Sleuthing leads to new findings about peculiar ocean fish

2018-06-09 10:42
opah, front left, are displayed along with tuna, swordfish, wahoo and other fish at the Honolulu Fish Auction run by the United Fishing Agency in Honolulu, Hawaii. (Justin Hospital, NOAA Fisheries via AP)

opah, front left, are displayed along with tuna, swordfish, wahoo and other fish at the Honolulu Fish Auction run by the United Fishing Agency in Honolulu, Hawaii. (Justin Hospital, NOAA Fisheries via AP)

Multimedia   ·   User Galleries   ·   News in Pictures Send us your pictures  ·  Send us your stories

The fish buyer noticed something different about the large, colourful disc-shaped opah waiting to be sold at the auction house in Honolulu. Among the differences: One fish had a bigger eye than the other.

His curiosity set in motion DNA testing and more sleuthing that led to the identification of three new species of opah– a peculiar deep-diving fish recently found to be the first fully warm-blooded fish.

"The more we looked, the more differences we could pull out," said Karen Underkoffler, lead author of a recently published paper in the peer-reviewed journal Zootaxa that describes the anatomical characteristics of the different species of opah, including one marked by its big eyes and a purple tongue.

In all, the team of scientists with NOAA Fisheries identified five distinct species of opah, revealing that there isn't a single global species. Three are newly identified, one was already named and researchers better identified another that had been previously described.

"We have known for quite some time that opahs in different parts of the world look different," Misty Paig-Tran, assistant professor of marine biology and biomechanics at Cal State Fullerton who was not involved in the paper, said in an email.

People were calling them all the same thing, and the paper clearly shows their differences, she wrote, adding that it's great to finally have anatomical descriptions and DNA to back those descriptions.

The researchers say knowing the population of opah – which has a silvery gray body, red fins and mouths, and white spots – is important to make sure they don't get overfished.

Popular

While opah isn't harvested by commercial fisheries, the fish is often caught incidentally in commercial fishing for high-value tuna or swordfish off the coasts of Hawaii and California.

Sport anglers also frequently catch the colourful fish, which on average weighs about 45kg and can be bigger than an automobile tire.

Opah is becoming popular at restaurants in Hawaii and elsewhere. The value of US commercial landings of opah has increased from just a few thousand dollars before 2000 to nearly $3.2m in 2016. The Hawaii-based longline fishing industry reported the catching of nearly 30 000 opahs by vessels targeting tuna and swordfish in 2015.

Most opah landed by those vessels arrive at the United Fishing Agency auction in Honolulu, where Underkoffler was working several years ago when Garrett Kitazaki flagged the big-eyed opah for her and her colleague Meagan Luers, another study co-author.

They took measurements, clipped fins and sent tissue samples to the Southwest Fisheries Science Centre in San Diego. From the samples collected at the auction, the team quickly determined the fish were distinct from each other.

"In that effort to find more, we stumbled across more very distinct opah species," said John Hyde, programme leader of genetics fisheries at the Southwest Fisheries Science Centre who did the DNA tests.

They put out a call to museums, ports and commercial fisheries to get samples of opah. They thumbed through literature dating back to the 1700s to find references and descriptions of the fish. Underkoffler even travelled to Monaco to check out a specimen.

"It kept building and building," said Underkoffler, who now works for NOAA's seafood inspection program in Seattle.

Hyde said that "when you realise there are five species instead of one, it tells us there's a lot to still discover out there".

KEEP UPDATED on the latest news by subscribing to our FREE newsletter.

- FOLLOW News24 on Twitter

Read more on:    us  |  fishing  |  marine life

Join the conversation!

24.com encourages commentary submitted via MyNews24. Contributions of 200 words or more will be considered for publication.

We reserve editorial discretion to decide what will be published.
Read our comments policy for guidelines on contributions.
NEXT ON NEWS24X

Inside News24

 
/News
Traffic Alerts
Traffic

Jobs in Cape Town [change area]

Jobs in Western Cape region

Reporting Accountant

Cape Town
Network Finance Professional / Prudential
R310 000.00 - R360 000.00 Per Year

IT Manager (contract)

Cape Town CBD
Communicate Cape Town IT
R330 000.00 - R458 000.00 Per Year

HSE Manager

Cape Town
Tumaini Consulting
R550 000.00 - R650 000.00 Per Year

Property [change area]

There are new stories on the homepage. Click here to see them.
 
English
Afrikaans
isiZulu

Hello 

Create Profile

Creating your profile will enable you to submit photos and stories to get published on News24.


Please provide a username for your profile page:

This username must be unique, cannot be edited and will be used in the URL to your profile page across the entire 24.com network.

Settings

Location Settings

News24 allows you to edit the display of certain components based on a location. If you wish to personalise the page based on your preferences, please select a location for each component and click "Submit" in order for the changes to take affect.




Facebook Sign-In

Hi News addict,

Join the News24 Community to be involved in breaking the news.

Log in with Facebook to comment and personalise news, weather and listings.