Competition Between Hatchery Fish and Native Fish
Thermal problems in the mainstem of the Klamath River (see Chapters 3 & 4) may be causing a substantial shortage in suitable habitat for outmigrating salmonid juveniles. Sullivan (unpublished) and Mills et al. (unpublished) have found that native chinook and hatchery chinook juveniles move down the main Klamath River throughout the summer. T. Mills (personal communication) has found large concentrations of juvenile salmonids congregated at the mouth of coldwater feeder streams, such as Blue Creek. Young hatchery chinook with fin clips have also been found holding upstream in these cold tributaries in late summer. Migrations of large numbers of juveniles have been noted moving up Indian Creek from the Klamath in summer when the river temperatures were high (Phil Baker personal communication).
In several published reports, fisheries biologists have found that high concentrations of fish result in increased competition for food and space and can decrease survival of both hatchery and native fish (Salo and Baliff 1958, Steward and Bjornn 1990). This phenomenon is termed "density-dependent rearing mortality." When planted, hatchery smolts are larger than native fish so they may displace native fish through competition (Smith et al. 1985). Stempel (1988) felt that problems related to competition between hatchery and native juveniles could be occurring in the main stems of both the Trinity and Klamath River resulting in reduced survival of native fish.
Studies by Mills et al. (unpublished) found that numbers of fall chinook salmon smolts coming from Bogus Creek varied widely between years. While Mills et al. (unpublished) has estimated outmigration of over 1,000,000 smolts in years of optimal escapement, after the storm of February 1986, he estimated that only 27,000 juvenile chinook were produced. In the spring of 1986, Iron Gate Hatchery released over 9,000,000 smolts. Forces of competition due to shear numbers may move the system toward hatchery dominated runs in years when over-wintering conditions are particularly severe.
Royal (1972) found that the survival rates of hatchery steelhead smolts decreased as distance from the ocean and numbers of fish planted increased. Lichatowich and McIntyre (1987) attributed this to higher density related mortality during migration. Chapman (1989) found that hatchery releases of juvenile chinook drew native chinook and steelhead downstream with them, which he termed "the pied piper effect." Noble, as cited in Royal (1972) also asserted that density dependent factors from planting in excess of carrying capacity can effect other species. The effects of large releases of chinook could be playing a role in decreasing native steelhead populations. Competition with hatchery fish may be much greater on those native stocks from upstream areas, such as the Shasta River, that are exposed to competition for a greater distance in the Klamath during outmigration.
Studies in the Trinity River found that steelhead released at less than six inches did not emigrate. Kerstetter and Keeler (1976) found that the timing of peaks in blood hormone levels that stimulated outmigration were different in native Trinity River steelhead than in hatchery steelhead. They felt that not releasing the fish when hormonal cues would have stimulated outmigration led to this "residual" behavior. Current Iron Gate Hatchery practices (CDFGa no date) call for taking 1,000,000 eggs and rearing 200,000 yearlings. All steelhead in excess of this goal are released to the river at a size less than six inches. If these fish manifest the same behavior as was exhibited on the Trinity, they may be living in the main river, competing for space and food with native fish, and even predating on both hatchery and native outmigrating juveniles. Large residuals have been reported by anglers (Dick Sumner personal communication) and guides have reported an increasing catch of 8 to 10 inch juvenile steelhead during winter (Bob Young personal communication). It is possible that competition from residuals could be one of the factors leading to the poor production of wild steelhead in the Klamath River. Observations on the lower river during 1978-82 indicated that hatchery steelhead may spend one additional year in the river after release, then migrate to the ocean (Dennis Lee personal communication).
Iron Gate Hatchery coho were outplanted in Elk, Grider, and Beaver creeks in the Middle Klamath region from 1986-88. Smith et al. (1985) said similar programs in Oregon "lacked biological benefit." Although stocked streams reared more juveniles, researchers observed that native juveniles were displaced by hatchery fish. Further, when hatchery adults returned to spawn with native fish, juvenile recruitment was greatly reduced due to less well-adapted offspring (Smith et al. 1985).
