FISH AND FISHERY VALUES

OF THE RAKAIA RIVER:

A PRELIMINARY RTPORT

BY

SALLY DAVIS

FISHERIES ENVIRONMENTAL REPORT NO. 2

N.Z. MINISTRY OF AGRICULTURE AND FISHERIES

CHRI STCHURCH

SEPTEMBER r979 FISI.IERIES ENV IRONMENTAL REPORTS

This report is one of a series of reports issued by Fisheries Research Division on important issues related to environmental matters. They are issued under the following criteria:

(1) They are informal and should not be cited wi thout the author's permission.

(2) They are for limited circulation so that persons and organisations normally receiving Fisheries Research Division publications should not expect to rece'ive copies automatica'11y.

(3) Copies will be issued in'itia'lly to organisations to which the report is directly relevant.

(4) Copies wiì1 be issued to other appropriate organisations on request to Fisheries Research Division, Ministry of Agriculture and Fisheries, Private Bag, Christchurch. (5) Tl.re¡e reports wì1.l be issued where a substantial report is requìred with a time constraint, e.g. a submission for a tribunal hearing. (6) They wi'll also be issued as interim reports of on-goìng environmental studies for which year by year or intermittent reporting is advant- ageous. These interim reports will not preclude formal scientific pub'licatjon. CONTENTS

Pàge

1. Introduction 1

2. Fish Resource 2

2.7 Native Fish 2

2"L"7 Migratory SpecÍes 4

(i) Estuarine specìes 4

Rhombosofea retiaria 4

GaJaxias macuLatus 4

(ii ) Lower river resjdents 5

Retropinna retropinna 5

Stokel-l-ia anisodon 6

Gobiomo rphus cotidjanus 6

(iii) 0thers 7

Geotria aust,ral-is 7

AnguiJJa dieffenbachjj ônd A. austral-is 9

Gafaxias brevipinnis 10

Cheimar richthg s fosteri 11

Gobiomorphus hubbsi 72

2.7.2 Non-Migratory Species 12

Gal-axias vulgaris I2

GaL ax i as pauci spondg Jus 13

GaLaxias prognathus 13

Gobiomorphus breviceps 13

2.2 Introduced Fi sh L4

Oncorhgnchus t shawgtscha t4

SaTmo gairdnerii ?I

Sal-mo trutta 2T

Sal-veJ- inus fonti na Li s 24

3. Food and Feeding of Fish With Particular Reference to 25

the Benthic Fauna Pagq

3.1 Factors Affectjng Invertebrate Distribution 26

J.L Effect of Reduced Fl ows 26 3.3 Rakaia Invertebrate Studies 28

3.4 Food l-labits ôf F'ish 30

3.4.1 Native fi sh 30

Gal-axias macuTatus 30

Rhonbosol-ea retiaria 31

Retropinna retropinna 31

StokeLLia anisodon 31

Gobionorphus coti di anus 31

Geotria ausÈra-7.is 32

AnguiTTa dieftenbachij âlld ¿. austraJ.js 32

Gafaxias vuTgatis 32

Cheimarrichthgs fosteri and Gobiomorphus hubbsi 32

Gobiomo r phu s brev i ceps 33

3.4.2 Introduced fi sh 33

Salna gairdnerii 33

SaLmo trutta 33

Oncorhgnchus tshawgt s cha 34

4. Util isation of the Resource 34

4.1 Recreational Fi shing 34

( j ) Trout 35 (i'i ) Sal mon 35

(iii) l,lhitebait 36

('iv) 0ther species 37

4.2 Commercial Fi shing 38

(j) Eels 38

(ji) Salmon 39

(iii) Kahawai 40

5. Di scu ss i on 40 6. Acknowl edgements

7. Literature Cited

1. Rakaia River system.

Patterns of majn migrations of fish'inhabitìng 42 the Raka'ia River system.

1. F'ish species inhabiting the Rakaia River.

2. Age structure of quinnat salrnon returns to 15 Gl enarì ffe.

Numbers of adul t salmon entering Glenariffe 77 Stream 1965-1981

4. Incidence (%) of scale nucleus types from the Rakaia River.

1.

1. I NTRODUCTION

Proposals for two irrìgation schemes and hydro-electric power generation exist for the Rakaia River downstream of the gorge.

Construction of the Lower Rakaia (Pendarves) Scheme is proposed to commence in late 1981 - early 1982, and Fisheries Research Div'ision

(FRD) understands that a water right for between 25-35 cumecs (l^J.J. Lewthwaìte, pers. comm.) will be applied for th'is year (1979).

However, at this stage (September 1979) the Ministry of l¡Jorks and

Development are unable to state exactly how much water will be appì'ied for.

The main consideration for the river inhabitants will be the effects of reduced flows due to water abstract'ion during the irrigation season (September 1 - Aprì1 30). The question we, as fìsheries b'io'logìsts, are beìng asked to answer is "how much water can be abstracted from the Rakaia River before the existìng fishery is affected?" This impl'ies that there is a minimum flow wh'ich will maintain all fish species and also tends to cons'ider only the introduced specìes which are fished for by anglers" It overlooks the periodic high flows necessary to move bed load and flush out sediments (Stalnaker undated). It also ignores the dynamic nature of fjsh populations and the long-term recovery requirements of stream biota after a severe drought (i.e. a l-in-10-year event)" The stress conditions associated with the 1-in-lO-year low flow should under no circumstances be permìtted to become the norm.

Stalnaker (undated) noted that aquatic ecology is more a descriptive science with a relativeìy recent and meagre theoretical basis for system simulation and prediction. Any hope that the aquat'ic eco'logist will be able to quantify the gaìns and losses in terms of number of fish produced in relation to any f'low regime is unfounded. Information on the timing of stream flows and the distribution of 2. hydraulic characteristics (depth and velocity) jn a stream are not sufficient to descrjbe fjsh production. To quote Stalnaker (undated) "until the physical scientists have developed predictive tools capable of describing changes in substrate distribution and channel form at the microhabitat level, the predictable quant'ification of the stream flow - fish production relationshìp under changing condit'ions will not be possible".

The Rakai a Ri veri s typical of Canterbury r j vers, bei ng characteri sed by a wìde, braìded, shingle bed. The braided nature of the river makes quantification of res'idual flows even more difficult. The distribution of water within the river bed under abstraction regimes also needs to be known and the nature of the changes in water distribution imposed by f'loods and freshes described. Until thjs is done, it ìs virtually impossible to describe the effects of the proposed abstraction of 25-35 cumecs of water on the fish populations of the Raka'ia River.

In thi s prel im'inary report, the f ish inhab'itants of the Rakaia River are described and their life histories, as far as is known, briefly discussed. The benthic invertebrates and their importance as fish food organisms are described and finalìy the recreational and commercjal values of the fish resource briefly outljned.

2. FISH RESOURCE

Table 1 lists the fish presently known to inhabit the Rakaia River system, with their scientific and common names.

2.T NATIVE FI SH Native fish resident'in the Rakaia River can be divided into migratory and non-m'igratory species. All the migratory species require passage at some stage of their life hìstory as well as habitat within the river itself. 3.

TABLE 1. Fish species inhabiting the Rakaia River.

(i ) ESTUARTNE SPECTES

* Gal-axias macufatus I nanga

Arripis trutta Kahawai

Al-drichetta forsteri Yeì 1 ow-eyed mul I et * RhombosoLea retiaria Black flounder

(ii) L0WER RrvER RESTDENTS * Retropinna retropinna Common smel t * StokeLfia anisodon Stokel I 's smel t

* Gobiomorphus cotidianus Common buì 1y

(iii) 0THERS (prsTRrBUTr0N frtAy BE RESTRTCTED)

* Geotria austraLis Lamprey

* AnguitJa d.ieffenbachii Longfinned eel

* anguiTTa ausÈra-Zjs Shortfinned eel

* Gafaxias brevipinnis Koaro

GaLaxias vuJgaris Common river galax.ias Gal,axias paucispondglus Alpine galaxias

GaLaxÍas prognathus Longjawed galaxias

* Sal-mo gairdnerii Rainbow trout

** salmo trutta Brown trout

* Sal-vel-inus fontinal-is Brook char ** oncorhgnchus tshawgtscha Quinnat salmon

* cheimarrichthgs fosteri Torrentfi sh x Gobiomorphus hubbsi Bluegilled bully Gobiomorphus breviceps Upland bul'ly

* Migratory species

+ Introduced species 4.

2.I.I l'ligratory Speci es

Those fish w'ith a migratory stage in their life cycle are marked

with an asterisk in Table 1.

(i) Estuarine Species

0f the estuarine species listed in Table 1, kahawai and yellow-eyed mullet are primarily marine. Both are known to enter river estuarjes on the rising tide, often in shoals" However, spawning and rearing of juveniles js marine in both species,

RhombosaLea retiaria The black flounder is the only spec'ies of flatfìsh which lives in estuarjes and enters freshwater. (The remaining ten species of flatfish

known from New Zealand waters are entirely marine (Manikiam 1969)). The

biology of the black flounder has not been studied, and nothing ìs known of its reproductìon. However, in most flounders the eggs are found free-floating in the surface waters of the sea and McDowall (19i8) suggested the black flounder does not enter freshwater untjl after

metamorphosis of the juvenile to the bottom-dwelling form. s.p. Hawke (pers. comm.) has observed juveniles moving into the Rakaia Lagoon in

0ctober and November.

Gal-axias macuLatus The inanga'is the best known of the species of Gataxias and its

iuvenile is the most important species in the whitebait catch. The inanga

is unusual amongst galaxiids in that the adults are found in shoals. The shoals occur mostly in open, genily flowing or still water, such as in the 'lagoon. The life history is quite well known (McDowall 196g). Gat_axias macuLatus matures during its first summer in freshwater, and the r-ipe adults migrate downstream to the river estuaries, usually in the autumn, aìthough breeding has been recorded from September until June. These migrations coìncide with the full and new moons, and thus w'ith the very high spring tides that occur on these phases of the moon. Spawn'ing takes 5. place at full tide. During the very high sprìng t'ides, the water in the estuaries floods across grasses and rushes on the river banks and the shoals of fish swim amongst the vegetation and spawn there. When the tide falìs, the eggs are washed down amongst the bases of the grasses where they remain, out of the water. However, the dampness of the grasses keeps the eggs moìst and prevents them from drying out. The eggs usually develop within two weeks and hatch upon immersion at the next spning tìde cycle"

The tiny larvae (7-8 mm jn length) are washed into the estuary and flushed out to sea as the tide fal'ls. Very lìttle is known of thejr life in the sea" When they migrate into freshwater as the familiar whitebait, the fish are about six months old and average 50-55 mm in'length. The peak migration period is usually between August and November, although a few migrating fish are found throughout the year.

