Investigators: Matthieu Le Corre (ECOMAR, Université de La Réunion; Rachel Bristol (Nature Seychelles); Jaime Ramos (Departamento de Zoologia, Universidade de Coimbra); Chris Feare (University of Leeds, UK and Island Conservation Society, Seychelles) and Gérard Rocamora (Island Conservation Society, Seychelles)
MAP OF STUDY SITES
Click on the white-marked areas to see a close-up on the study sites.
Human activities have an increasing impact on marine ecosystems of the western Indian Ocean but few indicators are developed to estimate these impacts at a regional scale. Among these activities, the industrial tuna fishery is the one that has increased most rapidly during the last 25 years. It may be now the main man-induced factor that influences ecosystem functioning at a regional scale. Natural variations of the marine environment, like El Niño Southern Oscillations (ENSO) are also major anomalies that have profound effects on ecosystem functioning. As top predators, seabirds are very sensitive to natural and man-induced changes in marine food webs. Furthermore, their peculiar way of life (marine when feeding but terrestrial when breeding) makes them very accessible and easy to study, compared to typical marine top predators. For these reasons seabirds have been used as indicators of natural or man-induced changes of the marine environment at various places of the world, but few of these studies have been conducted in tropical areas. However in the tropics, seabirds are closely associated with surface-dwelling tuna, a major target of tropical industrial fisheries. This association is generally regarded as near obligate commensalism for seabirds: by driving prey to the surface, tuna make them available to seabirds.
Twenty four species of seabird breed in the western Indian Ocean totalling ³7.1 million pairs with two major strongholds: the Mozambique Channel (3 million pairs) and the Seychelles Basin (3.4 million pairs). The remaining 0.7 million pairs breed on islands of the Mascarene Basin. Surprisingly very few studies have been conducted on the feeding ecology of these seabirds and none considered the interactions between tuna fisheries and seabird ecology.
The aim of this research project was to start a long-term study on the feeding ecology, breeding parameters and population structure on the main tuna-associated seabird species of the western Indian Ocean. The goal was first to assess the possible impacts on the seabird ecology of natural and man-induced changes in food webs of the region. This study has been ongoing since 2002 in the Mozambique Channel and the aim of this proposal was to extend it to the Seychelles Basin, where seabirds coexist with an important and growing purse-seine fishery.
Ultimately our goal was to use seabirds as bio-indicators of the health of marine food webs in the western tropical Indian Ocean in order to conduct an ecosystem-based management of the marine resources of this region. An important part of the project was devoted to training local students and staff, by increasing the links and exchanges between Seychelles institutions and NGO with the University of Réunion Island, in order to reinforce local research capacity.
This proposal was a joint project of seabird and marine scientists. It also involved the Division of Nature & Conservation, Ministry of the Environment of the Republic of the Seychelles, stakeholders from the Seychelles, notably the Seychelles Fishing Authority and the Indian Ocean Tuna Commission, and various NGOs.