Chapter IX

Small Scale Rearing and Fish Population Restoration

When many residents of the South Fork Trinity basin think of fisheries restoration programs, the first image that comes to mind is some kind of small scale hatchery program. The only in-basin supplementation program operated to date in the South Fork Trinity River basin has been the rearing ponds on Tule Creek that use fish rescued from above agricultural fish screens (Miller et al., 1990). Several other small scale hatchery programs have been proposed (Wood, 1984; Klempner, 1984; McCaslin, 1986) but not implemented. The California Department of Fish and Game has authority over all hatcheries and aquaculture in the state and has issued detailed guidelines for operation of such programs (CDFG, 1991).

Because salmon and steelhead have a complex life cycle, successfully supplementing populations is much more difficult than raising trout or other species. Sometimes, supplementation can have unintended side effects on wild fish populations and can actually decrease production. Interactions of fish raised and released in any supplementation program must also be assessed to insure that side effects, such as competition with wild fish or increases in disease levels, do not occur.

If there are fundamental ecological problems with stream or river systems, planting more fish may not result in a sustained increase in the fish population. The goal of restoration is to bring back stream health. The use of small scale culture would be only for the brief period needed to re-establish a healthy wild fish population.

What follows is a discussion of the feasibility of small scale hatchery operation in the South Fork Trinity River basin: anticipating what problems it might cause, understanding regulations and guidelines, defining what role it will play, specifying sites where it might take place, and formulating an evaluation program to monitor success or to learn how to improve operations.

Side Effects of Small Scale Rearing or Hatchery Programs

The objective of any small scale rearing or hatchery program in the South Fork Trinity River basin must ultimately be to improve wild fish populations or at least to do them no harm. Problems that arise from small scale supplementation are similar to those for large scale hatcheries. The primary exception is problems associated with broodstock handling. Since small scale hatchery programs use small numbers of adult fish, this poses a much greater threat of in-breeding.

a. Fish Diseases: The crowded conditions in rearing ponds and collective association of eggs in hatchery incubation trays make artificial culture subject to disease outbreaks. Disease outbreaks are common and frequently result in the loss of some or all of the fish raised in small scale hatcheries (Buck, 1990). A critical factor in controlling disease epidemics is having sufficient water flow and high water quality in late summer. The California Department of Fish and Game routinely monitors and treats all disease outbreaks at small scale rearing facilities. Diseases that are fostered in hatchery operations can often be spread to fish in the wild (PNFHPC, 1989). This is particularly true of "horizontally" transmitted diseases which can be passed from fish to fish through contact or fecal material. The greatest risk of introduction of disease is where hatchery programs are started with, or use, fish from other river basins.

b. Competition With Wild Fish: Problems with habitat bottlenecks, as described in other chapters, can lead to intense competition between hatchery fish and wild fish (Smith and others, 1985). Overcrowding in some habitats can sometimes cause "density dependent" mortality, leading to low survival of hatchery produced fish and also causing a decrease in wild fish populations (Steward and Bjornn, 1990). Hatchery fish often have a competitive advantage over wild fish because they are more numerous and also achieve greater size because of greater food availability in the hatchery. Any rearing program in the South Fork Trinity basin would have to be closely monitored to insure that competition problems do not occur.

Hatchery production or rearing pond programs involving steelhead may pose the greatest threat in this regard. Steelhead often spend one to three years in freshwater and may have variable internal and environmental cues that trigger downstream migration. In contrast, coho salmon all show identical urges to migrate downstream. If steelhead are released at a time that does not coincide with their urge to migrate downstream, they may take up residence in the stream (Kerstetter and Keeler, 1976). This phenomenon is known as residual behavior, and poses a substantial threat of competition with other native species (USFWS, 1991).

An increased resident population of large trout may directly predate upon wild steelhead young of the year or young chinook salmon. The high concentration of older age steelhead (1 and 2 year olds) in cascades, high gradient riffles, and cold water islands at stream mouths in the South Fork Trinity River and lower Hayfork Creek suggest that high levels of competition are already occurring (see Chapters III and VIII). Adding "residual" steelhead to these habitats is certainly undesirable.

Juvenile steelhead from the Tule Creek ponds have been planted in some years at the headwaters of nearby streams, including Big Creek and Salt Creek, for imprinting purposes (Cal Crawford, personal communication). When possible, fish rescued from various tributaries have been returned to the same stream. Van Deventer (1992) found that standing crops of juvenile, native steelhead in Salt and Big Creeks had shown a decreasing trend between 1985 and 1990. Although fewer fish were present, the average juvenile steelhead was much larger in size. It is possible that pond reared fish could be partially responsible for this trend, if the larger residual, "planted" steelhead are out-competing and feeding on the smaller native fish. Conversely, it is possible that drought years have impeded access for adult steelhead to spawning areas, resulting in lack of recruitment of younger steelhead (CDFG, 1993; Irizarry, personal communication).

c. Genetic Fitness of Wild Fish and Small Scale Hatcheries: Salmon or steelhead raised in a well run, small scale hatchery facility will enjoy a high survival rate, but may represent the genetic resources of only a few parents. Over several generations, changes in the genetic structure of the basin's salmon or steelhead can change rapidly if a disproportionately high number of the small scale hatchery fish dominate returns, and broodstock is not handled properly.

Large scale hatchery programs usually avoid problems with inbreeding simply from the large number of broodstock handled (Waples and Teel, 1989). Small scale rearing programs associated with restoration often spawn fewer than 50 adult salmon or steelhead, and may suffer severe problems if broodstock collection is handled and processed incorrectly (Simon, 1988). The public is familiar with inbreeding problems from examples of domestic pets, such as white German shepherds, that experience high incidence of rare diseases and other defects. The same problems can arise if just a few wild fish are used for a hatchery broodstock and then a substantial number of progeny of these fish are bred in future years as they return to the hatchery.

A common problem from inbreeding of hatchery fish is "inbreeding depression," in which fertility of hatchery broodstock may drop dramatically. Inbreeding is extremely undesirable, because even if fish are of local origin, they may become unfit to survive in the wild. If inbred fish spawn with wild fish, they can also decrease the success of natural reproduction. Brood handling practices necessary to avoid these problems can be found in the recommendations section. Rescue-rearing programs automatically avoid these problems because spawning still takes place naturally.

The worst side effects from salmon and steelhead hatchery programs occur when non-native broodstocks are imported into a basin. These non-native fish may have improper adaptations, such as the wrong run timing, lack of disease resistance, or other incorrect behavioral traits (CDFG, 1991). As hatchery fish stray into the wild to spawn, they convey these poorly adapted traits and decrease survival (Solazzi and others, 1983). CDFG policies no longer allow inter-basin stock transfers.

If spring chinook salmon or steelhead are captured low in the South Fork system, as opposed to specific reaches of the South Fork or sub-basin tributaries, there is still some risk that gene resources may be compromised. Although Baker (1988) and Hodges et al. (1989) did not find distinct races of steelhead in the South Fork, there was some species variation between sampled sub-basins. If steelhead brood fish are captured in Hyampom, for instance, while in route to specific sub-basins, intermixing of steelhead from all basin areas could cause loss of rare alleles. Planting juvenile salmonids away from the hatchery increases straying and could lead to similar problems. This may not be a concern for fall chinook salmon as they seem to intermingle on spawning beds in the lower South Fork Trinity River in and below Hyampom, and may represent a single breeding unit. Chapter 9 continued

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