N.Z. MARINE DEPARTMENT-FISHERIE,S BULLETIN No. .į

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gro\Ming season ancl_ consequently a longer periocl in which effects of competition and predation would be felt. So far as available evidence of causes of losses goes, it cliscloses rro reason for sttggesting that losses in New ZeaI¿.nclshorrlcl be ar.,1ilo*er than they are elsewhere. Untii they can be repiacecl by clata arising fro¡r ol¡servations nracle rrrcler New Zealancl conditions, tl-re estimates of losses given here shoulcl be acceptecl as nìore reliaL¡le tl-ran surmises which have less factuai basis. Eviclence of loss when fry are releasecl fronr hatcheries i' New Ze¿Lla.cl is not available. Flowever, eviclerce of loss of naturallv-proclucecl fry has recentr_v been giverr here bv AIle' (194s). His data from the Horokiwi stream indicate a loss of 95 per cent. of the fry availabre in october by the foilowing January and a reduction of 2s0,000 wild fry to t or z p". ""rrt. of that quantity within val oi 1 rt 2 per cer_,t.^ roay be compared with the eariier es fry in the rrnitecl ,iiffli :ï,äi,r,r._.r:Í.rJxî1.'li:Tï Allerr shows that, rn estimated at 250,000 fry in one year, the annual yield to angrers was usuaty onry about 350 lb. of fish. Allen's clata sl.row a survival 12 months latlr of 14 per cent. of the r-ratnral yearlings present in October. Fry or F'ingerlings? In ¿Ln earlier section artificial ancl natnral propagation were coulpare
S-inch fingerlings can be pr:oducecl at betrveen four ancl eight titires the cost of fry. In Canada Nîottley (1935') fotrnd that when fry were being handled in large quantities they could be produced for about .$1.75 per 1,000. The cost of 123,000 brown trout fingerlings of 3 inches was about $24.00 per 1,000. This amount includes tl-re cost of the 170,000 fry required to give a survival of 123,000 fingerlings, the cost of foocl, wages and one-tenth of the cost of ponds required to holcl tlie fish. These fingerlings, at thre:e months, cost 13 or 14 times as much as fry. That is to say, it cost 13 or 14 tirnes as much to produce fingerlings rvhich at an or-rtside estimation could not have had more than eight times the survival expectancy of fry. As Mottley's costing is for 3-inch fingerlir-igs elrcl the survival expectancv is taken from experiments with fish of 3 to 5 inches, it seerns safe to assert that a better return to-the angler rvould be obtained by buying fry than the much smallelntrmber of fingerlings rvtrich could be produced for the salne sll1l. This conclusion is in keeping r,r,ith that of l{eedharn and Sutlrner (1941) for' brook trout of difierent sizes leleasiecl into lakes at clifferent seaso11s. Small marked fish of 2 inches mean length were released in autumn and larger fish of 5f-inches were releasecl in spring. Although over fir'e times as many o{ the large fish were taken by anglers, tl.re cost þer fslt, creeled was tl¡ree times as great in the case of the larger fish. Wales (1946) has shown with reference to fingerlings of 1.5 to 3 inches ancl yearlings of 6 to 7 inches, stocked in a Californian lake, that in the case of brown trout added costs of producing larger fish were roughly proportionate to the increase in survival value. \Mith rainbor,v ancl brook trout in the same lake an advantage was gained because the survival value of the year'lings exceeded that of fingerlings by relatively more than the costs increased. It is apparent that relative costs of production of fish of different sizes rnay vary from place to place and that the relative expectancies of life of fish of different sizes ancl of clifferent species may vary according to conditiåns offering. Present evidence does not indicate that investmsnf ç'f money on large fingerlings or yearlings, rather than on production of fry, usually results in a greater benefit to the angler, although occasionally it may do so. In this as in most other branches of fishery management there is need for strict costing of operations ancl for careful lreasurement of results if management is to be otherwise than highly speculative. ltro private citizen or- trading corporation could afford to run a business r'vith the disregard for costs and the extraordinary absence of inforrnation on results occurring {rom the investment of money r'r'hich has characterizecl the so-called management of fisheries by State Departrnents and various organizations in this collntry and in others. Fingerlings and Larger Fish in U.S.A. Grorving know'ledge of the contribution to stocks from natural reproduction, clissatisfaction with results obtained in streams frotn release of fry in New Zealand and in the lJnited States of America have led to a demand for more ancl bigger' frsh. In the United States there is no generally accepted policy in this matter. Tl-re few States r,vhere substantial proportions of the trr.¡ut for release are helcl until they reach legal size have not contributed substantially to the investigations citecl earlier, which aim at learning the value of releasing fish. On the other hand, in Micl-rigan, Fisheries bulletin (N.Z. Marine Dept.) no. 9 (1948) I 103
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.ç N.Z. MARINE DEPARTMENT-FISHERIE
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Ito -il ,A f { I { tIô i N E W ZEA
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t ta t CONTENTS Part L-Historical I
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? e CONTENTS-Continued' DNiInonuBNr
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Plate t, Text LIST OF' ÍLLUSTRATIO
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PART I Historical INTRODUCTION 1.ur
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(15)Hitherto,restrictionsonangling,
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the transference of fish and had to
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187G80-Releases of brown trout were
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have been successfully introducecl
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poltv'ef, alx1 have clisclntgecl wa
