A brief look at coho

The complexity of the anadromous life cycle adds to the coho¹s vulnerability. Spawning is done in gravel; too much sediment there can destroy good spawning habitat. Emergent baby fish require shallow, quiet areas, and pools or side channels in which to grow. Young coho need cool water, adequate cover, and sufficient food to survive. There are completely different habitat requirements in the ocean and therefore different threats, including fluctuating ocean temperatures and fishing pressure. Then the migration back to freshwater is fraught with dangers from dams, culverts, and other impassable structures. Drought, flooding, mudslides, and other natural disasters can also impact the fish at any point in its life cycle.

Coho has experienced a rapid decline in numbers and range in the last few decades. Historically, coho were found in 582 California streams from the Smith River in the north to the Big Sur River on the central coast. Of these streams, an estimated 19–50% have lost their coho runs with the decline worse in the southernmost parts of the range. It is estimated that coho numbers in California are presently less than 6% of their abundance in the 1940s, with at least a 70% decline since the 1960s.

The decline of the coho is attributed to a number of factors, both human and natural. Among these is road and dam construction; timber harvesting, grazing and mining activities; urbanization; and overfishing. In addition, drought and other environmental conditions have played a role.

Coho is one of five species of salmon found in California. Salmonids are further differentiated into groups of genetically similar populations called evolutionarily significant units, or ESUs.

The National Marine Fisheries Service (NMFS) is the responsible federal agency for anadromous fish. NMFS has determined that three ESUs—the Central California, Southern Oregon/Northern California Coasts, and Oregon Coast—are threatened species, that is, they are likely to become endangered (in danger of extinction) in the foreseeable future.

Landowners can do much to improve habitat for coho salmon and help recover the species. Large woody debris and boulders in streams can improve conditions by providing escape cover, shade, and organic nutrients. Stream canopy is vital to maintain suitable water temperatures. Good road construction and maintenance are also extremely important (consider attending a roads workshop on April 26 or May 10—see calendar). For more information on what you can do, go to the articles ³Landowners can help in coho recovery² and ³How can you help the fish?² http://ceres.ca.gov/foreststeward/html/fishhelp.html