There were no stars from the original cast of “Jaws” — actors Robert Shaw and Roy Scheider are dead and Richard Dreyfuss was otherwise occupied — but this weekend’s Jawsfest was still a lot of fun for fanatics of the classic 1975 film directed by Steven Spielberg. Held on Martha’s Vineyard, where the blockbuster was shot over three decades ago, the event drew a few folks with special insight and expertise. Joe Alves, for example, is the production designer whose black-and-white renderings of a great white were the basis for the mechanical shark used in “Jaws.” Also there was Jeffrey Kramer, who may be best known as producer of “Ally McBeal” and “The Practice,” but who played Deputy Hendricks in “Jaws” and “Jaws 2.”