Lake Merwin is one of the best places in Southwest Washington to catch kokanee and the only place near Vancouver and Portland where you can catch a massive tiger muskie.
Sometimes called Merwin Reservoir, it stretches along the south side of State Route 503 only a half hour or so east of Interstate 5 at Woodland.
The reservoir, formed by the damming of the Lewis River, spans nearly 4,000 acres at full pool.
Lake Merwin may not be the best place to bring beginning anglers, as kokanee and especially tiger muskies can take a bit of skill to catch. But if you know your way around a tackle box, you can have quite a bit of fun on this reservoir.
Boat launches are operated by reservoir operator PacifiCorp, not the Washington Department of Fish and Wildlife or the county government.
The power company charges day use fees for its access points. While Speelyai Bay Park is open year-round, Cresap Bay Park is seasonally managed, open from late May through the end of September.
Fishing is open year-round on the lake, but the water level varies and can change where you fish and how you boat. Call (800) 547-1501 for current reservoir level information.
Shoreline access is limited at best, and bank fishing is particularly tough for the major game fish species here but might net you a northern pikeminnow or the very occasional wild trout.
Lake Merwin is subject to the same statewide rules and regulations as the majority of Washington’s lakes and reservoirs. That does include a requirement that bull trout or Dolly Varden be released if caught.
For the uninitiated, kokanee are sockeye salmon that live out their lives in freshwater instead of migrating to the ocean and back like their anadromous kin.
As a result of skipping their ocean migration, and missing the rich smorgasbord the ocean provides, kokanee are typically quite a bit smaller than oceangoing salmon.
But they also are available to anglers longer than anadromous salmon because they are fishable in lakes like Lake Merwin during the time their cousins are way out in the Pacific Ocean.
Kokanee are a bit oilier than their trout cousins, a trait that makes them particularly tasty when prepared in a variety of ways, including as small smoked salmon.
WDFW boosts Lake Merwin’s kokanee population with annual plants of the young salmon, which finish growing by feasting on the lake’s plankton population.
While fishing success here can vary year to year, kokanee can become a hot commodity at Lake Merwin some years as early as February, although spring and early summer is the classical “peak” of the season.
The key to catching kokanee is grabbing their attention.
Trolling is the most popular way to catch them, with veteran anglers often running a dodger or set of flashers (lake trolls) ahead of their brightly colored small lures, such as spinners, spoons and hootchies.
The attractors may resemble a feeding frenzy of these schooling fish, making the real fish want to join the party.
Kokanee will quite often travel and feed in schools, which can vary greatly in size, and can be especially grouped up in summer and early fall.
If you’re lucky enough to find a big group of kokanee, vertical jigging with a bright metal jig can be a great way to fill your bag with these sometimes tricky fish.
Kokanee tend to run closer to the surface when the water is still cold, in the early season, but those schools will find colder and deeper water as the hot weather sets in.
Regular kokanee anglers often employ electronic fish-finders to locate the schools and then downriggers or at least heavy weight to reach deeper fish.
Kokanee generally top out at rougly 12 inches in many Washington lakes (a little bigger in some spots), which is comparable to typical trout in Washington.
Don’t misjudge them by their relatively small size. They are frenetic on the line and can be tricky to bring all the way to the net. (Yes, you should bring a long-handled landing net.)
Kokanee are notorious for their soft mouths, so consider using a rubber snubber to increase your chances of keeping them on the hook long enough to reel them in.
Without the snubber to soften the impact of the strike, you’ll likely lose a few more kokanee when they hit and the hook tears free.
Tiger Muskie Fishing
Lake Merwin is considered one of the best lakes in Washington to fish for tiger muskies, an uncommon sport fish in the state.
In fact, some anglers will argue there’s no better spot in the state if tiger muskies are what you’re after.
Tiger muskellunge, as they are officially called, are actually a crossbreed between the true muskie (muskellunge) and the northern pike. These hybrids are sterile.
The Washington Department of Fish and Wildlife stocks tiger muskies both as a form of population control — they feed on other undesirable and overpopulated species of fish — and as a life pursuit for veteran anglers.
At Merwin, WDFW primarily plants tiger muskies every few years to help keep the northern pikeminnow population in check, which in turn helps the kokanee population.
Tiger muskies are known for being very difficult to catch. If there’s a fish that takes more time and skill to catch in the Northwest than steelhead, this is the one.
