Nicole Brann dips alewives May 15 at the headwaters of Seven Mile Stream at Webber Pond in Vassalboro, as Corey Cookson watches. The duo were harvesting the migrating fish for Ron Weeks, who holds the contract from the town of Vassalboro to sell alewife to lobster fisherman. Three dips filled a crate that weighed about 250 pounds, Cookson said, and held about 500 alewives.