Rattlesnake Creek, Plummer Creek, South Fork Mountain Tributaries, East Fork South Fork, Upper South Fork, Hidden Valley, Upper Hayfork Creek, Hyampom and Gulch watersheds. Past forest practices and wildfires have created most of these concerns. In the Hayfork Creek watershed water quality and fish habitat problems are more related to past placer mining, irrigation (water extraction), grazing and loss of riparian vegetation.
Important short comings in the State's forest practice regulations which may delay recovery of South Fork fisheries include relatively weak, non-prescriptive cumulative effects assessments, lack of regulations requiring long-term maintenance of roads and drainage systems (resulting in road abandonment), and lack of a formal mechanism to identify sensitive, unstable lands and to require meaningfully altered practices.
Future erosion along abandoned logging roads, especially on private forest lands, represents a significant threat to the watershed's depressed fish populations. Likewise, severely dwindling USFS road maintenance budgets means that the 7,800 miles of road on Shasta-Trinity National Forest may receive little or no regular maintenance, thereby increasing the risk of sedimentation to the watershed's streams.
6. Water Diversion and Water Pollution as Limiting Factors for Fisheries Resources
Water quality problems affect fish and fish habitat in both the main stem South Fork Trinity River and in its largest tributary, Hayfork Creek. In Hayfork Creek, water diversion, agricultural practices, residential septic systems, and industrial pollution all contribute to water quality problems. The entire Hayfork Creek watershed, above Little Creek, has been designated as a Critical Water Resources Overlay Zone because low stream flows have been found to damage fisheries and wildlife, restrict available water supply for residential, agricultural and industrial needs and to lower water quality for other beneficial uses. Many tributaries to Hayfork Creek lose their surface flow late in summer, particularly in drought years.
The main channel of Hayfork Creek in Hayfork Valley also has severe water quality problems in the summer with "dark sludge on the banks and foam floating on the water" and "dead fish including steelhead observed" (Frink et al., 1990). Water quality continues to be impacted by residential septic systems and livestock grazing. Nutrient enrichment and thermal pollution, caused by low flows and riparian loss, contribute to poor water quality and low fish densities in the valley. Grazing practices have also locally decreased bank stability, leading to locally high levels of fine sediment and contributing to elevated summer water temperatures.
Water quality and water yield appear to be the main limiting factors to fisheries recovery in the potentially productive Hayfork Creek basin. Technically, these problems can be remedied through the use of pollution control and water conservation measures, as well as riparian plantings along stream channels in the valley. Because lower Hayfork Creek has deep holes and a number of relatively undisturbed tributaries, increasing cold water flows could help bring about rapid recovery of fish populations.
Sediment over-supply and elevated water temperatures are the chief sources of water pollution in the main stem of the South Fork Trinity River. Summer water temperatures in the main stem may always have been relatively high. However, fires and land use, which causes reductions in riparian vegetation, and stream sedimentation, which causes loss of pool numbers and depth, have also contributed to elevated water temperatures. Water temperature problems in the main stem of the South Fork may take decades to correct but restoration actions such as riparian planting will result in water quality benefits in future years.
Recommendations for improving water supply and water quality in Hayfork Creek include replacing irrigation ditches with piped diversions, using a computer model to coordinate and time water withdrawals, acquiring assets to build a sewage treatment plant in Hayfork, excluding cattle from stream side areas and restoring riparian zones. Re-establishing a multi-tiered riparian forest, with willows and alders at stream side and cottonwoods or conifers on flood terraces, has also been recommended. Protection and re-establishment of riparian forests along the main stem South Fork Trinity River and its tributaries, along with reduction in sedimentation rates, are the most promising, long-term solutions to elevated water temperatures elsewhere in the fluvial system.
The long term goals for restoration of the South Fork Trinity River basin will be accomplished by controlling future sediment yield from disturbed lands, and by moderating water temperatures. For the Hayfork Creek drainage basin, the most immediate needs are to increase summer flows and decrease summer water temperatures.
7. Fishing as a Limiting Factor on South Fork Trinity River Stocks
Although harvest of steelhead stocks is not significant, salmon populations from the South Fork may have been negatively impacted by commercial and non-commercial fishing. Despite the public perception, there is no scientific evidence that high seas driftnet fisheries or factory trawl ships are depleting South Fork Trinity River salmon or steelhead stocks.
