Comparison of a flow through- and two recirculation systems for intensive rearing of cod larvae (Gadus morhua L.)

Transcription

1 Comparison of a flow through- and two recirculation systems for intensive rearing of cod larvae (Gadus morhua L.) Kari Attramadal 1, Gunvor Øie 2, Olav Vadstein 3 and Yngvar Olsen 1 1 NTNU, Institute of Biology, Trondheim,Norway 2 SINTEF Fisheries and aquaculture, Trondheim, Norway 3 NTNU, Institute of Biotechnology, Trondheim, Norway 1

2 Juvenile production of Atlantic cod in Norway Intensive production :Semi-intensive production Juveniles (thousend) Year 2

3 Are we giving the cultured fish the water we want to give them? Land based fish farm In the fish farm: Heating/cooling Disinfection Filtration Degassing/aeration Addition of oxygen Feeding High fish densities Unstable Intake pipeline At the seabed: A lot of particles A lot of organic matter Low redox potential Low oxygen levels Bacteria Dead, stable Algae Fish larvae in the sea Mud In the pelagic sone and upper layer: Pelagic fish larvae Algae High redox potential Low level of bacteria High oxygen levels Living, stable 3

4 Larvae vs juveniles: two different worlds biomass, loading, sensitivity Hatchery: low biomass, sensitive fish: Low production of waste (CO 2 and NH 3 ), low consume of O 2 Low organic loading, small particles Very sensitive to bacterial infections and oscillations in water quality Production imperative: stability + controlled bacterial environment Juvenile production: high biomass, tolerant fish: Waste products and oxygen determining for fish density/water exchange rate High organic load, larger particles Production imperative: removal of waste products/particles + addition of oxygen Water treatment components/systems are often dimensioned with ongrowing fish in mind 4

5 Extremely flexible experimental facility Recirculation system with UV (3 tanks) Recirculation system with ozone (3 tanks) Flow through system (3 tanks) Fishtanks Volume: 1,8m 3 Automatic cleaning arm on bottom Outlet from mid center Dry feed automats with feeding system Logging of temperature, oxygen, redox potential and ph 5

6 Recirculation system for rotifer production at SINTEF SeaLab. Rotifer density Wheel filter Temp., salinity, ph, O 2 Feed Rotifer: Brachionus plicatilis Production tank 6

7 Aquatic ecosystem High-density systems Designed for high-volume production: > 5000 rot/ml Systems are complete, including culture tank, filtration system, pure oxygen diffuser, feed and ammonia neutralizer dosing system Feed type used is Instant Algae marine paste Only 30 minutes of tank maintenance per day is required to produce 100 million to 2.5 billion rotifers per day Three sizes are available: 150-liter, 450-liter and 1000-liter systems 7

8 Biofilter Recirculation system with UV Vacuum aerator Sea water intake Fish tanks Protein skimmer UV Reservoir w/ 50 µm sieve 8

9 Ozone generator w/ ORP sensor Biofilter Recirculation system with ozone Vacuum aerator Sea water intake Activated carbon filters Fish tanks Protein skimmer Reservoir w/ 50 µm sieve 9

10 Flow through system Vacuum aerator Sea water intake Fish tanks 10

11 Materials and methods Cod larval performance (survival, growth, deformities and stress tolerance) Water quality (particles, nitrogenous waste products, organic matter, ph, etc.) Microbial environment (qualitative and quantitative) Respons to perturbations (new feed type, increased organic matter loading, increased water exchange rate) Comparison from hatching of larvae to day 30 post hatching: RAS with UV-treatment RAS with ozonation Flow through system Day 23 11

12 Density: 60 larvae L -1 Cod rearing regime Water exchange rate: 1-6 times tank volume per day Degree of recirculation: 95% Continuous lighting Central aeration Microalgae (Isochrysis galbana) added continuously from the day before hatching to day 23 ph Rotifers fed 3-4 times daily from day 3-23 ph Artemia fed 4 times daily from day ph Temperatures increased gradually from 7 (at hatching) to 12 C (photo: D.Mandiola) (Photo: T.Bardal) 12

13 Water quality in the start feeding tanks after stress test with dry feed addition Flow through Recirculation UV Recirculation ozone 13

14 Conclusions Better growth, survival and stress tolerance in the recirculation systems for the live feed period despite worse water quality conditions Day 30 Seemingly better results in the recirculation system with ozonation (the least disinfection activity?) Our tank water exchange rates were too low to hinder tank variations A great starting point for improving cod larval performance even more in recirculation systems: We are convinced of the beneficial effects of recirculation of culture water during the live feed period in production of cod larvae! 14

15 THANK YOU! Acknowledgements This work is a part of the Strategic University Programme CODTECH financed by the Norwegian Research Council and NTNU. 15