Studies by CDFG (unpublished) indicate that chinook juveniles did not spend extended periods in the estuary of the Klamath in 1983-85. Sullivan (unpublished) found no scale patterns in fall chinook to indicate extended estuarine rearing as well. In contrast, Snyder, reported in 1931 that juvenile chinook lingered in the estuary and showed their most rapid growth there. Estuarine studies in Oregon (Reimers 1973) found that high densities of chinook juveniles increased intraspecific competition that resulted in early ocean entry. Without the period of rapid growth in the estuary by fall chinook, the chances for survival decreased (Reimers 1973). The estuary appears to be an area where density-dependent rearing mortality could be decreasing the survival of both native and hatchery chinook. Nicholas and Hankin (1988b) suggested that some Oregon coastal rivers probably could not support increases from hatchery production because of the limited capacity of their estuaries.
McGie (1984), used the Ricker model to study the population crash of coho in Oregon in 1980, and concluded that density-dependent mortality occurred at sea between hatchery coho in years of poor upwelling. Riesenbechler and Emlen (1988), using the Beverton-Holt population model and data from Oregon coho, predicted that attempts to double present run size on the Columbia River by doubling smolt output would not succeed. Their study predicted that doubling current smolt output from 30 million to 60 million would only increase returns from the current run size of 1 million by 140,000 fish in good upwelling years and by only 80,000 in poor years. Since coho salmon from both Iron Gate and Trinity River Hatcheries are of Columbia River origin, they may be showing similar ocean migration patterns to those described in the case study above. Chinook from both hatcheries show considerable variation in ocean migration, as monitored by coded wire tags, and it is unlikely that chinook stocks from the Klamath are manifesting this problem.
Interbreeding Between Hatchery Fish and Native Fish
When hatchery broodstocks have non-native components or are inbred, they decrease the smolt production of native populations as they stray into streams to spawn with locally adapted stocks (Riesenbechler and McIntyre 1977, Chilcote et al. 1982, Royal 1972, Solazzi et al. 1983, Ryman and Utter 1987). Local populations may develop special adaptations to local watershed conditions (Ricker 1972). Even if the introduced stock is from a basin that has similar selective pressures, it may have evolved different genetic solutions to the same problem (McIntyre et al. 1988). Almost any survival trait is controlled by several genes referred to as a "coadapted gene complex" (Shields 1982). Because the gene coding was evolved separately for the native and introduced fish, "mingling of two different gene networks (mixing stocks) may disrupt the effectiveness of either" (McIntyre et al. 1988).
The Use of Non-Native Broodstocks
Riesenbichler (1988) found that the survival of transplanted coho salmon decreased in a linear fashion with the distance planted from their native watershed (Figure 5-2). The original coho broodstocks at both major hatcheries in the Klamath Basin were from Cascade Hatchery stocks in Oregon. The distance between their stream of origin, the Columbia River, and the Klamath River is over 800 km. The productivity of the stock is thus predicted to be very low (Figure 5-2). Problems with low productivity and erratic patterns of return of hatchery coho after introduction may have been attributable to the inappropriate adaptations of this stock. Recent improved performance of this stock may reflect adaptations to the hatchery environment (or domestication) allowing better survival under these artificial conditions. Problems with interaction with native populations may still occur, however.
Oregon hatchery programs used coho salmon large central facilities for all of the Oregon coast. As these hatchery coho, lacking adaptations to local conditions, strayed back to spawn with wild stocks, fewer viable smolts were produced (Solazzi et al. 1983). The program of outplanting coho fingerlings an yearlings in Elk, Beaver, and Indian Creeks may have had a negative impact on any wild stocks still remaining in those basins. While this program is currently being monitored to determine if the planting has led to increased self-sustaining coho production, Withler (1982), in a review of the literature, found that the introductions of Pacific anadromous salmonids, using non-native broodstock, have been unsuccessful in producing new self-reproducing populations anywhere on the West Coast.
Outplanting also causes increased straying (Royal 1972) so that the impacts of this stock, poorly adapted for local stream conditions, could be felt over a wide area. The number of non-native fish spawning with a local population is a key determinant of whether genetic damage will occur (Riggs 1990). Steelhead were planted away from the Trinity River Hatchery, as far downstream as the estuary, to encourage ocean migration (Bedell 1972). Substantial numbers of these steelhead, which had non-native broodstock components, strayed to Iron Gate Hatchery as a result (Marshall 1974). Offsite releases are no longer accepted practice at Trinity River Hatchery except for chinook salmon pond rearing programs.
