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Abalone farming is a growing aquaculture industry. New
frontiers are being explored to expand the production of this valuable
commodity, which has various researchers testing the waters in terms of
culturing the tropical abalone Haliotis asinina in sea cages.
Since studies have shown that stocking density has an inverse
relationship with the growth of abalone, the trick is to find a middle
ground wherein a given area could still be able to support the growth of
abalone.
This begs the question: Does the shelter surface area (SSA)
of mesh cages have an effect on the feeding, growth and survival of the
tropical abalone? To find out, Armando Fermin and Shela Mae Buen of
SEAFDEC/AQD embarked on the study by stocking cages with different-sized
shelters measuring 0.22, 0.44 and 0.66 sq. m with 227, 113, and 75
abalones, respectively. Other provisions like adequate aeration and
feeding with the seaweed Gracilariopsis bailinae were also given.
The experiment, conducted in 270 days, showed that shell
lengths, body weights and daily growth rates were not significantly
different in the first 13 weeks of culture. Abalone grown in cages with
SSAs of 0.22 and 0.44 sq. m had higher feeding rates. In spite of this,
the abalones reared in cages with 0.66 sq. m SSA were found to grow
significantly faster by the fourth culture month. By harvest time, body
size was significantly different between the cages with the largest and
smallest SSAs.
Why the difference? The higher shelter surface area-to-cage
volume ratio had a significant effect on the growth of H. asinina.
Limited attachment space in the cages with smaller SSAs caused the
abalone to stick to one another, thereby restricting movement and
feeding of the abalone located underneath.
It is always important, therefore, to increase the area for
abalone attachment to overcome the abalone’s tendency to stack.
Read more from the journal Aquaculture International
(2002) 9: 499-508.
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