The Board of Health voted Monday to ban dogs and all other pets from the town’s public beaches on Lake Massapoag from April 15 to Oct. 15, except for service animals and animals boarding boats in the launch area. The board was revisiting a June 4 ban aimed at protecting the public from bacteria left on the ground from dog feces; the new ban makes minor changes. In the intervening weeks, town employees monitored the beaches to determine whether dog waste posed a significant problem. In an e-mail, board chairwoman Susan Osgood Peck said feces were found, but were sometimes cleaned up before the animal control officer’s morning inspection. The policy imposes a fine of $25 for the first offense, $50 for the second, and $100 thereafter. The ban applies to all of Veterans Memorial Park and its beach, and the fenced area at the Community Center’s beach.