It may be the first occurrence of its kind in the United States, researchers said.

RIVERS
The Mattole is a remote, free flowing river with no dams and a wild population of steelhead. It is located in the Southwest corner of Humboldt county, about 65 miles south of Eureka and 260 miles north of San Francisco. There is approximately 26 miles of fishable water from the mouth to the town of Honeydew. The fish of this river are wild with no hatchery fish being introduced. Catch and Release is asked for these fish.
EEL RIVER
The Eel flows through some of the most beautiful redwood groves in the state, including Humboldt Redwood State Park. The Eel River flows for approximately 100 miles north through Mendocino and Humboldt counties and offers year-round fishing opportunities, with fall and winter salmon and steelhead runs being the best known. Shad fishing during the late spring and early summer offers the angler an exciting change of pace.
The primary fish of interest for the Eel include steelhead, Chinook, Coho, and sea-run cutthroat trout. Chinook start coming into the river in August. They tend to hold in the waters below Ferndale Bridge until rains allow them upstream. The Chinook run from August through December, with the peak in late October. The average Eel Chinooks are 8-15 lbs, with some up to 40lbs.
Winter steelheads are what the Eel River is known for. The winter steelhead start moving into the river in November running through March, with peak activity during January. The average Eel steely runs 8-10 lbs, with fish to 16lbs common and a number of fish in the 20lb class caught each year.
MAD RIVER
The Mad River is located 15 miles north of Eureka in Humboldt County. It originates at Ruth Lake about 100 miles to the southeast.
TRINITY RIVER
The Trinity River is world-famous for its fine steelhead and salmon fishing, as well as for trophy brown trout. Chinook salmon are the most sought-after gamefish in the Trinity River system. Spring-run salmon begin to enter the river in May and provide trophy fishing through November throughout the river.
Although brown trout are not native to the Trinity River, they were heavily stocked until the late 1970s. Today, a wild population continues to the upper river, providing fly and bait fishing for mostly 10- to 14-inch fish, although an occasional trophy to 10 pounds is sometimes landed.
The upper two miles of the river, from Lewiston Dam down to the Old Lewiston Bridge, is open only to fly-fishing.
KLAMATH RIVER
The Klamath River is the largest of the North Coast rivers of California stretching over 200 miles from its mouth to the Oregon border. Its mouth is located 60 miles north of Eureka and 20 miles south of Crescent City off Hwy 101. The fish of the Klamath are King and Silver salmon, Steelhead, and resident trout. The Kings start running in July with the best action near the mouth coming in August and running through September. Summer/Fall steelhead start running from late summer through October. The winter run starts in November and goes through February.
LAGOONS
BIG LAGOON and STONE LAGOON are brackish because their ocean barriers are breached by storms nearly every winter and are a favorite fishing spot for cutthroat trout.
BEACHES

