Haddock is a fish with low mercury levels. It is rich in nutrients like protein, magnesium, phosphorus, potassium, selenium, and copper. Magnesium and calcium are key nutritents, essential for the proper development of bones and muscles in an expecting mother as well as the baby. Magnesium relaxes muscles whereas calcium stimulates them to contract. Phosphorus is essential for proper nerve and kidney function, cell repair, blood clotting and normal heart rhythm.