 large size (Bartley et al. 1990). Their ability to mature and produce viable offspring remains unknown.
If first generation hybrids fail to produce viable offspring, at a minimum they can function to dilute the reproductive effectiveness of coho salmon that mate with them, as well as potentially competing with viable coho salmon individuals for food and space (Hindar et al. 1991). Transfer of genes from chinook to coho salmon via hybridization in Trinity River could underlie a detected increase in the susceptibility of (putative) coho salmon to infectious hematopietic necrosis virus (IHNV). Until recently coho salmon were considered resistant to this disease.
Monitoring has been insufficient to determine the possible incidence and long-range effects of hybridization problems. This is especially important given the widespread and increasing occurrence of situations where wild coho salmon populations are closely intermingled with hatchery salmon or artificially induced concentrations of salmon of multiple species on spawning grounds.
Failure to Adequately Monitor Wild Populations and Habitat
The failure of state and federal agencies to adequately monitor wild populations of coho salmon is a serious problem for protection and management of salmonids. In California, there is virtually no systematic monitoring of wild coho escapement by state or federal agencies. Wild coho in California are included in ocean harvests, but there has been no attempt to ascertain the effects of these harvests and mitigate their potential effects on wild populations.
No adequate monitoring of freshwater or ocean habitat, or yearly survival of coho in artificial propagation programs has been done to date. There are a variety of propagated fish species that may directly or indirectly impact coho salmon. In California there are only rudimentary monitoring and regulation of artificial propagation programs for a variety of fish species that directly or indirectly impact coho salmon. These programs are conducted by both large and small hatcheries throughout the state, by wide variety of volunteer and semi-official organizations and individuals. Although stock transfers, extensive trapping and broodstock collection efforts, and loosely regulated breeding, rearing, transportation, and stocking may pose a treat, there is little to no monitoring or regulation of such effects.
The coho salmon migratory and anadromous life history leads it through a diverse array of regulatory jurisdictions. The majority of the coho salmon life stages (egg, larval, juvenile and spawning adult) occur in freshwater and are thus affected by laws and policies designed or supposed to regulate inland watersheds and riparian zones.
Bacterial Kidney Disease (BKD) is a very debilitating disease that effects coho salmon in many stages of its life. Studies conducted in 1993 by Dr. Bill Cox showed all of coho salmon sampled in Scott Creek (Santa Cruz County) tested positive for BKD. One of the serious side effects of this disease is first demonstrated in low survival of eggs. Infected coho salmon females had only a 40% survival rate for eggs incubated at the hatchery. While females treated with erythromycin had egg survival rates of 80% (Dr. William Cox, California Department of Fish and Game). While living in fresh or saltwater life stages, the growth of BKD lesions on the kidneys can weaken and kill juvenile and adult fish. But it is theorized that serious losses occur when coho salmon transition as smolts from freshwater smolts to salt water and again as sea run adults transitioning back from salt water to freshwater. During this life stage the kidneys play a major role in this amazing adaptation that in fresh water allows coho to absorb salts and conversely in salt water, expel salts from the body. This transition is difficult for healthy fish, and it is theorized that a large percentage of coho salmon infected with BKD, are lost at both of these migration phases.
Ceratomyxa shasta, a parasite is present in the Colombia River system and is increasing (Ratliff 1983), and may be spre