Human activities such as water diversions that decrease flows or removal of streamside vegetation that shades the water, can lead to elevated water temperatures. Temperatures above 22 degrees can be stressful for steelhead trout. The mean temperature for sites tested was 14.6 degrees Celsius. Five sites, all located in Monterey County, had water temperatures above 20 degrees. Alisal Slough at 22 degrees and Moro Cojo Slough at 23.2 degrees.
All aquatic animals require dissolved oxygen to breathe.
The concentration of dissolved oxygen in the water column affects a wide range of behavior such as feeding, spawning, and incubation. Nutrients found in sewage, fertilizers, and manure provides a food source for algae and aquatic weeds, causing blooms and increased vegetation. This in turn depletes the amount of oxygen available in the water column. Dissolved oxygen levels are closely related to water temperature, dissolved oxygen levels decrease as water temperature increases. Accordingly, test results from a monitoring event on a cool and cloudy morning in April are unlikely to reflect yearly minimums.