Inanga have a maximum fife span of three years although near'ly all the adults die after spawning at one year o1d. However, Burnet (1965) found that some fish may delay spawn'ing untìl they are two years o'ld and a very few may delay until they are three yeans old.

('ii ) Lower Ri ver Residents

Stokell's smelt, common smelt and the common bul'ly are migratory species whose adults m'igrate upstream a few kilometres from the mouth, as opposed to the estuarine residents discussed above.

Retropinna retropinna

Common smelt (also known as silvery or cucumber) is anadromous, migrating upstream from the sea to spawn from early spring, over the summer until sometime in autumn. The spawning site is not known but McDowall (1978) stated that it is thought to be in or near estuanies, where the fertilised eggs sink to the substrate. The eggs develop there 6.

and when they hatch the tiny larvae are apparently washed out to sea. Nothing is.known of their life at sea. Four types of upstream migrants are known to occur (McDowall I972)z

(a) Immature one year olds, 45-60 mm in length m'igrate upstream, 'in spring, on the rìsing tide. These migrants are not present in all rivers, and it is not known if they occur in the Rakaia.

(b) Immature two year olds, 66-83 mm in length.

(c) Mature two year o'lds, 70-90 mm in'length, most of which die after

spawni ng .

(d) Mature three year olds, 100-120 mm in length. These fish are probably the survivors of the previous year's spawning and/or those whìch mìgrated as jmmature two year olds, and/or those which did not migrate at all unt'il the third year"

Stokel-l-ia anisodon The bioìogy of Stokell's smelt was studied by McMillan (tgOt) at the Rangitata River mouth. There is no reason to believe the population of the Rakaja River is different. Large shoals migrate jnto the rjver mouth from November-February, although the spawning season extends from

September to Apri 1 .

The fish migrate through the estuary into freshwater and spawn in silt-bottomed reaches where there is ljttle current. The eggs develop on the river bottom and the larvae hatch after two to three weeks. The larvae are washed out to sea, and nothing'is known of their life history unt'il the adults mature, probably at about two years old, and migrate back into the rivers to spawn. As far as is known, a'l'l the adults die after spawning (McDowall 1978).

Gobiomorphas eotidìanus

The common bul'ly spawns in spring and summer. The males become 7.

strongly territorial during the spawning period and occupy prìmìtive

nest sites either beneath or, less commonly, on the side or top of a

fìrm, flat surface (McDowall 1978). The female ìays her eggs in a 'layer s'ingle on the nest surface. After egg-laying is completed, she is driven from the nest and the male remains to guard the eggs, fanning them by movements of the pectoraì fins"

The larvae which hatch become pìanktonic and move downstream into the sea" Laterin the sprìng and summer, they m'igrate back into freshwater (at a size of 15-20 mm), where they grow to maturity. In rivers the common bu1ìy ís usual'ly found hidden amongst marginal cover - overhanging banks, logs, ìarge rocks and piles of debris in the river.

('iii) Others

Geotria austraLis Most of our knowledge of the life history of the lamprey is a result of Maskell's (1929) work. The lamprey commences life in freshwater.

A'lthough spawning has not been observed in New Zealand, in Australia it has been reported that many eggs are la'id in a nest excavated'in the streambed (McDowall 1978). Adults die after spawning. The larval stage which hatches from the egg is known as an ammocoete.

Ammocoetes are found ìn muddy backwaters and sandy shallows along river banks. They are regular'ly recorded at the Ministry's salmon trap at Glenariffe (see F'ig. 1). It is not known exactly how long 'it takes the ammocoete to grow to fulì s'ize, but it is probabìy four to fìve years (Todd 1979a). When the ammocoete is between 80-100 mm 1ong, a dramaûic metamorphosis occurs. The ammocoete changes from a grey-brown colour to the brilliant silver and blue of the macrophthalmia. Thìs transformation takes place in late summer (Todd 1979a). The macrophthalmia migrate to sea the following winter to begin the marine phase of their life cyc1e. Macrophtha'lmia have been observed stranded 'in pools in the Rakaja at low winter flows. FIGURE 1. Rakaia River system. 9.

Little has been discovered about the marine life of the lamprey, although it is known to be parasit'ic. It is not known prec'isely how ìong the adults remain at sea, but it is probab'ly about two and a half years (Hardisty and Potter 1971)" The final stages of maturation take place in freshwater" The adults usualìy re-enter freshwater durìng Juìy-0ctober, a'lthough upstream m'igratìons can occur throughout the year. In Lake Ellesmere, the peak of the run occurs in September

(P.R. Todd, pers. comm. ).

Lampreys are rarely seen swimming upstream in rivers, but this is probably because the upstream migration occurs mostly at night. 0nce they enter freshwater, lampreys do not feed, but live on food stored wjthin their bodies, as do salmon Spawning occurs in the tributaries.

AnguiTIa dieffenbacll-ji and a. austrafis The general life hjstory of longfinned and shortfinned eels are sjmjlar, and so are d'iscussed together here (see Cairns 1941). Eels breed at sea, and it is the juven'ile "glass eel" stage which enters freshwater. The gìass eel ìs transparent, and about 60-70 mm in length. Upstream m'igrations occur in the spring, at about the same time as the whitebait migrations. Jellyman (tglla) found from his work in the Makara Stream, hJellington, that glass eels enter freshwater over a six month period from July-December. Shortfinned eels were present throughout this period, but longfins were restricted to August and

September. Soon after entering freshwater, gìass eels begin to develop colouration and are then known as elvers.

Many ee'ls spend their first year in freshwater ìn the upper estuarine or tidal area of rivers (¡ellyman 1977b). In ìarge river systems, e'lvers apparently migrate successively further upstream each year for several years. The young of the longfinned eel penetrate to the headwaters of the Rakaia River system. This characteristic of i0.

longfins is common throughout New Zealand and longfinned eels are the most w'idespread species of fish in our rivers and streams (McDowaìl 1978). However, the shortfjnned eel has not been found above the

Rakaia Gorge.

Eels take many years to reach maturity. Todd (1980) has found that longfin males migrate to sea at between 12 and 35 years after first entering freshwater (average 23 years), but females migrate at 25 to 50 years (average 34 years).

Shortfinned eels are not quite so long-lived. Shortfin males migrate after 9 to 24 years of freshwater residence (average 14 years), while females migrate at 13 to 35 years (average 24 years).

The adult eels undergo several physical changes shortly before mìgrating and migrant eels are easily distinguìshable by their colouration, the shape of the head and size of the eye. t^Jhen they leave freshwater the adult eels cease feeding and the digestive tract degenerates. The peak migration of adult migrant eels from Lake Ellesmere occurs from late February to late May (p.n. Todd, pers. comm.) and there would be little difference in the Rakaia m'igrants. The migratory perìod for each spec'ies lasts about three and a half months and the sequence is: shortfin males folIowed by shortfin females, then Iongfin males, and

I ast'ly I ongf ì n femal es.

GaLaxias brevipinnis

Koaro (sometimes called mountain trout) is a resident of mountain streams, and the lowest site in the Rakaja system where adults are found is Boundary Stream (see F'ig. 1). These f ish l'ive in swift rapìds, usual 1y under boul ders.

The koaro is another whitebait species, beìng the second most abundant in the whitebait catch. The spawning habitat has not been 1i. described, but localities from which ripe adults have been collected were not different from usual adult habitats, suggesting that there may be little or no breeding migration (McDowall 1970).

Spawning occurs from March to May. 0n hatching the larvae are apparently washed downstream into the sea and develop there during winter.

The whitebait juvenìles migrate upstream in spring, prìmarily in September and 0ctober.

The koaro seems to reach maturity at about two years of age and almost certaìn1y surv'ives spawning once or several times. It probab'ly lives for six to eight years, perhaps longer (McDowall 1978)"

Cheimarrichthg s fo steri

The torrentfish is found mostly 'in unstable, shingìy rivers, such as the Rakaia, and, with the bluegil"led bu"lly, ìs the most common native species in this river. The fish are found in the tumbling, broken water of riffles and live on the river bed amongst the rocks. Their habitat is specialised in that there must be pìenty of cover in the form of large stones and the interstices between the rocks must be free of sediment. Very'little is known about the bio'logy of torrentfish" The distribution of adults in the Rakaia indicates that there is a spawning migration, although the timing is not yet known" During the wjnter, ìt has been found that all fish in the Jower eight km of river were males. Around State Highway No"1 bridge the ratio of the sexes was approxìmately 1:1, while at stee'les Road (see Fig. 1) the male:female ratio was 1:4.3. Above this point, aìl fish were females.

The larvae are not known in freshwater, and so probabìy either they or the eggs go to sea. Small torrentfjsh (30-40 mm in'length) were present in large numbers near the Rakaja mouth in winter, so a gradual upstream migration is thought to occur. The biology and tjming of the life history of this fish is currently under investigation in the Rakaia River. 12.

Gobiomorphus hubbsi The hab'itat of the bluegilled bully is similar to that of torrentfish, and the two species are often found ìn close proximity" Differences in preferred habjtat are not understood at present, but where both specìes occur there is a tendency for torrentfish to be in broken "white water", while the bluegilled bully occurs in the turbulent, but unbroken water of the periphery"

There is no marked difference in distribution of the sexes in bìuegilled bullies, but very little is known yet of their life history. Spawning is thought to be comparable with that of other bullies, with the eggs laid'in freshwater and the new'ly hatched young goìng to sea. Studies of the life history of the bluegilled bu'l'ly are continu'ing as a part of the overall Raka'ia programme.

2.I .2 Non-Mi gratory Spe_c-þ! A'll of the remaining nat'ive fishes I isted jn Table 1 are non-

mi gratory "

Gafaxias vuJgaris

The common river galaxias js so named because it is the commonest and most w'idespread of the gaìaxi'ids jn the rivers of Canterbury and Otago. In the Rakaia system it is most commonly found in tributaries above the gorge. The adult fish inhabjt swìftly flowing water, rarely entering poo1s. The adult is solitary and highly secretive, living amongst the boulders and coming out to feed at night (McDowall 1978).

