A major problem in developing the industry is that
growth in the wild is very slow. In the Waikato River
it can take the short finned eels 16 years to reach
the minimum commercial size.
This resulted in
NIWA undertaking
trials to ‘fatten’ shortfinned eels that were close to
commercial size. Their aim was to minimise cost for
this by using existing pond systems and using
inexpensive and local available foods.
Reporting the results
of their research in Seafood New Zealand
Ben Chisnall and Mike Martin wrote: "The
preliminary results of our fattening trials in farm
ponds and in a pond of treated dairy processing wastes
were encouraging.
They showed that
- female eels can be
reliably selected by grading commercial threshold
sized eels for ongrowing;
- wild stocks in poor
condition are not predisposed to poor growth;
- a proportion of
these eels can be rapidly fattened- some by up to 50
times their natural growth rate- in both farm ponds
and ponds containing treated effluent from dairy
processing."
The scientists found
that the Te Rapa dairy factory’s processing wastewater
mixing pond was one viable ongrowing site because of
the high volume of warm water passing through, the
high nutrient content and the minimal risk of
pathogens. Two hundred poorly conditioned shortfinned
eels were placed in the ponds and grew 27mm in length
and gained an average of 100 g in weight. Some gained
more than 200 g – up to 50 times faster than the
natural growth rate.
By Jenny Haworth
FIS.com
