New Zealand Journal of Marine and Freshwater Research abstracts
Enhanced growth of longfin eels, Anguilla dieffenbachii, transplanted
into Lake Hawea, a high country lake in South Island, New Zealand
Michael P. Beentjes
National Institute of Water and Atmospheric Research Limited
P.O. Box 6414
Dunedin, New Zealand
email: m.beentjes@niwa.co.nz
Donald J. Jellyman
National Institute of Water and Atmospheric Research Limited
P.O. Box 8602
Christchurch, New Zealand
Abstract Lake Hawea was stocked with c. 9500 juvenile
longfinned eels (Anguilla dieffenbachii Gray) (mean weight 173 g)
from the lower Clutha River of which a subsample of 2010 was tagged with
coded wire tags. Three years later, the eel population in Lake Hawea was
sampled resulting in 216 recaptures of transferred eels of which 42 were
tagged. Eels had grown an average of 14 cm and 325 g (all recaptures). Growth
rate of tag-recaptures averaged 4.1 cm year-1, was linear and faster than
pre-transfer when it was 2.4 cm year-1 (P < 0.01). Eels transferred
into Lake Hawea experienced accelerated growth and increased condition ascribed
to low density (density dependent) and abundant food. Eels dispersed throughout
the lake, but density was highest adjacent to “the Neck”, the point of release.
Eels caught outside the Neck were larger and in better condition than those
inside the Neck-further evidence of density-dependent growth. Recaptured
eels examined for sex were all females, indicating that either eels differentiated
into females because density was low, or that males moved out of the lake
to more preferred habitat downstream. Tag retention was high and tagging
had no adverse effect on growth. Enhancement or stocking with longfins is
viable for low density recruitment-limited, high country lakes, but growth
is likely to be density dependent.
Keywords longfin eel; coded wire tag; density-dependent
growth; enhancement; sex ratio; dispersal
M02040 Received 31 May 2002; accepted 2 September 2002; Published 20 March
2003
New Zealand Journal of Marine and Freshwater Research, 2003, Vol. 37:
1-11
0028-8330/03/3701-0001 $7.00 © The Royal Society of New Zealand
2003
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