Spanish mackerel is primarily a southern species, but it has been known to range as far north as Cape Cod. It has no distinct stripes on its body and has golden spots on its sides. King mackerel do not range farther north than North Carolina. They are large fish that average twenty pounds. Atlantic mackerel are smaller, averaging one to two pounds, and Spanish mackerel are intermediate in size, averaging two to four pounds.
Atlantic mackerel are fattest in the fall.
Because of their high fat content, it is necessary to handle mackerel with care. Pack them in ice as soon as possible to maintain their quality and to ensure that they will be safe to eat. All members of the Scombroid family have large amounts of the amino acid histidine and related compounds in their flesh. If bacteria are allowed to grow after these fish are caught, these compounds can be converted to histamine and other related compounds. This conversion can occur rapidly if fish are left at a high temperature for several hours.