The Klamath River has periodic high levels of the protozoan disease organism Ceratomyxa shasta. Marsh areas and lakes are thought to be optimal conditions for this protozoan although the life cycle of the organism remains unknown. All stocks of rainbow trout in the areas above Iron Gate Dam are resistant to this disease (Buchanan in press). Locally adapted steelhead stocks in the vicinity of Iron Gate Hatchery should also have evolved almost total resistance. Studies on the Nehalem River in Oregon found that introductions of Trask River coho decreased the viability of native Nehalem coho stock substantially because the introduced Trask fish lacked resistance to Ceratomyxa shasta (Kapuscinski 1984). Problems with disease outbreaks at Iron Gate Hatchery occurred as a result of introductions of steelhead strains that were not resistant to this disease. Periodic problems with losses of large numbers of hatchery steelhead continued into the early 1980's (CH2M Hill).
Carlton (1989) has found that chinook salmon at Iron Gate Hatchery have a 4 percent susceptibility to Ceratomyxa while Trinity River Hatchery chinook have a 12 percent susceptibility. Similar studies (Hubbell 1979) on steelhead found similar resistance of Iron Gate Hatchery steelhead and Trinity River Hatchery steelhead (12 percent). It is possible that Iron Gate Hatchery steelhead have less resistance to C. shasta than hatchery chinook because of the earlier non-native steelhead introductions and straying of Trinity River Hatchery fish. Therefore, there may be a difference in resistance between hatchery steelhead and native steelhead as well. Shasta strain rainbow trout were used to test for the presence of C. shasta at Iron Gate Hatchery during the summer of 1990, since this strain of trout is 100 percent susceptible to the disease. The disease organism was present, all Shasta rainbows died, but steelhead losses were not high (Mel Willis personal communication).
Even when hatchery broodstock is derived from local populations, inbreeding or improper broodstock management can result in considerable decline in genetic diversity of hatchery stocks (Allendorf and Phelps 1980, Ryman and Stahl 1980, Vuorinen 1984). These fish subsequently have decreased ability to survive in the wild (Phillip and Kapuscinski 1988). If genetic diversity decreases to very low levels reproductive capability drops. This condition is known as "inbreeding depression" and may require broodstock replacement. Inbreeding can result from initial broodstock being too small in size (less than 100 pairs) or subsequent generations of returns to the hatchery declining below these levels (Allendorf and Ryman 1987). Both hatcheries have had years when coho returns have dipped below 100 pairs.
Inadvertent selection, such as taking spawn from only early run fish or those large fish, can also lead to inbreeding (Allendorf and Ryman 1987). The amount of genetic diversity retained by a stock can be measured by a statistical method and is termed "effective population size" (Simon 1988). The number that results from genetic tests and statistical analysis is equivalent to an estimate of the number of fish in the founding broodstock. Despite large founding broodstocks and subsequent returns to some Oregon hatcheries in the thousands, Waples and Teel (1989) found that several large salmon hatcheries had effective population sizes that were substantially less than the founding broodstock and the average number of fish handled. Because of the large number of fish handled, the interchange between Bogus Creek native fish and hatchery broodstock, and current practices at Iron Gate Hatchery, problems with maintaining effective population size for chinook and steelhead seem unlikely. The draft Trinity River Restoration Mid-program Review (USFWS in press) stresses the need for conserving gene resources through appropriate practices at Trinity River Hatchery. The operation of the Trinity Hatchery is currently under review (Chuck Lane personal communication).
Disease Introductions a Side Effect of Large Scale Fish Culture
The introduction of broodstock or eggs from outside the basin represents an increased threat of introduction of non-endemic disease organisms (PNFHPC 1989). Because native fish are not resistant to such diseases, introductions can be potentially devastating. CDFG guidelines no longer allow fish from outside to be introduced into the Klamath drainage.
Problems with IHN at Trinity River Hatchery have been evident since the hatchery opened in 1963. Problems became particularly acute with regard to chinook in the early 1980's. The movement of Trinity River Hatchery fish below the North Fork of the Trinity was discontinued (CDFGb no date).
Native late run fall chinook were captured in 1987 in the Trinity at Hoopa and the females tested positive for IHN. The conclusion drawn was that IHN was probably present in the system before its discovery at Trinity River Hatchery. Stock transfers were resumed for pond rearing programs in Hoopa in 1989 (Bill Wingfield personal communication).
