State of Fisheries: Salmon and Trout in San Mateo and Santa Cruz Counties

Populations of coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss) have dramatically declined since the early 1900s in both San Mateo and Santa Cruz Counties. This section examines the current and historic population status and then introduces the concept of “limiting factors,” the key freshwater habitat and environmental conditions that, when significantly altered, can contribute to a decline in salmonid populations. Human activities in San Mateo and Santa Cruz Counties, in conjunction with natural events, have detrimentally impacted the environmental factors necessary to produce sustainable populations of coho and steelhead. In many cases, the poor quality habitat that results from these changes can be modified to restore environmental conditions that promote healthy salmonid populations.