A research team from Taiwan and Japan has found that mahi-mahi, also known as the common dolphinfish, are most active in waters where the temperature is 5°C to 6°C lower than the sea surface, a crucial finding for sustainable management of the fish, the Council of Agriculture’s Fisheries Research Institute said on Tuesday.
Ninety percent of the mahi-mahi caught near Taiwan are sold to the US, institute Director-General Chen June-ru (陳君如) said, adding that the fish is less popular among Taiwanese, as its meat is not as juicy as others.
In 2017, local fishers caught 11,163 tonnes of mahi-mahi worth up to NT$1.28 billion (US$40.8 million at the current exchange rate), Chen said.
Photo: CNA
Over the past two years, Japanese authorities and researchers have expressed concerns over the soaring number of mahi-mahi caught near their coast, so the institute and Japan’s Nagasaki University collaborated to explore the species’ habitat preferences.
The team in October last year installed 10 pop-up satellite archival tags, which cost NT$200,000 each, to track the fish’s movements, starting from Taiwan’s southeastern waters and Japan’s Kagoshima Bay, said Chiang Wei-chuan (江偉全), an associate researcher from the institute’s Eastern Marine Biology Research Center.
Only seven tags were left in the end, Chiang added.
Installing the tags on the slippery fish and analyzing their satellite data required experience, which is why the university sought to work with the institute, he said.
They found that the fish are active in areas where the temperature is 5°C to 6°C lower than the sea surface, meaning that changes in sea temperature and salinity levels might affect their distribution and movement, he said.
Satellite data showed that the fish once reached the north of the East China Sea, challenging the thought that they are only found in tropical and subtropical areas, Chiang said.
The team shared its findings in a paper titled “Movement behavior of wild and farm-raised released dolphinfish Coryphaena hippurus using pop-up satellite archival tags,” which was last week accepted by the Japanese Society of Fisheries Science journal, but has yet to be published, Chiang said.
Nearly 120,000 tonnes of the fish are caught worldwide every year, so more research would help experts determine a reasonable and sustainable limit for the amount of mahi-mahi caught, Chen added.
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