From ALLAN BERRY
The toxic marine algae Heterosigma akashiwo, which caused the recent farmed
salmon losses in the Bay of Camaret in Brittany (In Brief, 8 October), has
also been a problem for fish farmers in Scotland.
The fish deaths are associated with haemolytic toxins produced by the
rapidophyte H. akashiwo under conditions of nutrient stress, most probably
phosphorus deficiency. The algae are bacteriverous, and may be advantaged in
the competition for phosphate near marine fish farms, where 75 per cent of the
nutrient input is lost to the environment and subject to primary degradation
by bacteria.
H. akashiwo and other toxic microorganisms which cause great losses to the
aquaculture industry may have been introduced to Brittany and Scotland in
cargo ships’ discharged ballast water. Ballast water has been established as
the vector introducing many toxic species elsewhere in the world, causing
enormous loss to aquaculture.
The operation of the proposed superquarries in the Highlands and Islands
would certainly increase such risks, while it is almost certain that claims
for consequential loss would be very difficult to establish, and the shipping
responsible long departed.
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