Biological, socio-economic, and administrative opportunities and challenges to moving aquaculture offshore for small French oyster-farming companies
|Author(s)||Barillé Laurent1, Bris Anthony Le1, 2, Goulletquer Philippe3, Thomas Yoann4, Glize Philippe5, Kane Frank6, Falconer Lynne7, Guillotreau Patrice8, Trouillet Brice9, Palmer Stéphanie1, Gernez Pierre1|
|Affiliation(s)||1 : Université de Nantes, Laboratoire Mer Molécules Santé (EA 2160), Faculté des Sciences et des Techniques, BP 92208, 44322 Nantes, cedex 3, France.
2 : Centre d'Etude et de Valorisation des Algues, Presqu'île de Pleubian, 22610, France
3 : IFREMER, Direction Scientifique, Centre Atlantique, Rue de l'Ile d'Yeu - BP 21105, 44311 Nantes, Cedex 03, France
4 : Laboratoire des Sciences de l'Environnement Marin (LEMAR), UMR 6539 IRD/UBO/Ifremer/CNRS, BP70, F-29280 Plouzané, France
5 : Syndicat Mixte pour le Développement de l'Aquaculture et de la Pêche en Pays de la Loire, 3 rue Célestin Freinet, Bât B sud, 44200 Nantes, France
6 : Marine Institute, Aquaculture Section, FEAS, Galway, Ireland
7 : Institute of Aquaculture, University of Stirling, Stirling, UK
8 : Institut d'Economie et de Management de Nantes, LEMNA, Université de Nantes, Chemin de la Censive du Tertre, 44322 Nantes, Cedex 3, France
9 : Université de Nantes, CNRS, UMR LETG, Chemin de la Censive du Tertre, BP 81227, 44312 Nantes, Cedex 3, France
|Source||Aquaculture (0044-8486) (Elsevier BV), 2020-05 , Vol. 521 , P. 735045 (15p.)|
|WOS© Times Cited||8|
|Keyword(s)||Pacific oyster, Site selection, Off-shore aquaculture, Remote sensing, Dynamic energy budget (DEB) model|
Oyster production has historically taken place in intertidal zones, and shellfish farms already occupy large extents of the French intertidal space. The expansion of French shellfish aquaculture within intertidal areas is therefore spatially limited, and moving production to the subtidal offshore environment is considered to be a possible solution to this problem. Finding new sites along the French Atlantic coast was studied here from the perspective of small oyster companies run by young farmers, who are interested in offshore bivalve aquaculture expansion compatible with their investment capacity. In assessing the feasibility of such offshore production, we considered three main issues: (1) bivalve growth potential and (2) technical feasibility and conflicting uses, both within a spatial framework, as well as (3) the steps and barriers of the administrative licensing process. Oyster spat in an experimental offshore cage showed significantly faster growth, in terms of both weight and length, compared to those in an intertidal cage, mainly due to lower turbidity and full-time feeding capacity (i.e., constant immersion in the water). A combination of Earth Observation data and bivalve ecophysiological modelling was then used to obtain spatial distribution maps of growth potential, which confirmed that offshore sites have better potential for oyster growth than the traditionally oyster-farmed intertidal sites overall, but that this is highly spatially variable. Small-scale producers indicated two technical factors constraining where farms could be located: bathymetry must be between 5 and 20 m and the distance from a harbor no more than five nautical miles. These were included along with maps of various environmental and socio-economic constraints in a Spatial Multi-Criteria Evaluation (SMCE). Touristic traffic and bottom trawling by fisherman were found to be the two other most restrictive variables. The GIS-based SMCE developed in this study showed that there is almost 400 km2 of highly- to very highly-suitable area within which to develop offshore aquaculture using simple, low-cost bottom-cage techniques, and can be used to assist the shellfish industry in the Marine Spatial Planning decision-making process, still in progress in this coastal area. However, the complexity of the administrative processes necessary to obtain an offshore license is perceived as a stronger barrier by farmers owning small companies than site selection, technical feasibility, and required investments, and will be crucial to address in order to realistically proceed to offshore cultivation. The process demonstrated here, and the results are relevant to other coastal and offshore locations throughout the world and can be adapted for other species.