Selective opening of hydroelectric dam spillway gates for downstream migrant eels in New Zealand

Published source details Watene E.M. & Boubée J.A.T. (2005) Selective opening of hydroelectric dam spillway gates for downstream migrant eels in New Zealand. Fisheries Management and Ecology, 12, 69-75.
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This study is summarised as evidence for the following.

	Action	Category
	Modify operation of dams/barriers Action Link

Modify operation of dams/barriers

A study in 2000–2001 in a river in the Taranaki region, New Zealand (Watene & Boubée 2005) reported that a greater number of migrating wild longfin eels Anguilla dieffenbachii and shortfin eels Anguilla australis moved downstream past a dam when a spillway gate was partially opened compared to when it was closed, and most released eels that passed through the gate opening survived. esults are not based on tests of statistical significance. Overall, 39 wild longfin eels and 48 wild shortfin eels were caught downstream of a dam during 2.5 h when a spillway gate was partially opened, whereas 12 longfin eels and 12 shortfin eels (including eight dead) were captured during 9 h when it was closed. Seventy-two of 79 released shortfin eels (91%) survived after passing through the gate opening. Ten additional wild eels (seven longfin and three shortfin) caught alongside released eels showed no signs of injury. On 9 April 2000, a spillway gate in an 82-m high hydroelectric dam on the Patea River was opened by 150 mm from 19:30 to 22:00 h. Wild longfin (510–1,170 mm long) and shortfin eels (370–1,140 mm long) were captured 1.5 km downstream of the dam in a fyke net across the width of the river for 2.5 h during and 9 h after the gate was opened. In March–May 2001, on three occasions, tagged yellow and silver eels (18, 73 and 29 eels; 460–940 mm long) sourced from commercial fishers were released in front of the spillway gate (opened by 50–70 mm). Released eels were recaptured in a net across the base of the spillway.

(Summarised by: Vanessa Cutts)