Fish does shrink a bit when cooked. The heat of cooking causes the cells of the flesh to release water, which evaporates during the cooking process. Water content makes up a good portion of the size of the uncooked fish, so water lost during cooking will cause the fish to shrink as it cooks. The amount of water lost can vary with cooking technique. The good news? Fish shrinks less than other meats.

How Much Shrinkage?

It is impossible to state exactly how much, by percentage, weight, or volume, fish will shrink when cooked by any method because the variables are impossible to predict. The meat of some species of fish have a higher water content than others and this varies from fish to fish of the same variety. Size, age, storage and handling, cooking temperature, cooking technique, and cook time all play significant roles in the degree of shrinkage to expect when cooking fish. When a recipe calls for the weight of a fish in its ingredients list, it is raw fish that’s being specified. The recipe will take shrinkage into consideration when it specifies the number of servings it will yield.

Cooking Fish

Cook fish quickly — at high temperature for a short amount of time. Plan on cooking 10 minutes per 1 inch of thickness at 450 degrees Fahrenheit. Use the thickest part of the fish to estimate cook time. Fish is done when a meat thermometer reads 140 F at its thickest part. You also can microwave fish on “high” for 3 minutes per pound. Capture the released juices to flavor a sauce or keep them in freezer to add to fish soup stock at a later date.

Dry Cooking Methods

Shrinkage will be most apparent when dry cooking methods are used — baking, broiling, pan-fry and barbecue. Deep-frying is considered a dry cooking method but the quick seal of the batter in hot oil will trap most of the moisture inside the coating and minimize shrinkage. Smoking fish causes the greatest degree of shrinkage since, ultimately, the goal of smoking it is to dehydrate it for longer keeping and ease of transport when hiking, camping or enjoying similar activities.

Wet Cooking Methods

Cooking with moist heat, such as poaching or stewing in a soup or chowder, will also cause fish to shrink but the released fluids add flavor and nutritional value to the liquid in the dish. Shrinkage is visually less noticeable using these wet-cooking methods because fish is often cut into smaller, bite-size pieces for soup, stew, and chowder recipes.

Serving Size

According to the National Institutes of Health, an adult serving of cooked fish is 3 ounces, or a piece about the size of a checkbook; allow a minimum of 1 pound per four people to account for shrinkage. Realistically speaking, though, most people enjoy bigger portions than the NIH recommendation and most fish recipes call for bigger portion sizes, too. Fortunately, fish is such a beneficial part of a healthy diet that it’s OK to overindulge, as long as your overindulgence is on fish only and not salty, fat-laden batters.