The introduction of non-native steelhead into the Iron Gate Hatchery broodstock and widespread straying of Trinity River Hatchery steelhead, which also had non-native components, may have conferred some level of reduced resistance to Ceratomyxa shasta to native steelhead populations. Steelhead adults in excess of Iron Gate Hatchery needs were transferred to the Shasta River, Scott River, and other smaller Klamath tributaries. Trinity River Hatchery steelhead strayed to Iron Gate Hatchery at a high rate in the early 1970's (Marshall 1974). It is likely that they also strayed regularly into the wild to spawn.
Although no large scale pen rearing projects exist or are planned in the Klamath Basin at present, they could potentially pose the largest threat of disease introductions (Whiteley 1989, Sattaur 1989). Escape from pen rearing projects is a constant problem and escaping fish can introduce diseases directly into native populations as they stray into streams (Sattaur 1989), or reduce resistance of locally adapted populations to diseases already present. Pen rearing projects must use extremely high quantities of antibiotics. Strains of disease organisms may evolve in the rearing pen effluent that are therefore not treatable with currently available antibiotics (Whiteley 1989).
Stock Collapses Associated With Increased Smolt Production
The combined production of the Trinity River and Iron Gate Hatcheries of salmon and steelhead fingerlings and yearlings has increased substantially in recent years. Average plants from 1979 to 1984 were about 6 million fingerlings and yearlings of all species combined. From 1985 to 1988 the average annual plantings totaled 19,500,000. Increases in the number of juvenile salmonids planted do not always succeed in commensurate increases in adults returning to the river.
Oregon instituted a program of coho salmon enhancement using large centralized hatcheries in 1966. As the plants of coho presmolts increased through 1976, ocean harvest and returns increased (Figure 5-3). In 1981 Oregon coho populations crashed (Donaldson 1981). Follow-up studies found that hatchery coho juveniles had a lower survival rate, both in fresh water and in the ocean, and that the ratio of hatchery to wild coho had increased from 50:50 before intensive planting to 85:15 at the time of the study (Solazzi et al. 1983 and Nicholsen 1986). The significance of this latter finding was that native fish populations had been seriously harmed by the hatchery program. The native fish decline led to nearly total dependence on the hatchery coho and to much greater fluctuations in available fish in years of poor upwelling. Riesenbichler and Emlen (1988) and McGie (1984) both concluded that density-dependent factors were inhibiting hatchery fish survival in the ocean.
Stock collapse also occurred in British Columbia hatchery-supported runs of fall chinook (Paul Starr unpublished data). Again, an increasing production trend of hatchery chinook smolts at first brought increasing returns to the fisheries. As smolt plantings continued to increase, catches began to drop off sharply (Figure 5-4). The percentage of the hatchery fish in the Canadian catch remained high despite the drop in numbers of hatchery fish harvested, indicating a decrease in natural production. Canadian Department of Fisheries and Oceans staff also noted a sharp decline in the survival of hatchery smolts to adults as the numbers of fish reared and released increased (Figure 5-5).
Given the ecological problems of the main stems of the Trinity and Klamath Rivers (Stempel 1988), it is possible that the increased numbers of juveniles produced at Iron Gate and Trinity River Hatcheries could have adverse impacts on native juveniles. Poor habitat quality in the estuary may also cause problems with competition, particularly for chinook juveniles. While plants of fall chinook juveniles have increased substantially, adults returns have not shown commensurate increases. Ocean conditions may be responsible for the poor adult returns (Mel Odemar personal communication). Because the increases in planting were only began in 1985, not enough year classes have been completed to determine whether any inverse relationship between the number of hatchery fish planted and survival to adulthood. Trends should be monitored to insure that density dependent rearing mortality does not negatively impact survival of hatchery and native juveniles in the river and the estuary.
Small-capacity rearing ponds and hatchery programs have been attempted throughout the Klamath Basin (Table 5-7). Ponds have been used largely to rear Iron Gate Hatchery fish from the fingerling stage to yearlings, but several are making the transition now to capturing, hatching, and rearing local stocks. Pond programs usually get Iron Gate juvenile chinook in May and release them from the site in October. Trinity River Hatchery fall chinook have also been transplanted for rearing at Hoopa.
Cooperation Marks Current Efforts
Several small-scale programs are operated in the upper middle region of the Klamath Basin in cooperation between the Karuk Tribe and California Fish and Game, with the department providing supervision. These are the Indian Creek, Elk Creek, and Grider Creek rearing ponds.
