Opah

Opah
  • Scientific name: Lampris guttatus
  • Also know as: Moonfish, Spotted Moonfish, Sunfish, Red Fin Fish, Kingfish, Cravo, Opal Fish, Jerusalem Haddock
  • Size: Up to 6ft in length and 600lbs.
  • UK minimum size: N/a
  • UK shore caught record: No record stands. Qualifying weight set at 20lb.
  • IUCN Status: NE (Not Evaluated)
  • Distribution: Found worldwide but populations are diffuse. Sporadically found around parts of the British Isles.
  • Feeds on: Squid and other fish.
  • Description: Brightly coloured fish with a deep body which is almost circular. The body itself is a silvery-blue and covered in white spots and dots. Single dorsal fin which rises to a large point and then continues in a smaller ridge down the back. Pectoral and ventral fins are very long and narrow and the tail is deeply forked. All of the fins are bright red in colour. The mouth is relatively small with no teeth and the eyes are large.
  • Additional notes: Although this fish is sometimes called the ‘Sunfish’ it is not be confused with the Sunfish (Mola mola).

The opah is a colourful and exotic looking fish which is present throughout most of the world’s seas. Relatively little is known about the opah’s life cycle and feeding habits. Although very rare it has been observed in British and Irish waters and has a British boat caught record, although it does not yet have a shore caught record.

Distribution

The opah has a worldwide distribution but numbers are somewhat spread out and dispersed. It is generally found in tropical and sub-tropical waters, although they do seem to be able to live in temperate waters as well. The opah found in the North East Atlantic, in parts of the Mediterranean, off the coast of North and South America, as well as in Indian and Australia and Australian waters. Within British waters, the opah has been found washed up on beaches as far north as the Orkneys and is thought to be more common in the warmer waters to the south west of England and Ireland. However, global warming may see the opah becoming more common around Britain in the same way that the sunfish and triggerfish have increased in number in recent years.

Life Cycle and Behaviour

It is thought to be a solitary fish which lives and feeds for most of its life alone, although contradictory information states that opah have been observed in shoals. Despite their size and somewhat ungainly looks the opah is a relatively fast swimmer and is able to catch fish and squid. It is also thought that opah may have the ability to filter feed by straining krill, plankton and other microscopic marine life forms through their gills, although this is disputed by some scientists. In 2015 research revealed that Opah use a heat exchange system within their bodies to keep their blood and internal organs warm, explaining why they can be found in cooler waters.

Opah
An opah caught in American waters.

Opah generally stay away from land and live out in the open ocean, living in mid-water in seas at least several hundred metres deep. For these reasons the opah is rarely caught by shore anglers (the British shore caught record for this fish is vacant and the qualifying weight is set at 20lbs). There is a boat caught record of an opah of 128lbs, caught by an angler named A. Blewett who was fishing out of Mounts Bay, Penzance in 1973. In parts of the world where this species is more commonly found, such as the southeastern coast of the USA, opah is a target species of recreational fisheries.

Different Species of Opah

There were previously two recognised species of opah: the opah (Lampris guttatus) and the smaller southern opah (Lampris immaculatus) which is differentiated by its lack of spots and lower number of fin rays. However, a fish buyer at a Hawaiian commercial fish auction recognised that there were significant differences in the opah which were being sold. This was brought to the attention of scientists and it was eventually established that three new species of opah were present, and another species previously described in the 1800s was resurrected, meaning that there are now six species of opah in the world’s oceans. The difference between the six species are very difficult to identify, and many non-scientists simply refer to all of the various species as opah.

Commercial Value

The opah appears to be increasing in value as a commercial fish with growing demand from consumers due to the exotic looks of this fish and its delicate flavour. It is caught and retained as bycatch in pelagic trawls and is also caught on long-lines set for tuna, although some small scale fisheries actively target this species. In terms of cooking this species is usually filleted and pan-fried, while in Japanese cuisine the flesh is very thinly sliced and used in sushi and sashimi. Despite the large size of the opah, only around one-third of its weight is usable flesh, the other two-thirds being made up of the inedible bones, head and fins. The IUCN (International Union for the Conservation of Nature) classes this species as one of Least Concern.