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Hope for global tuna stocks

Rob Fletcher
Rob Fletcher
02 November 2017, at 1:24pm

Seventy-eight percent of the global tuna catch comes from stocks at “healthy” levels, an increase of 2 percent since last reported, according to a new publication.

The November 2017 International Seafood Sustainability Foundation (ISSF) Status of the Stocks report, which was published today, shows that 11 percent of the global catch came from overfished stocks, and another 11 percent of the catch is from stocks at an intermediate level of abundance.

Updated several times per year, Status of the Stocks ranks the 23 stocks of major commercial tunas around the world using a consistent methodology. The report assigns color ratings (green, yellow or orange) on stock health, alternately noted as “abundance” and “spawning biomass”; fishing mortality; and ecosystem impact.

There are some encouraging changes in tuna stock status since the previous February 2017 Status report. The November 2017 report reflects new data from 2017 tuna Regional Fisheries Management Organization (RFMO) meetings:

  • Abundance ratings improved for Eastern Pacific bigeye, Western and Central Pacific bigeye, Mediterranean albacore, and Western Atlantic bluefin.
  • Fishing mortality ratings improved for Western and Central Pacific bigeye, North Pacific albacore, and Indian Ocean albacore.

In contrast, two bluefin stocks (Southern and Pacific Ocean), one yellowfin stock (Indian Ocean), and one bigeye stock (Atlantic Ocean) remain overfished. See Tables 1 and 2 in the report for specific rating changes.

Inadequate bycatch monitoring and/or bycatch mitigation measures — represented by separate “Environmental Impact” scores, the third rating area — still are a concern in many of the tuna fisheries studied.

Key findings

1. Total catch:

In 2015, the total major commercial tuna catch was 4.8 million tonnes, a 4% decrease from 2014. More than half of the total catch (58%) was skipjack tuna, followed by yellowfin (28%), bigeye (8%) and albacore (4%). Bluefin tunas accounted for only 1% of the global catch. These percentages did not change from the February 2017 report.

2. Abundance or “spawning biomass” levels:

Globally, 57% of the 23 stocks are at a healthy level of abundance (an increase of 5% from the previous report), 17% are overfished, and 26% are at an intermediate level. Stocks receiving orange scores, indicating overfishing or overfished status, include both Southern Hemisphere and Pacific Ocean bluefin, Indian Ocean yellowfin, and Atlantic bigeye.

3. Fishing mortality levels:

65% of the stocks (an 8% improvement since the previous report) are experiencing a low fishing mortality rate, and 13% are experiencing overfishing. 

4. Largest catches by stock:

The three largest catches in tonnes are Western Pacific Ocean skipjack, Western Pacific Ocean yellowfin, and Indian Ocean yellowfin.

5. Tuna production by fishing gear:

64% of the catch is made by purse seining, followed by longline (12%), pole-and-line (9%), gillnets (4%) and miscellaneous gears (11%).

For the first time in Status of the Stocks history, the November 2017 report features an appendix with a list of fisheries certified by the Marine Stewardship Council (MSC).

“The MSC fishery certification scheme is the most widely recognized indicator of seafood sustainability,” explains Dr Victor Restrepo, Vice President of Science, ISSF. “The list helps us to track the tuna stocks and fishing gears that are certified.”