Spawn'ing occurs from late winter through spring. It is partìy controlìed by temperature, beginning downstream in warmer waters and graduaì1y extending ìnto the cooler, upstream waters (Benzie 1968). Juveniles and adults are often found in the same local'ity, suggesting that spawning occurs in or near the customary adult habitat. Benz'ie (1968) found that these fìsh mature after one year and the life cycle 13. may extend for at least five years with repeated spawn'ing.

The new'ly hatched young form small schools which face into the current, but seek out quieter places where they feed. Juveniles from several broods may merge into one shoal and many individuals are swept downstream. By the time the young fish are about 3"5 cm'in length they begin to leave the schools and become soì'itary and cryptic (Benzìe 1968).

Gafaxias pauci spondg Jus

The alpine galaxias occurs onìy in the swift, cold, snow-fed streams of sub-alpine and alpine Canterbury. Typicaìly, it is found in moderately deep broken-water riffles where the flot^t is extremely rapid (McDowaìl 1970). It has been found as low down as the gorge in the

Rakaia River but it is more common in the headwaters (Harper, Avoca, Wjlberforce and Acheron Rivers).

Very ljttle is known of the life history. Spawning probably occurs in spring, but the breeding s'ite is unknown (McDowall 1970). The habitat of the juvenile has not been described.

Gafaxias prognathus The longjawed galaxias has so far been found only in the upper reaches of east coast, South Island rivers. It is known to occur in the Harper, Avoca and hlilberforce Rivers, as well as in the Rakaia River itself, above the gorge.

Aga'in, very little is known of the life history. The adult is secretive, l'iving amongst boulders and gravel in shallow water. Spawning is thought to occurin sprìng (McDowall 1978), but the site is not known.

Gobiomor phus breviceps

The upìand bu'lly'is probably the commonest and most widespread bu11y in the South Island. It is present throughout the Rakaia River, usual'ly in gently flowing water amongst the rocks at the margins of poo'ls. 14.

Breeding occurs in spring and summer. The eggs are lajd on a firm object, üsually a rock. The males establish defended territories and stay to guard the nest and fan the eggs to keep them wel ì oxygenated and free from silt. Staples (tglS) found that the eggs take four to five weeks to deveìop and that the larvae at hatching are about 5 mm long. He found the juveniles to be free-swimming in the surface waters of lakes for up to six months before becom'ing bottom dwellers like the adults. tnjhether this also occurs in rivers'is not known.

Females reach maturjty'in one or two years while males take two to three years. The maximum life spawn is about five years for both sexes.

2.2 INTRODUCED FI SH There are four species of introduced salmonid fish found in the Rakaia River system - rainbow and brown trout, brook char and quinnat salmon" l^lith the except'ion of brook char, all are fished for by angìers throughout the river system.

O nc o rh _v n chu s t shawg t s c ha Quinnat salmon were first introduced to the Hakataramea hatchery on the Waitaki River, from a tributary of the Sacramento River, Calìfornia, in i901 (F'lain in press). Fry ra'ised at thìs hatchery were I iberated into other river systems, includ'ing the Rakaia. Adult salmon were first observed in the Rakaia Rjverin 1909 (Allen 1956)"

The life hjstory of salmon can best be described by start'ing with the adult fish, which migrate from the sea up the'ir river of orìg'in (salmon are well known for their homing ability). Adult salmon enter the Rakaia between late December and late June, the peak of the run fluctuating between January and March from year to year. Overseas observations indicate that salmon m'igrate upstream in response to freshes and that migration ceases during floods (Aìabaster 1970)"

The age of migrating adults varies from two to five (Table 2). TABLE 2" Age structure of quìnnat salmon returns to Glenariffe (Flain in press).

BROOD YEAR NOS. AGE OF RETURNERS

TOTAL MaleslFemales I and Femal es N (%) ln ø)

1965 841 r279 2L20 403 (8.6) 2859 (61"25) t404 (30. 1) 2 (0. 05 ) 4668 (73.3 1966 560 572 7132 143 (to.s¡ 998 ) 220 (16 "2) 0 136 1 (0.2) L967 1033 739 t772 90 (ta.z¡ 294 (5e.5 ) 109 (22 "1,) 1 494 1968 1492 1783 3275 IT4 (4.3) 1948 (73. 5 ) 590 (22.2) 0 2652 1969 r20q 1286 2490 362 (i3.o) 2270 (81.e) 136 (4. s1 5 ,r::, 2773 r970 382 247 629 184 (40.o) 225 (47 "7) 63 (ts"a¡ 0 472 I97I 1315 1091 2406 63 (20. 1) 220 (io. 3 ) 30 (e.6 ) 0 313 I972 1432 1613 3045 156 (e.0 ) 1395 (80"6) 180 (to"+1 0 773r

r973 263 161 424 564 ( tz . s ¡ 2250 (6e. e ) 404 (n"a¡ 0 32LB

r974 275 772 447 158 (tz.z7 1039 (80.3 ) 97 (z.s) 0 I294 r975 1186 803 1989 344 (li.0) 1435 (71.o) 24r (tz"o¡ 0 2020

I976 1066 I522 25BB 245 (8.3 ) 2420 (82.3) 277 (e"4 ) 0 2942 r977 1010 777 1787 233 875 256 r978 889 888 1777 380 t978 r979 1350 r544 2894 192 *1980 940 592 L532 *i981 1i 58 1268 2426

* 1980 (includes 160 adipose removed fish) * 1981 ('incl udes 497 adi pose removed fish) 16.

The dom'inant age is three, wjth fewer four year old fish. Five year olds are rare and none older have been found. (This djffers from the North American situation where six year old fish have been recorded.) Significant numbers of two year olds also occur, most of which are males"

In addition to mìgratory adults, the spawn'ing population includes a few young males that have remained in freshwater and reached maturity after on'ly one year (McDowall 1978). Overseas some of these fish, termed precocious males, are known to survive to adulthood (Fla'in 1970), but their fate in New Zealand is not known.

Adult salmon cease feeding once they enter freshwater. As they migrate up to the spawning streams the gut degenerates and the reproductive organs develop.

The'ir rate of progress up the river is not well known for New Zealand conditions. In North America, where the rivers are much longer but not braided, distances of e'ight kilometres per day are consìdered very s'low (Rutter 1903). Limited local angling records show that the greatest catches of salmon occur near the Rakaia Gorge in January and February, suggesting that passage from the mouth to the gorge probably takes less than a month. However, 15 years of Glenarjffe Salmon Trap records show that the peak of the run into thjs spawning stream almost aìways occurs in Apri1, w'ith sign'if icant numbers entering in May (Table 3).

'large Observations of numbers of salmon in deep holes 'in the Rakaia River above the gorge (J.R.Gal1oway, pers. comm.) suggest that the fish ho'le up for a month or more before movìng into the spawn'ing streams.

This length of time is probably required for gonad maturation. As mentioned previously, many North American rivers are much longer than those in New Zealand (the Sacramento js 1200 km, c.f. the Rakaia which is only 140 km), and in those rivers maturation of the gonads probably TABLE 3. Numbers of adult salmon entering Glenariffe Stream, 1965 - 1981

Year Jan Feb Mar Apr May Jun Jul Aug Total

1965 11 1188 933 56 2188

1966 1 7 671 417 37 2 1 135

1967 3 3 958 632 131 4? 1769

1968 1 31 4B 2124 1045 20 2 327I

1969 1 I 29 1347 1065 43 2493

r970 2 10 22 258 zIB 100 15 4 629

I97T 4 7 1034 r276 84 2405

r972 4 1 57 1605 L292 70 15 3044

r973 1 11 252 I12 48 424

r974 8 275 139 25 447

r975 2 38 L027 875 49 7 1 1999

1976 I7 7L 13 53 1068 56 2565

L977 6 4 22 855 805 84 15 179I

I97B 6 43 753 891 82 8 2 1785

7979 2 116 7567 7I22 70 6 2883

1980 L2 107 763 467 169 i1 I529

1981 J 133 7299 729 265 1 2430 lB. occurs during the longer upstream migration period. In shorter North American rjvers, salmon are known to rest in poo'ls in the main river and onìy move into the streams when ready to spawn (Rutter 1903).

0nce the fish enter the spawning stream, pairing occurs. The female selects the nest site (known as a redd). Females may dig trìal redds until an area with suitable gravel size, water velocity and dissolved oxygen concentration is found. The redd js a large ho'l'low excavated ìn the gravel by flexions of the female's body. The male fertilises the eggs as they are laid in the depression created by the female, who then moves upstream and repeats the process of gravel excavation. The displaced gravel is carried downstream by the current and settles, filling in the depressìon and covering the eggs. This process is repeated several times so that several egg pockets may occur wjthin a redd (Hawke 1978).

Redds are usually easily visible for up to six weeks after construction as areas of clean, disturbed gravel, contrasting with the aìgal-covered gravel surrounding them. After spawnìng all the fish die.

Depending on water temperatures, the fry emerge from the gravel two to three months after egg deposjtion (ealloway 1979). Between 91 and 98% of the juveniles leave the Glenariffe Stream during August-

October as fry (mean size = 3.4 cm, M.J. Unwin, pers. comm.). The remainder mjgrate from November onwards as fingerlìngs,-or as yearìings the following spring.

Untìl recently it was thought that most juveniles which left the Glenariffe as fry perished in the Rakaia, or did not survive the transition to salt water. Since August 1978, however, regular netting of the Rakaia River has shown that a signìficant amount of juveni'le rearing does occur there. Evidently some of the early outmigrant fry survive and grow in the main river. 19.

Juvenile residents in freshwater appear to develop in one of two distinct ways. One type of iuvenile (Type 1), represented by the 2-9% of Glenariffe juveniles which do not mìgrate as fry, remains in the spawning stream for approximateìy three months. The second type (Type II), are the survivors of the initial mass migration of fry. These surv'ivors take up res'idence in the upper reaches of the Rakaia and move slow'ly downstream, continually being replaced by newly emerged fry.

The appearance of ìarge numbers of these resident fish near the mouth in

0ctober-November suggests that the down-rìver journey takes about three months (M.J. Unwin, pers. comm. ).

Both types of Juvenile resjdent contribute sign'ificantly to the returning adu'lt runs. Those adults which reared as juvenìles in the

Rakaia are thought to contrìbute from 50% to 90% of the return'ing adults (M.J. Unwin, pers. comm.). Current research is aimed at clarifying the relative importance of these two juvenile types and thus the role of the

Raka'ia i n reari ng of sal mon juveni 1 es.

