Shellfish Team Viking Fish Farms Ltd, Ardtoe Marine Laboratory

Shellfish Team Viking Fish Farms Ltd, Ardtoe Marine Laboratory

Introduction History of Ardtoe Marine Laboratory Native oyster production methods and facilities Microalgae production Broodstock Conditioning Larval rearing Settlement Nursery In house and funded research

Viking Fish Farms Ltd- Ardtoe Marine Laboratory

Began in 2008 Oyster Production Both production and research From 35K in 2008 to 3 million spat produced 2012. SARF project 063-01 (Jan 2010- Dec 2012) Overcoming bottlenecks in the intensive commercial production of native oyster spat. Feeding: alternative to live algae (?) photo-bioreactor (?) Settlement (from plastic substrates to micro-cultch) Production (from extensive out-door to Intensive in-door) Feasibility of producing Native triploids

Microalgae Production Intermediate cultures (1-10l) Master cultures (100-250ml)

7-14 days Bag cultures (100l)

Broodstock holding and conditioning tanks 10 x 150l troughs with ambient water supply, UV treated and filtered to 25µm. Aquarium heaters in conditioning tanks 150l troughs for broodstock

Broodstock holding and conditioning tanks: Currently for O. edulis: 1 holding tank at ambient temperature and 2 conditioning tanks. Oysters in holding tank Oysters in conditioning tank

Conditioning Water temperature increased by 1-2 C per day from a mbient up to 19-20 C. Water flow set at 25ml/min/adult Feed is supplied in the form of live algae: Chaetoceros muelleri Tetraselmis suecica Isochrysis galbana Dunaliella tertiolecta Phaeodactylum tricornutum food ration (g DW of algae) is 6% of the DW of oyster flesh per day

2-stages Conditioning Moderate temperature (15 C) and 6% feed ration for 4 to 6 weeks followed by full conditioning temperature (19-20 C) with ration reduced to 3%. Under this process, our oysters failed to spawn. All oysters held 24:0 light:dark (?)

Broodstock Feed Sheet: 1. Input wet weight oysters 2. Input ration required 3. Input optical density from spectrophotometer 4. Input proportions of algae/ paste required 5. Quantities of algae/paste calculated automatically Cells/ml of algae are calculated using the optical densities (ODs) and an equation derived from pre-determined concentrations and their OD s.

Spawning 45µm mesh under outflow to collect larvae. Any further larvae collected by draining the broodstock tank. Larvae counted and stocked at 5-10 per ml in larval tanks. Larvae swimming in tank after release. 45µm mesh basket under outflow Larvae collected in mesh basket

Larval tanks Larval tanks 3 x 450l square-conical tanks. 2 x 350l square-conical tanks. Static system with water supplied from 1,500l heated reservoir. Aeration via 5 air lines (1 central, 1 in each corner) 450l square-conical larval tanks

Larval feeding: 1. Input number of larvae per tank 2. Input average larval size in microns 3. Number of cells Iso equivalent/day calculated 5. Input proportions of algae required. 6. Quantities of algae calculated automatically 4. Input optical density from spectrophotometer

Larval feeding continued: Our calculator uses these numbers to calculate not only Iso but other algal species cell numbers, taking into account the cell size differences (as Iso-equivalent). Calculator is based on the number of Iso-equivalent ingested by larvae per day at each size. For C. gigas, we feed only Iso/Chaeto until larvae reach 125µm, then Tetra is added; For O. edulis Tetra is added from the start Water changed every 48 hours from 1,500l heated (22-23 C) reservoir. Residual algal quantities checked daily to avoid overfeeding

Swimming D-larvae Eyed larvae Larvae settled on cultch (Spat) Larvae with foot, searching for suitable substrate to settle

Settlement Cultch now used Size of particles 250-500µm. Ground, aged oyster shell Calcium carbonate particles from marble factory Cultch added when >50% of eyed larvae show signs of substrate searching behaviour. Cultch placed in a very thin layer on 125µm - 250µm mesh basket. No air lift throughout the day and gentle air lift overnight. Up to 150,000 larvae per mesh basket in 90l paxton containing 70l water. Larvae settle between 4 and 7 days.

Settlement Ground oyster shell vs marble Results showed that the oysters prefer to settle on ground oyster shell if both are provided. But still settle on marble if only substrate available. tends to clump, harbour more algal growth and makes grading difficult. Survival during settlement has been between 40 and 98%.

Spat tanks 19 x 90l paxtons containing mesh baskets. Static water, exchanged via 1,500l reservoir. Daily water change. Down-welling via air-lifts. Spat tank (mesh basket with air lift) Mesh basket containing spat

Micronursery with built-in heater and light can support up to 10 upwelling tubes. Micro-nursery (from side, showing control panel) Micronursery (from above)

Spat Feeding Summarised print out Same input method as broodstock feed sheet (based on weight) but with additional ability to set an overall reduction of feed when algae is limited (as highlighted).

Grading After 4 weeks, the newly settled spat are graded off the microcultch. Subsequently, every fortnight, the spat are graded over a series of sieves and sample weights are taken to determine numbers. Ideally, spat would be sold when they attain 10-15mm (shell length), but with algal limitations at VFF and new developments in nursery rearing, customers are willing to take 2mm (sieve size) oysters.

Pond trial Large 10m diameter pond tank (160m 3 ) filled with overflow from main header tank and inoculated with microalgae from bag culture. Agricultural fertiliser added and tank bloomed. Algae air lifted indoors to a reservoir tank. After salinity was adjusted, it was fed to two trial paxtons. Two paxtons being fed bag cultured algae provided a control. Over two weeks, the pond water fed oysters lost weight. Algae analysed (CCAP, Oban) and thought to be a Nanno/Chlorella which was deemed too small/ nutritionally poor to sustain the spat.

Further R&D Alternative artificial diets (Single Cell Detritus?). Extensive microalgae production in outdoor pond tank. Other designs or up-scale of upwelling systems. Further studies on the different cultch materials.