266 



dlfTenentiy. short-tcnn pniflts versus the Inng-tcnn sustainable economic benefits thai the coho fishery could 

 provide. 



LOSS OF HABITAT 



The long-tcnn decline of coho salmon populatioa*; is highly correlated with deterioration of freshwater habitat 

 caused by human distuihances. Coho are especially vulnerable to loss or degradation of spawning, summer 

 rearing, and winter rearing habiiai-s. Loss of woody debris and liabiiai complexity in estuaries may reduce survival 

 of outmigrating smolts- and wimcr migrants, Cnho habitat is lost when large woody debris and (he stable, complex 

 channels and wetlands associated with floodplain forests are damaged or destroyed by logging, grazing, 

 channelization, cropland agriculture, or urbanization. Flow diversion for irrigation and hydropower generation pose 

 serious problems for coho salmon in many area.s. Sedimcnution, debris flows, and increases in stream temperature 

 often result from disturbance of headwater areas by logging roads and timber harvest, and these impacts alone may 

 be sufTtcieni to damage or destroy coho populations even where riparian buffer zones are left along fish-bearing 

 streams. Habitat loss and the simplificailon of river ecosystems appears to be the most fundamental and imivcrsal 

 factor underlying coho dcplctioas regionwide. 



HATCHERIES 



In general, there are very few (if any) examples of hatchery programs that led to .successful re-building of wild 

 populations of Pacific salmon within their native range. When successful in terms of producing hatchery fish, 

 hatchery breeding tends to reduce, rather than increase, diversity of wild populations. The capture of fish for 

 breeding purposes can be destructive of sroaU or declining wild populations. Due to small brood^tock 

 populations, prcspawning mortality during capture or transport, imnatural mating combinations, disease, or artificial 

 selection, wild brood stock typically contribute little genetic diversity to subsequent generations of hatchery fish. 

 The taking of larger numbers of wild fish for broodstock in an attempt to overcome these problems in hmchery 

 stocks merely lncrea.ses the risks for wild populations. 



Large or repeated intioductioas of hatchery fish pose additional risks for wild fish. Introduction of hatchery fish 

 can adveniely affect wild fish through competition for food and .space, disease irarusfer, attracting predators, 

 competition for mates, intcibrccding, and other processes. Pooriy adapted characteristics may persist in the 

 population, particularly where wild population densities are low or habitat has been altered. 



ADVERSE OCEAN CONDITIONS 



Ocean conditions have generally been deteriorating for colio in the lower 48 states during the past two decades, 

 and there is little indication this situation will reverse. Mo<si variation in ocean mortality apparently occurs during 

 the first few weeks of life so that near-shore conditions during late spring and eariy .summer along the coasts of 

 Washmgton, Oregon, and California dramatically affect the number of young coho of that year Uiat survive the 

 first few week. Coho along the Oregon and California coasts may be especially sensitive to the upwelling of cdd 

 nutrient rich currents from the deep ocean, because these regicms lack extensive bays, straits, and estuaries to 

 buffer oceanographic effects. 



Page 2 



Coho Petiliun; Summary 



