Fish of the. Gulf. Hauraki. in brackish or sheltered conditions. N.Z. ECOLOGICAL SOCIETY 45. south-east of the outer Gulf) in

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1 NZ ECOLOGCAL SOCETY 45 more exposed shores and the replacement of C columna tself by Elmnus modestus n bracksh or sheltered condtons The effect of the type of substrate can be seen n the absence of Apophloea snclar from Watemata sandstone and the lower mdlttoral domnance of the Hormosra-corallna assocaton on ths substrate The combned effects of both factors can be seen n the replacement of the Hormosra-corallna assocaton on exposed coasts by red and green algal mats (eg Lttle Barrer) The sublttoral frnge s clearly defned on the exposed coasts but ths zone dsappears at the more sheltered statons and here the frnge speces are those domnant n the sub- lttoral eg carpophyllum maschalocarpum - have dvded the sublttoral nto upper md and lower sublttoral Brown algal speces such as the carpophyllums characterse the upper sublttoral and a red algal belt composed of Pteroc/ada-Vdala-Melanthala the mdsublttoral Then follows a further brown algal zone n deeper water wth Ecklona radata as the physognomc domnant Only f the water s suffcently deep do all these sublttoral zones occur and on sheltered coasts there s frequently a telescopng of the upper and lower sublttoral wth the excluson of the red algae of the mddle zone REFERENCES HELLOW U V ]955: rak Gulf New Marne algalcc()1ogy of the bm- ZeWand Trans Roy Soc NZ 8;~ 1-91 S[RPKKSON l Aana Sn;PH<;NSON A 1949: The unyerfal felh:t-ure:; of zonjruton b~h"fen tde markl on T"o(~kyeoa:><ts1 Reol n 289-:105 Fsh of the Haurak Gulf M K McKenze Fsheres Laboratory Marne Dept Wellngton Ths paper presents some bologcal and ecologcal nformaton obtaned from records of the last sx years of catches n the nner Gulf and adjacent fshng areas by the Marne Departments fshery research trawler katere ABUNDAKC: Snapper was the most abundant commercal speces caught by katere n the nner Gulf wth gurnard second and trevally thrd John dory mackerel kahawa leatherjacket varous rays (especally the eagle ray) and spotted dogfsh were all reasonably common Flounder and lemon sole were caught n small numbers along the south-eastern and eastern shores Tarakh second n commercal mportance to snapper was plent ful n the outer Gulf and Bay of Plenty (mmedately south-east of the outer Gulf) n the deeper waters where t accounted for practcally the entre dfference between snapper and the total marketable catch Annual percentages of snapper n relaton to the total marketable speces are shown n Table 1 Numbers alone do not gve a measure of productvty A unt whch ncludes fshng effort (e numbers of legal-szed fsh per fshng hour) has therefore been ntroduced nto the table for comparson Ths unt s not readly compared wth commercal standards of weghts and values but t s farly adaptable and shows clearly the relatve states of the varous grounds as judged by kateres trawlng records The total marketable catch has been chosen for ths comparson because ths affects the avalablty of fsh to the publc rather than a unt nvolvng one partcular preferental speces

