Science Centres: Fisheries

Work with NIWA on underwater lighting has virtually eliminated early maturation at The Isaac Salmon Farm Ltd, Christchurch.

Michael Field-Dodgson, company manager of The Isaac Salmon Farm Ltd, in Christchurch, is hailing a research project conducted with NIWA as ‘an unqualified success’.

The project was funded by Isaac Salmon and the Foundation for Research, Science & Technology. It tackled the problem of early maturation of the salmon, which Michael Field-Dodgson describes as the farm’s Achilles heel. Early maturation is one of the most significant problems in salmon farming, because as salmon approach sexual maturity their flesh loses condition and can deteriorate to the point where it is no longer saleable.

Michael Field-Dodgson: ‘We are a warm water facility and it would appear that the faster the salmon grow initially, the greater the percentage that mature a year early. We have tried restricting food to slow down fish growth and so restrict early maturation, but this is a mediocre method and basically a lose:lose situation – we lose potential growth and still end up losing fish.’

NIWA scientist Martin Unwin designed a series of experiments, at NIWA’s Silverstream salmon hatchery, using underwater lighting to manipulate the amount of light the salmon were exposed to. Isaac Salmon tapped into these results and mirrored some of the work in their own raceways. The farm’s early maturation rate is now almost zero (19 fish in 22 500).

‘The impact of this on the profitability of Isaac Salmon is huge,’ says Michael Field-Dodgson. ‘We can buy in less smolt, we can grow fish at maximum potential, we do not have to sort maturers any more, we do not waste any of our production, and with no early maturation and faster growth we are able to expand our harvest window by 2–3 months.’