Of the Lower Clutha River
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rssNo113-25o4 New Zealand Freshwater Fisheries Report No. 98 Fish stocks and fisheries of the lower Clutha River lllirlrrlrll'l I It { '.. " ,. ". .-:tùt{ !'I I )t¿¡".. ".,"..'... It tI MAFFish New Zealand freshwater fisheries report no. 98 (1988) New Zeal and Freshwater Fjsherjes Report No. 98 Fish stocks and fisheries of the lower Clutha River by Y.M. Pack D . J. Jel ìyman Freshwater F'isheri es Centre MAFFi sh Chri stch urch May i988 New Zealand freshwater fisheries report no. 98 (1988) NEl^l ZEALAND FRESHWATTR FISHERIES REPORTS This report js one of a series jssued by the Freshwater F'isherjes Centre, MAFFish, on jssues related to New Zealand's freshwater f i sherj es. They are 'i ssued under the fol I owi ng cri teri a: (1) They are for ljmited circulatjon, so that persons and organ'isations normal ly rece'ivìng MAFFish publ ications should not expect to recejve copies automatically. (2) Copjes w'ill be'issued free only to organìsat'ions to whjch the report is djrect'ly relevant. They wì11 be issued to other organi sat'ions on request. (3) A schedule of charges js included at the back of each report. Reports from N0.95 onwards are priced at a new rate whjch jncludes packagìng and postage, but not GST. Prices for Reports Nos.1-94 contjnue to jnclude packaging, postage, and GST. In the event of these reports going out of print, they wjll be reprinted and charged for at the new rate. (4) 0rganisatjons'l'ist may apply to the lìbrarian to be put on the mai I'ing to rece j ve al I reports as they are publ'ished. An invojce w'ill be sent with each new publicatjon. rsBN 0-477-08163-0 MAF Fish MAFF j sh 'is the f j sheries bus'iness group of the New Zealand Minìstry of Agriculture and Fjsheries. It was established on 1 Aprì1 1987 and combines the functions of the old Fisheries Research Division and Fisheries Management Djvision, and the fjsheries functions of the old Econom'ics Divis'ion. The New Zealand Freshwater Fisherjes Report series contjnues the Fisheries Env'ironmentaì Report series. Enquirjes to: The Li brari an Freshwater F'i sher i es Centre P0 Box 8324 Rì ccarton, Chri stchurch New Zealand New Zealand freshwater fisheries report no. 98 (1988) CONTENTS Page S ummary 8 1. I ntrod uct'i on 9 2. Methods 12 2.I Netti ng T2 2.I.I Fyke Nets 12 2.1.2 Gill Nets T2 2.1.3 Sei ne Nets 13 2.2 Trapp i n g 13 2.2.I Mi nnow Traps 13 2.2.2 F'i sh Trap T4 2.3 El ectri c F'ishi ng 14 2.4 Spawn'i ng Surveys 15 2.5 Invertebrate Sampl'i ng 15 2.5.L Grab Sampl ing 16 2.5.2 Surber SamPling 16 2.5.3 Drìft Samp'lìng 16 2.6 Ageì ng of F'ish 17 2.7 Cond i t'i on Factors 17 2.8 Di et 18 3. Ecology of Fjsh Stocks 18 3.1 Lamprey 18 3.2 Short-fìnned Eel 20 3.3 Long-fi nned Eel 20 3.4 Koaro 25 3.5 Common River Galaxias 29 3.6 Torrentf i sh 31 3.7 Common Buì 1y 31 New Zealand freshwater fisheries report no. 98 (1988) Page 3.8 Upl and Bul ly 34 3.9 Perch 35 3.10 Rainbow Trout 36 3.11 Brown Trout 4I 3.11.1 Results 42 3.11 .1 . 1 Di stri buti on 42 3 .II .I .2 Spawn ì ng 43 3.11.1.3 Juvenile Rearing 48 3.11.1.4 Age and Growth 52 3.11.1.5 Feeding 55 3.LI.2 Di scuss i on 58 3.I2 Quinnat S al mon 64 3.r2.I Lake Roxburgh Stocks 65 3.I2.2 Cl utha R'iver Stocks 67 3.r2.3 Di scussi on 7T 4. I n vertebr ates 78 4.I Benth'i c Invertebrates ìn Lake Roxburgh 78 4.2 Clutha River Tributaries 83 4.2.I Benthi c Fauna 83 4.2.2 Drift Fauna 85 5. Di scussion 85 6. Acknowl edgments 94 7. Literature Cited 95 Append'ix I . Physìcaì descrìption of sectjons jn the Tjma 105 Burn, the Benger Burn, and Carsons Stream Append'ix I I . Summary of data on whitebaìt stages of 106 I acustri ne popul at'ions of koaro Appendix III. Summary of monthly length data of juvenìle 107 brown trout from varjous sampììng sìtes jn the study area, September 1983-April i984 Appendix IV. Summary of length-frequency d'istributjon of 108 brown trout captured i n the study area New Zealand freshwater fisheries report no. 98 (1988) Page Append'ix V . Length-weight relationsh'ips for brown trout 109 captured in the study area Appendjx VI. Analysìs of stomach contents of brown trout 110 from Lake Roxburgh Appendr'x VII. Analysis of stomach