2 46 NZ ECOLOGCAL SOC ETY ~--- - nner Gulf Outer Gulf We5tern Bay of Plenty Year Ca(ch (Md Jlarket Market % Snapper Yo Snapper Market Legal FshjJlsJtfllg llour Speces Speces Spec:es % Snapper ~ ~ "--" :1 ]otal Crutch ~{ 0 - Logal Sre 1lG25 85~/o 1839 (\0% 0 - Logal Ftlh/<"shng lour ]:W ;)4 j()tnl Catch 86:J:1 83% ]327 71% % Legal Sze ) (}21o l:!:n 0/ >~rx 0 " 0 T(Jgal F~h/F~hng Hour 15(; <) a5 - " 1955 Totnl Cateh 1:n4 99% :1570 Legal Sze ]150 99% 0-41)] Legal F~h/l"shng Hour ~t34 2{ - " 195G o{al (4thh ~\]49 78% JegaJ Sze 0) r:: 69) 97% % LeglL Fhh/Fshng Hour 4( :~ otal Catch GO 9% Legal Sze ]898 "77 (j ] Log-al Fsh/Fshng Hour 1:J ] Total Cuteh 2:JG8: % % LegW Sze ()~o )" "/0 Legal ]~h/fshng Hour ~ ]207 - ]953 Tot-al Gakh (2(6~: % to Legnl Sze fo GlOl (Wo :18]8 24% 1958 LegaJ F~h/Fshng Hour lahtf 1-Nmncrcul GatCh of Rnapper Gomparetl 11!th Total Mark:erllble Spr:c(; Fgures for the nner Gulf were generally much hgher than for the other regons However much of the nner Gulf s closed to commercal trawlng and dansh senng the combned efforts of whch account for 8810 of the total landngs at Auckland The fshng effort for these confned waters contrasted markedly wth the other two open areas whch supply a major porton of the commercal catch LENGTH FUEQUENCJ<:H AND GROWTH RA: Because of ts commercal mportance snapper has receved the greatest attenton Measurements have been made of the forklength n half nch ntervals Modal lengths were usually clear n fsh below 12 nches but were unrelable age-length ndcators beyond ths due to the reduced growth rate The most comprehensve and comparable data have been selected for Table 2 The catch for December 1958 showed few modes due to the large mesh used thus allowng an easy escape of small fsh The sgnfcance of ths wll be dscussed under the headng of mgraton Growth rates of other speces are stll n doubt Modes from a sample of 6416 gurnard taken durng the summer of showed at 6 9 possbly 11 12\1 and 13\1 nches These lengths probably represent fsh of one to fve years Catches of small trevally n the Gulf have been too few for growth rate determnatons Of 817 fsh taken durng the summer of the most persstent modal length was 13 nches whch probably ndcated the sze of the major schoolng populaton RRlHODUCJON Snapper are known to spawn n the nner Gulf between md-november and md-january between Tr Tr sland Kawau sland and the western coast Another small ground n the south-eastern area has been reported by Thames fshermen the spawnng takng place about sx to eght weeks earler Ap-

3 SOCETY NZ ECOLOGCAL 47 parently ths speces requres a surface water temperature of about 19C for spawnng and t s not yet known whether the fsh shed ther eggs n the water mass above the thermoclne or ndscrmnately throughout Eggs of a varety of szes were dstngushed n the surface plankton samples collected durng successful snapper spawnng seasons n the nner Gulf Average szes of the common sphercal eggs were as follows :-snapper 091 mm gurnard 133 mm john dory 195 mm trevally and kahawa both mm and yellow-eyed mullet 087 mm Of these gurnard eggs were very common The ellptcal anchovy eggs were sporadcally numerous All these speces are known to be capable of spawnng durng the snapper season Several speces of undentfed eggs were present n small numbers All the above speces except yellow-eyed mullet have a sngle ol globule and are very smlar n appearance except for sze The early development of the snapper has been closely observed from artfcally fertlsed eggs to the stage of the absorpton of the larval yolk sac However the young larvae have not been found n the surface plankton samples n contrast larvae and post-larvae of gurnard john dory and anchovy have probably been dentfed n plankton samples collected for tarakh lfehstory projects FOOD Our present knowledge of the food taken by the commonest commercal speces has been restrcted to trawl-caught fsh For snapper the general det conssted manly of bottom fauna ncludng varous crustaceans (especally hermt crabs) shellfsh (manly bvalves) brttlestars and worms Occasonally small squds were taken whle salps were voracously devoured n season The food elements were generally large enough to be recognsed by the unaded eye A sample examned from any sngle trawl catch generally showed a farly large proporton of fsh wth empty stomachs and guts Thus bottom-dwellng snapper were there for two purposes-feedng and restng However the type of det stated above may be confned to the more sedentary populaton of snapper mmedately pror to and durng the spawnng season school snapper become very promnent n the nner Gulf These fsh are of unform sze (about 12 nches) are brghtly coloured and move n large groups They have sharp teeth n contrast to the blunt almost plate-lke teeth of the "resdents" School snapper appear to come from the outer Gulf and may have been lvng a more actve md-water exstence wth a consequent change n det The feedng habts of gurnard have been mpossble to assess from trawl-caught specmens because they have come on board wth the stomach almost nvarably everted However Graham states that they use ther dgt-lke free pectoral fn-rays for feelng ther food whch conssts of moble bottom fauna manly together wth free-swmmng shrmps cephalopods and small fsh Trevally have also been examned but not from ths partcular regon Ther food has been smlar to that of bottom-dwellng snapper but the elements have been smaller :\f GRA TQ:\B Most of the taggng n the Gulf has been concentrated on snapper Trawl-caught fsh are useless for the purpose but over 2000 lne-caught fsh have recently been tagged manly n shallow waters round Great Barrer sland durng the summer months Spawnng fsh and those n deeper waters have not yet been successfully tagged Returns of tagged snapper have shown some nterestng facts So far of nneteen detaled recoveres ffteen were taken wthn a mle or two of the ponts of release Two tagged n the nner Gulf were found about 25 mles away one from the outer Gulf about 40 mles and the fourth from Great Barrer about 260 mles beng recovered off the northern headland of Poverty Bay (south of East Cape) four months after ts release The other travellers had been at lberty from eght to sxteen months Thus" the majorty of these nshore snapper appeared to be "resdents" although they may have moved away and returned the followng summer-a possblty whch s ndcated by the recovery date of some of the fsh agreeng closely wth the annversary of the taggng

