New Zealand Journal of Marine and Freshwater Research abstracts
Factors influencing juvenile eel (Anguilla spp.) survival in
lowland New Zealand streams
E. Graynoth
National Institute of Water and Atmospheric and Research
Limited
P. O. Box 8602
Christchurch, New Zealand
email: e.graynoth@niwa.co.nz
R. I. C. C. Francis
National Institute of Water and Atmospheric and Research
Limited
Private Bag 14901
Wellington, New Zealand
D. J. Jellyman
National Institute of Water and Atmospheric and Research
Limited
P. O. Box 8602
Christchurch, New Zealand
Abstract Factors influencing the survival rates of
juvenile longfin (Anguilla dieffenbachii) and shortfin
eels (A. australis) (<400 mm total length) were investigated
in three lowland New Zealand streams to manage and conserve eel stocks
and fisheries. A survival model which included terms for recruitment,
growth, up-stream movement, and vulnerability to sampling was fitted to
3 years of field data using a maximum likelihood approach. The
proportion of 0+ glass eels of either species that survived to 400 mm
in length was highly variable and ranged from 0.02% to 20% in different
streams. Juvenile longfins generally had higher annual survival rates
(0.78–0.96) than shortfins (0.43–0.90). Small eels (<150 mm)
experienced low and variable survival rates (0.41–0.99) and although
survival rates increased (0.80–1.00) for intermediate sized fish
(150–299 mm) they then declined (0.23–0.85) for large juveniles
(300–399 mm). The decline in survival rates for large juvenile eels
supported a habitat bottleneck hypothesis and was possibly caused by
competition from adult eels for limited areas of suitable cover (bank
cover and debris clusters), although competition for food may also have
been important.
Keywords habitat bottleneck hypothesis; maximum
likelihood survival model; population dynamics; growth; recruitment;
migration
New Zealand Journal of Marine and Freshwater Research,
2008, Vol. 42: 153–172
0028–8330/08/4202–0153 © The Royal Society
of New Zealand 2008
M07120; Online publication date 29 April 2008
;
Received 11 December 2007; accepted 10 March 2008
PDF file of entire paper: Print-quality
(672K) | screen-quality (588K)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
