Towards sustainable octopus and sea cucumber fishing: use of half-sphere artificial reefs for habitat restoration

José RANDRIANANDRASANA1*, Faustinato BEHIVOKE1*, Andriamanjato RAZAKANDRAINY1, Gildas G.B. TODINANAHARY1, 1. Institut Halieutique et des Sciences Marines, Université of Toliara, Madagascar

Category: Poster-student presentation The first author is a student *Contributed equally to the work

Presenting author: [email protected] Co-author: [email protected] Co-author: [email protected] Co-author: [email protected]

Topic/submission theme: Environmental and Climate Vulnerability, Resilience & Adaptation

Abstract Bio ecology of coastal marine species depends on coral reef. Indian Ocean Island States’ small-scale fishery, like the southwestern Madagascar, focuses on reef resources exploitation including octopus and sea cucumber. With traditional fishing technique (gleaning) on a reef flat, reef habitats are victims of trampling and coral inversion. The ecosystem is continuously degrading and very tangible effects are the accumulation of dead coral debris or coral rubble. To repair degraded habitats, we valorised coral rubble to build artificial reef modules which imitate natural habitats. Modules were handcrafted by trained fishermen. After six years of experimentation, a prototype called "half-sphere" was finally produced. This prototype of artificial reef is one of the models of Fishes Banking ecotechnology®. In December 2017, 300 prototypes were immersed in degraded and non-productive sites, with 0.5 m of interval, at Nosy Tafara reef flat in southwestern Madagascar. After five months of immersion, "half- spheres" attract gleaners and the sites become productive again. Restored habitats are inhabited by various invertebrates, including high commercial species value such as sea cucumber and octopus. On april 2018, a gleaning experimental fishing was conducted. 60% of the immersed prototypes were colonised by Holothuria leucospilota and Stichopus horrens, and 15% by Octopus sp. Relatively low value on octopus may be due to presence of predator species such as morays and spatial competing sea urchin. These structures are very resistant to gleaning, compared to coral habitat, which gives a certain advantage to the traditional fisher communities.

Keywords: reef flat, coral rubble, artificial reef, ecological restoration, sea cucumber, octopus, Fishes Banking ecotechnology®