Fisheries and aquaculture are confronted with continuing problems such as climate change, growing human populations, low income of small scale fishers and fish farmers, and competitive production and trading conditions. People should be confronting and discussing the challenges in order to come up with solutions on how we can respond; and the community should be resilient and adaptive in combatting the challenges. We cannot immediately solve some problems, such as overfishing, illegal fishing, depletion of marine resources, as they have deep root causes, but we are learning how to address them. Governments do their best to manage fishery resources to meet these challenges. Decision makers and the public also need to continually listen to new information so that they are equipped with knowledge for sustaining marine and aquaculture resources and protecting people who depend on them for nutrition, livelihood and business. Research is an important information gathering tool that contributes to policy and decision-making. The Asian Fisheries Society and its partners are taking a lead in making new information accessible through its platform AsiaPacific-FishWatch providing essential information on fish harvested or farmed for food in Asia-Pacific. I am pleased that AsiaPacific-FishWatch gives attention in its profiles and posts to the critical social, economic and market character of the value chains. The Asian Fisheries Society emphasises equally social and economic knowledge and biological, physical and technical knowledge.

Prof. Alice Joan G. Ferrer, PhD, President, Asian Fisheries Society

 
 
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ASIAPACIFIC-FISHWATCH

Bigeye tuna live in tropical and warm temperate waters of the Atlantic, Pacific and Indian oceans. They are pelagic and exhibit several dispersion patterns. The Western and Central Pacific Ocean and the Indian Ocean bigeye are each considered single and separate stocks; although considerable mixing occurs, Western and Central Pacific Ocean and Eastern Pacific Ocean bigeye tuna populations are assessed separately for management purposes.

Bigeye tuna form free schools or may swim associated with floating objects such as logs. Juvenile bigeye will form schools with juvenile yellowfin and skipjack tunas. Bigeye tuna tolerate warmer and deeper waters and lower oxygen and salinity levels than other tropical tunas. They may live to at least 15 years of age. They grow more slowly than yellowfin tuna, have lower natural mortality, and are less abundant.

FISHERIES

Bigeye tuna is important in commercial fisheries around the world, accounting for nearly 10% of the world’s catch of major tunas. In the Central and Western Pacific Ocean, 6% of the tuna caught are bigeye and, in the Indian Ocean, 9% are bigeye. Juveniles are caught by both surface gears such as purse seines and, in the Indian Ocean, by gill nets. As valuable adult fish, they are caught by longline and other gears. They are a principal target species of both the large, distant-water longliners from Japan, Korea, China, Taiwan and the smaller, fresh sashimi longliners based in several Pacific Island countries.

SUSTAINABILITY AND MANAGEMENT

The bigeye tuna stock of the Western and Central Pacific appears not to be overfished nor subject to overfishing. However, the stock is considered to remain in a state somewhat more depleted than most other tuna stocks in the Western and Central Pacific. The Indian Ocean bigeye stock is not overfished, nor subject to overfishing. The catch of juvenile bigeye in surface fisheries that target skipjack and yellowfin tuna, e.g., purse seine and gillnet fisheries, is increasing, thus decreasing the biomass of adults in the deeper water longline fisheries and the maximum sustainable yield of the stocks.

Bigeye tuna resources are managed by the Western and Central Pacific Fisheries Commission (WCPFC), the Indian Ocean Tuna Commission (IOTC), and national governments. Sub-regional fishing interest groups, international environmental organisations and market controls also have a strong influence on the governance of bigeye tuna fisheries.

VALUE CHAINS

The meat of bigeye tuna is highly prized and is processed into sashimi in Japan (and western countries). Bigeye is marketed mainly in canned, frozen, or fresh forms. Prices paid for both frozen and fresh product on the Japanese sashimi market are the highest among all the tropical tunas.

FOOD

As food, bigeye is a very good source of low-fat protein and is low in sodium, but has a moderate level of cholesterol. Fat content in bigeye tuna is higher than in other tuna species, yet it is a good choice for low-fat diets.

ECOSYSTEM AND CLIMATE

Bycatch of fishing for bigeye tuna and other pelagic species includes bigeye tuna juveniles, and also sea turtles, sharks, seabirds and other marine fish species and is a significant environmental issue. Among all fishing gears used for bigeye tuna, longlines and gillnets have the greatest bycatch rates.

Longline and purse seine fishing are among the most energy intensive fishing operations as measured by greenhouse gases produced per tonne of fish landed. Also, unless strictly managed, fish canneries may have negative effects on surrounding land and sea environments and the resources they support.

The area of suitable bigeye tuna habitat changes with seasons and with inter-annual climate variability and this is reflected in the catches of bigeye tuna. In the Western and Central Pacific Ocean, the El Niño Southern Oscillation events affect catches of bigeye tuna which are higher during the warmer El Niño period and lower during the cooler La Nina periods.

Global warming affects the distribution and catchability of bigeye tuna stocks which are sensitive to changes in oceanic circulation, the stratification of the water column and water temperature and density.

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