Examination of the scales of adult salmon provides 'information on the age and early life history of a fish. There are three distinct'ive types of salmon scale nucleus (Flain in press), corresponding to three types of freshwater orig'in:

(a) 0cean nuclei - All the first year's growth consists of widely spaced c'ircul i 'indicating rapid growth in seawater. This

pattern means that these fish entered the sea at an early age

(fry), with subsequent rapid growth"

(b) Stream nucle'i - All the first year's growth consists of closeìy spaced c'irculi, indicating slow growth in freshwater.

(c) Intermediate nuclei - A variable proportion of the fjrst year's growth shows a stream pattern of circuli, while the remainder 20.

of the growth to the annual check shows more widely spaced circuli. These fish spent a proportion, but not al'1, of theìr

fìrst yea.r in freshwater before passìng out to sea, and would include most Type I and Type II juveniles.

Correlation of specific lengths of time spent in freshwater with stream patterns of cjrculi is current'ly under investigation.

The incidence of each type of scale nucleus, from angler-caught fish, shows that very few ocean type nucle'i occur in scales of returning

Rakaia adults (less than 2%) (Table 4). This means that 98% of returning adults spent a proportion of their first yearin freshwater before entering the sea. Forty per cent of these resjded a whole year, and migrated to sea as yearlings.

TABLE 4. Incidence (%) of scale nucleus types from the Rakaia River (F'lain in press).

Year Stream I ntermedi ate 0cean Total Nos.

1967 28.4 69. 1 2.5 81

1968 19.6 80.4 0.0 51

r973 17.8 82.2 0.0 135

r974 34.0 66.0 0.0 4t2

r975 19. 1 80. 4 0.6 525

r976 14.0 85. 5 0.5 193

Average 23.2 76.4 0.4 r397

From Glenariffe records we know that a maximum of 2% of those iuveniles which do not migrate as fry, migrate as yearlings. This is in sharp contrast to the above figure of 40% which represents the proportion of returning adults which mìgrated as yearlings. Evidently the great majority - probably over 90% - of adults w'ith stream nuclei must 2I.

have reared jn the Rakaia, rather than in the spawning stream.

SaLmo gaìrdnerii Rainbow trout, which are native to the Pacific coast of North

America, were introduced into New Zealand in 1883 when ova were imported from California by the Auckland Acclimatisatjon Society (Scott et al.

1978 ) . Progeny f rorn thi s shi pment were wi de'ly d'i stributed throughout

New Zealand. However, liberations into South Island rivers have general'ly not been very successful and here rainbows are usuaìly found in lakes. Allen and Cunningham (1957) described the present day dìstribution of rainbow trout in New Zealand.

Numbers of rainbow trout in the Rakaia River are not known, but angìers catch them'in small numbers at the gorge and upstream. Rainbow trout are known to use the Glenariffe Stream for spawning, but few data are avallable due to the method of operation of the trap, which ceases fishing upstream mìgrants in July before the rainbow trout spawnìng run has finished.

Rainbow trout spawn in tributary streams, usua'lìy in June and July, a1 though Hobbs ( tgSZ ) noted that ra i nbows i n l¡Ji nd'ing Creek (a tri butary of the Waimakariri River) spawned from August to mid-October.

Trout dig redds of similar form to those of quinnat salmon, except that they are made of smaller diameter stones and are usually much smaller in size. Most adult trout survive spawn'ing and recover condition sufficiently to spawn a second time, sometimes more often.

The eggs take six to eight weeks to hatch, depending on water temperatures" Juvenjles usually rear in the spawning streams and become disp'laced downstream as they grow and take up larger territories"

Sal-mo trutta

The earliest introductions of brown trout into ttlew Zealand rivers 22.

and lakes were made in 1867, from Tasmania, where trout had been successfuììy imported from Britain a few years before. Further inmportations were made direct from Britain ín subsequent years, but the introductions were so successful that within a few yeat^s the

species was firmìy established throughout most of the South Island a.nd

the southern part of the North Island (Allen 1957).

Brown trout are distributed throughout the Rakaia system. Like rainbows, they spalvn in the Glenariffe Stream, runs of 200-300 fish

beìng recorded. At the mouth, sea-run brown trout are also caught by anglers" These fish spend most of their lives in the sea or estuary,

but migrate upstream to spawn.

The peak spawnìng of brown trout usua|ry occurs in May and June,

precedìng that of rajnbows. However, Hobbs (1937) noted that brown trout in Slovens Creek (a tributary of the Waimakariri River) spawned unti I 'l ate Ju1y.

Brown trout usualìy use tributary streams for spawnìng. However, below the Rakaia gorge there are only twa tributaries - a small unnamed stream on the south bank and Boundary Stream on the north bank, both just downstream of the gorge. In June 1979 both tributaries vúere surveyed on foot to determine whether trout (or salmon) utilised them for spawning. At the time of the survey there was a gradient obstruction at the confluence of Boundary Stream and the Rakaia" Water discharging from Boundary Stream dispersed into the gravels, so there was no continuous passage for fish. The d'ischarge at the Rakaia Gorge on that day was 120 cumecs (J. Fenwick, pers. comm.).

Twelve trout redds were observed in Boundary stream, and it is presumed these belonged to resident fish. Electric fishíng of thjs stream in February 1979 produced large numbers of juveníle brown trout (size range 70 - 198 mm). These were last year,s progeny, so this stream is evidentìy also important for rearing. 23.

The unnamed stream had been used by salmon for spawning (six

salmon redds and two salmon carcasses were observed), but no trout or trout redds were found.

The question arose as to whether trout were spawnìng in suitable side braids of the main river or mìgrat'ing above the gorge to the tributaries.

It appears trout spawn in both places. Aerial counts of fish and

redds made by helicopter between the gorge and the mouth on 29 June

1979, showed that trout were spawning in the main river between Hìghbank

Power Station and the pylons spanning the riven below State Highway

No.1 Bridge. Redds were constructed in smal'ler s'ide braids, and were numerous where they occurred. However, many areas that appeared

su i tabl e were not uti I i sed .

In the past it has been thought that any spawnìng in the maìn river would be unsuccessful due to floods washing out redds andlor juveniìes" However, because the Rakaja 'is princìpaìly snow-fed, the lowest flows occurin winter and the river can be low and stable for

long periods. Such a situation occurred this winter (in fact seems to be quite common), and spawning in the rjver should be successful under these conditions. Electric fishing surveys to assess presence and abundance of trout fry wiì'l commence ìn September-October to confjrm the success of trout spawning this year (1979)"

Aerjal trout spawning surveys wi1'l be repeated in future years so that the relative importance of spawning'in the main river can be assessed.

The habjtats of juvenile trout'in the Raka'ia are also under invest'igation" Electric fishìng surveys indicate that they general'ly occupy backwater areas where the water velocìty is slower and there is plenty of cover in the form of ìarge boulders, overhanging rocks 24.

or banks, trees or any other vegetation trapped in the water" A few juveniles have been found'in rjffle areas, but only where large rocks are present.

Future work will be concerned with describing the precise habitat requirements of juvenile trout. How the existing habitat will be affected by changes in river flows will need to be known before predictions can be made regarding the possible effects of water abstracti on .

A trout tagging programme has recentìy been initiated" Tag returns by ang'ìers and recaptures by electrjc fishing will provide essentjal information on trout distribution, movements and growth rates in the Rakaia. Trout greater than 10 cm which are caught by electric fishing are being measured, tagged and released. A'lso, tagging of yearìings and adult trout moving out through the Glenariffe fry trap commenced in August 7979"

SaLveLinus fontinaLis Brook char (or brook trout) were introduced from the eastern

U.S.A. in 1877 and I iberations were made around Auck'land, hleìl ington and Christchurch (Thomson 1922). It 'is now quite widespread in inland Canterbury and Otago (McDowall 1978).

Brook char do not seem to be able to coexist well with other salmonids, and are usually found upstream from brown and ra'inbow trout (Lane and Skrzynski L972)" Spawning of brook char in New Zealand has not been described. In North America it occurs during autumn and wjnter jn the moderately swìft water at the Jower end of pools. The incubation period of the eggs varies jn duration with water temperature (as in other salmonìds), taking from one to four months, and the young emerge in early sprring (McDowall 1978). 25.

In the Rakaìa River system brook char are known from records at the Glenariffe salmon trap and from electric fishing in a tributary of Lake Coleridge.

3. FOOD AND FEEDING OF FISH WITI-I PARTICULAR REFERENCE

TO THE BENTHIC FAUNA

A major considêration in the habitats occupied by fish is the availabil'ity of food organisms. The productivity, djversity and composit'ion of the benth jc community is an extremeìy 'important component of the freshwater ecosystem" Besides providing the major source of food for fishes, benthic invertebrates are good indicators of ecoìogical conditions.

It seems appropriate to quote here the three eco'logical princip'les of Thienemann (1954) as quoted by Hynes (1972). They are:

(a) The greater the diversity of the conditions in a locality

the larger is the number of species which make up the biotic

commun ì ty .

'in (b) The more the cond'itions a locality dev'iate from normal , and hence from the normal optima of most species, the smaller is the number of species which occur there and the greater the number of indiv'iduals of each of the species which do occur.

(c) The longer a localjty has been jn the same condition the richer is its biotic community and the more stable it is"

These principles should be consjdered when changes to aquatìc hab'itats are proposed.

Once irrigation withdrawals from the Rakaia River commence the inhabitants will be subjected to reductions in flow during the summer. 26.

Physical changes associated with reduced flows include decreases

in wetted perìmeter, depth, sunface area and current velocity. Under abstract'ion regimes. current velocity is reduced more than any other physìcal characterist'ic (Curtis 1959; Kraft L972) "

3.1 FACTORS AFFECTING INVERTEBRATE DISTRIBUTION Many factors reguìate the occurrence and micro-distrìbution of benthic invertebrates. The most important are current velocìty, temperature and substrate (rincluding vegetatìon), aìthough dissolved oxygen, food organisms and occurrence of droughts and floods are also ìmportant (Hynes 1972).

