Trout! Wow!

For the past few weeks, I have been working with the San Francisco Bay Area Network (SFAN) at Point Reyes National Seashore within the fisheries division to support the Inventory and Monitoring (I&M) program. Work days have been consumed by fieldwork in various freshwater streams and intertidal areas. Such areas have been primarily sampled for environmental DNA (eDNA)  for several ESA-listed freshwater species such as steelhead trout (Oncorhynchus mykiss), California red-legged frog (Rana draytonii), foothill yellow-legged frog (Rana boylii), and northwestern pond turtle (Actinemys marmorata). As discussed in my prior blog post, sample collection areas have also been surveyed using physical aquatic sampling techniques, such as electrofishing or seining. For the past couple weeks, these techniques have been conducted; however, they have resulted in minimal viable evidence for these species living in these areas – until yesterday. 

While electrofishing a site on East Schooner Creek we were fortunate enough to catch a resident rainbow trout in our downstream bag net (featured image). With a fork length of 203mm, this trout displayed many characteristics of the non-anadromous rainbow trout. 

Steelhead and rainbow trout are the same species with several differences in their life histories and visual characteristics. Steelheads are anadromous, meaning they spend part of their lives in the sea before going to rivers to breed. Whereas rainbow trout spend their lives mostly or entirely in freshwater. Due to these differences, rainbow trout and steelhead are different in appearance, most noticeably in size and color. 

Through close observation, we were able to determine that this individual fish was likely a resident rainbow trout that will continue living in freshwater creeks and streams. Despite our goals to capture physical samples of our targeted species, this find was quite exciting! Furthermore, this sample provides the crew with some type of evidence that can be compared to the results provided by the eDNA database once our samples are processed. I would like to know if there is some type of population density dependence relationship between these trout populations and if competition may arise during the steelhead spawning season. In other words, how much habitat is necessary for both of these populations to survive?