Ben and Matt enjoy a break from joining up the components of the system
A sample of the Kaldnes K1 fluid filter bed beads
The delivery and return lines are situated between the rows of tanks, away from the working area
The new indoor production system is attached to the existing purging system and packing area
Water is from a 12m deep water table. The bore pumps just under 2.5ML a day and the property has a licence for 540ML a year. "The water quality is spot on," said Paul. "It has a pH of seven, hardness is 9mg/l. and an alkalinity of 60mg/l. The water comes out of the ground at 22˚C with a DO of 3mg/l. So why wouldn't you put in a re-circulation unit?" asked Paul. Pond temperatures reach 20˚C around mid November
and fall back below that around early April. This leaves only eighteen to twenty weeks of optimum growing time. With the temperature control offered by the re-circulation unit the Trevethans expect to be able to cut the last summer off the pond growing. The savings are fundamental and immediate: reductions in the cost of fi sh space on the farm, and increased productivity. Paul was non-committal, but suggested around a third for each.
THEY LEAVE THE FINGERLINGS IN THE POND TO TAKE FULL ADVANTAGE OF THEIR GROWTH
Normally growers buy their seedstock as 25-35mm fry from dedicated hatcheries. The Trevethans operate their own 0.2ha plankton pond in which they raise larvae, purchased from recognised hatcheries in the region, to fry stage. "The genetics would probably be better than anything we could breed ourselves at this stage, and we can be very busy from time to time. You can get 100,000 larvae in the boot of a car, all we have to do then is manage the plankton bloom." They leave the fi ngerlings in the pond to take full advantage of their growth during the summer months until the weather falls away in April. By then, the fi sh range between 5g and 15g. They're graded into the tanks in the shed and fed. Grading is ongoing throughout the winter. Once the pond water reaches
Peter pointis out how the airline is incorporated in the water delivery lines for tidiness
20˚C the fi ngerlings are returned to the cheaper-to-operate growout ponds. By this stage they average 120g. The Fresh By Design indoor system has six 9000 litre, seven 5000 litre and seven 2000 litre aquaculture tanks. The water is gravity fed to the 40µm Faivre Drumfi lter that passively
MAY/JUNE 2012 ■ NZ AQUACULTURE ■ 7
