The start of the commercial Dungeness crab season in the Bay Area is delayed until at least Dec. 1 to reduce the risk of migrating humpback whales becoming entangled in trap lines. This is the sixth year in a row the California Department of Fish and Wildlife has imposed restrictions to prevent fishermen from ensnaring whales. Even as more humpbacks feed along the coast thanks to growing food sources, trap restrictions have reduced entanglements, and…