If you can't eat shellfish, substitute a mild white flaky white fish such as tilapia. Although salmon has a more assertive flavor, the texture of salmon lends itself well to fish cakes and the spices in these Maryland crab cakes work with salmon. You could also use imitation crab, which is made from surimi, a paste made from minced and washed mild white fish. The main ingredient is usually Alaskan pollock or another type of white fish.