They are almost purely sought out as a sport fish; state regulations limit anglers to one per day, and only the largest of them at that; no tiger muskie smaller than 50 inches long can be legally taken, primarily as trophies.
There are also many better-tasting fish that are easier to catch, including Lake Merwin’s kokanee, so don’t worry you’re missing out on a great meal by releasing your catch.
The fun of fishing for tiger muskies is the challenge of it. Tiger muskies can grow well over 4 feet long. The largest caught on record in Washington weighed a whopping 38 pounds.
Tiger muskies are powerful fish as well.
While not considered a danger to humans in the water, they do have rows of sharp teeth, so use caution when handling them and removing hooks to avoid lacerations. Many anglers will carry long-handled pliers to safely remove hooks without fear of a bite.
Large lures are often used when fishing for tiger muskies, since tiger muskies favor large prey. Spinners and jerkbaits are also among popular gear to draw these fish’s attention.
The best tiger muskie fishing tends to be during the warmer months, typically meaning they will bite best from late spring, through summer and into very early fall.
They will be even harder to catch than normal in cold water although they are built to survive cold temps as the progeny of two northerly species.
The most important thing to practice when fishing for tiger muskies is perseverance. Even the most skilled anglers can spend entire days’ worth of fishing without successfully landing even one tiger muskie.
Tiger muskies are very particular about when they feed, they may or may not show any interest in a lure even when they are hungry, they can be hard to find with their tendency to seek cover in vegetation or beneath logs, and once on the line, they are among the most challenging fish in Washington to land.
You’ll mostly be looking for tiger muskies in shallower waters. Look for cover not far off the shorelines, not in the depths where summertime kokanee go.
Recommended gear includes: a strong monofilament or braided line, able to handle up to 30 pounds or more; a fast-action, medium-heavy rod with good balance and durability; and a very large landing net or cradle. Many anglers will use a wire leader due to the muskie’s sharp teeth.
Once caught, a tiger muskie should be returned to the water quickly. Have a plan for lifting it out, removing your hook and snapping your photo before releasing your catch. Managing adrenaline is key.
Read our full run-down of all of Washington’s best tiger muskie fishing spots.
Other Lake Merwin Fish
There are a modest number of trout at Lake Merwin, but it is not stocked and the wild trout here aren’t caught in large numbers.
WDFW reports bull trout in the lake, which are protected and may not be targeted. If you catch one incidentally, it must be released unharmed.
Other sources suggest there are some wild cutthroat and rainbow trout in the lake as well, which would make sense because they are native to the Lewis River and tributaries.
WDFW lists both coho and Chinook salmon as lake residents.
Northern pikeminnows are fairly common in the lake, especially in shallow areas, and are a major reason WDFW planted tiger muskies.
There may be a smattering of other fish here as well, but the kokanee and tiger muskies are the two main draws for anglers.
Planning Your Trip
Lake Merwin is an easy day trip from much of Western Washington and even from the Portland area of Oregon.
Where is Lake Merwin?
Lake Merwin is about 12 miles east of Woodland along State Route 503, straddling the line between Cowlitz and Clark counties.
It’s the lowest of three big reservoirs on the Lewis River, which below this reservoir is among the most important salmon and steelhead fishing rivers in Southwest Washington.
Lake Merwin is about an hour’s drive from Vancouver, Washington, or Portland, Oregon, two hours from Olympia and about three hours from Seattle.
Take exit 22 off Interstate 5 onto State Route 503 and simply follow the highway up the Lewis River.
The other reservoirs on Lewis River include the next one upstream, Yale Lake, which is another kokanee fishery, and then above that Swift Reservoir, better known as an excellent rainbow trout spot.
Access and Amenities
PacifiCorp manages the recreational facilities at Lake Merwin along with its hydropower operations.
Speelyai Bay Park on Lake Merwin is open year-round.
It’s on a finger of the reservoir sticking north toward the highway from near Lake Merwin’s east end. The day use park has parking, restrooms and a two-lane boat ramp. There’s also a swimming beach, so be aware and cautious when there are people in the water.
Camping is allowed at Cresap Bay Park, but the park, campground and boat launch there are seasonally managed.
Cresap Bay Park opens for the season on the Friday before Memorial Day and closes at the end of September.