MAF Brown and rainbow trout spawning migrations in tributaries of the lower Waitaki River, 1981 - 1983 ISSN 0113 -2504 New Zealand Freshwater Fisheries Report No. L25 Brown and rainbow trout spawning migrations in tributaries of the lower Waitaki River, 1981 - 1983 by M.IV. Webb RG. Dungey E. Graynoth Report to Electricorp Freshwater Fisheries Centre MAF Fisheries Christchurch Sewícíng freshwater fisheries and aquaculture May 1991 NEW ZEALAND FRESHWATER F'ISIIERIES REPORTS This report is one of a series issued by the Freshwater Fisheries Centre, MAF Fisheries. The series is issued under the following criteria: (1) Copies are issued free only to organisations which have commissioned the investigation reported on. They will be issued to other organisations on request. A schedule of reports and their costs is available from the librarian. (2) Organisations may apply to the librarian to be put on the mailing list to receive all reports as they are published. An invoice will be sent for each new publication. ISBN 0-477-08426-5 Edited by: S.F. Davis The studies documented in this report have been funded by the Electricity Corporation of New Zealand Limited. MINISTRY OF AGRICULÏURE AND FISHERIES TE MANATU AHUWHENUA AHUMOANA MAF Fisheries is the fisheries business group of the New Zealand Ministry of Agriculture and Fisheries. The name MAF Fisheries was formalised on 1 November 1989 and replaces MAFFish, which was established on 1 April 1987. It combines the functions of the former Fisheries Research and Fisheries Management Divisions, and the fisheries functions of the former Economics Division. T\e New Zealand Freshwater Fßheries Repon series continues the New Zeal.and Ministry of Agriculture and Fßhertes, Fisheries Environmcntal Repon series. Enquiries to: The Librarian Freshwater Fisheries Centre MAF Fisheries PO Box 8324 Riccarton, Christchurch New Zealand CONTENTS Page SUMMARY 1. INTRODUCTION 5 2, STUDY AREA 5 2.t Hakataramea River 5 2.2 Maerewhenua River 5 2.3 Welcome Stream 7 3. METHODS 7 4. RESULTS 8 4.I Size of the Annual Spawning Runs 8 4.2 Timing of the Brown Trout Spawning Migration 9 4.3 Timing of the Rainbow Trout Spawning Migration 12 4.4 Length of Brown and Rainbow Trout L2 4.5 Condition Factor 15 4.6 Sex Ratios, Maturity, Fecundity, and Number of Ova Deposited 15 4.7 Age aud Growth I7 4.8 Movement and Survival T7 5. DISCUSSION T7 5.1 Size of Spawning Runs T7 5.2 Length and Condition Far;tor T7 5.3 Sex Ratios 18 5.4 Survival Rates of Trapped Trout 19 6. IMPLICATIONS FOR POWER DEVELOPMENT 20 7. ACKNOWLEDGEMENTS 20 8. LITERATURE CITED 20 F reshwater Fisheries Centre Page TABLES 1. Factors influencing the number of brown and rainbow trout trapped in the Hakataramea and Maerewhenua Rivers and Welcome Stream from 1981-1983, and estimated size of runs 2. Number of brown and rainbow trout trapped in the Hakataramea and Maerewhenua Rivers and Welcome Stream, 1981-1983 3. Potential number of eggs deposited by the estimated average run of brown and rainbow trout in the T6 Hakataramea and Maerewhenua Rivers 4. Mean lenglh of repeat spawning trout at initial tagging, and growth rate per year (365 days) between L6 tagging and recapture 5. Tagged fish recaptured in traps one yeår later and caught by anglers in the season after release l8 6. Estimated size of brown and rainbow trout spawning migrations in the Waitaki River system t9 7. Mean length, condition factor, and sex ratio for brown and rainbow trout trapped in the Waitaki 19 system FIGI]RES 1. The lower Waitaki River and its tributaries, showing localities mentioned in the text 6 2. The Welcome Stream trap site, June 1982 7 3. Plan of wire mesh fish trap 8 4. Number of brown and rainbow trout captured per day in the Hakataramea River trap, 1981-1983 l0 5. Number of brown and rainbow trout captured per day in the Maerewhenua River trap, 1981 and l1 1982 6. Number of brown trout captured per day in Welcome Stream trap, 1981 and 1982 t2 7. Number of trout captured per day, mean water temperature, and mean daily flow during the 1982 t3 spawning run in the Hakataramea River 8. Number of trout captured per day, mean water temperature, and mean daily flow during the 1983 t4 spawning run in the Hakataramea River 9. Length frequency of male and female brown and rainbow trout captured in the Hakatarameå ttap, L982 r5 and 1983 10. Changes in mean length of brown and rainbow trout trapped in the Hakataramea and Maerewhenua 16 Rivers and Welcome Stream, 1981-1983 11. Changes in the condition factor of brown and rainbow trout trapped in the Hakataramea and t6 Maerewhenua Rivers and Welcome Stream, 1981-1983 Freshwater Fisheries Centre SI]MMARY and fisheries (Graynoth er al. 1981, Graybill et al. 1988). Since 1979, investigations have been undertaken into the Little was known of the value of the tributary streams potential