tection is the key to conservation and recovery of wild coho salmon, because the technological ability to restore habitats once they are damaged is severely limited, mostly due to our lack of understanding of how to best provide for coho salmon and the need for improvements in the technology. Although millions of dollars have been invested in artificial habitat alterations in attempts to improve habitat for coho and other fish, there have been few examples of successful large-scale recovery of coho populations attributable to man made habitat improvements. Unfortunately the cost of restoring a significant portion of altered streams using these technologies is prohibitive (Pearcy et al. 1992). In many streams in the Pacific Northwest existing technology for channel restoration has failed to treat the causes of habitat degradation (e.g., Klamath Basin Fisheries Task Force 1991). Furthermore, because the largest share of coho habitat is surrounded by private land (The Wilderness Society, report in preparation), recently proposed reforms in federal forest management (FEMAT 1993), will not be sufficient to safeguard this species from further decline and widespread extinction across a significant portion of its range.
Adverse Ocean Conditions
Ocean conditions have generally been deteriorating for coho in the lower 48 states during the past two decades (Lawson 1993), and there is little indication that favorable conditions will return in the near future. Most variation in ocean mortality of coho salmon apparently occurs during the first few weeks of ocean life (Pearcy and Fisher 1988), so that near-shore conditions during late spring and early summer along the coasts of Washington, Oregon, and California dramatically affect year-class strength. Evidence that upwelling along the Pacific Coast of North America is driven by 40-60-year cycles in wind patterns. Following an interval of generally favorable conditions in 1945-1975, upwelling declined along the Oregon coast and marine survival of coho salmon declined at a similar rate (Pearcy et al. 1992). Coho along the Oregon and California coasts may be especially sensitive to upwelling patterns, because these regions lack extensive bays, straits, and estuaries to buffer oceanographic effects. Assuming Ware and Thompsons hypothesis is correct, ocean conditions are likely to remain generally unfavorable at least through the next two decades.
Evidence suggests there have been extensive changes in marine food webs during this century, and these changes may reduce survival of coho salmon at sea. The abundance of two species comprising a large share of the pelagic biomass of the Northeast Pacific Ocean, Pacific sardines and hake, have collapsed during this century, and failed to recover during the most recent period of favorable ocean conditions. Overfishing of these species during low-productivity periods may have contributed to their collapse and failure to recover, and resulting changes in the marine food web (i.e., predation shifts from pelagic to near-shore and migratory species) could adversely affect coho and other anadromous fishes.
Assuming oceanographic and atmospheric relationships of recent centuries hold in the future, anticipated climate warming during the next several decades is likely to cause continued adversity, or perhaps progressive deterioration of marine habitat for coho salmon. This could forestall or curtail the future recovery of ocean conditions postulated by Lawson (1993).
Given that manipulation of ocean and atmospheric behavior is beyond human capability, the deterioration of ocean conditions clearly makes the quality of freshwater habitat more critical for short-term productivity and long-term survival of the species (Lawson 1993).
Overfishing is often cited as a principle factor causing decline of salmon runs. However, there are few historical or recent records to indicate that curtailment of fishing has lead to increased spawning abundance of coho salmon. For example, curtailment of fishing seasons has been thought to have reduces harvest-related mortality