There is one thing to note that is a very big difference in nutritional value between fin fish and shell fish. The higher omega 3 count contain in fin fish does not carry over the shell fish. Shell fish has a high omega 6 count which can increase inflammation.
Umm.....
Mussels are low in fat, only containing 0,7g of saturated fat in a 3oz portion. They are, however an extremely rich source of Omega-3 fatty acids, which are found in oily fish and other foods but are not produced by the body.
Clams like other bivalves are low in fat, high in protein and omega-3 fatty acids. Clams are also a rich source of potassium and are relatively low in calories.
Shrimp are rich in long chain omega-3 EFAs that are, as we have seen, the brakes fo the immune system.
(Doc Ed, The Longevity Institute)
Total fat content in one crab leg is 2.1g. Of this total fat, there are 0.7 g of polyunsaturated fat, 0.2 g of monounsaturated and 0.2 g of saturated fat. King crab legs are a good source of omega-3 fatty acids containing 614 mg.
Oysters are high in Omega-3 fatty acid and taurin, know to clear the arteries and benefit the central nervous system.
Inter-tidal herbivorous shellfish such as mussels and clams can help people reach a healthy balance of omega-3 and omega-6 fats in their diets, instead of the current Western diets. For this reason, the eating of shellfish is often encouraged by dietitians. Shellfish, however, are a rich source of the amino acid taurine.
I could go on, but that 1 minute of using google before I posted some information that might discourage people un-necessarily from doing something healthy, hurt my brain.
All that Omega 3 and Omega 6 stuff is a bit of a red herring. Eat natural foods, and you will be fine. Your body actually needs both Omega 3 and Omega 6. Your immune system needs some practice, and like everything (Yin / Yang) balance is important.
Your worst source of bad fat is probably a deep fryer and processed foods. Stay away from those and eat all the healthy fish you want - especially farmed mussels.
I can't say enough good things about farmed mussels, which are good for you, very low mercury, sustainable, cheap, easy to prepare, and yummy. Note farmed mussels are unlike other farmed fish, and are actually sustainable and healthy - often more healthy and less polluted than wild mussels.
*I should note that means at least Canadian farmed mussels, which are probably the best in the world. Check where and how yours are raised. If they're grown on ropes in open water, they are probably just as good for you and the environment as the Canadian farmed mussels.