Not all fish are edible as not all of them is safe either. It is same with plants that not all can be eaten by humans. Fish has many species and you must know what kind of fish can be eaten or not to avoid any problems it cause like food poisoning. Fish that can be eaten is a good source of fatty acids specifically the omega-3 that can promote brain development. That is why there are many fish products in the market that advertise them as a good source of omega-3 fatty acids.
The common example is canned tuna. But if it’s the albacore type of tuna it should be eaten not exceeding 6 ounces a week.
On the other hand there are fish that cannot be eaten and it includes swordfish, king mackerel, shark and tile fish. They are predatory fish and large in size. They are not good to eat as they have high level of mercury. Seafood that have low content of mercury are tilapia, shrimp, salmon, tuna, catfish and cod.
When a woman is pregnant there are more restrictions as to her diet. There are foods that is not good for her and seafood is not an exemption. As a pregnant woman she cannot eat foods that will affect the health and growth of her baby because whatever she eats her child also. It is more safe to buy fish from sellers who have undergone as they are monitored by specific agencies.