Benthic ìnvertebrates living in running water (as opposed to still water) have developed many anatomical and behavìoural adaptations. Some species are restrjcted to running water because their respiratory

rate is directly related to current speed; for examp'le, the Ephemeropteran Baetis, the Trichopteyãî Rhsacophita (Jaag and Ambuhl 1964) and the

Plecopterð,î Acroneuria (Knight and Gaufin 1963). 0ther species, such as those of the famì]y Hydropsychiidae (Trìchoptera) have feeding mechanisms which depend on the current. Particular species are often

confjned to specific velocity ranges (e.g.scott 1958) but, as Hynes

(r972) noted, since current varies with discharge, no absolute values of current requirement or tolerance are obtainable from most field

studies. A wide range of depth preferences 'is also exhibited, however,

it is often diffjcult to separate the effects of velocity and depth when studying the habjtat preferences of different species.

3.2 EFFECT OF REDUCED FLOWS

Overseas stud'ies have shown that invertebrate production is highest in riffle areas (Church et al . 1979). These areas are also significant for shelter required by young fish (Fraser 1972) and in the

Rakaia River, juvenìle trout are found in such areas. t^Jhen flows 27. diminish, surface,area, average depth and cover are reduced to a greater extent in runs than in pools, whereas reduction in current velocity is greaterin pool s than in runs (Kraft 1972).

In his study of the effects of low flow condttions on the 'invertebrates of the 0pihi River, Fowles (1972) concluded that both the benthjc and drift fauna were detrimentalìy affected by low f'lows during late summer" Benthjc numbers were consjderab'ly reduced, especiaìly those of ¿eleatidiurn Spp. and Pgcnocentrodes aureoLa"

He also concluded that although flash flooding has a deleterìous effect on the benthic fauna, recovery fo'llowing a flood is genera'lly quicker than recovery fol'lowing a period of dessication.

Sedimentation is also associated with reductions in flow. Accumulation of si'ìt amongst and over the substrate causes a loss of 'invertebrate habitat, by fìllìng the interstices between stones.

Hynes (1972) stated that the ìarger the stones, and hence the more compìex the substrate, the more diverse is the invertebrate fauna" 0n stony substrates, the presence of silt reduces and changes the fauna. Generally, the fauna of stony runs is richer than that of silty reaches and pools, both in number of species and total biomass.

Briggs (1948) found that depositìon of sand and silt below a dam caused a change in the composition of the jnvertebrate fauna from predom'inantìy Ephemeroptera and Plecoptera to more silt-tolerant chironomid larvae, which have a much lower value as fjsh food"

Increased algal product'ion is usually associated with reduced flows and stable cond'itions" However, aìgae can flocculate the fine suspended material typically carried by rjvers such as the Rakaìa, creating a further bu'ild-up of silt. Such a situation has occurred this wìnter in the Rakaia River. Since April 1979 the flow has been relativeìy stable and dense growths of brown and filamentous 28. green algae have appeared in many areas. Much of the algae and silt will be scoured from the river bed durìng the spring floods, but jf summer low flows become the norm (as seems ì'ikeìy under the proposed abstract'ion regimes ) i ncreased al ga'l growth i n summer wi I I occur.

A'lgaì productì v'ity i n summer wi l l be h i gher than that occurri ng naturally in winter, due to increased light and water temperatures. This could have a serious effect, on the fishery.

Reductions in discharge can also result in increased water temperatures, raising monthly averages and summer maxima. There is little information available on the direct effects of high temperatures on benthos, although Spruìes (1947) found fewer species of Plecoptera, but more species of Trichoptera and Ephemeroptera, in streams with high average summer temperatures. The relatìonship between temperature and oxygen requirements must also be emphasised - as temperatures rise, dissolved oxygen concentrations are reduced. Many stonefly, mayfly and caddisfly larvae are very sensitive to reductjons in djssolved oxygen levels (Philipson 1954; Nebeker 1972). However, Morgan and Graynoth (tgZg) found that there was no jnformation ava'ilable on the oxygen tolerances of invertebrates from New Zealand.

3.3 RAKAIA INVERTEBRATE STUDIES The'invest'igations of the benthos that are seen as relevant to the fishery are:

(a) t¡lhat is the composition, distribution and relative abundance of the invertebrate fauna of the river

(b) how 'is it utilised by the fish populations

(c) how is 'it I ikely to be affected by reduced flows?

From the l imited sampl ing to date, ourimpressions on the d'i stri bution of the benthos are: 30.

3"4 FOOD HABITS OF FISH It must be emphasised that our invertebrate studies are still at the preliminary stage, so very'little further can be stated on our own studies at the present time" However, there is a little pub'lìshed information on the food habìts of some of the fìsh species recorded from the Rakaia River, and the literature is briefly revìewed here.

3.4. 1 Nati ve Fi sh

Gal-axias macul-atus The adult inanga is a genera'l carnivore, eating a wide variety of aquatic and terrestrial organjsms. In his study of the food of 'inanga 'in the trJaikanae River, McDowa'll (1968) found that 81 "7% of lhe stomachs examined contained food of three categories:

Chironomidae larvae and pupae (2I.6%), Copepoda (39"4%) and the gastropod mol I usc potamopsrgus (20.7%) .

Aìthough these three groups were consistently ìmportant in the food analysis, their proportions varied wideìy w'ith season, fish sìze and fish habjtat. However, neither potamopgrgus rìot representatives of the copepod group of Crustacea have so far been found in benthic sampìes from the Rakaia River.

McDowall (1968) also found that e" macut-atus readiìy eats terrestrial invertebrates fal'ling onto the surface of the water" He considered that the quantìty of terrestrial food in the diet was probably limited ìarge'ly by availability of such food and perhaps by the abundance of stream invertebrates as alternative food sources" The number of terrestrial insects in a stream was reported by Giger (1973) to be a function of the proxim'ity of overhang'ing vegetatjon rather than the surface area of water. Near the Rakaia mouth, where'inanga are found, there is more vegetatìon in the rjver bed than there is further upstream and so terrestrial insects probably also comprise part of the d'iet of the Rakaia inanga populatjon. 29.

(a) Riffles contain more benthic 'invertebrates than either pools or runs.

(b) Margins of channels contain greater numbers than the centres

of the same channels.

(c) The major braids of the river have a very sparse invertebrate fauna, even in riffles and along edges. Presumabìy thìs is a result of the frequent natural freshes, particularly during

spring and summer. During these freshes channels may change

course and, at the least, the river bed becomes unstable and mobile. This physical action would severely disrupt benthic communities.

(d) The greatest invertebrate abundance occurs in the riffle areas of minor braids. Here the bed appears more stable and thus the effects of floods and freshes are probably less severe. Therefore these areas are the most critical for benthic production but they are also the areas which wjll be most severely affected by abstraction.

In terms of species composition, mayf'ly (oeJeatidium spp.) larvae have been the most numerous 'invertebrates, typ'icaì ly be'ing found clingìng to the under-surface of stones durìng the day. Areas where stones are free of silt normally support mayflìes. These condjt'ions are characterìstic of rìffles and it is here that mayflies appear to be most abundant.

Free-living forms of caddisfìy larvae of the famil'ies Hydrobiosinae and Hydropsychidae have been less numerous than mayf'ly larvae but are an ìmportant group in terms of biomass. Lìke mayf'ly larvae they are found on the undersurface of stones. 32.

The common bul'ly is an ìmportant food resource for oither fish. Phi'll ìpps (ßZq) reported that it was probably the most important

trout fish food 'in New Zealand rivers.

Geotria austraLia

Adu'lt lampreys do not feed in freshwater. The ammocoete larvae and macrophthalmia I ive in mud and feed by pump'ing water ìn through the mouth and out the gi'11s, fjltering m'icro-organisms from the water as it passes through.

Anguilla dieffenbaehii and A. austral-is When they are smal1, eels feed on small insect larvae from the benthos - caddis and mayfìy larvae, snaìls, chironomids, etc. It is onl.y the larger eels which feed on fish such as bullies, smelts and young trout (Caìrns 1942).

GaLaxias vuTgaris

Cadwallader (1975) found that the basic food of the common rjver galaxias in the Glentui River, Canterbury, consisted of Ephemeroptera, part'icularly the larvae of oel-eatiriium spp", CoLobur.iscus humera-Zj*s dttd

Nesamel-etus ornatus" Secondary food consjsted of ETmidae (Coleoptera), terrestrial arthropods, the larvae of Rhyacophil ìdae (Trichoptera),

Archichaul-iodes diversus (Megaloptera), Chironomidae and Simul iidae (Diptera).

The diet was found to vary seasonaìly and w'ith the size of fish. The common river galaxias changes its habitat when the fish reach about 40 mm ìn length, moving from quiet stretches of rjver into riffles. In riffles, they have access to a more díverse fauna

(Mclay 1968)" Benzje (tgOg) found that in slower movìng waters, some individuals feed in midwater, like trout.

Cheimarrichthgs fosteri a.nd cobiomor.ohus hubbsi Little is known about the feeding of torrentfish or bluegilled 31.

Rhombosofea retiaria

'l Black flounder, ike most flounders, 'is a predatory carnivore.

It feeds on benthic insects and snail s, and al so on small fish. During spring, ìt feeds heavily on the migrating whitebait (McDowalì 1978).

Retropinna retropinna

As they migrate upstream common smelt are eaten by adult brown

trout and eels. It is also likely that fish-eating birds such as gu1ìs, herons and shags feed on smelt. However, at present nothing js known about feeding of the smelt itself.

Stoke]l-ia anisodon

McMillan (1961) found that Stokell's smelt formed an ìmportant part of the ecology of the Rang'itata River mouth, due to the length

of its spawning season and the enormous size of the shoals. The situat'ion ìs probably sìmilar at the Rakaia mouth. Stokell's smelt was the dominant component'in the diet of black-b'illed (zuru" bulleri) and black-backed (2,. dominicanus) gulls and white-fronted terns (st.rr,r striata striata). Schools of kahawai also fed on the shoals, fo'llowing them into thb river mouth, where they (ìn turn) were preyed upon by gulls. Flounders, eels and yellow-eyed mullet were found to

incl ude Stokel I 's smel t 'in their diet.

McDowall (i978) noted that Stokell's smelt js much sought after

by trout fishermen for bait, which may suggest that trout al so feed

on smel t in estuaries "

Again, the food of the smelt itself is not known.

