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

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\tLrT)t)\- ( Ill,_ I,lK ( Lalic .\lcxanclrina-Soutlr Cautcrbrrr."' l)istrict). ()rc.i t*'o s¡rztu'rrirrg trib,tzLrics of r¿rinl-¡orr. trout c'tcri.g Lali(., Âlcxa'dri.a frorrr rl'hich cggs lravc I¡ccn collcctctl for hatchirrg ar
It will be observed from the foregoing records that the foocl of the large black shag varies according to the food available u,here it chooses to feecl; cloubtless, a wider range of foods would be shown if material was collected froll salt water. To what extent it selects or shows preference for special foods of those available where it chooses to feed is not known, except that generally fisli of one kind or another comprise the bulk of its food. Present eviclence simply shows that it feeds on such food as is available. There is no eviclence that it chooses certain areas because of the abundance of any particular kincl of fish or that its distribution is even principally governed by considerations of abunclance of food in general. The bird is knor,vn to nest and roost especially on cliffs on the sea coast and in trees overharging or near streams or lakes inlancl. Suitable cliffs are found only on parts of the coast, for example, round Banks Peninsula, and suitable inland sites vary in local abundance. It is not known whethel there are seasonal changes in the feeding grouncls of the coastal ancl inlancl colonies, to what extent inter:change and recruitment of one stock from the other takes place, or, indeed, whetl-rer cólonies remain, throughout the year, sufficiently distinct to vl'arrant separate consideration. To sum up the eviclence as regarcls the l{orth Island and Marlborough and Car-rterbury in the South Island, it is clear that a general condemnation of the black shag is unwarrantecl. The bird is shown to feed largely on trout in inland waters which contain trout, and largely on eels in shallow lakes and lagoons. A mixed cliet in r,vhich trout, eels, flounders, and mullet are conspicuous is taken in some tidal waters. The shag is not sho'rvn to be beneficial in any way to trout fisheries, for the only eels consurled, which were specifrcally identified, were of the shortfinned species (Falla and Stokell-Lake Ellesmere material). This species is not known to attack trout. It is 'Lrsually of a more suitable size for shags to eat, ancl is the numerically don-rinant eel at Lake Ellesmere and in the lower Waikato basin ancl generally in coastal lagoons and sluggish ticlal reaches of rivers, u,here shags have been reported most frec¡rcntly to take eels. The evideuce, so far as it extends, suggests that, on inland waters in tl-re parts of ldew Zealancl uncler discussion, the black shag is harmÍul rather than beneficial to trout fisheries. Too little is known o{ tl-re total number of bircls freciuenting inland lvaters to enable the significance of their depredations in lrlelv Zealand r¡iaters generally to be assessecl. Falla ancl Stokell cliscuss numbers of bircls in the <strong>No</strong>rth lsland and in Marlborough ancl Nelson. The numbers reported to ther-n lîay or may not be correct, ltut in the aggregate they suggest that the black shag is greatly less abundant inland than is suggested by annual reports of the Department of Internal Affairs. Reports for the four years ended March , 1941, show that the mean annual number of shags destroyecl in the Taupo and Rotorua districts was 1,311. Thereafter the total fell, at a time when ammunition was difÊcult to procure and most able-bodied men were in the armecl services. Reports from acclimatization societies do not usually give clear statements of.the numbers of shags destroyed and places lvhere thel' were killecl. More often they give the amount spent on bounties, sometimes without speciflcation of the amounts for different predators and often without clear statements as to numbers clestroyed by their staffs. Evidence of the feeding habits and local abundance of the large black shag in fresh waters in the southern half of the South Island is given by Williams (1945). Fisheries bulletin (N.Z. Marine Dept.) no. 9 (1948) ltze
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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
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the same as the number of eggs stat
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û Exclusive of Taupo and Rotorua t
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handled where eggs are collected, a
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Í- stage.Subsequentlosses,aSgivenl
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L The reports of the Ballarat Fish
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J be seen, when abnormal losses are
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'] as -to losses in two lots of bro
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715,000 fish distributed. This numb
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which those estimates were based an
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CONSTRUCTION OF SPAWNING REDDS OF B
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A con-iparison of losses recorded i
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to time, abnormal flooding, occurri
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It .n,otrlcl appear fronr the facts
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'I'he fìoocl-trrcached rack in thc
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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 and 120: - is nothing to srlggest that any s
Page 121 and 122: S-inch fingerlings can be pr:oducec
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: Setti;rg an cel baskct u'hcrc it is
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
Page 171 and 172: egulations can have no general sign
Page 173 and 174: tìature of this iure nc¡r the rno
Page 175 and 176: è organization in the provision of
Page 177 and 178: larger ones. However, larger societ
Page 179 and 180: L G o 4 equitably to obtain a more
Page 181 and 182: ç o ç ,) of negative interpretati
Page 183 and 184: 0 õ o paid in licence fees, can le
Page 185 and 186: I ,} o ê REFERENCES Arrrl, K. R. (
Page 187 and 188: I Jl f Neeouau, Peur, R., & Slerr*.
Page 189 and 190: J I APPENDIX A The 1941 Census of t
Page 191 and 192: !L 't ,APPENDIX B Interference with
Page 193 and 194: fl tf -ì APPENDIX C Injuries to Tr
Page 195 and 196: APPENDIX D Claims of Success of Hat
Page 197 and 198: å t.: I -'l t ta ¡ ,} f (3) Cessa
Page 199 and 200: maxirnum'density. It is possible al
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N.Z. MARINE DEPARTMENT-FISHERIE,S BULLETIN No. .į

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