Mokau River and Tributaries Draining the Mokau Coalfield
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lssN o1 13-2504 New Zealand Freshwater Fisheries Report No . 110 Fish and fisheries values of the Mokau River and tributaries draining the Mokau coalfield ï¡;t. 'Ll:..".! tiH::::: i'.,....'.'....'....' MAFFish New Zealand freshwater fisheries report no. 110 (1989) New Zeal and Freshwater Fjsheries Report No. 110 Fish and fisheries values of the Mokau Ri ver and tributarjes dra'inìng the Mokau coalfjeld by S.M. Hanchet J.t^l. Hayes Report to : N. Z. Coal CorPorat'ion Freshwater Fisheries Centre MAFFISH Rotoru a June 1989 New Zealand freshwater fisheries report no. 110 (1989) NEt^l ZEALAND FRESHWATER FISHERIES REPORTS This report is one of a series issued by the Freshwater Fjsherjes Centre, MAFF'ish, on issues related to New Zealand's freshwater fisheries. They are'issued under the following criteria: (1) They are for limited circulatjon, so that persons and orgàn.isations norma'l1y receiving MAFFìsh publications shóuld not expect to receive copíes automaticalìy. Q) Copies wiì'l be'issued free on'ly to organisations to whjch the report is djrect'ly relevant. They wjlì be jssued to other organ'i sati ons on request. (3) A schedule of charges is jncluded at the back of each report. Reports from N0.95 onwards are priced at a new rate whìch includes packaging and postage, but not GST. Prices for Reports Nos. t-g+- conti nue to j ncl ude packagj ng, _postage, and GST. In the event of these reports go'ing out of pfiint, they wìll be reprinted and charged for at the new rate. (4) Organisations may apply to the librarian to be put 91 the malling lìst to recejve alì reports as they are published. An jnvõice will be sent with each new publìcatjon. ISBN 0-477-08178-9 The stud i es documented 'in th i s report have been funded by N.Z. State Coalmi nes (now Coal Corporat'ion of New Zealand Ljm'ited). MAF Fish MAFFjsh is the fisheries business group of the New Zealand Ministry of Agriculture and Fjsheries. It was establjshed on 1 April 1987 and combjnes the functjons of the old Fisheries Research Division and Fisheries Management Djvjs'ion, and the fisheries functions of the old Economics Divis'ion. The New Zealand Freshwater Fisherjes Report series continues the Fisheries Environmentaì Report series. Enquiries to: The Li brari an Freshwater Fisheries Centre P0 Box 8324 Riccarton, Chrì stchurch New Zeal and New Zealand freshwater fisheries report no. 110 (1989) CONTENTS Page Summary 8 1. I ntrod uct i on 8 2. Study Area 9 2.I Mokau River 9 2.2 Awakino River 13 2 .3 Cl i mate 13 3. B'ioìogy of Freshwater and Estuarine Fish Species 13 3.1 Eels T4 3.2 Bul I i es and Torrentfi sh 14 3.3 Gal axj i ds 15 3.4 Smel t 15 3.5 Salmoni ds 15 3.6 Lamprey 16 4. Electric Fjshing Survey 16 4.I Methods 16 4.1.1 Fish Samplíng 18 4.I.2 Phys i ca'l Measurements 18 4.1.3 Data Anaìysis 19 4.2 Results 20 4 .2 .I Spec i es Compos i t i on 20 4.2.2 Classification and 0rdination 22 4.2.3 Distribution of Fjsh Assemblage Groups 22 4.2.4 Correlat'ion of Fish Assemblage Groups wìth 25 Habi tat Vari abl es 4.3 Discussion 32 5. Survey of Fjsh and Fisherjes of the Mainstem 37. 5.1 Methods 37 New Zealand freshwater fisheries report no. 110 (1989) Page 5.2 Results 40 5.2.I Sa'linìtY 40 5.2.2 Species L'ist 4T 5 .2.3 Wh i teb a'i t 4T 5.2.3.1 Fish'ing Effort 4T j 5 .2.3.2 Speci es ComPos t i on ln the 44 Mokau Ri ver 5.2.3.3 SPecies ComPos jt jon in the 47 Awaki no Ri ver 5.2.3.4 Si ze at Mi gration 49 5.2.3.5 SPawning of Inanga in the 49 Mokau Ri ver 5 .2.4 Fl ounders 52 5 .2.4.1 The Fi sherY 52 5.2.5 Kahawai 53 5.2.5.1 The FjsherY 53 5 .2.6 Mul I et 53 5 .2.6 .I The Fi sherY s3 5.2.7 Eel s 54 5 .2.7 .l The Fi sherY 54 5 .2.8 Trout 55 5.2.8.1 The FjsherY 55 5.2.9 Shellfìsh 55 5.2.10 Marine Species 55 5.3 Discussion 56 6. General Di scuss'ion 60 7. Recommendat'ions for Further [,Jork 65 8. Acknowl edgements 66 9. L'iterature Cì ted 67 Appendix I. Habjtat data sheet 7T New Zealand freshwater fisheries report no. 110 (1989) Page Appendix II. Species-abundance-by-site data matrix for 73 the electric fishìng survey of trjbutaries of the Mokau and Awakino Rivers Appendix III. Correlation of the various habitat variables 77 and de-trended correspondence analys'is (DCA) AXES Appendi x IV. Effects of preservation on whitebait 78 jmì 79 