4 Modal Lengths Expressed n nches Area Source Date Mesh Sze n /0 under /0 over ~-~of Net lon 12 n Age n Years:- 1 t 2 21 " ;\ Gulf Marne D~ Bull 11 Waheke & Aug! n % nner Gulf Envrons Outer Gulf Danels :Mereury s- Aug 11 n /0 400/ JanjFeb Hn! % Outer Mercury 18-! Gulf Barrers 1957 nner Longhurst :Ua!re!h - Gulf J/F Tr Tr nner Longhurst - }f{uch Gulf ScaJe Dam 1958 nn" Vaheke- Dee 5 n Gulf COTomandel % 337% TABLE2-LengthFrequ-ences of Snapper n Haura1d Gulf

5 NZ ECOLOGCAL SOCETY 49 Besdes ths factual evdence there also appears to be a seasonal nshore-olshore movement-the larger commercal-szed fsh beng found nshore n wnter whle the smaller fsh frequent these waters n the summer Ths s borne out n the shallow water catch fgures lsted n Table 2 When a small mesh net was used 31 %-35% of the catch was mmature (under 10 nches) durng August whle t roseto about 53% durng the summer The 5-nch mesh noted n the last entry would allow most of the mmature fsh to escape yet the percentage stll stood at 365% thus ndcatng a much hgher proporton of small fsh n the nshore populaton durng December males Movements of other speces n the Gulf are very lttle known Records of trawl catches however seem to show some sexual segregatons and mgratons n certan Elasmobrachs Durng the sprng and summer eagle rays showed a proporton of three to one female (150 specmens) n the nner Gulf compared wth two females to one male (66 fsh) n the outer Gulf Durng : the wnter both regons produced a preponderance of females (67 specmens) Sexual segregaton of spotted dogfsh has also appeared n the eastern shallow waters of the nner Gulf durng sprng and summer three males were caught to every two females (140 fsh) whle the poston was exactly reversed n the wnter months on the western sde of the nner Gulf (51 specmens) Outer Gulf fgures showed no such segregaton durng the summer (63 fsh) but durng the sprng females outnumbered males by fve to one (29 fsh) Other Elasmobranchs were too few for such examnaton but sexual segregaton was not obvous Ths contrbuton deals wth only those fsh whch spend some part of ther tme on or near the sea-bottom The recently acqured md-water trawl net wll open up entrely new felds of research nto the bology ecology and behavour of our marne fshes and the effcent handlng of t s awated wth keen nterest Nmu;:\CJJALURE lbloo:rt$: Flounder (<<l:tb) GUTlmrd 1ohn 1>ory Kaba;wa Leather hu~k (cream fsh) Lemon sole MnckC<r~l (yeu()w-tnl) Snapper "mkhl lrm"ally Yellow-eyed mullet Elasmoblancls: Eagle ray Spotted dobmhl1 (pok~) 01< FSH - Rhomuosolca plebea - Trgla kumu - Zeus faber - Arrps trutta - Canthernes scaber - Pelotrets ftavlatus - TrachurUs declrs - Chrysophrys auratuf -ChlUodadylus macropterus - Caranx lutescens - Agnostomus for<;te1" - Aetobatus tenucaudatu8 - M uselus antarctcus RE>ERENOES ANON 1958: NZ Marne Dept Ann RQp 1957 CASSE R M 1955: The Eseacpement of Small Fsh fr()ll Trawl Nets Fsh Bull Wellngton NZ : Ettr1y Devehpme-bt of the Snapper Chrysophrys auratus FQJ"frter Trans Roy Soc NZ 8:~ (4): 705-7;~ - 195(: Age and Gt<owltJ]lof the Snapper Ckrysophrys ajlwatus FwStol n Haumk Gulf Trans Roy Soc NZ 84 (2): GRAHAM D H 1953: A Treasury of New Zealand Fshes A Hand A W Reed \Vellngton LONGHURSTA R 1958: Raefl Dff()rences ~n Sze ant] Growth n the New Zeahmd Sru:tpper NZ 1 Sc 1 (4)