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Reference to forest fires causing h
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shadowed urater, and that the penet
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occurred fairly generally, may be n
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ö drainage has led, it is said, to
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The existing laws, which are a strr
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years ago" from the Lee. In 1883 he
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Orcti Ri 11 (St|. Is.) bct¡-een Di
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eaches of the Oreti the fish were o
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iÀr River !Vaipa.hi ....'. tt Slia
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N) \o River Lure Period 1880-18m' 1
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CHA}{GE I}f SIZE OF TROUT-SOUTH ISL
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fr) River Lure Period 1880-1890 189
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(¡ of sorle inadequacy of specific
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fallen in inverse proportion to the
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without a corresponding decrease 'o
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the Waipahi, increase in numbers bu
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\iVhile the number of anglers has i
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cent. in the smaller east and west
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Data from the special licensing are
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(Above) I)rought conditions at Quad
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PART II Recent Management of Fisher
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important sources of income in the
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v aim 'is solely one of transfer, i
Page 69 and 70: the same as the number of eggs stat
Page 71 and 72: û Exclusive of Taupo and Rotorua t
Page 73 and 74: handled where eggs are collected, a
Page 75 and 76: Í- stage.Subsequentlosses,aSgivenl
Page 77 and 78: L The reports of the Ballarat Fish
Page 79 and 80: J be seen, when abnormal losses are
Page 81 and 82: '] as -to losses in two lots of bro
Page 83 and 84: 715,000 fish distributed. This numb
Page 85 and 86: which those estimates were based an
Page 87 and 88: CONSTRUCTION OF SPAWNING REDDS OF B
Page 89 and 90: A con-iparison of losses recorded i
Page 91 and 92: to time, abnormal flooding, occurri
Page 93 and 94: It .n,otrlcl appear fronr the facts
Page 95 and 96: 'I'he fìoocl-trrcached rack in thc
Page 97 and 98: oclies has been devotecl to recorcl
Page 99 and 100: In 1935, which was a peak collectin
Page 101 and 102: of the examìnation ol 2,883 birds
Page 103 and 104: stations in the country in a year.
Page 105 and 106: fry of rainbow trout recorded as re
Page 107 and 108: Ë eggs. The "bag" of the other rvh
Page 109 and 110: (t seasons, have used stationary li
Page 111 and 112: t PART III Recent Investigational W
Page 113 and 114: LAKE ALEXANDRINA_SOUTH CANTERBURY O
Page 115 and 116: TABI-E XIX Duration of Species Size
Page 117 and 118: ti 't becoming available. The short
Page 119: - is nothing to srlggest that any s
Page 123 and 124: -ì has shown that the estimated to
Page 125 and 126: ,t Its contributiori to the èatch
Page 127 and 128: Discussion The various overseas stu
Page 129 and 130: there are fundamental biological re
Page 131 and 132: lnanagement to leave well alone anc
Page 133 and 134: f of the lakes, where, in the absen
Page 135 and 136: RIVER POLLUTION-Thc photographs ill
Page 137 and 138: If man is to improve the fertility
Page 139 and 140: excess, but to the quantity of t.he
Page 141 and 142: with incligenons forms only where t
Page 143 and 144: -È-' e tial increase of trout. Con
Page 145 and 146: here. At present, it is justifiable
Page 147 and 148: t- of fish from streams. Under tr)r
Page 149 and 150: Setti;rg an cel baskct u'hcrc it is
Page 151 and 152: It will be observed from the forego
Page 153 and 154: d as the present v/fiter has on the
Page 155 and 156: Environment Improvement-Physical LI
Page 157 and 158: (3) \A/here the deficiency of cover
Page 159 and 160: esselltial. Because, r,vith excessi
Page 161 and 162: ,.) in rivers of considerable size
Page 163 and 164: ( 1) The relative al,seuce of angle
Page 165 and 166: !r'i11 not necessarily be the optim
Page 167 and 168: fo¡gariro lìivcr-Iì¿unous rainL
Page 169 and 170: ¿> lin,it to llin. would result in
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egulations can have no general sign
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tìature of this iure nc¡r the rno
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è organization in the provision of
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larger ones. However, larger societ
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L G o 4 equitably to obtain a more
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ç o ç ,) of negative interpretati
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0 õ o paid in licence fees, can le
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I ,} o ê REFERENCES Arrrl, K. R. (
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I Jl f Neeouau, Peur, R., & Slerr*.
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J I APPENDIX A The 1941 Census of t
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!L 't ,APPENDIX B Interference with
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fl tf -ì APPENDIX C Injuries to Tr
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APPENDIX D Claims of Success of Hat
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å t.: I -'l t ta ¡ ,} f (3) Cessa
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maxirnum'density. It is possible al
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N.Z. MARINE DEPARTMENT-FISHERIE,S BULLETIN No. .į

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