Chichagof island is a wondeful place to visit for fishing and wildlife sightseeing. Fishing by guide boat is best, since halibut and salmon are easy to find and catch, but you can fish in the dozens of wilderness creeks. Wildlife sightseeing is outstanding. Eagles and deer are everywhere, and brown beers are easy to find since northeastern Chichagof has the highest concentration of brown beers in the world (about 1.8/mi2, over 4000 bears), and they are huge (up to 1200 lbs & 5' at the shoulder). There are lots of humpback whales and seals, and some killer whales, all of which are sometimes seen in in the harbor. Icy Straight Point is the main tourest facility for the cruise ships that visit. There are restaurants, taverns, shops, a museum, indian culture center, kayaks, bikes, and they claim the longest zip line in the world (really fantastic), and of course lots of sightseeing trips to see the bears, whales, the town, the Vortex Mountains, etc.
PS: Sitka is not on Chichagof island, it's on Baranof island to the south.