Your best chance to catch a cusk is through the ice, because you are allowed to fish up to 6 NH Fish and Game Department defined "Cusk fishing device(s)":
A device for storing line in a manner which is not free-running and is securely attached to the device and to which is attached a sinker, weighing at least one ounce, not more than 6 inches above, and independent of, an attached single hook for bait. The weight must rest on the bottom of the lake.
What they don't mention is you need to tie the other end of your line around the middle of a piece of scrap wood (eg 2"x2" 12+"), label it with your name and address, and then lay it down so it straddles your hole overnight...yupp, go home and get a goodnights rest. The bait to use is live baby suckers, which are as tough as nails and will swim about all night stirring up the silt and thereby attracting your prey. As such, I don't think its necessary to spend your money on chum bait and wouldn't waist time fishing over rocks.
Delicious chowder, they make!