impact of a major power development scheme as spawning grounds for the river's brown and rainbow on the fish stocks and fisheries of the lower Waitaki trout stocks. Therefore, during their spawning River. This report describes studies on the brown trout migrations, wire-mesh barrier traps were placed in the Hakataramea (Salmo mtna) and rainbow trout (Oncorhynchus tttykßs) two major lower Waitaki tributaries, the and Rivers, and a minor tributary, spawning runs into the two major tributaries of the Maerewhenua in Welcome Stream. lower Waitaki, the Hakataramea and Maerewhenua Rivers, and into a minor tributary, Welcome Stream. The purpose of the study was to determine the number of trout spawning in these tributaries so that their Brown trout spawning runs were estimated at about 390 importance to the present Waitaki River and to the fish in the Hakataramea,2TO in the Maerewhenua, and proposed residual river could be a.ssessed. The 150 in Welcome Stream. Rainbow trout runs averaged opportunity also was taken to tag trout and to collect 170 the Hakataramea, and 90 the Maerewhenua. in in information on the timing of the runs and on the length, weight, condition factor, fecundity, and movements of The main runs of brown trout into the tributaries the trapped fish. occurred in May, whereas rainbow trout entered in August and September. Males of both species tended to arrive in the tributaries before the females. The time 2. STT.JDY AREA lag between the sexes was greater for rainbow than for brown trout. Brown trout spawning runs into the tributaries began earlier and lasted longer the fi¡rther 2.1 llakataramea River upstream that the tributary was situated. The Hakataramea is the largest tributary of the lower Hakataramea trout generally were larger than Waitaki River, its confluence being approximately 65 Maerewhenua and Welcome Stream trout. Brown trout km from the Pacific Ocean (Fig. l). It is about 60 km were larger than and males were larger rainbow trout, long, and has a mean annual flow of 6.0 m3/s. Pasture than females. The condition factor was higher for and tussock are the predominant bank vegetation, females than for males. The sex ratio for both species together with willow (Salix spp.) and matagouri of trout was nearly l:1. (Dßcaria toumatou). Both species had high mortality after first spawning. The Hakataramea is an important spawning stream for The rate was particularly high for rainbow trout. quinnat salmon (Oncorþnchus tshawytschø), rainbow Repeat spawners comprised 5.8Vo of the brown trout trout (O. nUkßs), and brown trout (Sabno trutta), and and, 2.6% of the rainbow trout runs. All repeat it supports a small population of brook char (Salvelinus spawners returned to the tributary in which they had fontinalis) in a headwater stream. Two species of bully previously spawned. (Gobiomorphus cotüianus and G. breviceps), one species of æl (Anguilla diefenbøchií), two species of The conservation of rainbow trout stocks in any future galaxiid (Galaxias brevipinnß and G. wlgark), and the residual river, constructed as part of the proposed lamprey (Geotria australß) also are present in this river power development scheme, will depend upon access system (FFC unpublished data). to, and the maintenance of, adequate flows in the Hakataramea and Maerewhenua Rivers. 2.2 Maerewhenua River I.. INTRODUCTION The Maerewhenua River is the second largest tributary of the lower Waitaki River, with its confluence at Duntroon, about 36 km from the sea (Fig. 1). It has a The Waitaki River is alarge, braided river on the e¿st mean annual flow of 3.4 m3ls and is about 4O km in coast of the South Island, with a mean annual flow of length. The dominant vegetation cover in the upper 364 rÑls. Since 1979, staff of the Freshwater Fisheries catchment is snow tussock (Festuca spp.). In the lower Centre (FFC) have investigated the potential impact of reaches, riparian vegetation includes willow, gorse a major power development scheme on its fish stocks (UIu europaeus), and broom (Clsrl,szs scoparius). Freshwater Fisheries Centre FIGTIRE 1. The lower Waitaki River and its tributaries, showing localities mentioned in the text. Freshwater Fisheries Centre 3. METHODS Brown and rainbow trout are found throughout most of the river. Native fish include the six species found in the Hakataramea River, together with torrentfish From 1981 to 1983, traps were located in each of the (Ch eirnnnichtþ s fo s t erl . three tributaries described above, at various distances upstream from the Waitaki River. In 1981, traps were placed about 500 m upstream on the Hakataramea 2.3 Welcome Stream River, about 7 km upstream on the Maerewhenua River, and I km upstream on Welcome Stream (Fig. 2). 1982, the Maerewhenua trap was moved 3 km This small, stable, side stream of the lower Waitaki lî downstream.