Regional Tuna Tagging Project - Indian Ocean

The importance of Tuna in the Indian Ocean

Concerted fishing for the three species of tropical oceanic tunas (Skipjack, Yellowfin and Bigeye) has been conducted in the Indian Ocean using traditional methods for over 1,000 years. In 1952, the first industrialised longline fisheries entered the Indian Ocean, followed in the mid-1980s by purse seiners. Over the last 25 years catches have increased tenfold and now exceed 700,000 tonnes per annum to the value of more than 2 billion USD (estimated at landing). This makes the Indian Ocean tuna fishery one of the largest and most valuable tuna fisheries in the world. In the regional context, the tuna fisheries of the coastal nations and in particular those of small island developing nations, are crucial to the welfare of their populations.

Objectives and expected results of RTTP-IO

The overall objective is to reinforce regional management capacity, leading to a sustainable exploitation of tuna resources. Specifically, this involves reinforcing scientific knowledge of tropical tuna stocks, including the rate of exploitation, by obtaining the crucial model parameters necessary for stock assessment. RTTP-IO is expected to achieve:

• The tagging of a critical mass of fishes (minimum 80,000)
• A significant percentage of tag recovery
• The processing and interpretation of the recovered data and the design of scientific models for tuna stock assessment
• The reinforcement of the capacity of Regional Fisheries organisations and participating institutions in stock assessment and management

RTTP-IO is a multi-organisation development project

The Regional Tuna Tagging Project-Indian Ocean (RTTP-IO) is a 9th European Development Fund (EDF) project coordinated through the Inter-Regional Coordination Committee (IRCC) which includes the institutions of COMESA, IGAD, EAC, SADC and IOC. The Indian Ocean Commission (IOC), based in Mauritius, is the Contracting Authority for this project, while technical supervision is executed by the Indian Ocean Tuna Commission (IOTC), based in the Seychelles. The European Commission signed a Financing Convention with IRCC in December 2003, agreeing to be the sole financial donor for this project to the value to 14 Million Euros.

There are 3 private contractors employed to implement project activities. AZTI Tecnalia was awarded service contracts for chartering the project's 2 pole and line fishing vessels. MacAlister Elliott & Partners Ltd (MEP), a highly reputed fisheries consultancy based in the UK, was awarded the service contract for the provision of technical assistance to the project. Thirdly, Dr Jean Pierre Hallier, a French marine biologist, was recruited to act as the project's Chief Coordinator.

RTTP-IO explained

During the course of the tagging programme, large numbers of tuna will be captured and released alive after a small plastic tag has been attached to their bodies. The tuna will be tagged just behind the second dorsal fin. Each tag is 11 to 15cm long, and bears a unique number that identifies the fish and IOTC's contact details.

Artisanal and industrial fishers are expected to eventually recapture some of these tagged fish and the information from these recovered fish will allow scientists to better understand their biology and behaviour and ultimately better assess the status of the stocks. This in turn will greatly improve the certainty of information available for management decisions.

For such a large-scale scientific study, it is necessary to tag large numbers of tunas of different sizes and ages. Two pole and line vessels have been chartered for two and a half years to range widely over the western Indian Ocean for this purpose. The use of pole and line vessels is vital to the success of the project as this method of capture is not as stressful to the tuna as other methods. Tunas must be kept in good condition so as to have a good chance of survival after being released. The vessels need to use bait-fish to attract the tuna. These live baits are small fish such as sardines, anchovies and sprats (from 5 to 15 cm long). In tropical waters, these baits are generally quite fragile and cannot be kept on board for long periods. The baits are collected in bays or lagoons in shallow areas (between 20 and 50 m) and the vessels visit bait fishing grounds on a regular basis to reload their bait tanks before resuming tuna tagging.

For the success of the project, all tagged fish that are recaptured have to be accounted for. Therefore a Publicity and Tag Recovery Scheme is currently under way to help to maximise the number of tags recovered and reported. This campaign will last the full duration of the project, 5 years, whereas the tag release phase will only last for the first 2½ years. It is designed to implement different working strategies throughout the Western Indian Ocean region depending on and adapted to country size, cultural characteristics and tag recovery potential. It is expected that some tags will also be recovered internationally, outside the region. This website provides the necessary information to enable the recovery of such tags. Within the Western Indian Ocean region, networks of national counterparts are being put in place. Designated National Focal Officers and Recovery Officers play a vital part in the recovery of tags and reporting them to the project. RTTP-IO is fortunate to have encountered so many persons willing to cooperate with the project and help it to achieve its objectives.

How tagging will improve our understanding of tuna

It is expected that data obtained by the project will enable scientists to make further scientific study of:

• Stock structure and migrations
• Growth parameters
• Natural mortality as a function of age and sex
• Size of stock and fishing mortality
• Interactions between different fisheries
• Behaviour of tunas as a function of their environment
• Impact of FADs (Fish Aggregation Devices) on the resource

To achieve the different scientific objectives of this project, several types of tag and tagging methods are used:

• YELLOW TAGS

  The conventional "spaghetti" tag is used to estimate the exploitation rate, study horizontal movements and fisheries interactions.

• WHITE TAGS

  A white tag indicates that the fish was tagged with an antibiotic, oxytetracycline. The fish's head needs to be collected so the otoliths (ear bones) can be removed and examined and used to study the fish's growth.

• RED TAGS

  A Red Tag denotes the presence of an electronic archival tag implanted in the fish's abdominal cavity. These tags record parameters such as depth, internal and external temperature and light intensity and are used to study the biology and behaviour of the tuna. In addition to the tag and the head of the tuna, the project needs to recover this small electronic device to be able to recover this information.

All tagged fish that are recaptured have to be accounted for and the following information should be collected:

• Tag number
• Tuna species
• Fork length (in cm)
• Name and address of recoverer
• Date and location of catch

Rewards are offered during the course of the programme to encourage people who find tagged fish to report them to RTTP-IO headquarters in Seychelles or to the nearest tag collection centre.