The American Heart Organization recommends including fish in your diet at least twice a week. Not only does fish include a lot of protein, fish can also be relatively low in fat and calories and rich in Omega 3 fatty acids. Knowing what to look for when purchasing fresh fish will not only make for a better meal, but it can also keep you from getting sick.

Ask About Freshness

In the ideal situation, you would be able to eat any kind of fish that you could ever want right after the fish is pulled from the water. Unless you only eat local fish you purchase right off the boat, you'll most likely be buying your fish at a grocery store or specialty fish market.

No matter where you buy your fish, it is important to ask what the "fresh" label means. Does "fresh" mean that the fish arrived today or four days ago?

Look at How the Fish is Displayed

Markets should display fish on fresh beds of ice. The case should also be refrigerated so that the ice doesn't melt. It is even better if the display has a plastic cover, one that you can see through and can be opened when necessary, but helps prevent insects and other contaminants from coming in contact with the fish.

Beware of Fish Smells

If a fish smells "fishy," the fish is probably past its prime. In general, fresh fish should smell like the sea if the fish lived in the ocean. Fresh water fish should smell like fresh, clean river water.

If your nose is trained, individual types of fish have different smells when fresh. For example, when fresh:

• The smell of whitefish may resemble cucumbers.
• The smell of halibut should be smoky.
• The smell of salmon may resemble cucumbers or melon.
  

Pay Special Attention to the Fish's Appearance

Take a close look at how the fish appears. When looking at a whole fish, the clarity of the fish's eyes can be an indicator of freshness for many types of fish. For these fish, the eyes should be clear rather than cloudy. Some fish, such as grouper and walleye pike, have naturally cloudy eyes. You may need to do some light research to determine the correct eye clarity of your fish of choice.

Fresh fill will also have red gills without any mucous as well as shiny, bright skin. While you may think that bloody fish gills indicates poor handling, bright red blood actually is an indicator of freshness.

Skinned fresh fish should not be dry or discolored around the edges. Each piece should look moist and firm without looking mushy. Regardless of whether the fish is whole or in pieces, the fish shouldn't look slimy or have any dark spots or unusual coloring.

Buying Live Crabs and Lobsters

You are in luck if you have the opportunity to buy live shellfish such as crabs, lobsters, oysters, muscles or clams. If you are interested in purchasing live crabs or lobsters, make sure that the crabs or lobsters that you buy are still moving around or at least can move their legs. These creatures can spoil quickly after they die, so it's important to cook them quickly after your purchase.

Buying Fresh Fish & Live Clams, Mussels and Oysters

You can also use tricks to figure out if clams, mussels and oysters are alive even though these shellfish can't kick. These shellfish will close up shop when tapped. In other words, oysters, clams or mussels with open shells are still living if their shells close when you tap the outside of the shells. Don't forget to tap ones that are only slightly open. This is the normal "openness" for these kinds of shellfish when the shellfish are "relaxed."

Clams and mussels don't have to be completely submerged in water to stay alive. They will live if they are kept damp. Regardless of whether you are looking at mussels, clams or oysters, avoid ones that have cracked or broken shells. These animals are probably already dead.

If you eat fish that smells bad, the smell indicates that the fish is not likely to taste good. In general, that fishy smell also indicates that eating that fish may lead to gastrointestinal problems later.

The Food and Drug Administration (FDA) has established special regulations for certain types of marine fish. Some types of ocean fish that haven't been processed or handled properly can develop toxins called scombrotoxin, which when eaten at high levels, can cause humans to become ill.

Symptoms of scombroid poisoning can start within minutes of eating tainted fish and can include dizziness, nausea and symptoms that resemble an allergic reaction. At the severe end, scombroid poisoning can make it hard to breathe and cause blurred vision. The symptoms of scombroid poisoning can last for up to two days.

Fish that can develop scombrotoxin include:

• Mahi-mahi
• Tuna
• Mackerel
• Anchovies
• Sardines

The FDA regulates how all fish are handled from the moment they are caught until they are purchased by a consumer. Not only does knowing this kind of information help you ask questions about the proper handling of these kinds of fish before purchasing them, but it will help you decide whether it is safe to eat these fish when fresh caught. If your local fishmonger gives you some fish that hasn't been kept properly cooled, that fresh fish may make you sick.