How do u do this on a lake? River I understand . But what trap cages ?

You can search in the forums here at WA Lakes, lots of info!

You can buy the basic Frabill traps, but you have to cut a 3"x5" panel out in upper half and use 100% cotton cord 1/8" or less to re tie it back in for escaped, this is to meet WA fish rules. These traps are only $10 or less, then just get a float and some line, or no float if you throw your trap from shore. I suggest not using the square traps, as most lake and river bottoms are not perfectly flat. The round cone style tilt to one side or the other and allow easier access for craws to get in and don't get caught up or snagged as easy and allow water and current to pass through better when in the rivers. I also make my own escape wire's to add around entrance holes so they don't get out after entering. Also add some weight to the bottom of traps so they always land correctly. Total cost $20 or so, Rebuilt Trap, Float, Line.
You can do this or go to Terry Bullard's or Trapper Arne's websites, they have great information and sell great traps, you may still have to make sure you have the required 3"x5" panel for WA rules, tied closed with biodegradable or cotton line, and make sure your float have your name and address (required by WA rules). So if you have a boat get out there and set some traps, 5 max per person, read your fishing rules of WA. If you don't have a boat, try shoreline areas that have rock and structure. You can catch craws from 1 or 2 feet down to 45' or so. I do really well at 15'-20' in lakes and in back eddy's on rivers at about 2' - 6'. These depths all depend on lake, and structure.

Good luck!!

Let me also say 10# is the limit per day and make sure you read and understand the WA rules pages 130-135, and the difference between our native crawdad's ( signal crawdad ) and all other non native species and that they must be killed before leaving water. Only native craw's can be removed from the vicinity alive. Here is a list below of county's and lakes and rivers that have craws, not all rivers or lakes are listed, as I have found others that have good populations of craws.


Crawfish Lakes and Streams in Washington


-County
-Lake or Stream


Adams
Cow Lake
Sprague lake

Chelan
Chelan Lake

Clallam
Aldwell Lake (Res.)
Anderson Lake
Crescent Lake

Clark
Bachelor Slough
Battleground Lake
Buckmire Slough
Camas Slough
Columbia River
Cushman Lake #1
Lackamas Lake (Res.)
Lake River
Lewis River
Merwin Lake
Vancouver Lake
Washougal River
Woodland Slough
Yale Lake (Res.)

Cowlitz
Coal Creek Slough
Cowlitz River
Fisher Island Slough
Horseshoe Lake
Kalama River
Merrill Lake
Silver Lake
Toutle River
Wind River

Dougless
Coffee pot lake
Twin lakes

Ferry
Curlew Lake

Franklin
Snake River

Grant
Alkali Lake
Ancient Lake
Banks Lake
Blue Lake
Burke Lake
Cliff Lake
Cup Lake
Coulee Lake
Crab Creek
Crystal Lake
Deep Lake
Dusty Lake
Evergreen Reservoir
Goose Lake (upper)
Lenore Lake
Moses Lake
Potholes Res.
Quincy Lake
Snake River
Soap Lakes
Soda Lake
Stan Coffin Lake
Sun Lakes
Warden Lake

Grays Harbor
Copalis River
Hoquiam River
Humptulips River
John's River
North River
Satsop River
Sylvia Lake
Wishkah River
Wynoochee River

Island
Cranberry Lake
Deer Lake

Jefferson
Anderson Lake

King
Angle Lake
Boren Lake
Cedar Lake
Elbow Lake
Green Lake
Green River
Margaret Lake
Mill Creek
North Lake
Pine Lake
Portage Bay
Rattlesnake Lake
Sammamish Lake
Sammamish River
Sammamish Slough
Snohomish River
Soos Creek
Steele Lake
Trout Lake
Union Lake
Walsh Lake
Washington Lake

Kitsap
Kitsap Lake
Island Lake

Kittitas
Easton Lake
Taneum Creek
Yakima River

Klickitat
Horsethief Lake
Klickitat
Roland Lake

Lewis
Chehalis River
Mayfield Lake
Mineral Lake
Skookumchuck River

Lincoln
Lake Roosevelt

Okanogan
Alta Lake
Bonaparte Lake
Buffalo Lake
Campbell Lake
Conconully Lake
Conconully Res.
Crawfish Lake
Omak Lake
Osoyoos Lake
Palmer Lake
Patterson Lake (Res.)
Pearrygin Lake
Salmon Lake
Sidley Lake
Whitestone Lake

Pacific
Grays River
Harts Lake
Loomis Lake
Middle Nemah River
Naselle River
North Nemah River
Smith Creek
Willapa River

Pend Oreille
Browns Lake (on Brown Cr)
Calispell Lake
Cooks Lake
Conklin Lake
Davis Lake
Half Moon Lake
Mystic Lake
No Name Lake
Shearer Lake
Vanee Lake

Pierce
Alder Lake (Res.)
Bonnie lake
Clear Lake
Kapowsin Lake
Nisqually River
Silver Lake
Spanaway Lake
Steilacoom Lake
Wapato Lake

Skagit
Beaver Lake
Big Lake
Campbell Lake
Caskey Lake
Cavanaugh Lake
Clear Lake
Cranberry Lake
Erie Lake
Everett Lake
McMurray Lake
Minkler Lake
Pass Lake
Shannon Lake (Res.)
Sixteen Lake
Skagit River
Whistle Lake

Skamania
Drano Lake
Goose Lake
Mosquito Lake
South Prairie Lake
Stump (Tunnel) Lake
Swift Lake (Res.)

Snohomish
Ballinger Lake
Cassidy Lake
Chaplain Lake
Flowing Lake
Goodwin Lake
Ki Lake
Martha Lake
Pass Lake
Roesiger Lake
Serene Lake
Shoecraft Lake
Silver Lake
Snohomish River
Stevens Lake
Stickney Lake
Storm Lake

Spokane
Badger Lake
Chapman Lake
Eloika Lake
Fish Lake
Hangman (Latah) Creek
Liberty Lake
Little Spokane
Long Lake
Marshell Creek
Newman Lake
North fork of the little Spokane
Silver Lake
Spokane River

Stevens
Long Lake

Thurston
Black Lake
Deschutes River
Deep Lake
Hicks Lake
Lawrence Lake
Long Lake
McIntosh Lake
Patterson Lake
Skookumchuck River
St. Clair Lake
Summit Lake
Ward Lake

Wahkiakum
Deep River
Elochoman River
Skamokawa River

Whatcom
Baker Lake
Budd Lake
Bug Lake
Caine Lake
Diablo Lake
Fishtrap Creek
Johnson Creek
Nooksack River
Padden Lake
Ross Lake (Res.)
Terrell Lake
Toad or Emerald Lake
Wiser Lake

Whitman
Boyer Park
Palouse River
Rock Creek
Rock Lake