The current percentage-from-healthy-stocks figure, while in need of improvement, has stabilized recently following several years of decline: In 2011, 94 per cent of the catch came from healthy stocks, followed by 86 per cent in 2012, and 87 per cent in 2013.
There were no dramatic changes in tuna stock status since the previous November 2016 Status report covering 2014 data; the updated report reflects new data made available at late 2016 tuna Regional Fisheries Management Organization (RFMO) meetings.
Skipjack tuna stocks — at healthy levels in all ocean regions — once again constituted more than one-half of the 2015 total catch.
Yet RFMO data spurs continuing concern about commercial tuna abundance and/or fishing mortality worldwide, particularly for certain bluefin and bigeye stocks.
Updated several times per year, Status of the Stocks assigns color ratings (green, yellow or orange) on stock heath, stock management, and ecosystem impact. The report ranks the 23 stocks of major commercial tunas around the world using a consistent methodology.
In the February 2017 report, Indian Ocean yellowfin, Pacific Ocean bluefin, Western and Central Pacific Ocean bigeye, and Atlantic Ocean bigeye score poorly for both abundance and fishing mortality. Most bluefin stocks and one albacore stock are overfished, but combined they are a relatively small fraction of the total catch.
All ocean regions have stocks with mixed scores for abundance and fishing mortality. Inadequate bycatch monitoring and/or bycatch mitigation measures — represented by the “Environmental Impact” scores — remain a concern in many tuna fisheries studied, most acutely in Mediterranean and Indian Ocean albacore fisheries.
Key Findings in Updated Report
Other notable statistics and findings include:
- Total catch: In 2015, the total major commercial tuna catch was 4.8 million tonnes, a 4 per cent decrease from 2014. Fifty-eight percent was skipjack tuna, followed by yellowfin (28 per cent), bigeye (8 per cent) and albacore (4 per cent). Bluefin tunas accounted for only 1 per cent of the global catch. These percentages changed only slightly from the Nov. 2016 reporting period.
- Abundance or “spawning biomass” levels: Globally, 52 per cent of the stocks are at a healthy level of abundance, 31 per cent are overfished, and 17 per cent are at an intermediate level. Stocks receiving orange scores, indicating overfishing or overfished status, include Mediterranean albacore, Western Pacific bigeye, Atlantic Ocean bigeye, Pacific Ocean bluefin, Western Atlantic Ocean bluefin, Southern Hemisphere Southern bluefin, and Indian Ocean yellowfin.
- Fishing mortality levels: 57 per cent of the stocks are experiencing a low fishing mortality rate, 17 per cent are experiencing overfishing, and 26 per cent have a high fishing mortality that is being managed adequately. Stocks receiving orange scores, indicating overfishing or overfished status, include Western Pacific Ocean bigeye, Atlantic Ocean bigeye, Pacific Ocean bluefin, and Indian Ocean yellowfin.
- Largest catches by stock: The three largest catches in tonnes were Western Pacific Ocean skipjack, Western Pacific Ocean yellowfin, and Indian Ocean yellowfin.
- Tuna production by ocean: Most (54 per cent) of the world’s tuna is harvested from the Western and Central Pacific Ocean, followed by the Indian Ocean (19 per cent), Eastern Pacific Ocean (13 per cent), and Atlantic Ocean (10 per cent).
- Tuna production by fishing gear: 64 per cent of the catch is made by purse seining, followed by longline