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CONSERVATION OF BIODIVERSITY VIA AQUACULTURE

Context and objectives

Coral reef ecosystems represent a considerable challenge for the future whether in relation to the economic activities depending on them or the food security of people in emerging countries. But today coral reefs and their resources (fish, crustaceans, molluscs, and so on) are highly endangered. Such a situation requires the implementation of coastal zone management measures aimed in particular at the preservation of the biodiversity of the coral reef ecosystem and sustainable exploitation of the activities dependent on it. This programme aims to reconcile the objectives of conservation and development of coral ecosystems.

Most reef fish have a complex life cycle with a larval stage in a pelagic environment (dispersion phase), after which the larvae return to the coral reef to continue their development as juveniles and adults adapted to the reef environment (benthic phase). Taking as a starting-point the fact that the mortality rate of post-larvae is higher than 90% when they move from the open ocean to the reef environment, a small portion of post-larvae are captured by light traps before they are settled on to the reef without disturbing fish populations or habitat.

At the intersection of fishing and aquaculture, PCC (Post-larval Capture and Culture) aims : (1) to improve knowledge of larval fish flux and quantify it, the larval phase being essential for the maintenance of biodiversity ; (2) to develop sustainable economic activities, since post-larvae can be reared as ornamentals or food-fish, and/or for restocking a depleted coral reef ecosystem.

Methods

Post-larvae are captured with light traps that attract them by photochromism when they are looking for a shelter to protect themselves from predation upon approaching the coral reef. Then they are sorted and placed in an aquarium to be reared. Some of them will be sacrificed to study their larval stage through analysis of the otolith (a fish’s “black box”) to improve understanding of their larval stage. Rearing techniques must be adapted to local conditions and objectives. Duration of rearing will depend on objectives : aquarium and restocking (15 days to 1 month) or food fish (<12 months).

Capture with a light trap (CARE)

From sorting the post-larvae to rearing them in aquariums

Possible economic uses of the post-larvae : ornamentals (A), food-fish (B) and restocking coral reefs (C)

ornamentals food-fish restocking coral reefs

The findings will verify the biological (quantification of the larval flux) and economic feasibility of PCC in the Indian Ocean (Reunion, Madagascar).

Collaboration

The ARDA and the IRD, in collaboration with private companies Hémisphère Sud (Reunion) and Ecocéan (France).

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