The rearing project at Camp Creek, near Orleans, has enjoyed the cooperation of several entities. The Six Rivers National Forest and CDFG helped capitalize rearing facilities, CDFG supervises and the Karuk Tribe has cooperated in supplying staff. Emphasis has shifted from pond rearing Iron Gate fall chinook to capturing native late run chinook for broodstock since 1986. Due to low numbers of returning late fall run adults, the Camp Creek facility has not been at capacity. The U.S. Forest Service built permanent rearing ponds at Bluff Creek and helped with siting ponds at Red Cap Creek. CDFG funds and supervises programs at these two sites in the lower middle Klamath Basin, and the Karuk again provide staffing. Spawning migrations in Bluff Creek were completely blocked by channel changes caused by the 1964 flood. A fish pass was constructed to aid fish upstream migration. After several years of the pond rearing programs using Iron Gate Hatchery fall chinook, spawning activity was re-established.
The Perch Creek ponds are operated to raise steelhead by the Orleans Rod and Gun Club and supervised by CDFG. Some broodstock for this program was procured by angling in the Salmon River but Iron Gate strain steelhead were imported in order to fully utilize the production capabilities.
In the lower Klamath, the Yurok have begun tank and cage rearing programs, initially using Iron Gate fall chinook. All Iron Gate chinook were transported upstream to Indian Creek for release (Ronnie Pierce personal communication). Initial capitalization for rearing facilities was provided by CDFG and the BIA in 1986. Native late fall run chinook broodstock are now being captured to a limited extent at weirs in Hunter Creek and Pecwan Creeks but mostly in the main river with gill nets. The expenses involved in fish capture have been funded by the BIA. Incubation has occurred at Spruce Creek and at Cappell Creek. Grow-out ponds are then stocked with these fish at High Prairie Creek, Cappell Creek, and Omagar Creek. Some fingerlings are transferred to Pecwan Creek and Hunter Creek for cage rearing.
Current funding for rearing comes from the Klamath River Task Force. The depleted state of native late run fall chinook and the resultant difficulty in capturing the broodstock has kept this program from realizing its potential as yet, but some adult chinook from early plants have returned to Hunter Creek (Pierce 1988).
Figure 5-6 -- Small-scale rearing facilities, like this one operated by the Yurok Tribe at Cappell Creek, use locally-adapted salmonids as broodstock.
Small scale facilities are also being operated on the lower Trinity River on the Hoopa Square and at Horse Linto Creek. The Hoopa Fisheries Department has operated small scale artificial culture facilities since its inception (Hoopa Fisheries Annual Reports 1984-1989). Initial efforts were aided by USFWS and were geared toward pond rearing of Trinity River Hatchery fall chinook from fingerling to yearling size. Fall chinook fingerlings were supplied in some years by Iron Gate Hatchery when concerns over IHN made Trinity River Hatchery fish unavailable. Steelhead from Iron Gate Hatchery were also reared in 1985. Current Hoopa Fisheries enhancement is geared toward capture of late run fall chinook broodstock. The program has succeeded in increasing natural spawning in streams on the Reservation. Spawning counts in 1989 were higher than any recorded in recent years with a high percentage of the carcasses bearing coded wire tags from the program (Mike Orcutt personal communication).
The project at Horse Linto Creek appears highly
successful. Operated jointly by the Pacific Coast Federation of Fishermen's
Associations and the USFS, with supervision from CDFG, the program captures
late run fall chinook broodstock and has released an average of 25,000
yearlings over the last three years. All fish have been fin-clipped and
coded wire tagged to avoid using artificially-reared fish as broodstock
in succeeding years. Slides within the watershed have been stabilized and
spawning areas increased through use of instream structures. Once this
newly restored habitat is fully seeded by the hatching and rearing program,
artificial propagation may no longer be needed and efforts can be focused
on another watershed.
A spawning channel has been operated by CDFG, in cooperation with the Klamath National Forest, on Kelsey Creek in the Scott River drainage since 1985. A ladder was built into the lower area of the creek where chinook had been unable to access. The first year brood fish were captured in the main river, but thereafter an average of nine pair of chinook and three pair of coho have used the channel. After emergence, fish were held in a dammed portion of the creek and fed to yearling size in 1986 and 1987. No staff is hired now for supplemental feeding. The channel has also had considerable use from spawning steelhead.