Sport, commercial and Indian fisheries harvest Klamath basin wild salmon stocks, including those from the South Fork Trinity River. Until 1991 and 1992, the vast majority of Klamath chinook salmon were caught by commercial salmon trollers. However, record low abundance of Klamath fall chinook salmon stocks has caused severe restrictions on commercial harvest in recent years. Ocean sport fishermen catch fewer Klamath basin chinook salmon, but harvest far more coho than commercial fishermen. Native American harvest was relatively minor prior to 1980, but has accounted for a much higher proportion of the harvest in recent years. Currently, poaching in the South Fork appears to be low, but it too could contribute to loss of populations, such as South Fork Trinity spring chinook, when they are at such extremely low levels.
Beginning in the mid-1980's, the Pacific Fisheries Management Council began to manage Klamath basin fall chinook salmon to achieve a minimum escapement rate of 34% or a minimum of 35,000 natural spawners. Despite this effort, fall chinook salmon returns to the basin set three consecutive records for low escapement in 1990-1992. Preliminary estimates of the 1993 fall chinook natural escapement for the Klamath basin are about 21,000 fish, still considerably below the minimum escapement level established by the Pacific Fisheries Management Council. A PFMC "overfishing committee" was recently convened to study this problem and found that pre-season stock abundance was typically over-estimated and the pre-season estimate of ocean fishing impact was under-estimated. The overfishing committee also found indications that some factors other than harvest had contributed to low escapement. No effort is currently directed at governing harvest of spring chinook or coho salmon in the Klamath basin yet these species may be in even greater need of protection.
It is thought that wild fish can probably withstand a harvest rate of only 65% and still return in sufficient numbers to maintain a viable population. However, hatchery fish can be harvested at a much higher rate, since mortality of eggs and juveniles in a hatchery are much lower than in the wild. Unfortunately, wild and hatchery fish are not differentiated during harvest and high harvest rates in a "mixed-stock" fisheries may contribute to population declines. The failure of stocks to recover can be attribute to over-fishing of wild stocks and to the limitations imposed by poor watershed conditions and stream habitat.
To limit the future impacts of mixing and harvesting wild and hatchery stocks, it is recommended that the PFMC require universal fin clipping of all hatchery salmon and selective harvest in all fisheries, where feasible, to try to resolve mixed-stock fisheries problems. The South Fork Trinity River basin CRMP is encouraged to be attentive to harvest management issues and to make sure that their interests are represented in the harvest management forum. Poaching may have decreased substantially in recent years but recommendations are also made for community education programs, similar to those in the Salmon River, to help eliminate this activity as a potential source of impacts to depressed salmon and steelhead stocks in the South Fork.
8. Large Scale Hatchery Production and Potential Impacts on Wild Salmon and Steelhead Stocks
The two major fish hatcheries in the Klamath basin were built to mitigate for blocked salmon and steelhead spawning and rearing habitat above Iron Gate Dam (Klamath River) and Trinity Dam (Trinity River). Potential impacts on South Fork Trinity River wild salmon and steelhead from operation of these hatcheries have not been well studied, but might include increased competition (for food and rearing habitat), spread of disease, and/or decreased fitness as a result of native stocks breeding with hatchery strays.
Stray rates of hatchery fall chinook into the South Fork Trinity River have ranged from 4% to 29% since monitoring began in 1984. Hatchery coho have also been counted in the basin, but there is no evidence of stray hatchery steelhead or spring chinook in recent years. Problems have arisen at Trinity River Hatchery with the fish diseases IHN and BKD. The degree to which these may have been transmitted to wild fish is unknown. Fish health tests in the lower Trinity River recently found wild steelhead to have a 20% infection rate with BKD. A high percentage of female fall chinook salmon have died before spawning in the South Fork Trinity River, which also gives rise to skewed sex ratios and concerns about potential links to disease.
High numbers of hatchery releases from 1986-1989 may have had some bearing on the very low abundance of all Klamath fall chinook stocks in 1990-1992. Record numbers of hatchery-raised fall chinook fingerlings were planted in those years. The hatchery fingerlings were planted at a small size (which leads to slower downstream migration) and summer river temperatures were warm due to drought conditions. The survival rate of released hatchery fingerlings from 1986-1989 was the lowest on record, and this would be consistent with density related mortality in the river or estuary caused by competition. While competition between hatchery and wild fish has not been conclusively proven, the California Department of Fish and Game recently reaffirmed their commitment to limiting production at the basin's two large hatcheries to levels needed for mitigation.
It is difficult to determine the degree to which the basin's hatcheries have impacted the currently low populations and poor recovery of South Fork Trinity River salmonids. However, recommendations have been made for continued study of fish health in the Trinity River basin and implementation of a state-of-the-art disease control and prevention program at Trinity River Hatchery. Scientific studies are also recommended at the two large hatcheries to determine the timing and optimal number of juvenile releases which can be made to maximize returns while minimizing competition and other impacts on native stocks. Table of Contents