New Zealand Journal of Marine and Freshwater Research abstracts

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M00012
Received 27 March 2000; accepted 18 July 2000

Factors regulating the downstream migration of mature eels (Anguilla spp.) at Aniwhenua Dam, Bay of Plenty, New Zealand

JACQUES A. BOUBéE¹
CHARLES P. MITCHELL²
BENJAMIN L. CHISNALL¹
DAVE W. WEST¹
EDDIE J. BOWMAN¹
ALEX HARO³

¹National Institute of Water & Atmospheric
  Research Ltd
 P. O. Box 11 115
 Hamilton, New Zealand
²Mitchell & Associates
 Ohautira Rd
 R.D.1 Raglan, New Zealand
³S. O. Conte Anadromous Fish Research Centre
 Biological Resources Division
 U. S. Geological Survey
 P. O. Box 796, Turners Falls
 MA 01376, United States

Abstract   The downstream migrations of mature longfinned eels (Anguilla dieffenbachii Gray, 1842) and shortfinned eels (Anguilla australis Richardson, 1848) were investigated at Aniwhenua Dam on the Rangitaiki River between 1992 and 1998. Migrants were mostly females over 1000 mm total length (TL) with otoliths indicating rapid growth rates. Migrations, which occurred on a few nights each autumn, generally began once water temperatures began to decline and ended when temperatures dropped below c.11deg.C. Rainfall and flow increases were found to be key factors triggering migration events. Rainfall exceeding a cumulative total of 40 mm over 3 days accounted for 60% of migrant eels arriving at Aniwhenua. It is proposed that such rainfall triggers could be used as predictors to instigate mitigation activities that would allow mature eels to proceed uninjured past barriers such as hydro-electric dams.

Keywords   eels; dams; fish-passage; fish migration; growth; Anguilla australis; A. dieffenbachii

New Zealand Journal of Marine and Freshwater Research, 2001, Vol. 35: 121-134

0028-8330/01/3501-0121 $7.00 (c) The Royal Society of New Zealand 2001

PDF file of entire paper: medium quality (1005K); (scanned from paper original: notes about this process)

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