58
The Last Resaurce
sh farming, although it is still too early to make a reliable guess at
when it might become economical. Take the question of feeding. To
produce one pound of edible sh requires ve pounds of food so
that a farmed plaice might easily cost £I per pound. In the future,
specially bred hybrid sh may give better conversion rates or the
farmed sh may be weaned on to cheaper foods, perhaps sh meal
made from sh or sh waste not suitable for human consumption.
In the marine ‘elds’ one cannot even be sure that all the food
reaches the sh. The Danish marine scientist Professor Gunnar
Thorsen has thrown some light on the fate of potential sh food,
although his studies relate to the open sea. He found that three
quarters of the food which could be eaten by sh, in this case
ounders, is in fact eaten by other unwanted animals such as
starsh, molluscs and crabs. And what is more, they do not even
compete on equal terms. Weight for weight, these ‘pests’ eat four
times more food than the ounders. Various suggestions have been
made as to how these pests can be controlled but the fact that many
of them start life oating in the plankton aggravates the problem. It
is rather like trying to cultivate a eld surrounded by a hedge of
ourishing weeds and being powerless, for territorial reasons, to
remove it. However, before despair sets in, it is worth remembering
that the experimental cultivation of plants and animals on the land
has been carried out for several centuries whereas the very rst sh
farms belong to the late 19605.
_
What form the nal marine ‘elds’ will take is still a matter of
debate. Much of the marine ‘eld’ at Ardtoe lies within the influence
of the tides so that dams had to be built to prevent it from becoming
too shallow; a depth of at least six to ten feet of water is essential to
develop a standing crop of phytoplankton using fertilizers. With this
‘closed’ system, scientists can study the various factors inuencing
the conditions within the eld and the growth of the sh, but there
may well be less demarcation between open—sea and commercial
marine farms. In japan, for example, sh and crustacea are reared
in areas enclosed with nets. Other barriers have also been suggested.
‘Curtains’ of air bubbles have been used in the USA to herd sh
shoals towards nets. The sh only break through the screen of
bubbles coming up from a perforated pipe towed by a trawler if the
shoal is herded too closely or the sh are badly frightened. The
Russians have simulated sounds produced by feeding sh to bring
them within range of their nets. Perhaps a barrier produced by
The Last Resaurce
sh farming, although it is still too early to make a reliable guess at
when it might become economical. Take the question of feeding. To
produce one pound of edible sh requires ve pounds of food so
that a farmed plaice might easily cost £I per pound. In the future,
specially bred hybrid sh may give better conversion rates or the
farmed sh may be weaned on to cheaper foods, perhaps sh meal
made from sh or sh waste not suitable for human consumption.
In the marine ‘elds’ one cannot even be sure that all the food
reaches the sh. The Danish marine scientist Professor Gunnar
Thorsen has thrown some light on the fate of potential sh food,
although his studies relate to the open sea. He found that three
quarters of the food which could be eaten by sh, in this case
ounders, is in fact eaten by other unwanted animals such as
starsh, molluscs and crabs. And what is more, they do not even
compete on equal terms. Weight for weight, these ‘pests’ eat four
times more food than the ounders. Various suggestions have been
made as to how these pests can be controlled but the fact that many
of them start life oating in the plankton aggravates the problem. It
is rather like trying to cultivate a eld surrounded by a hedge of
ourishing weeds and being powerless, for territorial reasons, to
remove it. However, before despair sets in, it is worth remembering
that the experimental cultivation of plants and animals on the land
has been carried out for several centuries whereas the very rst sh
farms belong to the late 19605.
_
What form the nal marine ‘elds’ will take is still a matter of
debate. Much of the marine ‘eld’ at Ardtoe lies within the influence
of the tides so that dams had to be built to prevent it from becoming
too shallow; a depth of at least six to ten feet of water is essential to
develop a standing crop of phytoplankton using fertilizers. With this
‘closed’ system, scientists can study the various factors inuencing
the conditions within the eld and the growth of the sh, but there
may well be less demarcation between open—sea and commercial
marine farms. In japan, for example, sh and crustacea are reared
in areas enclosed with nets. Other barriers have also been suggested.
‘Curtains’ of air bubbles have been used in the USA to herd sh
shoals towards nets. The sh only break through the screen of
bubbles coming up from a perforated pipe towed by a trawler if the
shoal is herded too closely or the sh are badly frightened. The
Russians have simulated sounds produced by feeding sh to bring
them within range of their nets. Perhaps a barrier produced by