Match your cooking method: for pan-sear/grill, prioritize halibut or sablefish; for bake, cod or haddock works best.
Match thickness to avoid dryness: target similar thickness to your striped bass; if using tilapia, expect a shorter cook.
Season to compensate: use a touch more salt and a brighter acid (lemon or vinegar) if the substitute is leaner than striped bass.
Check doneness early: pull the fish when it flakes in the thickest part (it keeps cooking for 1–3 minutes off heat).
Rest and serve: rest 2–5 minutes so flakes set; serve with the same sauce you planned for striped bass.