The world's fish farmers could dramatically increase their harvests if an extraordinary experiment by a Canadian scientist bears fruit.
Edward Donaldson, of the West Vancouver fisheries laboratory, has been injecting growth hormones from chickens and cattle into young salmon, and has found that the fish grow up to 50 per cent faster than normal - with no side-effects in the way of feathers or horns.
The findings, if applicable commercially, could be a key factor in increasing fish supplies. Harvests from natural sources has recently levelled off at about 70m tons a year, and the next developing area is likely to be factory farming, in such areas as Norway, Scotland and Iceland.
Now that the problems of breeding, health and diet have been largely overcome, the most vital economic factor governing expansion is likely to be how fast farmers can grow the fish. So far the only means of speeding up the development of young fish is to grow them in warm water - which is expensive in northern climes unless a power station outlet or hot spring is available nearby. Another method is cross-breeding with fast-growing stock, which takes years of waiting for the generations to mature.
Growth hormones can now be made in a very pure form and in large quantities by inserting the gene from the hormone into bacteria and growing the bacteria into large cultures. Dr Donaldson injected the chicken and bovine hormone weekly into the body cavities of anaesthetised young salmon, and their growth rate increased from a normal 1.48 per cent a day to as much as 2.38 per cent a day.
The next step may be to inject doses of the salmon's own growth hormone, but this has only just been isolated. When this can be used it could have even more dramatic effects on the growth rate.
