‘Unique cooperation between Scottish farmers to fight water moulds’

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Scottish farmers have joined forces with scientists to fight saprolegniosis, and to identify the main risk factors that cause this disease in salmon during the fresh water stage.

The project is led by Pieter van West, director of the International Centre for Aquaculture Research and Development at the University of Aberdeen.

Van West is originally from the Netherlands and graduated from Wageningen University in molecular plant pathology.

In his Aberdeen laboratory with fifteen researchers, the majority are working on saprolegniosis. “Saprolegnia is a big problem for Scottish aquaculture. It causes significant losses for salmon farmers every year.”

Pieter van West, credit ICARD.

Saprolegnia is a water mould, naturally present in all rivers and streams, and related to seaweeds, explains van West. “Unlike what most people think it is not a fungus, it’s actually related to Phytophthora infestans, which causes potato blight. These organisms are more related to seaweeds, like brown algae and diatoms.”

Joint effort

The cooperation of the salmon farming companies – Marine Harvest Scotland, Grieg Seafood Hjaltland UK; Landcatch Natural Selection; Scottish Sea Farms; Cooke Aquaculture Scotland – is unique, as far as he knows. “I don’t recall any other concerted effort to fight a problem like this. It started as a result of an RSPCA meeting last summer, in which the idea for this joint effort came up.”

All the companies involved will help with the project, both financially and with support in kind. “The salmon farmers will be collecting data for us and providing personnel to do the sampling. We will be collecting from about twenty farm sites weekly to take various samples. These will be used to examine 40 different parameters, such as water quality and spore counts.”

Defence mechanism

Most of the research in my lab focuses on how the moulds infect fish, says van West. “Saprolegnia injects proteins inside the cells of the fish, and it seems as though it consumes the cells from the inside out, so the fish is probably not even aware it is attached, at least in the early stages of infection. Therefore the defence mechanisms may not react in time.”

Saprolegnia has caused losses for the Scottish aquaculture sector for many years.

“Farmers have experienced significant losses at the hatcheries and also in the growth stage. The disease hits salmon in the fresh water stage and it’s a big risk factor following vaccination of smolt. We don’t know how or why, but after vaccination the young fish become more susceptible to Saprolegnia.”

The goal of the 36 month project is to be able to predict the risk factors for Saprolegnia, Van West explains.

“Using the parameters we will be developing a predictive tool to discover when the water moulds are most likely to attack the salmon.”

“With our research we are also trying to create a tool that will predict when the fish are most vulnerable to Saprolegnia. The most important thing we want to get out of this is prevention. Ultimately, of course, we would like to farm fish without pesticides.”

Funding and participants

Other participants in the project are Benchmark holdings, Pulcea, RSPCA, Scottish Salmon Producers’ Organisation, and the University of Glasgow.

The €1.2 million project is supported by funding from the Scottish Aquaculture Innovation Centre (SAIC) and the UK research council BBSRC.