Programs

Napa Sustainable Winegrowing Group

The catch from the rotary screw trap

The rotary screw trap is a device that nondestructively traps fish in a waterway. Fish are kept alive in the trap's holding area, and released once they are counted and measured by biologists. The trap is a great tool for monitoring the number of Steelhead trout and Chinook salmon smolts that are migrating out to the ocean in the spring.

The RCD monitors a rotary screw trap located in the Napa River in the spring. The trap is checked every day that flows accommodate the trap. Although the trap doesn't catch every fish that is moving through the river, it catches enough to give us a snapshot of the population size of salmon and trout, as well as the diversity of fish that live in the watershed.

Read the final report describing results of the rotary screw trap monitoring program in the Napa River in 2010

Learn more about fish monitoring and the 2009 catch here

2010 Total Fish Count

Fishing period: February 18 to June 14

Origin	Type of fish	How many?
Native	Chinook salmon	1373
	Chum salmon	192
	Unknown salmonid species*	318
	Steelhead trout	315
	California Roach	3571
	Lamprey Sp. (Adult)	93
	Lamprey Sp. (Ammocete)	155
	Pacific Chorus Frog (Tadpole)	32
	Pacific Lamprey	11
	Prickly Sculpin	124
	River Lamprey	2
	Sacramento Pikeminnow	87
	Sacramento Splittail	6
	Sacramento Sucker	419
	Sacramento Sucker larvae	25644
	Three-spine Stickleback	76
	Tule Perch	28
	Western Brook Lamprey	93
	Western Pond Turtle	1
Nonnative	Bluegill	100
	Brown Bullhead	3
	Bullfrog (Adult)	2
	Bullfrog (Tadpole)	1401
	Crayfish Sp.	11
	Louisiana Crayfish	233
	Signal Crayfish	103
	Fathead Minnow	4
	Golden Shiner	11
	Green Sunfish	2
	Inland Silverside	12
	Largemouth Bass	1
	Largemouth Bass (larvae)	969
	Red-eared Slider Turtle	3
	Red-eared Sunfish	8
	Striped Bass	2
	Wakasagi	2
	Western Mosquitofish	9
	White Catfish	1

*Identification of unknown salmonid species if being pursued. Preliminary results show that at least some of these fish are sockeye salmon.