Appendìx V Results of prel nary nett'ing survey TABLES 1. Frequency of occurrence of each species jn each fish 24 as semb'l age grouP jn 2. Frequency of occurrence of fish assemblage.groups each 25 water tyÞe, land use, and rìparìan vegetation category 3. Group means (+ S.E.) for the five environmental variables 27 used jn the multiple discrìminant analys'is for sjtes belong.ing to each of the four ISA fìsh assembìage groups and fõr [he group of sites where fjsh were absent 4. Standard'ised canonical coefficients of discriminant 28 functions generated to djscriminate between (¿) the four ISA físh assemblage groups and (b) the'four ISA fish assemblage groups and the "fjsh absentr¡ group, us'ing fjve envjronmental vari ables 5. The number and percentage of the 96 sjtes class'ified the four ISA fish ássemblage groups by mu'ltipìe into jronmental d ì scrimi nant ana]ys'is on f i ve env vari ables 6. The number and percentage of 115 sites class'ified into 32 the four ISA fish assem6lage groups and the "fish absent" group by multipìe discrjmjnant ana'lys'is on fi ve environmental vari ables 33 7 . 0bserved and expected frequenc'ies and standard'ised residuals of sìtes from the four ISA fish assemblage groups in three categories of land use jts 8. Specìes of fìsh caught in the Mokau Rjver and 42 tributaries 9. Headcounts of whitebaiters on the Mokau River at 43 weekends and on weekdaYs 10. Estimated fjshing effort on the Mokau River whjtebait 43 f ì shery 11. Seasonal composit'ion of the whjtebajt catch jn the 45 Mok au and Awak i no R'i vers ' 1986 New Zealand freshwater fisheries report no. 110 (1989) Page 12. Mean ìength to caudal fork of each whitebait spec'ies 49 at mjgration for the Mokau and Awak'ino Rivers 13. Fisheries of the Mokau River 57 FI GURES 1. The Mokau and Awakjno Rjver systems 10 2. Locat'ion of electric fishing sites on the Mokau and 17 Awaki no Ri ver tri butaries 3. Frequency of occurrence of fish specjes jn trjbutaries 2T of the Mokau and Awak'ino Rivers 4. Percentage composjtjon of fjsh species caught 'in 27 tributaries of the Mokau and Awakino Rivers 5. Dendrogram from the ISA class'ificat'ion showing 23 indicaior species and relationsh'ips between the four fish assemblage groups 6. 23 analysis (ISA) 7. Geographi caì d'i strj butj on of fi sh assembl age groups 26 8. Posjt'ion of the "means" of the four ISA fjsh assemblage 29 groups jn discrjminant space, obtained by muìt'ip'le ðisciiminant analysis on five environmental variables 9. Position of the "means" of the four ISA fjsh assemblage 31 groups and the "fish absent" group in djscriminant space, õUtained by multjple discrjminant analysis on five environmental vari ables 10. Netting ìocations on the lower Mokau Rjver durìng the 38 f isheries survey 11a). Combined daìly catch of two whitebaiters fjshìng 46 the Mokau River, 1986 11b). Seasonal variatìon in the percentage composition of 46 the whitebait catch from the Mokau Rjver' 1986 LZ. Seasonal distribut'ion of Galaxias maculatus and 44 G. fasciatus in the whíteffi Mokau RîVer,T986- 13a). Da'i'ly catch of one whiteba'iter fìshing the Awakjno 48 Ri ver, 1986 New Zealand freshwater fisheries report no. 110 (1989) Page 13b). Seasonal variatjon 'in the percentage compositjon of 48 the whitebait catch from the Awakino Rìver, 1986 14. Seasonal d'istribution of Galax'ias maculatus and 47 G. fasciatus 'in the whiteffi Ãwakino Ri-ver, 1986 15. Length frequency djstrjbutjons and mean lengths 50 of tfre three main whitebait specìes (Mokau and Awakino Rivers combined) 16. Seasonal variation in the mean s'ize of Galaxias 51 maculatus whjteba'it jn the Mokau and Awakjno R'ivers, 1986 17 . I,Jei ght-'length rel atìonships for three whitebait species 51 from the t'lókau and Awak'ino Rivers (combined), 1986 New Zealand freshwater fisheries report no. 110 (1989) I SUMMARY 1. Fourteen species of freshwater fjsh have been recorded from trjbutaries of the Mokau and Awak'ino Rivers, and at least two more are 'likely to be present. Although thìs number compares favourably with other North Island rivers, at the sjte leveì, spec'ies diversìty and species abundance are generaìly ìow. 2. Fish distribut'ion in trìbutaries of the Mokau River was associated wjth djstance from the sea, gradient from the river mouth, substrate coarseness, land use, and, to a lesser degree, wjth water velocìty and depth.