contents of brown trout 113 from the Clutha River Appendix VIII. Results of salmon spawning surveys from 116 the Roxburgh Dam to Tuapeka Mouth reported in the literature TABLES 1. Catch effic'iency of giI1 nets of varying mesh size for 13 brown trout in Lake Roxburgh and the Clutha Rjver 2. Fish species recorded jn the lower Clutha R'iver study 19 area 3. Age and length of long-finned eels from Lake Roxburgh 24 4. Stomach contents of koaro 28 5. Stomach contents of common bullies 33 6 . Stomach contents of upì and bu I I i es 34 7. Mean back-calculated and direct-calculated lengths per 36 age class of perch 8. Stomach contents of ra'inbow trout 40 9. Brown trout spawnìng and presence of trout fry in Lake 44 Roxburgh and the Clutha River, Aprìl 1983-Aprì'l 1984 10. Number of spawn'ing brown trout and new redds recorded 47 f rom secti ons j n the Benger Burn, the T'ima Burn, and Carsons Stream, May-July 1984 11. Age of brown trout at fjrst spawning 48 12. Recaptures of tagged brown trout released in Lake 54 Roxburgh 13. Summary of brown trout stomach contents 56 14. Comparison of angler catch rates from the study area 59 w'ith rates from other southern South Island waters 15. Month'ly catch di stribut jon and sex rat'io of quìnnat 66 salmon from Lake Roxburgh 16. Quìnnat salmon spawnìng ìn the lower Clutha Rìver, 69 May-June 1983 New Zealand freshwater fisheries report no. 98 (1988) Page 17. Number of new quinnat salmon redds and adult salmon 70 recorded from sections in the Benger Burn, the Tima Burn, and Carsons Stream, May-July 1984 18. Age structure of wild quìnnat salmon from the lower 72 Cl utha R'iver 19. Mean lengths of anadromous quìnnat salmon from the lower 73 Cl utha Ri ver, 1960-84 20. Summary of benthjc ìnvertebrates 'in Lake Roxburgh, 79 February 1984 2I. Mean density of benthic invertebrates from B sampling B0 s j tes 'in Lake Roxburgh, February 1984 22. Di stri but'i on of benth i c i nvertebrates wi th depth i n 81 Lake Roxburgh 23. Dens'ity of invertebrates from riffles ìn the T'ima Burn, 84 the Benger Burn, and Carsons Stream 24. Density of invertebrate drjft fauna in the T'ima Burn, 86 the Beñger Burn, and Carsons Stream, 6-7 June 1984 F I GURES 1. Lower Clutha Rjver, showing samplìng sites and local'itjes 11 mentioned in the text 2. S'ites at which lampreys, short-fjnned eels' and long-finned 2I eel s were recorded 3. Growth rate of long-finned eel elvers from the Roxburgh 22 Dam 4. Length-frequency distrìbut'ion of long-fìnned eels from 23 Lake Roxburgh and the Clutha River 5. Sites at whjch koaro, common rìver ga'laxias, and torrentfish 26 were recorded 6. Length-frequency d'istrjbutjon of largest samples of 27 koaro 7. Length-frequency distributjon of common river gaìaxias 30 8. S'ites at wh'ich common bullies and upland bullies were 32 recorded 9. Growth rates of rainbow trout 'in Lake Roxburgh and the 38 lower Clutha River 10. Catch per unit effort per month of brown trout jn Lake 43 Roxburgh and the Clutha Rìver New Zealand freshwater fisheries report no. 98 (1988) Page 11. Length mean, range, and standard devjatjon of fry and 49 yearl'ing brown trout from Section 3 of Carsons Stream 12. Density of brown trout in sections of Carsons Stream, 50 November 1983-Apri I 1984 13. Densjty of brown trout fry and qu'innat salmon fry from 51 Sect'ion 2 of the Benger Burn, November 1983-Apri1 1984 14. Growth rate of brown trout in the lower Clutha River 53 15. Mean growth rate of brown trout from Lake Roxburgh, 54 compared with rates from Lakes Benmore and Coleridge and the Mataura R'iver 16. Growth rate of quìnnat salmon from Lake Roxburgh 67 17. Length mean, range, and standard devjatjon of juvenile 7I quinnat salmon from Section 2 of the Benger Burn New Zealand freshwater fisheries report no. 98 (1988) B S UMMARY This study was one of an integrated series designed to document the bìo'logicaì and physìcal resources of the lower Clutha Rjver from the Roxburgh Dam to Tuapeka Mouth, and to predìct the 'impact of various hydro-eìectrjc development options. Lake Roxburgh was jncluded jn the present study to provide an ìndjcation of the type and extent of fish stocks that might be expected to deveìop jn any downstream reservo'irs.