Elk Creek Watershed Council, Umpqua Basin, Oregon

Coho Salmon

The Elk Creek watershed is an important spawning and rearing area for endangered coho salmon, as well as other aquatic species such as Chinook salmon, steelhead, cutthroat trout, and Pacific Lamprey. It was designated a Tier 1 Key Watershed by the Roseburg District BLM in the Northwest Forest Plan (1994). The entire Elk Creek watershed is listed as "critical habitat" in the Oregon Coast Coho Recovery Plan (2016).

The Elk Creek watershed has 327 miles of anadromous fish (coho salmon) habitat. Of this, 172 miles are characterized as "High Intrinsic Potential" by Oregon Department of Fish and Wildlife (ODFW). This means that these streams have the "potential" to support healthy populations of coho salmon.

Unfortunately, much of this habitat has been degraded by past land management actions, and cannot support the numbers of fish that it has in the past. Declining numbers of coho since the 1960s have led to its listing as "threatened" under the Endangered Species Act.

Salmon are an important cultural and economic icon of the Pacific Northwest. Coho salmon are by far the most abundant salmonid in the Elk Creek watershed. After the fall rains begin to raise water levels, adult coho return from the ocean to the streams in which they were reared. Here they spawn and then die.

These streams are the smaller, low-gradient tributaries to the Elk Creek mainstem, the same tributaries that the early settlers built their farms and ranches on. Over the years, as these settlers and those that followed began to make their living off the land, many of their land management actions have taken a toll on the habitat that supports the coho.

Coho salmon are unique from many other salmon species in that they remain in the fresh water streams for an entire year before migrating to the ocean. During this year they must overcome a range of physical threats, and survive in degraded habitat conditions. The eggs must have cool, clear water and clean gravel in which to grow. In many of our eroded, bedrock-dominated streams, there is very little gravel for adults to lay their eggs in, and where there is suitable gravel, excess fine sediment in the water can bury the developing eggs and deprive them of the oxygen they need.

This section of Cox Creek has good clean gravel and is a favorite spawning area for coho.

As the young fry emerge from the gravel, they need to find areas of slow moving water, to find food, and to escape predators such as blue herons or cutthroat trout. Again, in incised, bedrock channels, there is little slow-moving water or cover to escape predators. There is also little gravel to support the invertebrates that the young fish rely upon for food.

This bedrock stream has no gravel for spawning, few areas of slow-moving water, and almost no cover for young fish to escape predators.

In the summer, the juvenile fish still need cover to escape predators, and to find food, but as summer water temperatures rise, they also need cool water. Water moving across bedrock, especially in areas without shade, heats up very quickly. Young coho can survive as water temperatures approach 70 degrees, but unless they can find cooler water in smaller tributaries or deep pools, their growth and migration timing is impaired.

Beaver ponds are some of the very best habitat for young coho. They provide slow water, cover from predators, and a source of food.

Those young fish that are fortunate enough to survive the summer must next find refuge in areas of slow-moving water to keep from being completely washed away during winter storms . One of these areas is the floodplain, the low, flat areas along the banks of the stream. As the streams rise during storms, they overflow onto the floodplains. Juvenile coho will follow the slow-moving water on the edges up and out of the torrent in the main channel. After the storm, as the water recedes, they will return to the channel.

This log structure has slowed water and allowed it to overflow onto the floodplain. As the water recedes, the young fish will return to the main channel.

When streambeds are eroded down to bedrock, as many in our watershed and elsewhere are, they become so incised that they don’t have room to overflow. There is no place for the young fish to escape, and many are swept away. ODFW estimates that as many as 80 to 90% of the juvenile coho that survive the summer are lost during the winter.

The streambed in this straightened channel has eroded down to bedrock and is disconnected from the floodplain. There is little shelter for juvenile coho from high flows during winter storms.