Looks like a very fancy and weatherproof seine skiff. When the boat sets her net she drops off the seine skiff with one end of the net attached to it, and then the two vessels take off in opposite directions around the school of fish, with the larger vessel paying out the net. When they meet up the seine skiff passes its end of the net to the mother ship, which then pulls in both ends together using that big block on the boom, "pursing" the net and capturing the fish. Hence the term "purse seiner" for fishing boats like Lady Janice II.

John