A combination hatchbox and pond rearing facility was operated on the South Fork of the Salmon River between 1985 and 1987. The average annual production at this site, which was a PCFFA/CDFG joint venture, was about 12,000 yearling chinook. Problems with trapping fall chinook, cold winter water temperatures and warm summer water temperatures led to the closing of the site. Ponds were set up along the North Fork of the Salmon River but never used. Ah Pah Creek was the site of a combination hatchbox and rearing pond facility from 1985 to 1987, but operation there has been discontinued.
Opportunities for Project Expansion and Development
Rearing ponds were formerly operated by the Karuk Tribe and CDFG on Thompson and Beaver Creeks in the upper middle Klamath region, but operations ceased in 1984. These sites are currently under consideration for reopening. The Salmon River may also have sites more appropriate for small scale facilities than the ones tried in 1985. CDFG is currently exploring options for renewed efforts in that drainage (John Hayes personal communication).
The rearing of green sturgeon is under study in the lower river for commercial purposes (Pat Foley personal communication). Green sturgeon would be captured for this venture using gill nets and their spawn would be removed surgically. After stitching the body cavity closed, the adult fish could be released. These fish spawn approximately every three years, so adults would continue to contribute to natural green sturgeon production in the future.
While hatchbox programs offer native salmon and steelhead a higher chance of survival through the critical egg-to-fry life stage, these operations can pose threats to the remnant populations that are the target of restoration. Atlantic salmon restoration workers reported that when plants of fry exceeded carrying capacity, that survival of fish planted decreased sharply (Gee et al. 1978). Since there were no remaining native stocks in the stream, effects were limited to those fish planted. In Klamath tributaries, wild stocks could be negatively impacted (Smith et al. 1985) if too many fish were planted for available habitat. Expanding one portion of the remnant population through artificial means, while increasing mortality due to crowding of those fish naturally produced, can decrease genetic diversity without increasing smolt output, if habitat is limiting.
When dealing with small remnant populations, genetic diversity can be decreased or lost if broodstock management is handled incorrectly (Phillip and Kapuscinski 1988, Nelson and Soule 1986). If fish from artificial rearing programs are not marked and are "crossed back" with each other in subsequent generations, they can become inbred much faster than large hatchery populations (Allendorf and Ryman 1986). Thus the genetic integrity of the local population, and its ability to survive long term, could be compromised. Fin clipping and coded wire tagging have not been practiced universally in hatchbox and rearing programs heretofore. There have been no clear guidelines for broodstock handling to maintain genetic diversity.
Transplanting chinook for pond rearing over wide geographic areas serves to homogenize the genetic material of the various sub-populations of chinook in the Klamath system. Runs of chinook salmon stemming from pond rearing programs using Iron Gate Hatchery stocks show compressed run and spawning times (J. West personal communication). As we expand this stock, returns to the river will be similarly compressed. Ocean migration patterns may be different with various stocks so the ocean "pasture" may ultimately reach carrying capacity if all Klamath Basin chinook production were of hatchery origin (Riesenbechler and Emlen 1988). Gall et al. (1989) found some indication of genetic differences from various areas of the basin. To maintain genetic diversity and survival characteristics of smaller sub-populations, Krueger et al. (1981) stress the importance of using fish for rearing from adjacent areas that are genetically and ecologically similar to the host population.
Figure 5-7 -- Juvenile salmonids can be coded wire tagged and finclipped on site at small scale hatcheries by this CDFG mobile crew.
Although Iron Gate Hatchery fall chinook are from native broodstock, as they are transferred further from their area of origin, they may prove less able to survive and reproduce. Rainfall, streamflows, temperatures, and numerous other factors are quite different in the lower river than in the upper Klamath Basin. Highly unstable bedload in creeks feeding the lower river have been documented by Payne and Associates (1989). Similar conditions in Oregon and Washington have selected for late run fish that spawn after peak flood events (Frissell and Liss 1987, Cedarholm 1983). Since Iron Gate fall chinook are early spawners, they may contribute early spawning tendencies to the local population that would confer a disadvantage under current environmental conditions. While pond rearing programs using Iron Gate Hatchery fall chinook help short term goals for increasing fish for harvest, they may be counterproductive to the goal of maintaining genetic diversity.
Pond rearing programs in the Hayfork drainage of the South Fork of the Trinity River using rescued steelhead smolts had a significant problem with fish remaining as residents after release. If future projects for pond rearing rescued steelhead are funded by the Restoration Program, a strategy must be devised to avoid problems with residualism.
