Tag team meeting the tuna challenge

Most countries depend on tuna fish. But are we fishing it sustainably? In an attempt to provide answers to this vital question, a major project, the Regional Tuna Tagging Project (RTTP), is underway to increase what is known about this staple part of so many diets and economies. It involves putting small plastic tags on tens of thousands of fish, putting them back in the ocean, and - hopefully - recovering them. No small challenge. Project Publicity and Tag Recovery Officer Teresa Athayde takes up the story.

Chief Coordinator of the project Jean Pierre Hallier measures and tags a tuna © RTTP


A tagged tuna is released back into the Ocean © RTTP

Tag team © C.Jameson

The tuna fisheries of the Indian Ocean are probably the most valuable in the world. Some 1 million metric tonnes of tuna with a processed value in the region of 2 billion Euros are harvested each year from the Indian Ocean. Tuna stocks constitute the single largest marine resource available to the island and coastal countries that are members of the regional organisations participating in the RS/RIP for Eastern and Southern Africa: the so-called 'focus' countries. Sustainable management of tuna and associated resources is clearly of critical importance.

An effective fisheries management system requires a good knowledge of the main characteristics of the resource, namely, its size and productivity. If this knowledge is not available, then management actions are typically more cautious, so as not to compromise the sustainability of the fishery. Almost always, this means that the potential benefits from the optimal utilisation of the resource are not fully realised. In the case of the Indian Ocean, the responsibility for the conservation and management of the tuna resources lies with the Indian Ocean Tuna Commission (IOTC), an international agency involving the participation of more than 30 tuna fishing countries. Under IOTC coordination, scientists routinely analyse the data collected from the fishery operations together with biological information from research programmes. Using computer models, they provide assessments of  the status of the populations of the major tuna species.

Although great improvements have taken place in fishery and biological data collection in recent years, there are still significant gaps in the knowledge required to obtain precise estimates of population status. This is where the tagging programme is expected to make its biggest contribution, by providing an opportunity to better estimate the size of the populations of each of the main species. Once scientists have better estimates of this elusive quantity, they will be able to better determine what would be a safe level of catches.

The major beneficiaries of long-term, sustainable management of these major food resources will be the focus countries and their populations. The RTTP will benefit the local fishing communities and the rapidly developing local fishing industries as it will enable focus countries to more clearly understand how much tuna they have access to and better enable them to contribute to the regional management of the resources. The project will also have a positive impact at global level by contributing to the overall scientific understanding of large pelagic species and of large marine ecosystems in general.

Before we get there, we have a few goals to reach:

  1. To tag a critical mass of about 80,000 tuna
  2. To encourage the return of all the tagged fish recaptured.
  3. To process and interpret the data from the recoveries, incorporating them into models for tuna stock assessment.
  4. To reinforce the capacity of the regional scientific institutions in stock assessment and management.

"The major beneficiaries of long-term, sustainable management of these major food resources will be the focus countries and their populations".

A reward scheme is in operation to encourage those who recover tagged tuna to contact the RTTP. Finders will be asked to provide tag number, fish length, address, tuna species and date/location of catch. More than 800 tags have been recovered (October 2005), from just over 12,000 fish.

The RTTP is a five-year project from the Commission de l'Océan Indien, financed by the European Development Fund and supervised by the Indian Ocean Tuna Commission.

The tag and rewards system

Three different colours of tags are used, according to their purpose:

Yellow: these plastic tags are to be put on 80,000 fish and are used to estimate population size, movement rates and interaction between fisheries.

Orange/red: these tags indicate a fish that has an internal mini-computer inserted in its abdomen, recording depth, internal and external temperature and light intensity, to help understand more about the biology, behaviour and movements of the fish. Around 400 fish have these. Extra incentives are offered for the reporting of orange/red tags.

White: indicates that the fish was tagged with a small amount of antibiotic, oxytetracycline, which helps researchers determine age and growth rates of fish. It is harmless to the fish and consumers. Around 2,000 fish will have this.

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