New Zealand Journal of Marine and Freshwater Research abstracts

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Seasonal arrival patterns of juvenile freshwater eels (Anguilla spp.) in New Zealand

D. J. JELLYMAN

National Institute of Water & Atmospheric
 Research Ltd
P. O. Box 8602
Christchurch, New Zealand
email: d.jellyman@niwa.cri.nz

B. L. CHISNALL

National Institute of Water & Atmospheric
 Research Ltd
P. O. Box 11 115
Hamilton, New Zealand

M. L. BONNETT
J. R. E. SYKES

National Institute of Water & Atmospheric
 Research Ltd
P. O. Box 8602
Christchurch, New Zealand

Abstract  The arrival season of glass eels of both New Zealand species of freshwater eel, the shortfinned eel (Anguilla australis (Richardson)) and the longfinned eel (A. dieffenbachii (Gray)), was studied by electric fishing of 13 streams/rivers throughout east and west coasts of both North and South Islands at 14-day intervals. Sites were usually located at the most downstream riffle exposed at low tide, and sampled by single-pass electrofishing. The species composition was dominated by shortfins, with exceptions being west coast sites, one in the North Island and two in the South Island. From a comparison of species proportions in adjacent catchments, it was concluded that glass eels make choices about entry in particular water-types. As the stage of pigmentation advanced during the arrival season, "early stage" glass eels were defined and densities of these compared to show seasonal arrival patterns--densities were generally low in August, highest in September-October, and declined during November-December. Patterns of arrival varied from almost continuous in some streams to "intermittent" in others. Longfinned glass eels preceded shortfinned glass eels, and probably arrived in the North Island before the South Island; shortfinned glass eels showed the opposite trend. Possible migration routes to New Zealand are discussed.

Keywords  glass eels; arrival times; pigmentation; riffles; species proportions

M98073
Received 2 October 1998; accepted 9 December 1998

PDF file of entire paper: medium quality (878K); (scanned from paper original: notes about this process)

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