Gobiomorphus eotidianus

There have been no detailed studies of the food of the common

bul ly. McDowal I ( 1978) stated that it js I ike'ly the fi sh feed on

a wide varìety of benthic jnvertebrates. Large ones may be fi sh-eati ng,

preying on smal I bul I ìes, whitebait, etc. 33. bullies. Stomach samples from torrentfjsh, bluegjlled bulljes and upland bull ies from the Rakaia R'iverindicate that these f ish consume largeìy the same prey species. Chironomidae and Defeatidium lar[¡ae occur in large numbers 'in samples of all these fish. Free-living caddis (Rhyacophilidae) of various specìes occur in smaller numbers, whìle cased caddjs normally occur on'ly in fish from lower reaches of the river. There may be differences in the time of feedìng, and/or in the size range of prey species preferred by each predator, but the data have not yet been analysed to ascertain th'is.

Gob i onorphus breviceps The upland bul'ly is primari'ly a benthic carn'ivore (Staples 1975). Both Hopkins (1970) in a river-dwelling population, and Staples (1975)

'in a lake-dwel I ing population, found that Chìronomidae formed a major component of the diet of young up'land bullies. The diet changes to insect larvae such as Del-eatidium spp. as the fish increase in age and size. Staples (1975) found that older up'land bull jes also ate young of ìts own spec'ies.

3"4.2 Introduced tjsh

SaJ-mo gaird4erii Ra'inbow trout are carn'ivorous, generally feeding on whatever is available. They will feed at the surface, either on float'ing terrestrial 'insects such as beetles, or on surface-l jving fish such as smelts. They also feed on the bottom, taking animals such as bullies, freshwater crayfìsh (earanephrops) and insects (McDowall 1978).

Safmo trutta Brown trout in rivers tend to be surface feeders, rìsing to the surface to take the hatching adu'lts of mayfl ies, caddisfl ies, etc., and drifting organisms. This habit is the basis of the fly fishing technique used extensively by anglers. The food preferences of trout change with the size of the fish (Burnet 1969). Ch'ironomid 34.

larvae were found by Hopkìns (i9i0) to be the major food of trout fry, being replaced by Det-eatidium 'in older f ish. Yearl ìng trout from the'Raka'ia River have been found to contain ìarge numbers of both types of food.

l,rlhen very large, brown trout may feed on small fish, and large terrestrial insects are also known to be eaten (McDowa'll 1978).

Hopkins (1970) found that food of terrestrial origin made up 5.4% of all food items in trout.

Sea-run brown trout feed extensively in estuaries on whitebait and mìgratory smelts (at appropriate times of the year) and also on bottom-dwelling bullies (McDowaìl 1978). Stomach contents of sea-run brown trout from the Rakaia have not so far been examined.

Oncorhg nchus ts hawgt scha Adult salmon do not feed in freshwater. Little is known about feeding of juveniles. A very few juvenile stomach samples have been examined from the Rakaja River. Nearly all contained Delearidium spp. Anaiysis of the food of juvenìles is currently ìn progress.

4. UTILISATION OF THE RESOURCE

4"7 RECREATIONAL FISHING The prìmary recreational resources of the Rakaia River are its salmon stocks and to a lesser extent its trout stocks. 0f all the major salmon rivers jn New Zealand, onìy the Rakaia and the Waimakariri still ex'ist in a relatively unmodified state. Consequently, any proposals which will affect the natural fìow regime of the Rakaia are viewed with concern by those jnvolved wjth the recreational fìshery.

In a survey conducted by Octa Associates (1976) on behalf of the North Canterbury Acclimatisation Society, the Rakaia River was 35. nominated as the second most popular fish'ing area w'ithin the North

Canterbury distrìct, being fished regularly by 39% of the respondents. 0n'ly the lower Waimakariri River attracted a higher percentage of anglers. However, it was not possible to obtain estimates of anglers' catches for each rjver from the survey. It js considered that Rakaja anglers catch more f ish than hlaimakariri anglers (J.R. Ga'l'loway, pers. comm. ) .

( i ) Trout Very little jnformatjon 'is available concerning the trout fishery.

Gîaynoth and Skrzynskì (1974) stated that "most ang'lers come to the Rakaia in an attempt to catch salmon. The trout stocks are virtualìy unused." Brown trout are fished at the mouth from the openìng of the fish'ing season ìn 0ctober (J.R. Ga'lloway, pers. comm. ) and also provide an important'interim fishery between the end of the whitebait season (November 30) and the beginning of the salmon run (S.P. Hawke, pers. comm.). In the upper reaches of the river, younger members of family fishìng pgrtìes often use worms to catch rainbow trout (G.4. Eldon, pers. comm. ).

(ii) Salmon The Rakaja salmon fishery has been jncluded ìn a number of angler surveys sjnce 1947, but these have provjded l'ittle quantìtative information of angler effort and total catch. The on'ly reliable estimates of angler-catch come from two postaì surveys of the 1973/74 and 1974/75 fishing seasons (West and Goode in press). For each season, the total catch of salmon from the Rakaia and the number of anglers who fished the river were estimated. For the 1973/74 season, the estimates were 3218 fish caught by 4405 anglers, and for 7974/75,4416 fish caught by 5332 anglers.

However, the runs of adult salmon into the Glenariffe Stream

(where the Ministry's salmon trap is located) during the two seasons 36.

covered by west and Goode's surveys were the two lowest on record

(see Table 2)" Both runs were under 470 fish. less than 25% of the

average Glenariffe run of 1900 fish. The overall Rakaja run and

hence the angler catch would thus have been low.

The distribution of angl ing pressure has changed significan¡y in recent years. Whereas five years ago most anglers fjshed near the mouth (R.H.Goode, pers. comm.) the effort is now spread over the full length of the river. Fisherjes officers working at Glenariffe last

season (1978/79) estimated that on some days over i00 fish were taken from the Rakaia above the l^Jilberforce confluence. Since catch rates are lowest at the river mouth (n.H. Goode, pers. comm.), this shift in fishing pressure has almost certaìnìy ìncreased the total catch"

Adult whole season fishing ricence sales in North canterbury

rose from 7,8r8 in 7974 to 10,915 in lg7l, an increase of 40%. Thís increase in licence sales ìmplies a corresponding increase in the

number of angl ers f i sh'ing the Raka ia .

currently, FRD in christchurch is setting up a posta'l survey of anglers in the North Canterbury and Ashburton Accl.imatisatjon Districts.

This survey wiì1 estimate the number of angìers fishing the Raka.ia, the total catch of salmon and trout, and the total number of angìer-days spent on the Rakaia River" The survey will begin wjth the rglB/7g season, and continue for at least three years. It is hoped to have results for the 7978/19 fishìng season available early in 19g0.

('iii) t¡lhiteba'it

The whitebait fishery at the Raka.ia River mouth is parily a recreational fishery and partly a commercial fishery, although no licences are required for commercial selling. The successful whitebajter with a surpìus will sell it, sometimes to friendss or passersby, or to the local fish merchant. 37.

The Rakaja mouth attracts whitebaiters from Christchurch, Rakaia township, Ashburton and all the areas between these and the coast" The fishìng effort varies from season to season, depending on the size of the whjtebait runs, the tide and the time of day.

At peak times jt'is common to see 100-150 peopìe whítebaiting (S.P. Hawke, pers. comm.). The individuals fishing at any one time

continually change, and so the total number of whjtebaiters per day may

be consìderabìy hìgher. Last season (1978), approximately B0 peopre

were observed whitebaiting one Sunday (M. Tayìorr pêr"S. comm.)"

Individual catches range from very little (50-100 gm) for the

inexperienced and those in less favourable pos'itíons, to anything up

to 25 kg in a day. Catches vary considerably, but there are days

when the collective catch could be as hìgh as zzs kg (s.p. Hawke, pers. comm. ). There is one authenticated catch of an individual taking 600 lbs (270 kS) in a week, twelve years ago" Last season (i979) eight peopìe are known to have caught in excess of 45 kg each for the

season (M. Tayì or r pers. comm. ) .

The whitebait run depends entirely on the river mouth being open to the sea.

(iv) Other Species

Kahawai provide good sport for anglers when it runs into the estuary (usually ìn summer), although it js not usually favoured for eatìng.

Ye1ìow-eyed mullet'is commonly caught by youngsters and is said by

Graham (i956) to be excellent eating. There is a small commercial fishery for yeì1ow-eyed mullet in Lake Ellesmere, and the fish are sold on the local market (P.R. Todd, pers. comm.).

Flounders are netted regu'lar'ly in the Rakaia I agoon " During 0ctober 1978 one fisherman caught 178 flounders over nine days 38.

(D. Halewell, pers. comm.). There are no conmercial licences for flounder at Rakaìa Lagoon, and so the dai'ly limit catch ìs 24 per person. At the weekend, up to 20 flounder nets may be set in the lagoon (S.P. Hawke, pers. comm. ), usually by hut owners.

A substantial commercial flounder fishery exists in Lake

Ellesmere. The Rakaia Lagoon and Lake Ellesmere black flounder popuìations appear to be linked in that there may be an influx of flounders ìnto the Rakaia Lagoon when Lake Ellesmere is closed

(P.R. Todd, pers. comm" ).

Common smelt was former'ly used by the Maorìs as food and in some North Island rivers, smelt are caught like whitebait and sold on the Auckland fish market as "second class whitebait" (McDowall 1978).

However, in the Rakaia, these fish are usually considered more of a nuisance, as they have a strong, distinctive, cucumber-like smeì'1, wh'ich can tajnt a whitebait (cataxias spp.) catch if not removed.

4.2 COMMERCIAL FISHING

(j) Eel s

The New Zealand eel f i shery i s fragmented, in that 'it 'is scattered over many rivers, streams and lakes throughout the country. Lake

Ellesmere, which accounts for up to 30% of the total New Zealand eel catch, is an except'ion. Thus, any small commercìally fished area such as the Raka'ia R'iveris an integra'l part of the whole New Zealand eel fì shery.

The commerc'ial eel f i sh'ing season lasts from approx'imately September to Aprì.l. Last season (1978/79) there were three eel fishermen operating on the Rakaia Rjver. Approximately 15 tonnes were caught (mostly

ìongfins), which represent 0.75% of lhe total New Zeal and eel catch.

The export value of these eels would be about $30,000 f.o.b.(P.R. Todd, pers. comm. ) . 39.

In 1978, eels were the third most valuable N.Z. fin fish export, valued at $4.07 million. Exports totalled 2,177 tonnes (Todd 1979b).

It js not possible to define the importance of the Rakaia eels as a conservation resource, part'icular'ly with respect to maintenance of the Lake Ellesmere eel fishery. The long'life history of the eel means that changes ìn the Ellesmere populatjon due to fishing pressure may not appear for many years. Majntenance of eel spawnìng stocks is necessary for continued recru'itment of eel s 'into Lake El I esmere. Thus contjnued access for migrant eels from rivers such as the Rakaia is essential.

