I never really had a chance to target these lagoons other than occasionally as I only visited our Eureka office a few days a month. If I lived there - I would have been all over the coastal cutthroat scene. There are some real trophies in those lagoons.
A little history:
California does have a history of propagating and planting coastal cutthroat along CA's north coast, primarily in the coastal lagoons. Originally a brood stock was maintained with fish originating from the Alsea River in Oregon. That broodstock program was discontinued in the late 1970's. In the late 80's to mid 90's, Humboldt State University's fish hatchery (along with the Mad River Hatchery) took over propagation. This was accomplished through collecting eggs originating from local wild adults and rearing to fingerling and sub catchable size. This was also discontinued due to concerns over cutthroat predation on tidewater gobies.
These lagoons have self sustaining, in some cases thriving cutthroat populations - most exhibiting the adfluvial life history with occasional forays into the salt. These highly productive lagoons range in size from 500 acres to nearly 7,000 acres with Lake Earl being one of the largest coastal lagoons in the US. All three are reputed to have (and continue) to produce trophy class coastal cutthroat. California doesn't officially recognize subspecies in their freshwater records but the unofficial state coastal cutthroat record is 5 lbs 12 ounces taken in the 1980's from one of the lagoons.
There's been documented hybridization between steelhead and cutthroat in two of the lagoons and a master's thesis was done about this in 1997. I have seen some enormous "cutthroat" that I would bet have some rainbow mixed in. There were a couple of Humboldt State (now Cal Poly Humboldt) kids that were catching monsters and posting them on social media. Here's a few images that I grabbed from their social media:
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