Kevin Chilman and his wife Josie work at the Sevrup Fisheries hatchery, breeding and grading salmon and ocean trout, readying them to be transported to sea pens in Macquarie Harbour, near Strahan, where they grow to full size.
At Sevrup, Chilman’s chief responsibility is maintaining brood-stock quality in order to produce fingerlings (tiny fish of only a few centimetres) of consistent number and quality.
They are capable of producing 650,000 fingerlings annually for transfer to sea cages. To meet this demand, five million eggs must be incubated in the hatchery every year.
Ocean trout spend five weeks in incubation before hatching, and Chilman ensures direct contact with UV light is avoided in the incubation pens, as the light can penetrate the eggs and kill the fish. Once hatched, the fish sink to the bottom of the tanks, feeding from the egg’s yolk, which remains attached to the body for around eight weeks after hatching. When the yolk is consumed, the hatchling rises to the water’s surface in search of food.
The first solid the fish consumes is a formula containing vitamins, proteins and fats. The formula is made locally at Cambridge, which has established itself as a centre for development in marine biology. Isolated strains of algae are also cultivated in Cambridge for use in the hatcheries.
The fish are theoretically ready for transportation once they reach a weight of 120 grams, but are kept at the hatchery for up to a year for rigorous grading. At the time of our visit, 80,000 ocean trout were being held in an outdoor pen, awaiting grading and their final journey to the sea pens, where they spend another year to eighteen months.
Grading is a time-consuming procedure: each fish is inspected individually for any defects. Size and colour are also checked, and any fish that don’t make the grade are sold to farm dams to be sold locally. This is a costly but necessary elimination process. According to Chilman the market is becoming more and more particular and the grading ensures that only the finest quality fish make their way to the grow-out pens and eventually to market.