('ii) Salmon At present (August L979), two commercial salmon farming operatìons are proposed for the Rakaia River. The first, to be located at the Lake Colerìdge Power Station tailrace, has been granted a water right by the Regìonal Water Board. The second, proposed for a stream on

Blackford Station, on the south bank of the River (see Fig. 1) has applied for its water right. Under the Freshwater Fish Farmìng Regulations 7972, both require I'icences from the Minister.

Government poficy at present'is to have onìy one salmon farm per river system. However, the Freshwater Fish Farming Regulations are currently being updated and this policy may change.

Both farmers plan to use the ocean ranchìng method, whereby fry are reared to approximate'ly 10 gm in art'if icial raceways, and then released 'into the river. These fish will return after two, three and four years, theoretically'in sufficient numbers to allow the farmers to perpetuate the run at a commercìal level. Overseas, a return of I.7% of adults is considered adequate to maintain a viable commercial operation" The farm sited on the power statìon tailrace has raceways under construction at the present time and proposes to make its first release of one million salmon fingerlìngs in early 1980. 40.

Therefore, the Rakaia salmon run will be increased by 10,000 fish if there is a 1% return and up to 50,000 fish w'ith a 5% return (wh'ich js what the operators are a'iming for) . Over the next five years they propose to increase the releases to 10 million fingerlings per annum. The number of returning adults at th'is time would be in the range of 100,000 - 500,000 fish. The effects of such an'increase in the salmon run on the number of angìers fishing the river cannot be predicted, but it has been suggested that the Rakaia salmon fishery could become more important as a tourist attraction.

Commercjally caught fish are expected to sell for $B - $10 per kì1ogram. The average weìght of three year o1d salmon 'is between

7-10 kg. Thus these fish will have a value between $SO - $100 each.

(1rr) Kanawa'r

Two commercial fjshermen have recentìy purchased a "Shark Cat" Catamaran, powered by two jet units, to fish out of the Rakaia R'iver mouth all year round. Investment in the boat and gear ìs approximately $32,000. It is proposed to fish for kahawai, groper, rig, and eìephant f ish. The kahawa'i w'ill probab'ly be exported, as it 'is from the Waìrau R'iver (Marl borough) offshone f ìshery.

This enterprise may be the beginning of a small fishing fleet utilising the local off-shore fish resource. Traditionally this area has been fished by boats from Akaroa, but current fuel prices and supply may make'it uneconomíc to travel to this area in the future.

Obviously, continuous access from the lagoon through the river mouth wilI be essential for the commercial fishermen based at Raka'ia.

5. D ISCUSS ION

The potential effects of fl ow reductions on fish inhab'it'ing the

Rakaia River include restrictions on passage, reduction of habìtat, 4r. increased temperatures, lowered d'issolved oxygen concentrat'ions, increased sedìmentation due to lack of flushing flows and rapidly fluctuating flows (due to the management of water withdrawals) result'ing in stranding of fish.

Most species of fish from the Rakaia River are migratory and unrestricted passage wìthin the river and through the mouth are of prìme importance. F'igure 2 illustrates the complexìty of the patterns of migrations of Rakaia fish. Each species differs in t'he t'iming of its 'l ìfe cycle, and d'ifferent stages of the I ife history often have different hab'itat requirements. In particular, it should be noted that the timìng of the irrigation w'ithdrawals (September - March) coincides with the upstream m'igrati'on of salmon. The difficulty of establish'ing a residual flow to meet the requirements of each specìes during the period of abstractìon for irrigation'is not hard to apprec'iate.

Fi sheries Research D'ivì s'ion are partìcular'ly concerned about the possìble effects of reduced flows on closure of the mouth. Kirk et al. (1977) noted that draw-off for irrigation works during summer may e'ither increase the size of the lagoon, or, more seriously result ìn closure of the mouth. Yet consideration of the effect on the river mouth of drawing off low flows for ìrrigation appears to have been largely ignored by the irrigation developers. At the mouth of the Hurunui River

(a much smaller river than the Rakaia) constriction and part'ial closure of the mouth were observed to occur naturally during March 9-23 L978.

The mean discharge for March 1978 was 2I.9 cumecs, while the mean monthly discharge for the period of records (1957 - present) is 30.6 cumecs; i.e. a reductìon of approxìmately one third of the mean monthly discharge resuìted in partiaì closure of the mouth, and thìs prevented salmon from entering the river (C.R. Docherty, pers. comm.).

The physical habitat occupìed by a fish can be described in SALMO TRUTTA

ONCORHYNCHUS TSHAWYTSCHA

GALAXIAS BREVIPINNIS

ANGUILLA SPP

GEOTRIA AUSTRAL!S

STOKELLIA ANISODON

RETROP¡NNA RETROPINNA

GALAXIAS MACULATUS

RHOMBOSOLEA RETIARIA

IUPSTREAM AUG SEPT OCT NOV DEC DOWNSTREAM FGURE 2. PATTERNS OF MAIN MIGRATIONS OF FISH INHABITING THE RAKAIA RIVER SYSTEM. 43. terms of depth, velocìty and discharge, although, obvious'ly, other factors such as cover, temperature, sediment, dtssolved oxygen etc. determine the presence of fish in any particular area. Water abstraction causes reduced discharge and changes in the pattern of water velocities and depth below the jntake. At present there is little informatjon on the hydraulic geometry of braided rivers such as the Raka'ia, or on how the geometry changes w'ith discharge. There ìs also no information on how the d'istributjon of the water within the brajds of the river changes. Is a constant percentage of water removed from each braid, or do the smaller braids dry up? From our studies so far, it appears that the side braids are more important for fish and benthic product'ion than the main channels. Therefore these areas must be reta'ined at reduced flows.

There is no information on the annual temperature regime of the Rakaia River. Lìmjted numbers of spot temperatures have been recorded and these show an annual range of 6 - 19oC jn the main braid and up to 22'C 1n sjde braids in February. Water temperature is a function of ambient air temperature, insolation, water depth, velocity and discharge, and thìs expla'ins the higher water temperatures 'in smal ler braids.

Automat'ic temperature recorders wil I be instal I ed 'in d jfferent types of bra'ids of the Rakaja River by FRD for mon'itorìng daily temperature fluctuations this summer.

Morgan and Graynoth (1978) reviewed the current state of know'ledge of temperature tolerances of New Zealand fish, and outlined some of the literature concerning effects of temperature on fish. The effect of increased temperatures in reduc'ing dissolved oxygen concentrations should also be noted. A critical oxygen/temperature situation may occur for salmon at temperatures above 22"C (Church et al. 1979).

The effects of sedimentat'ion on benthic invertebrates were discussed in section 3.2. Sed'iment 'i s tran sported at rate s wh'i ch 44.

depend on water velociities and size of the sed'iment particles (Morisawa 1968). Sediment js deposited when water velocitìes drop. Morgan and Graynoth (1978) reviewed the effects of sed'iment on native fish, trout and other sal mon'ids .

Kì rk e"L aL. ft977 ) dese ribed the effects of modify'ing fl uvial fl ow regìmes" D'isruption of sediment supplies to the coast can accelerate coastal eros'ion and poss'ibly jncrease flood rjsks adjacent to the lower reaches of the channels. They suggested that considerabje future study of the morphologìca1 and quantitative pattern of fluvial-littoral exchanges of rivers and beach systems subject to major catchment development proposals for hydro-electrìc and/or irrìgatìon works is neces sary.

Final'ly, rapìd'ly fluctuating flows below intakes should be avo'ided by carefuì management of the rate of change of irr'igation withdrawals. Swift reductions ìn discharge can cause unnecessary stranding of fish in poo'ls and backwaters, whereas gradual changes in flow permit fish to move out of areas which become unfavourable.

In summary, âh in'itial assessment of the composition of the fish resource of the Raka'ia River has been made, but there is little information on the quantity of the fjsh stocks. The complete life histories of specìes such as the torrentfish and bluegilled buì'ly are as yet unknown, but are currentìy under invest'igation. A survey of trout distrìbut'ion and growth rates has been initiated, but this is a long-term project and'it wjll be two-three years before sufficient data are ava'il abl e .

Investigations into the composition, distribution and relative abundance of the invertebrate fauna and jts utjlisatjon by the fish popuìatjons is currently under investigation. Again, this 'is a long- term project, and it will be two-three years before sufficient data have 45.

been collected so that the effects of reduced flows can be assessed.

Estimates of the numbers of anglers fishing the Rakaia River, the total catch of salmon and trout, and the total number of angler

days spent on thb Rakaia will be made over the next three years, and

an estimate of the total run of salmon'into the Raka'ia River is to be

attempted during the 7979/80 fishing season.

Clearly, this summary of our knowledge of the fish and fìshery values of the Rakaia River is only a progress report. Future studies

may modìfy or completely change some statements which have been made,

and the interim nature of much of the'information contaìned herein must be stressed.

6. ACKNOI^ILEDGEMENTS

I thank my coììeagues at Fisheries Research Division for their respective contributions to this report - Dr Peter Todd on'lampreys

and eels, Tony Eldon on some species of natjve fishes, Martin Unwin

on juvenile salmon and Selwyn Hawke on whitebait. I also thank Paul Sagar and Dr Bob McDowall for reading and commenting on the

manuscri pt.

7. LITERATURE CITED

Alabaster, J.S. 7970. R'iver flow and upstream movement and catch

of migratory salmonids. Journal of Fi sh Bioloq.y 2(1): 1-13.

Allen, K.R. 1956. The geography of New Zealand's freshwater fish. N.Z. Science Review 14(3): 3-9.

Allen, K.R. 7957. Freshvrater fishes. pp. 78-87. In: Callaghan, F.R.

(fA.¡ Scjence in New Zealand. A.H. and A.W. Reed, Well ington. 272 pp. 46.

Al I en , K. R. and Cunn i ngham , B.T. 1957. New Zealand angl ing 1947-52. Results of the diary scheme. .l\.2. Marine Dep_artment, Fjsheries Bul I eti n No. 12. 153 pp.

Benziê, V. 1968. The life history of Gafaxias vuJsarjs Stokell, with a comparison w'ith c. macufatus attentuatus, N.Z. Journal of Marine and Freshwater Research 2(a): 628-653.

Briggs, J.C. 1948. The quantitative effects of dam upon the bottom fauna of a small California stream. Transactions of the American F'isheries Society 78: 70-81.

