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Opah is landed year-round, but landings appear to peak between April and August. The inconsistent supply is due to the fact that opah does not school and is not easily harvested in large quantities.
One opah consists of seven different cuts from three different parts of the fish: top loin, mid loin, center loin, back tail, belly, abductor, and adductor. All parts are rich in fish oils, protein, Omega-3, selenium, and vitamins. The top, mid, and center loins are a light pink color and run along the backbone from the eye to the tail and are the most tender parts. The back tail and belly are two salmon-pink cuts from the side portion of the fish, which is slightly more stringy at the top and fatty towards the bottom. Both of these larger portions turn white when cooked and have a rich, creamy taste and firm, fatty texture, similar to swordfish. The abductor and adductor, found underneath the abductor, is the dark red cheek meat found underneath the pectoral fin on either side. Their taste is similar to raw tuna, but both lean muscles cook like beef or pork and can easily be used as a substitute.
Health & Nutrition
- Total Fat8.00g
Recommended Servings per Month
- Kids 6-121
- Kids 0-50
Opah are large fish, roughly the size of a car tire, with a maximum length of 6.5 ft (2 m) but a common length of 3 ft (0.9 m). The highest published weight of an opah was 595 lbs (270 kg) but they usually average around 100 lbs (43 kg). Opah have very distinct shape, coloring, and markings. They have thin and round bodies, red mouths, and gold-rimmed eyes. They have long, scarlet pectoral fins with similar pelvic fins. Their main body is a dark steel blue shading into green, with silver and purple iridescence, and a rosy body. Their entire body is covered with silver, irregular spots.
Opah are oceanic and solitary fish. They are the first known fully warm-blooded fish, being able to circulate heated blood throughout their body just like mammals and birds. This natural adaptation happens via counter-current heat exchange in their gills, giving them an advantage in deep, cold ocean waters. They are capable of traveling long distances, often in response to changing oceanic conditions like water temperature. They swim by rapidly flapping their pectoral fins, like wings, rather than with their tail. This constant flapping heats its body, speeding its metabolism, movement, and reaction times. It also helps opah see more sharply. This is also the reason why their abductor muscle underneath their pectoral fins are a dark red color. Fatty tissue surrounding the gills, heart, and muscles help further insulate their bodies.
Not much is known about opah’s life and reproductive history, but they are estimated to live to about 6 years old, based on the fin markings from those that have been caught. It is estimated that they grow quickly. They likely seasonally spawn several times in the spring in cooler waters and spawn throughout the year in warmer waters. Because exact size and age at maturity is unknown, juveniles are defined as those up to 8 in (20.3 cm) in length, while adults are any individual greater than 41 in (104 cm).
They feed on midwater fish and invertebrates, mainly squids. Their main predators are great white sharks and mako sharks.
Opah is primarily known as a Hawaiian species in the US market, but it is actually found worldwide in tropical to temperate waters. In the Western Atlantic, they can be found from the Grand Banks and Nova Scotia, Canada all the way down to Argentina. In the Eastern Atlantic, they are found from Norway and Greenland south to Angola, as well as in the Mediterranean. In the Eastern Pacific, they can be found as far north as the Gulf of Alaska and as far south as Southern California.
They are a migratory bathypelagic (deep-water) species and can be found between 0-1,640 ft (0-500 m). At each life stage, opah can live in a different part of the water column.
Opah is also known as moonfish, likely due to its large, round profile. Opah has never been assessed, so fishing rates in the US are unknown. This is because they are not a major commercial food fish and live in the deep ocean. However, there is no evidence that populations are declining or that fishing rates are too high. In general, more data is needed on the basic biology and ecology of opah. To fill in some data gaps, NOAA’s Southwest Fisheries Science Center (SWFSC) began collecting biological samples in 2009 and initiated an electronic tagging program in 2011. By tagging opah, scientists are hoping to learn about their movement and range, which will inform the basic life history information necessary for future stock assessments and management.
