Plaice farming
Scientists revive interest in plaice farming
LAICE has long been a dinner favourite in Britain, but wild stocks are subject to fishing and environmental pressures, especially in the North Sea.
So, what if it could be cultivated in the same way as salmon and trout? The last time an attempt was made to breed plaice was just after the war – almost 75 years ago and at a time when there was an abundant supply of fish from the sea.
Left to their own devices, plaice can live for up to 50 years, but they grow and reproduce very slowly leaving them vulnerable to overfishing. Some populations are facing a serious risk of decline.
Now scientists at Norway’s Institute of Marine Research (IMR) are reviving interest in plaice farming, using previous knowledge gained over the past 30 years from halibut breeding trials.
IMR researcher and sustainable fish farming project manager Birgitta Norberg says halibut is probably the most difficult species of all to cultivate. It is both complicated and expensive.
Yet, thanks in part to previous research, a number of companies in Norway are now looking at adding halibut farming to their commercial operations, along with cod - and even warm water prawns.
Meanwhile, back at the Institute, a group of marine scientists are working to see if the experiences gained with halibut can act as a model for breeding plaice and possibly other flatfish
Norbert explains:
‘To understand the process, we have to find markers in the genome, which say, for example, why one type of fish grows faster than another.
‘In this way, we can better understand biology, and in the longer term choose which individuals to breed.’
The goal, she says, is to produce plaice at around a kilo in weight, more than three times that of the fish today found in certain parts of the North Sea.
When research into plaice farming was last carried out in the 1940s, scientists were able to breed several thousand fish from fry.
‘This was a major breakthrough and was largely due to the use of live-fed artemia, as we still do today,’ said Anders Mangor-Jensen, another IMR researcher.
‘In retrospect, there has been some work on the species, but HI researchers have not published anything on the plaice breeding since 1946.
‘We don’t know anything about the growth or the quality of the fish.What we know so far is that it takes three times less time to produce plaice fry than halibut, and with minimal mortality. Now we have to make the way as we go.’
The plaice fry has been produced in two large, round vessels. Over 10,000 larvae have been breeding over the last couple of months. Eventually they will be moved to a flatter vessel where they can grow further.
According to the researchers, it seems that, like turbot, the plaice prefers to lie somewhat layered.And one of the problems the researchers struggled with when it came to halibut was to
make them develop from the larval stage in 50 litre vessels.
Mangor-Jensen said:
‘By using many of these little guys at the same time, the researchers can compare the results between them. Plaice works well in small systems. We have not had any mortality’.
He said the plaice currently being produced were only at the fry stage.The next step was to perform growth tests which will show how fast they can grow.
Currently, the plaice produced in Austevoll is only in the fry stage.The next step is to perform growth tests, which will show how fast the plaice grows.
Footnote: The term plaice comes from the 14th century Anglo-French plais which in turn derives from the Latin word platessa simply meaning flat fish.There are four main plaice species, European, American, Alaskan and scale eye. But commercially, the most sought after variety is European.
"The goal... is to produce plaice at around a kilo in weight"