Merwin (Lake) Reservoir (4,090 acres): This North Fork Lewis River impoundment located near the town of Ariel is shared by Clark and Cowlitz counties, with 2,400 acres in Clark County and 1,690 in Cowlitz. Landlocked coho salmon and kokanee are the main target. Angling is best in early spring, with fish in the 10-inch class. Small northern squawfish can be numerous and pesky. Tiger muskies were planted in 1995 to help control squawfish populations. Be sure to check the current reg for size limits.