The olive flounder (''Paralichthys olivaceus''), bastard halibut or Japanese halibut, is a temperate marine species of large-tooth flounder native to the North-western

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

. It is often referred to as the Japanese flatfish or Korean flatfish (광어) when mentioned in the context of those countries. It is the highest valued finfish in the world, known to be excellent for aquaculture due to a rapid growth rate and popularity in Korea. It reaches a length of and a weight of . In 2017 its genome and transcriptome was sequenced as a model to study flatfish asymmetry.

Habitat and diet

The olive flounder is often found in soft and muddy offshore, coastal areas where the water level goes down to 100 m in depth. The temperature of water in these areas range from 21- 24 °C or 69 -75 °F. Some flounder have been found in the

Mariana Trench The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maximum know ...

. Olive flounder typically eat fish spawn, crustaceans, polychaetes, and small fish.

Life cycle

Olive flounder spawn anytime from January through August in shallow water, roughly about 70 cm in depth. The egg and larvae remain that way for about 24–50 days after hatching. Once they begin their metamorphosis process, they move towards more sandy areas and feed on shrimp. After achieving metamorphosis, the flounder move offshore and begin feeding on bigger fish in order to grow to their adult size.

How they become "flatfish"

Olive flounder first start out upright like normal fish, but then after 24 to 50 days after hatching they turn onto their side. Their previous side now becomes their belly or their backside and then their eye and nostril move towards what is now considered the back. This process is typically called the "metamorphosis."

Aquaculture

The olive flounder is the most common

flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish order (biology), order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the ...

species raised in

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

in Korea. They are raised in Japan and China as well. It is the most highly prized of the Japanese flounders. Although the aquaculture for the olive flounder started from the late 1980s, its commercial production didn't begin on a major scale until the 1990s in Korea.

Parasites and food poisoning

The

myxozoa Myxozoa (etymology: Greek: μύξα ''myxa'' "slime" or "mucus" + thematic vowel o + ζῷον ''zoon'' "animal") is a subphylum of aquatic cnidarian animals – all obligate parasites. It contains the smallest animals ever known to have lived. O ...

n '' Kudoa septemlineata'' has been described in 2010 from olive flounder from Korea. This microscopic parasite infects the trunk muscles of the olive flounder where it causes myoliquefaction. Ingestion of raw fish containing ''K. septemlineata'' spores has been reported as a cause of food poisoning (

gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydra ...

) in Japan since 2003. However, laboratory studies performed in 2015 and 2016 on adult and suckling mice showed that ''K. septemlineata'' spores were excreted in faeces and did not affect the gastrointestinal tract.

Appearances in media

The olive flounder has appeared in the video game series ''

Animal Crossing is a social simulation video game series developed and published by Nintendo. The series was conceptualized and created by Katsuya Eguchi and Hisashi Nogami. In ''Animal Crossing'', the player character is a human who lives in a village inhabi ...

'' as one of the various fish species the player is able to catch using a fishing rod.

References

Korea-US Aquaculture: Olive Flounder
{{Authority control

olive flounder The olive flounder (''Paralichthys olivaceus''), bastard halibut or Japanese halibut, is a temperate marine species of large-tooth flounder native to the North-western Pacific Ocean. It is often referred to as the Japanese flatfish or Korean fla ...

Fish of Japan Fish of Korea Fish of East Asia