It is legal to catch them but they must be released or killed:
Brook, brown, bull, cutthroat, golden, lake (Mackinaw), rainbow (including steelhead), splake and Sunapee trout; trout hybrids; Chinook, coho, Atlantic, and kokanee (blueback) salmon; grayling; whitefish; cisco;
crappie; perch; bass; catfish; bullhead; sunfish; sturgeon; northern pike; tiger muskie; walleye and sauger; and burbot (Ling).
Bullfrogs and crayfish are also defined as game fish.
Holding Live Fish:
No permit is required to keep game fish alive that have legally been reduced to possession, in a live well, net or on a stringer while at the body of water from which they were taken. All fish must be killed or released
prior to leaving the water body. However, anadromous salmon and steelhead must either be killed or released after landing.
Movement and Introduction of Live Fish:
It is illegal to release or allow the release of any species of live fish (including crayfish and bullfrogs),