Knowledge Based Bio-Economy


Preserving ocean biodiversity through by-catch reduction

Project acronym: MADE

Title of project: Mitigating adverse ecological impacts of open ocean fisheries

Research area: Fisheries & Aquaculture (Mitigating adverse impacts of fisheries)

Contract No: 210496

EU contribution: €2 980 000

Start date: May 2008

Duration: 48 months


The European open ocean tropical and Mediterranean pelagic fishing industry (Spain, France, Portugal, Italy, and Greece) is one of the main sources of catch, income and employment for the European fishery, with interactions with many developing countries. Various methods are used to catch larger fish in the open ocean. These include the use of the pelagic longline and purse seine, the latter using fish aggregating devices (FADs) to enhance catches of tropical tuna in particular).

The pelagic longline comprises large numbers of baited hooks attached at regular intervals to a mainline suspended from surface buoys that can be many kilometres long and carry thousands of hooks. This makes it a very effective system for catching large fish. However, longlines may also accidentally catch large numbers of non-target fish, sea turtles and seabirds. Attempts have been made by longline fisheries worldwide to reduce the catches of non-target species by adopting ‘by-catch’ mitigation methods, but thousands of non-target species are still killed each year with some in danger of extinction.

FADs are floating objects used by tropical tuna purse seiners to find and catch tropical tuna. Fishers exploit the behaviour of tuna (and other species) which naturally gather around objects floating on the ocean surface. It has been suggested that tuna could be trapped within networks of FADs, resulting in modified behaviour – changing their migration routes and affecting other biological functions. FADs are also responsible for major catches of juvenile tuna and non-target pelagic species. It is therefore a priority to study the effects of FADs on the behaviour and biology of tuna and other species.

The main objective of the project is to develop measures to mitigate such adverse impacts of fisheries targeting large pelagic fish in the open ocean – that is, purse seiners’ use of FADs and longlines.

Expected impacts

The project will work in close association with fishermen from the beginning of this research. It should result in reductions in the by-catch of sharks and juvenile swordfish by pelagic longlines as well as a reduced by-catch of sharks and turtles by tuna purse seiners, promoting best practices of the use of FADS. Results will no doubt be of scientific value to various tuna-fishery management bodies including the Indian Ocean Tuna Commission, the International Commission for the Conservation of Atlantic Tunas, the Western Central Pacific Ocean Fisheries Commission, and the Inter-American Tropical Tuna Commission.

Expected results

The project will report on two main categories of mitigation measures investigated as a means of reducing the loss of biodiversity caused by open ocean fisheries catching non-target fish. These cover both spatial management issues (e.g. closure areas) and technical solutions to reduce such by-catch in these fisheries, following a multi-disciplinary and comparative approach. The project will generate reports that will combine biological and technological studies with economical analyses for various sites in the Indian and Atlantic Oceans as well as the Mediterranean Sea. The reports will provide answers based on high-tech methods and novel approaches, including electronic tagging, as well as in situ experiments. They will also ascertain the effects of FADs on fish ecology and establish to what extent the release of FADs modifies their habitat. From observations of fishermen’s behaviour and related studies it will establish to what extent loss can be mitigated by adopting an accepted three-prong strategy. This depends on attempts to reduce by-catch before reaching the fishing zone and to find out if fishermen can voluntarily avoid some areas so as to limit their by-catch or if there is a need for time-closure areas? It will also suggest how to reduce the vulnerability of some by-catch species when fishermen are in an area "ready to fish". Advice will also be developed by identifying ways of improving the chance of survival of by-catch species once they are released by the fishermen. It will improve knowledge of the behavioural ecology of pelagic sharks as well as tropical tuna, contributing to the necessary baseline for the development of efficient mitigation measures. It will produce databases covering catch/effort and observers’ data, collect economic data on fisheries and accumulate empirical knowledge of fishermen’s behaviour. It will also make suggestions for alternative fishing methods based on the design and testing of prototypes of alternative fishing techniques, and will carry out bio-economic forecasting to measure the effects of the mitigation measures on the fishermen’s revenues.

Website of


Coordinator: Laurent Dagorn,

Organisation: Institute of Research for Development, France,


The Seychelles Fishing Authority, Seychelles,

Free University of Brussels, Belgium,

AZTI-Tecnalia, Spain,

Aquastudio, Italy

The Hellenic Centre for Marine Research, Greece,

Federal University of Pernambuco, Brazil,

University of Reunion, France,

French Research Institute for Exploitation of the Sea, France,

University of Montpellier II, France,

Genoa Aquarium Foundation, Italy,

Institute of Marine Research, Portugal,

University of Patras, Greece,