The first crowd of walkers to crest the highest point of the sidewalk on the Causeway Bridge did so under a gray sky midmorning Saturday with some carrying signs supporting whales and a few sporting bright blue hats shaped like a whale. As they concluded the mile walk that began at Mallard Island Yacht Club, they waved the signs.

That’s how Walk the Bridge, a rally to protect the New Jersey coastline and marine mammals many believe are threatened by offshore wind development, unfolded for a good…