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Recent
monitoring by Department of Conservation has confirmed that catfish
numbers have stabilised in Lake
Taupo at levels, well below the peak recorded in 2000 says Glenn
Maclean of the Taupo Fishery Area. Numbers have consistently been
about a third of the peak since then, including over this summer.
Such a pattern of increasing numbers and
then a decline to a more stable population
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common with the introduction of a new species says Glenn. Generally
it appears catfish find conditions a bit tough in Lake Taupo and
amongst more than 10,000 catfish caught by DOC, the largest is only
370mm and 895g or just under 2lb. This is considerably smaller than
the maximum size recorded else where in New Zealand.
With the downturn in the trout fishery over the
last 18 months, anglers often raise catfish predation on smelt,
the main prey of trout as the cause. However Glenn says catfish
are poor feeders on highly mobile prey like smelt, feeding by touch
and smell rather than sight. “Our analysis of their diet shows
smelt are a very minor part, and the ones that are eaten are often
dead ones on the bottom”. Interestingly the peak in catfish
numbers in 2000 coincided with the last major peak in the trout
population, so clearly their impact then was not significant says
Glenn. |