Burnet, A.M.R. 1965. Observat'ions on the spawning migrations of Gal-axias attentuatus. N.Z. Journal of Science 8(1): 79-87.

'inter-rel Burnet, A.M.R. 7969 " A study of the at'ion between eel s and trout, the invertebrate fauna and the feeding habits of

the fish. N.Z. Marine Department_, Fisheries Techn'ical Report No. 36. 23 pp.

Cadwallader, P.L. 1975. The food of the New Zealand common river Galaxias, caJaxias vutgaris Stokell (Pisces : Salmoniformes). Australian Journal of Marine and Freshwater Reåearch 26(1):

1 5-30 .

Cairns, D. 1941. Life history of the two species of New Zealand freshwater eel. I. Taxonomy, age and growth, mìgration,

and d'istribution. N.Z. Journal of Science gnd Technqlqgy : 53-72. cairns, D. 1942. Life history of the two species of freshwater eel in New Zealand. II. Food and inter-relationships with trout. N.Z. Journal of Science and Technolog.y 823(4): 132-748. 47.

Church, D.F., Davìs, S.F" and Taylor, M.E.U. 1979. A review of the

habítat requirements of fish in New Zealand rivers. l¡Jater and

So'il Techn jcal Publ ication No. 12. 48 pp.

CurtiS, B. 1959" Changes in a river's physica'l characterist'ics under substantjal reductions in flow due to hydro-electrìc diversion.

Cal ifornia Fish and Game 45: 181-i88.

Flain, M. 19702 Precoc'ious male qu'innnat salmon, oneorhgnchus tshawgtscha

(Walbaum) in New Zealand. N.Z. Journal of Marine and Freshwater

Research aQ) : 2I7 -2?2 .

Flain, M. In press. Quinnat salfiþt1 oncorhgnchus tshawgtsc¡a (Walbaum)

runs 1965-1978 in the Glenariffe Stream, Rakaìa River, New Zealand. N.Z. Mjnistry of Agriculture and Fisheries, Fisheries Research Division 0ccasional Publication No. 28.

Fowles, C.R. 1972. Some effects of low flow condjtions on the invertebrate fauna of the 0p'ihi R'iver, South Canterbury, 1972. Report to the South Canterbury Catchment Board. 75 pp.

Fraser, J.C. L972. Reguìated discharge and the stream environment. pp. 263-285. In: 0glesby, R.T., Car'lson, C.A. and McCann, J.A. (Eds.). River Ecology_and Man. Academic Press, New York. 465 pp.

Galloway, J.R. 1979. Salmon research at Glenariffe. N.Z. Minìstry of Agriculture and Fisheries, Fisheries Research Djv'ision Informat'ion Leafl et N0.8. 18 pp.

Gìger, R.D. 1973. Streamflow requirements of salmonids. Oregon Wildlife Commissjon. Federal Aid Progress Report, Fisheries AFS-62-1. 117 pp.

Graham, D.H. 1956. A Treasury of New Zealand Fishes. A.H. and

A.W. Reed , Wel I i ngton . 424 pp. 2nd Ed. 48.

Graynoth, E. and Skrzynski, trrl. 1974. The North Canterbury trout and salmon fishery. N.Z. Ministry of Agriculture and Fisheries, Fisheries Technical Report No. 90. 41 pp.

Hardisty, M.W. and Potter, I.C. (Eds. ) I97I. The Bìo'logy of Lampreys. Vol. I. pp. I27-206. Academic Press, London.

Hawke, S.P. 1978. Stranded redds of quinnat salmon in the Mathias

River, South Island, New Zealand. N.Z. Journal of Marine and Freshwater Research 12(2) : 767-I71.

Hobbs, D.F. 1937. Natural reproduction of quìnnat salmon, brown and

raìnbow trout in certain New Zealand waters. N.Z. Marine

Department, Fi sheries Bul I et'in No .6 . 104 pp.

Hopk'ins, C.L. 1970. Some aspects of the b'ionomics of fish in a brown

trout nursery stream. N.Z. Marine Departlent, Fisheries Research

Bul I eti n N0.4. 38 pp.

Hynes, H.B.N. 1972. The Ecology of Running Waters. Liverpool Universì ty Press. 555 pp.

Jaag,0. and Ambuhl, H. 1964. The effect of the current on the composit'ion of biocoenoses in flowing water streams. pp. 31-49. International Conference on Water Pollut'ion Research, London. Pergamon Press,

London.

Jeì'lyman, D.J. I977a. Invasion of a New Zealand freshwater stream by

glass-eels of two Ansuitta spp. N.Z. Journal of Marine and Freshwater Research 11(2): 193-209.

Jellyman, D.J. I977b. Summer upstream migration of juvenile freshwater

eels in New Zealand. N.Z. Journal of Marine and Freshwater Research 11(1): 6I-7I. 49.

Kirk, R.M., 0wens, I.F. and Kelk, J.G. 7977. River suppl'ies of coastal sediment in Canterbury and the role of low flows'in littoral by-passing. Paper presented to the Annual Symposium of the N.Z. Hydrological Society, held in Christchurch, November 1977. 9 pp., plus 3 figures.

Knight, A.l^1. and Gaufin, A.R. 1963. The effect of water flow, temperature and oxygen concentration on the Plecoptera nymph, Acroneuria pacifica Banks. Proceedings of the Utah Academy of Scìence 40: 175-184.

Kraft, M.E. 1972. Effects of controlled flow reduction on a trout stream. Journal of the Fisheries Research Board of Canada

2e(10): 1405-1411.

Lane, E.D. and Skrzynski, W. 7972. Distribution of native and introduced fishes in the Hinds Rjver system. N.Z. Minìstry of ngriculture and Fis 29 pp.

McDowall , R.M. 1968. Gal-axias macul-atus (Jenyns), the New Zealand whitebajt. N.Z. Marine Department, Fisheries Research Bulletìn No.2 (new serìes). 84 pp.

McDowall, R.M. 1970. The galaxiid fishes of New Zealand. Bulletin

of the Museum of Comparative Zoolog.y 139(7): 34I-432.

McDowall, R.M. 1972. The taxonomy of estuarine and bracki sh-l ake

Retropinna from New Zealand (Galax'io'idei : Retropinnidae).

Journal of the Ro.yal Soci et.y of N. Z . 2Ø) : 501-531.

McDowall, R.M. 1978. New Zealand Freshwater Fishes. Heinemann Educational Books (N.2.) Ltd, Auckland. 230 pp. 50.

Mclay, c.L. 1968. A study of drift in the Kakanui R'iver, New Zearand.

Australian Journal of Marine and Freshwater Research 19: 138-149.

McMillan, H.M. 1961. An addition to the knowledge of the fish Retropinna anisodon Stokell (Retropinnidae). Transact'ions of

the Royaì Society of N.7., Tooloq.y 1(tO): 139-144.

Manikiam, J.S. 1969. A guide to the flatfishes (Order Heterosomata)

of New Zealand. Tuatara 17(3): 118-130.

Maskeì1, F.G. 1929. 0n the New Zealand lamprey, Geotria austrat-is

Gray. Part 1. - Bjoìogy and life history. Transactions and

Proceedings of the N.Z. Institute 69(1): 167-204.

Morgan, D.R. and Graynoth, E. 1978. The 'influence of forestry practìces

on the ecology of freshwater fish in New Zealand. An introduction to the literature. N.z. Minìstry of Agriculture and Fisheries,

Fisheries Research Division Occasional Publ icati-qn Io . 14. 36 pp.

Mor j sawa, M. 1968. Streams: Thei r Dynam'ics and Morphol oq.y.

McGraw-Hjll, New York. 175 pp.

Nebeker, A.v. 1972. Effect of low oxygen concentration on surv'ival

and emergence of aquatic insects. Transactions of the American Fisheries Society 101: 675-679.

Octa Associates Ltd. 1976. Report on the North Canterbury Acc'limatisat'ion Society survey. 30 pp.

Philipson, G.N. 1954. The effect of water flow and oxygen concentration on six species of caddis fly (Trichoptera) larvae. proceedings of the Zoolog'ical Society of London I24: 547-564.

Phillipps, w.J. 1924. Food supply and deterioration of trout in the thermal lakes district, North Island, New Zealand. Transactìons

and Proceedings of the N.Z. Institute 55: 381-391. 51,

Rutter, C. 1903. Natural history of the quìnnat salmon. A

report of investigat'ions in the Sacramento River, 1896-1901. Bulletin of the U.S. Fish Commission 22: 65-141.

Scott, D. 1958. Ecologìcaì studies on the Trìchoptera of the R'iver Dean, Cheshire. Archiv fllr Hydrob'iologie 54: 340-392.

Scott, D., Hewitson, J. and Fraser, J.C. L978. The orig'ins of

rainbow trout sal-mo gairdneri Richardson, in New Zealand.

California Fish and Game 64(3): 270-218"

Sprules, W.M. 1947. An ecological invest'igatìon of stream insects in Algonquin Park, Ontario. University of Toronto Stud'ies, Biologicäl SerieS No.56. 81 pp.

Stalnaker, C.B. Undated. Myths concernìng instream flows. Unpubl ished report, U.S. Fish and hlildl ife Service, Colorado. 13 pp.

Staples, D.J. 197. Production biology of the up'land bully ehitspnoaon

breviceps Stokell in a small New Zealand lake. I. Life history, food, feeding and activity rhythms. Journal of Fìsh Bioloqy 7(1): I-24.

Thienemanh, A. 1954. Ein drittes b'iozënotisches Grundprìnzip. Archiv ftlr Hydrobiologie 492 421-422.

Thomson, G.M. 1922. The Naturalisation of Animals and Plants in New Zealand. University Press, Cambridge. 607 pp.

Todd, P.R. I979a. I,.langanui ìamprey fìshery. Catch 79 (March): 19-20.

Todd, P. R. I979b. Eel exports cl ìmb . Freshwater Catch No .3: 1 .

Todd, P.R. 1980. Size and age of migrating New Zealand freshwater eels (ensuitta spp.). N.Z. Journal of Marine and Freshwater Research 14(3) z 283-293. 52.

West, I.F. and Goode, R.H. In press. A postal sample survey of anglers fishing for sea-run quìnnat salmon (oncorhgnchus

tshawgtsc.rra) on the Rakaja River, Canterbury, New Zealand, for the seasons 1973/74 and 1974/75.