ALMOST £70,000 is being
spent to see whether a curtain of air bubbles rising from the
seabed can protect Western Isles fish farms from attacks by
millions of tiny jellyfish from the Pacific Ocean.
The farming of fish like salmon in sea cages
leaves them exposed to losses from attacks by jellyfish and
algal blooms. Scottish Executive figures say that four million
fish, worth around £32m, were lost over the past two years.
In August 2002, the Western Isles Seafood
Company (Wisco) alone lost 625 tonnes of salmon, worth £1.8m,
at two Lewis sites after jellyfish attacks. The main species
that hit the islands was solmaris, transparent and less than a
centimetre in length.
Regis Philippe, Wisco's technical manager,
said that so far there had been no reliable system of defence
against jellyfish attack. The huge shoals drifted with the
tide and enveloped the salmon in the cages, poisoning and
suffocating them.
"They come from the Pacific and we don't
know why they are coming here. If the fish were encountering
just two or three of them they would have survived, although
perhaps a little damaged. But there are so many of them the
water becomes like a soup.
"There are millions of them. The fish
swallow them and they go through their gills actually
suffocating the fish. Solmaris feed on plankton, but can't
swim against the current. So if the cages are protected by
this curtain of air bubbles, the current should no longer
sweep them into the fish. That is what we are going to try."
Wisco, a subsidiary of Norway's Fjord
Seafood ASA, employs about 50 people farming Atlantic salmon
from four sites in the Western Isles and one in Ross-shire. It
also has contracts with two companies in Skye and Lewis.
Preliminary work is hoped to be complete by
next month with full-scale tests under way by April/May on one
of the firm's sites.
If the results are favourable, the defensive
shields of air will be put in place by late summer, when the
chance of attacks is at its highest.
The total cost of the project is £68,155,
with Western Isles Enterprise putting in £44,000. Two years
ago, WIE backed an earlier research and development project by
Wisco for the use of a type of fish called goldsinny wrasse to
act as a biological control against sea lice infestation on
salmon farms. This was successful and the system is now in use
on two sites.
Taytech, the firm involved in devising the
air bubble equipment, has been testing the best combinations
of equipment and these will be taken to the test site soon.
The project will be monitored over 12 months by the Institute
of Aquaculture at Stirling University.
By David Ross
