Fish can provide an excellent low-calorie protein source without the fat and cholesterol of red meats. However, some varieties such as shark and mackerel are very high in mercury. Mercury is a known carcinogen and a pollutant of the habitats for many fish, including farmed fish, according to the Washington State Department of Health. The USDA recommends eating at least eight ounces of healthy, low-mercury fish per week. Limit your consumption of high-mercury fish to no more than 12 ounces a week.
This family of fish falls into the shellfish group and includes king, blue and snow crab. Crab is an excellent source of many nutrients including protein, vitamin B12, and vitamin C, and it has only 82 calories per three-ounce serving. Crab is readily available at grocery stores and seafood marts, but avoid the canned or artificial versions. These can have excess sodium, which is hard on the kidneys and heart.
When enjoying catfish, choose the American kind -- raised, procured and sold as an American product. Imported catfish may contain high levels of cancer-causing toxins. Broiled or grilled catfish is high in omega-3 fatty acids, which are important for heart and brain health, and selenium, which is important for cell metabolism.
Scallops are a small mussel and safe to eat two to three times weekly. Low in toxins and high in protein, these mussels are delicious alone or on a salad. Scallops come in a variety of sizes, including the large Atlantic version and tiny bay scallops.
Salmon is a heart-healthy food that is rich in omega-3 acids. The larger and older the fish, the more mercury it might contain. Therefore, limit farm-raised or Atlantic salmon to one serving every two months, but enjoy canned Pacific salmon two times a week, according to the Association of Reproductive Health Professionals.
Perhaps a neighbor just returned from a weekend fishing trip and has some trout to spare. Freshwater trout is best and can be enjoyed biweekly, according to the Washington State Department of Health. This fish is rich in omega-3 fats, which are good for the heart.
Canned tuna is a popular pantry staple for good reason. It is a quick, cheap source of low-fat protein and is rich in vitamins B12 and D, calcium and iron. However, albacore tuna contains almost three times as much mercury as skipjack tuna, according to the Environmental Defense Fund. Therefore, pregnant women and young children should focus on consuming primarily skipjack, or light varieties of tuna. Furthermore, canned tuna can be high in sodium, so look for low-sodium versions if you're watching your salt intake.
Raw or steamed, oysters are a rich source of protein and omega-3 fats. The Washington State Department of Health states that oysters are low in mercury and can be enjoyed two to three times weekly. Those with health conditions, however, such as immunodeficiency disorders like AIDS or cancer, should avoid oyster consumption due to their potential bacteria containment.
About 3 inches in length, crayfish are similar to tiny lobsters that turn bright red when cooked and contain juicy white meat. Sometimes referred to as crawdads, crayfish are a healthy fish to eat, but only the American kind that is farmed mostly in Louisiana and the Mississippi.
Rich in iodine, shrimp is a low-fat, low-calorie shellfish that can be enjoyed weekly, according to the Association of Reproductive Health Professionals. Shrimp can be boiled, grilled, sauteed or added to a salad while still retaining the same delicious taste.
The smaller the fish, the less mercury it contains. Older, larger fish eat the small fish and therefore absorb their mercury and toxins. Sardines, such as herring, are small fish that are low in mercury and high in essential omega-3 fatty acids, calcium, vitamin D and several B-vitamins. They are sometimes enjoyed plain on crackers or out of a can. Because many canned versions are high in sodium, consume them in moderation or look for low-sodium canned versions if you are controlling your sodium intake.