Dozens of species of fish and shellfish are caught in New England’s waters. But only a handful show up in most seafood retailers. You can probably list them: cod, haddock, scallops, clams, lobster. Now, it’s not just anecdotal. A citizen science initiative has found that five species dominate at New England seafood counters and that some of the species that are most common out in the ocean are the rarest in our markets.