Scientists at SWFSC were also the first to discover that the opah’s unusual gill design makes it the first fully warm-blooded fish. They found this by collecting temperature data from opah caught off the US West Coast during surveys and discovering that their body temperatures were regularly warmer than the surrounding water. Attached temperature monitors further confirmed this by showing that their body temperatures remained steady during dives into the cold, deep water. They maintained an average muscle temperature about 9°F (5°C) higher than the surrounding water without having to resurface, even 1,000 ft (305 m) below. Although tuna and some shark species can also warm certain muscles to boost their swimming performance, their internal organs cool off quickly and slow down at cold depths, forcing them to swim back up in the water column to warm up.
There were previously only two known named species of opah; however, at a United Fishing Agency (UFA) fish auction in Honolulu in 2018, scientists discovered there are now six known different species of opah globally. Each species is distinguished by their eye size, fin length, and other measurements.Management:
Hawaiian fishers used to give opah away as a goodwill gesture because opah was thought to bring good luck. Prior to the 1980s, there was little demand for opah. However, in the late 1980s, its popularity began to increase when Hawaii began to promote it as an underutilized species. Today, it is often taken as incidental catch in the driftnet and longline fisheries targeting tuna and swordfish, from New Zealand to Hawaii and California. In the US, it is considered a secondary target because they are legally landed and sold. Commercial landings of opah in Hawaii in 2016 totaled over two million pounds, valued at $3.3 million.
In the US, NOAA Fisheries and the Pacific Fishery Management Council manage the California opah stock under the Highly Migratory Species (HMS) Fishery Management Plan (FMP). These opah are incidentally caught in the California drift gillnet fishery targeting swordfish. In the Pacific Islands, NOAA Fisheries and the Western Pacific Fishery Management Council manage that stock under the Fishery Ecosystem Plan for the Pelagic Fisheries of the Western Pacific. These opah are caught using deep-set longlines targeting bigeye tuna.
Management measures do not specifically apply to opah, but general management measures can be applied to the fisheries that incidentally catch opah. These measures include:
- Limited number of permits
- Requirement to record catch
- Gear restrictions and operational requirements to minimize bycatch and potential gear conflicts
- Area closures to certain gear types
- Vessel monitoring system program
- Required observers onboard
- Annual training in safe handling and release techniques for protected species
Impact on Stock
There is little population data on opah, but the population is presumed stable. NOAA research surveys have caught more opah in recent years, although the reason is unknown. Current conditions could be favorable, or their populations are growing. More information is needed to better inform management decisions.
Opah are considered incidental catch and a secondary target in the driftnet and longline fisheries. Because these gear types typically do not contact the ocean floor, habitat impacts are considered minimal.
Because there is no directed fishery for opah, bycatch in the tuna and swordfish fisheries is minimized through gear restrictions.
US management is considered effective as the California drift gillnet and US longline fisheries both are extensively regulated and monitored by several management bodies. These vessels frequently carry government observers onboard to quantify total catch. Bycatch is limited and strategies are in place to reduce the amount of bycatch and release unintended catch. The California drift gillnet fishery is additionally required to have mandatory gear requirements and time-area closures that include the Pacific Leatherback Conservation Area Closure (PLCA).
|Pacific Ocean - Northwest
|Pacific Ocean - Southwest
|Pacific Ocean - West Central
|Unassessed Fishing Methods
|USA - California
|USA - Hawaii (FIP)
|USA - Hawaii (Including vessels landing in California)
|Anderson Seafoods Inc.
|Blue Circle Foods
|District of Columbia
|Catalina Offshore Products
|Catanese Classic Seafood
|Diamond Head Seafood Wholesale, Inc.
|Euclid Fish Company
|Fresh Island Fish, Inc.
|Garden & Valley Isle Seafood, Inc.
|Hilo Fish Company, Inc.
|Intercity Packers Meat & Seafood
|Lee Fish USA
|United States, United States, United States
|Monterey Fish Market
|Norpac Fisheries Export
|North Atlantic, Inc.
|Northeast Seafood Products, Inc.
|Pacific Harvest Seafoods
|District of Columbia
|PT. Hatindo Makmur
|Real Good Fish
|Royal Hawaiian Seafood
|Seafood Merchants Ltd.
|Seattle Fish Co
|Seattle Fish Company - Kansas City
|Star Fisheries Inc.
|The Fish Guys Inc.
- NOAA Fisheries
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