1983-2005 More than 20-year development of the King scallop (Pecten maximus) sea-ranching industry in the bay of Brest (France) P.G. Fleury, J.P. Carval, M.L. Muzellec, A. Gérard, J. Barret, J.C. Cochard, C. Lambert* & J.C. Dao Association Ecloserie Tinduff Crédit photos: Ifremer, CUB, Régis Lasbleiz
1. Background 2. The sea-ranching industry 3. Results and limits
King scallop production in Brest from 1950 bay of to 1990 Brest 2000 mt 1000 mt Engines 1953-54 Cold winter 1962-63 1950 55 60 65 70 75 80 85 90
2. The sea-ranching industry Funding Production techniques Fishing management
Funding (infrastructures and research) 1983-88 and 1989-93: two contracts French state + Brittany region 1993-96 : Europe Bay contract for the bay of Brest (pilot program for scallop industry) + Concerted Action / scallop seeding
Three main rearing stages: Hatchery Intermediate culture at sea Production techniques On growing on sea bed
Hatchery: Le Tinduff 5/6 months: From larvae to 2 mm Conditioning hatchery nursery
Algal culture in batch Four main species Skeletonema costatum Chaetoceros calcitrans Isochrysis affinis galbana (T-iso) Pavlova lutheri. 2 and 10 liter flasks 300 L cylinders
Conditioning and spawning -Adults selected from the wild -2 to 3 month conditioning: maturation -Spawning induced by thermal shock
Larval stage ovocyte 21 to 30 days at 18 C Before metamorphosis 450 L cylinders
Nursery: from post-larvae to 2 mm Two months
Intermediate culture Bay of Morlaix Bay of Brest Bay of Saint-Brieuc Brittany 100 km
Intermediate Culture Intermediate culture, at sea (6-10 months) From 0.2 to 3 cm
On growing on sea-bed On growing on sea-bed (2-3 years)
Evolution of the program 1983-88: Restocking On growing 5 years on sea-bed create an additional brood stock (+ 500 tons within 5 years) Since 1989: Sea ranching In fishing areas on growing 2 years on sea-bed (with wild stock) additional production for the fishery In restricted area (closed for 3 years) on growing 3 years on sea-bed (till opening of the restricted area) give production when fishing yields decrease
Fishing management > Licenses: 60 to 70 x 4500 > Minimum Shell size : 10.5 cm > fishing period: - from October 1st to May 15th - Duration of fishing decided before each new period > Max engine power: 150KW > Max size of the boat: 11 m
3. Results and limits
400 350 300 250 200 150 100 50 0 Seeding production 83/84 84/85 85/86 86/87 87/88 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 00/01 01/02 02/03 03/04 Seeding / bed Seeding / restricted area Wild Metric Tonnes tons Year Années ± 300 tons /year Seeding: from 1/3 to 2/3 fished scallops
Technique Limits (Among others) Algae production (quantity, quality ) Larval rearing prophylaxis Stress due to the transfer of juveniles when seeded Environment Competitors: Crepidula Predators : starfish, whelks, crabs, polydora... Vermin Gymnodinium, Pseudo-nitzschia (ASP amnesic shellfish poison )
Conclusion Use of aquaculture appeared successful to partially restore the scallop fishing in the bay of Brest and to develop new integrated management tools however the scallop network appeared still fragile due to technical problems but above all to new and/or uncontrolled environmental hazards.