Are perch the new wrasse?

PACIFIC perch are proving to be efficient cleaner fish in trials with farmed Atlantic salmon in British Columbia, according to Aquaculture North America.

Research so far has produced promising results, said Dr Shannon Balfry, who leads a team investigating the use of local perch as cleaner fish.

‘We expected our first trial to last two to three months. When we checked back after five days, the sea lice were all gone and so was the evidence [that they were ever there].

‘We now have so much evidence that the perch eat the sea lice,’ said Balfry. ‘We find the lice in their stomachs and we have video of the perch picking lice off the salmon.’

This research, at the Fisheries and Oceans Canada Centre for Aquatic and Environmental Research in West Vancouver, is the first of its kind on the west coast.

‘Marine Harvest (BC) phoned and asked if I knew about salmon farmers in Norway using lumpfish and wrasse as cleaner fish in their net pens,’ said Balfry.

‘We don’t have wrasse or lumpfish in BC, but when I went back through the literature I found several reports from the 70s, of researchers observing cleaning behaviour in local kelp perch (Brachyistius frenatus) and pile perch (Rhacochilus vacca).’

Balfry says her next work will be in deployment research to determine the optimal stocking ratio of perch to salmon and how to scale up the culture of perch.

‘A perch breeding programme and hatchery will be needed to stock the net pens, so there is lots of work to do with the perch.’

There is much to learn as well about perch physiology, health and nutrition, she said. The team expects to start cage studies in 2018. Above: Pacific pearch