Jérôme HUSSENOT Centre de Recherche en Ecologie Marine et Aquaculture

Transcription

1 Extensive Jérôme HUSSENOT Centre de Recherche en Ecologie Marine et Aquaculture CNRS-IFREMER aquaculture systems L Houmeau France

2 Classical Definition Extensive aquaculture usually involves: Ranching or restocking Stocking of wild juveniles (or from hatchery) in natural habitat, either in pens or ponds. Management to enhance natural productivity Low densities of organisms Low input of nutrients or food Polyculture (associating herbi- and carni- vorous) Harvest by fisheries techniques (active or passive) Extensive aquaculture is similar to free range terrestrial farms.

3 System Extensive to Intensive: A CONTINUM Extensive Semi-intensive Natural/Pond Food Organisms A poorly studied field in aquaculture Intensive Fish Stocking Density Exogenous or Artificial Feeding

4 Extensive to Intensive: a continum Semi-extensive/Semi-intensive systems are real production practices They are used in sensitive coastal areas maintaining rural activities in salt work or wetland areas. Example: In Andalucia (Spain) production in extensive to semi-intensive fish ponds (1-4 kg/m 3 ) represents 66% of the marine aquaculture production.

5 Large units (1000ha): lakes, lagoons, fjords Typology Medium units (100 ha): enclosures, valli Small units (1ha) : pond, saltworks

6 POLYCULTURE The freshwater example: carp pond culture Some new polyculture systems in marine ponds

7 Polyculture Systems Multiple species in the one system, All species benefit from the enforced coexistence to some extent. Polyculture can be cheaper as only one species needs to be fed Examples: scallops, algae and sea cucumbers or carp polyculture

8 Carp polyculture Silver carp 1 Bighead carp 2 4 Grass carp 3 Common carp

9 Polyculture Oyster-Shrimp In France, oysters (Crassostrea gigas) are associated in semi-extensive shrimp ponds (Metapenaeus japonicus) Use of supplementary feed (low protein level) Resuspended phytobenthos by shrimps is filtered by oysters Result: more economic profit

10 Polyculture Sole and Seabream In Spain and Portugal soles are produced in extensive, associated to semi-intensive sea bream production. OM (feces and non-ingested feed) are stimulating polychaetes (Nereis) used by soles

11 Supplementary feed in EAS A different approach than IAS

12 Pond Nutrition(Hepher s theory) CSC Unnecessary to use a complete feed in a semi-extensive system to maximize growth Better to introduce the supplementary feed before the natural preys disappear

13 Choice of organisms low on food chain The lower an organism is on the food chain the cheaper it is to feed. Herbivores and omnivores are the best organisms for extensive aquaculture. Fish and marine invertebrates are 1.5 times more efficient at converting food into flesh than pigs and chickens and twice as effective as cows and sheep

14 Species Phytoplankton Macroalgae Zooplankton Polychaetes Molluscs Shrimps Mullets, Atherina

15 Past Research programs

16 Maricult Project ( ) Area 3: Methods in extensive aquaculture How to enhance the production and harvesting potential of marine organisms through natural or controlled fertilization? Potential and constraints of future extensive aquaculture methods in coastal zones and open ocean

17 Periphyton-based aquaculture What is it? A complex of sessile aquatic biota with associated detritus, A bio-film including phytoplankton, phytobenthos, zooplankton, zoobenthos, microbes, detritus. Fertilisation possible in association Results 700 to 2400 kg/ha/year Traditional practice Benin «Acadja» South Asia «Katha» INCO-DC project

18 POND, AQUAFARM models Dept. of Bioresource Engineering Oregon State University D.H. Ernst et al. : Aquacultural Engineering 23 (2000)

19 Partitioned Aquaculture System University of Clemson (USA) Algae culture populations (cell ages of 2/3 days) Fish production of catfish and tilapia (max rate 17 to 19 Mt/ha per season)

20 RESEARCH PROSPECTS technical aspects environmental aspects

21 Technical Aspects

22 Questions on pond management Predator Control Crabs, birds, fish, Competitor control Upogebia, Vegetation Control Macroalgae in saltponds Pond bottom Control POC limits, RedOx, H 2 S Water quality Control T, O2, ph Stocking and survival Optimal stocking size? Maximum Standing crop Carrying capacity? Polyculture Species to mix? Natural productivity Fertilisation and BMP? Supplementary feeding Type of feed? Wintering BMP for survival? Harvesting BMP for quality?

23 Research priorities Algae control (macroalgae in lagoons, ponds) Mass production of fry for stocking EAS, Pond nutrition strategy (fertilisation and supplementary feed), Species diversification (Microalgae, Zooplancton, Artemia, Polychaetes, ) as preys or products, Optimizing fish stocking and fertilisation in EAS using ecological modelling, Best management practices

24 Pond nutrition strategy Input of nutrients and organic carbon Periphyton supports (Acadja) Artificial Recruitment of preys (Chironomides, Nereis, ) Use of local wastes, by-products (fishfarming, melasse) Supplementary feed

25 Environmental Aspects

26 Bird predation Daily fish predation g / ind. How to solve it?

27 Research priorities Physical knowledge of complex systems as wetland, lagoons and salines areas (GIS) Management of multi-activities and potential conflicts (social science research) Sustainable management of fisheries, carrying capacities of lagoons, fjords (ecological modelling) EAS and Coastal Wetland Restoration

28 Conclusion

29 Traditional extensive aquaculture must be modernise Increasing the standing crop to cover the labor costs, or associating extra returns Making up new semi-extensive systems, diversifying species, producing new products Associating extensive and intensive steps, to produce one species, Including EAS in a multi-usage water management (= multi-activity), Using EAS to remove intensive aquaculture wastes (integrated systems),

30 Options for a modern (semi-) extensive aquaculture Economically profitable directly or indirectly to be sustainable Promoting diversity Combining on-farm and off-farm activities (pluriactivity) Including in ICZM approach

31 Larger Modern Definition A non-intensive production system of aquaculture, where natural preys are promoted to feed (partially or totally) aquatic products A production system for a species in a fish farm can have alternatively extensive and intensive phases

32 Discussion

33 Open Discussion Definition and limits of EAS? Role in environment preservation? What level of enrichment is acceptable to increase the productivity of EAS? How promoting EAS in ICZM?