New research by NOAA Fisheries has revealed the opah, or moonfish, as the first fully warm-blooded fish that circulates heated blood throughout its body much like mammals and birds, giving it a competitive advantage in the cold ocean depths.

The opah fish reproduce by spawning. These fish are known to spawn over immense areas home to the Pacific, especially in warm surface waters. In the tropics, the spawning season of these fishes lasts throughout the year.

Opah is a pelagic species, often found with tuna and billfish. The fish is found in southern waters and has recently become popular with restaurants in Hawaii. All of the opah landed in Hawaii are caught by longlining. Almost all opah sold in the U.S. market are from Hawaii.

guttatus) grows to a length of about 2 metres (7 feet) and a weight of 140 kg (300 pounds), although larger specimens have been reported. The southern opah (L. immaculatus) is smaller, averaging about 110 cm (43 inches) and 30 kg (66 pounds).

Instead, moonfish are caught as bycatch in commercial tuna and swordfish fisheries. “[Opah] can be eaten raw, but they’re also great on the barbecue or smoked,” says Snodgrass.

Health Benefits Opah is a rich source of omega-3s, protein, niacin, vitamins B6 and B12, phosphorus, and selenium. It is also low in sodium.

While known primarily as a Hawaiian species in the domestic market, opah is found worldwide in tropical and temperate waters. It is often taken as bycatch by longliners targeting tuna from New Zealand to California and also is harvested off the California coast….Opah.

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• Albacore tuna.
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Anela Choy“We found that predatory fish that feed at deeper depths in the open ocean, like opah and swordfish, have higher mercury concentrations than those that feed in waters near the surface, like mahi-mahi and yellowfin tuna,” said Brian Popp, a professor of geology and geophysics at the University of Hawaii at …

Here are the fish with the highest amounts of mercury:

• Marlin – 69 micrograms of mercury.
• Tuna (Bluefin, Bigeye, & Albacore) – 54 – 58 micrograms of mercury.
• American Lobster – 47 micrograms of mercury.
• Cod (Atlantic & Pacific) – 14 micrograms of mercury.
• Mackerel Spanish (Atlantic & Pacific) – 8 – 13 micrograms of mercury.

However, there are some types of fish that shouldn’t be eaten raw, as they could make you sick….Know Your Fish: Which Ones Are Safe to Eat Raw?

• Safe: Salmon.
• Not Safe: Pollock.
• Safe: Tilapia.
• Not Safe: Largemouth Bass.
• Not Safe: Haddock.
• Safe: Yellowfin Tuna.

Atlantic and Pacific Bluefin, Albacore, Yellowfin…they are all to be avoided. Canned tuna is one of the most consumed fish in the U.S., and that’s depleting the fisheries. (Here are four canned fishes you should avoid at all costs.)