FADMALDIVES - FAD Research in Maldives

Fish aggregating devices or FADs are being used all around the world to help fishermen catch tunas and other species. The reasons for which tunas and other species aggregate around FADs are still unknown. Fréon & Dagorn (2000) and Castro et al. (2002) reviewed the different hypotheses, but so far none of them could be demonstrated. Two main hypotheses are considered as the most valid ones:

  1. The meeting point hypothesis (Dagorn & Fréon, 1999), which suggests that fish can make use of FADs to increase the encounter rate between isolated individuals or small schools and other schools, to form larger schools. The evolutionary advantages of these are the same as those for schooling (reduces risk of predation, better foraging and feeding).
  2. The indicator-log hypothesis (Hall 1992), which suggests that natural floating objects are often indicators of productive areas, either because most natural floating objects originate in rich areas (i.e. river mouth) and remain within these rich bodies of water, or because they aggregate in rich frontal zones. The association of tunas with any floating objects may result from an evolutionary process where tuna use these indicators to stay in contact with rich waters.

After first studies in the 1980s and the 1990s, mainly from active acoustic telemetry (which helped find that yellowfin tuna could orientate to FADs from distances of about 10 km), there was a new phase of FAD research that started in the early 2000’s with 2 international projects in the USA and in Europe.

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The Pelagic Fisheries Research Programme funded a project in Hawaii to monitor the behaviour of tunas in a network of FADs for several months through the use of acoustic receivers attached to FADs and tunas equipped with acoustic tags. Dagorn et al. (2007) founded that yellowfin tunas stayed an average of 1 week around FADs, that fish rarely visited other FADs, but when visiting other FADs, they had a tendency to visit neighbour FADs.

The European Community (FP5) funded a research project named FADIO (Fish Aggregating Devices as Instrumented Observatories of pelagic ecosystems), with the aim to develop new technologies and methods to study fish around FADs and use FADs as scientific platforms. This project contributed to identify two key research priorities for future research on FADs:

  1. To assess the effects of FADs on the behaviour and ecology of tunas and other species
  2. To use FADs as scientific platforms to help for stock assessment, management of fisheries, monitoring of biodiversity

The first priority is to assess the effects of artificial FADs (anchored and drifting) on tunas and other species, wh47821232212215receiver1750.jpgich is essential for efficient FAD fisheries management:

1: Do FADs modify the large-scale movement patterns of tunas and other species?
2: Do FADs modify the biology of tunas and other species?
3: What would be the effects of increasing the density of FADs on the spatial dynamics of tunas and other species?

The second priority corresponds to a new research area. Because FADs naturally attract tunas and other species, they represent ideal platforms to observe the behaviour and abundance of those species which are generally difficult to access. By instrumenting FADs with permanent scientific equipment, FADs are not only fishing tools, but they can also become scientific tools.

The Maldives have a long history of FAD fishing. A network of about 40 fixed FADs has been maintained by the Maldives for about 3 decades to help Maldivian fishermen catching skipjack and yellowfin tunas. Therefore, the Maldives represent an ideal site for conducting research on FADs and can be considered as a “natural laboratory” to study the behaviour of fish at FADs. Moreover, the Marine Research Centre gathers scientists with expertise on tunas and FADs which would make the MRC an excellent partner for international collaborations.

Objectives and Research questions

The research objectives of FADMALDIVES are:

  1. To assess the effects of FADs on the behaviour and ecology of tunas and other species
  2. To use FADs as scientific platforms to help for stock assessment, management of fisheries, monitoring of biodiversity


FADMALDIVES will in fact be the Maldives component of the research being undertaken by other institutes in the world (IRD France, University of Hawaii USA, AZTI Spain, Université Libre de Bruxelles Belgium, Seychelles Fishing Authority Seychelles, etc.) through existing and future projects on this field. FADMALDIVES will therefore:

  • Contribute to the international effort to improve our knowledge on FADs
  • Allow MRC to be a member of this international research network
  • Provide results that will help for better management of Maldivian tuna fishery based on FADs.


More specifically for the Maldives, this project will help addressing some key questions that directly concern the management of the Maldivian FAD fishery, such as:

  • How long do tunas stay around FADs in the Maldives?
  • How long do tunas stay in the network of FADs in the Maldives?
  • What would be the effects of increasing or decreasing the number of FADs on the spatial dynamics of tunas in Maldivian waters?
  • Can we use FADs to monitor the abundance of tunas and other species (including monitoring of pelagic biodiversity) in the Maldivian waters?


Answering these questions is now possible thanks to the theoretical and technological advances of the research projects mentioned above.

Funding

New projects just started in 2008 on FADs:

  • BIOPS, funded by IFB, which aims at assessing the biodiversity of fish at FADs from visual census in the Indian Ocean (Mayotte, Mauritius, Seychelles, Maldives). MRC is a partner of this project and receives funding for conducting visual census around FADs.
  • MADE, funded by the European Commission, which aims at mitigating adverse ecological impacts of open ocean fisheries. This project targets pelagic longliners and tuna purse seiners, and will propose measures to decrease the possible negative impacts of those fisheries on pelagic ecosystem. Among the several objectives of this project, one of them is to study the effects of FADs on the ecology of tunas and sharks. MADE plans to deploy some acoustic receivers at FADs in the Maldives, and tag tunas and sharks to observe their behaviour. It is also planned to use this opportunity for capacity building of Maldivian researchers (in particular MSc of a scientists of MRC).
  • OTN (Ocean Tracking Network), which is an international project that aims at deploying large arrays of acoustic receivers in order to monitor the behaviour of many species. The Western Indian Ocean is one of the 12 regions of this project, and inside that region, it was decided to deploy acoustic receivers in the Maldives and in the Seychelles to observe any possible large-scale movements of pelagic animals in the Indian Ocean. Acoustic receivers from OTN should be available in 2009.
  • Marine Research Centre: MRC is expected to support logistics and field work for this project.

Those 3 projects allow the start of the FADMALDIVES project. An effort will be made to look for new funding opportunities and further develop FAD researches in the Maldives.

Read Divehi version of this entry:

19 January 2009:

Read Divehi version of this entry

FAST FACTS

78091232809937bullet2.jpg Maldives has the largest network of anchored FADs used in a tuna fishery in the world. Currently at 45 they are located around 12-15 miles offshore from the atolls.


78091232809937bullet2.jpg Pole-and-line fishery of the Maldives currently produces over 150,000 mt of tuna every year earning the over 100 million US$ in in direct revenue to the country.


78091232809937bullet2.jpg FAD deployment started in the Maldives in 1982- thanks to a UNDP assisted project which helped Maldives to pilot the activity,