Coastal Aquaculture and Mariculture

Unit 5 - Major groups of Fisheries in India

5.1.6. Tuna
The tunas also known as the "tunnies" are fishes of the family, Scombridae. They are shoaling pelagic fishes. They constitute one of the economically important marine fisheries resources, but are caught mainly by small scale sector. The meat of tuna both in fresh and processed form is much in demand all over the world. They are tropical and subtropical in their distribution in the world oceans. They commonly occur in the oceanic waters beyond the territorial limits of the fishing nations than in the coastal waters. A few of them are neretic occupying shallow waters and are called coastal tunas. The coastal tunas are cheaper than the oceanic tunas. Tunas are very popular as one of the best table fishes in western and other eastern countries whereas, in India, tunas are not relished as good as their counterparts like seerfish and mackerel. While comparing to other developed and developing countries involved in tuna fishing, the exploitation of tuna along Indian waters is limited to the coastal neretic zone and remain to be in its infant stage.
Distribution
Global
Tuna is distributed in the tropical and subtropical regions of Pacific Ocean, Indian Ocean and Atlantic Ocean. Japan, Philippines, Indonesia, USA, China, Taiwan, Spain, Korean Republic, France, Mexico, Thailand, Venezuela and Maldives are the leading tuna producing countries in the world. Bulk of the Indian Ocean tuna are caught by Japan, USSR, Taiwan, Korea and other countries.
India
Tuna is distributed along the south-west and east coast and Lakshadweep. They are highly abundant in Lakshadweep islands, Goa, Vizhinjam and Ratnagiri coasts.
Common tuna species
The commonly occurring tuna species in the fisheries are Euthynnus affinis (Little tuna/Kawakawa), Auxis thazard (Frigate tuna), A. rochei (Bullet tuna), Katsuwonus pelamis (Skipjack tuna), Thunnus tonggol (Longtail tuna), T. albacores, (Yellowfin tuna) and Sardo orientalis (Striped bonito, Oriental bonito), Gymnosarda unicolor (Dogtooth tuna) and Thunnus obesus (Bigeye tuna).
Production trend
Tunas of the oceanic region remain underexploited in the Indian EEZ. Among the resources identified, the yellowfin tuna constitutes the major species in all the regions. Bigeye tuna dominates in the equatorial region, while skipjack tuna is abundant in the northwest region. The potential of coastal tuna resources and oceanic tuna resources from the Indian Ocean have been estimated at 2, 35,000 t and 50,000 t respectively. At present, tuna fishing is restricted to near shore waters only. Except the Lakshadweep group of Islands where organized fishery for skipjack tuna takes place, in other regions, there is no organized fishery for tuna. In India, the total annual catch is about 40,000 - 60,000 t, fonning about 3.5% of the total pelagic fish production and 2% of the total marine production. Region-wise production indicated that the northwest coast contributed 24.1% south-west 41.2%, Southeast 16.6%, northeast 1%, Andaman-Nicobar Islands 2.5% and Lakshadweep 14.8% of the total tuna landings during 1985-2000. State-wise production indicated that among the maritime states, Kerala contributed 36 % of the total landings, followed by Gujarat 18.1%, Tamil Nadu 11.6%, Maharashtra 5.9%, Karnataka 5.3%, Andhra Pradesh 4.4%, Goa 2.2% and the rest by the Andaman-Nicobar and Lakshadweep islands during 1985 - 2000. Pre-monsoon and monsoon seasons are the productive periods along the southwest coast of India and the post-monsoon period along Maharashtra and Gujarat coasts. Productive periods for tunas in Lakshadweep is December - February and in Andaman - Nicobar islands is March -August.
Recent production
Tuna contributed 3 - 4% to the total pelagic fish landings during 2002 - 2006. Its production (in tonnes) during 2001 -2006 is as follows:

(Source: CMFRI, Annual Reports)

Species composition
The tuna fishery is mainly dominated by Euthynnus affinis (about 50%), followed by, Auxis thazard (16%), T. albacores (10%), Katsuwonus pelamis (9%), Thunnus tonggol (9%), A. rochei (3%) and Sarda orientalis (3%). E. affinis and A. thazard are the major species along both the coasts whereas T. tonggol and T. albacares are along the northwest coast. Sarda orientalis support a minor fishery along the southwest coast. Gymosarda unicolor is mainly caught by handlines in Andomans and by pole and line at Lakshadweep.

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Mode of exploitation
The pole and line with live bait is used in the traditional tuna fishery in the Lakshadweep islands. Principal gears employed are drift gillnets, hook and lines, purse seines, pole and lines and troll lines. Long line gear is employed in the fishery for yellowfin and bigeye tunas in the oceanic waters. Drift gill nets contributed 56%, hooks and lines 16%, pole and line 11 %, purse seine 9% and troll line 8% during 1985-2000. Purse seining has been introduced recently in the Indian Ocean which is the most important gear in this ocean. The live-baits commonly exploited for tuna pole and lining in Lakshaweep islands include the sprats, apogonids, caesionids, artherinids and pomacentrids.
Fishing season
Though tunas are caught throughout the year, the peak season extends from October -May for the most of the species. Fishing season of Auxis thazard is from August to December; Sardo orientalis; August. October; Gymnosarda unicolor: January -March; Euthynnus affinis: October -May; Thunnus obesus: October -May; Thunnus albacores: Oct -Jan and Skipjack tuna: December - March.
Food and feeding
Tunas are carnivores and the major food items include crustaceans (larvae, juveniles and adults of shrimps and crabs), cephalopods Guveniles and adults), eggs, larvae and juveniles of fishes, whitebaits and other small pelagics.

Size at first maturity
The size at first maturity of E. affinis is 43 - 44 cm; A. thazard - 30 cm; .A. rochei - 23 cm; K. pelamis - 44 - 45 cm.
Spawning season
E. affinis spawns during the premonsoon (April- May) and Post-monsoon (October -November); A. thazard -August -November; A. rochei -August - October; Skipjack tuna spawns throughout the year with the peak from January - April. The spawning seasons of yellow fin tuna are January -May; November- April; December -June in different oceanic sectors of the Indian EEZ.
Age and Growth

Factors affecting tuna fishery
1. Temperature
2. Current velocity
3. Food availability

Utilization
In general, about 73% of the total tuna landed are iced and marketed fresh for consumption. 10% are used for Masmin production; Masmin is exported to Sri Lanka, Malaysia and Singapore. 9 % are frozen, chilled and exported chiefly to the Gulf countries. Yellowfm tuna, skipjack tuna and bigeye tuna are the main tuna species exported as frozen tuna. 4% of them are used for canning; 3% are salt dried for internal market.
Conservation and management
The use of improved gear and mechanisation resulted in the increase in production of bullet tuna (A. rochei) from southwest coast, longfin tuna (T. tonggol) and young yellowfin tuna (T. albacares) along the northwest coast. Similarly, strategy should be adopted in other parts of Indian coast also. However, mostly tuna fishing is done only in the inshore region and there are no well organised tuna fisheries. Hence, most of the tuna landed are of small species and juveniles. The major resources are exploited by foreign fleets. Hence, it is necessary to utilise the deep sea oceanic resource by using purse seine.