There is only one fly, to have a great day w/ Bluebacks (sea-run cutties). The Borden Special. Period. Old timers, every year, buy them by the DOZENS! When old timers buy dozens, of a specific fly/lure--you KNOW that, they WILL catch fish! Another one to try, would be a Brown Teeny Nymph.
And for spin fisherman...HOT PINK Rooster Tails, are the bomb on sunny days. On cloudy days, switch to Brown Roosters.
Brown Nymphs / Rooster Tails, imitate Blueback protein snacks (small crawdads).
And keep in mind that Bluebacks inhabit slack water pockets, undercut banks w/ slower moving water, backwater eddies, etc. You won't find them, typically, holding in the faster water. They do not require the same cold temps / higher oxygen levels that, 'bows need to have.