128 W e a t h e r and Climate (1991) 11: 128-131

CLIMATIC WARMING AND NEW ZEALAND MARINE FISH

C D PaulinNational Museum o f New Zealand

Climatic warm ing i n t h e N e w Zealand reg ion w i l l a f f ec t t h e f i s h f auna , increasingdiversity i n t h e n o r t h a n d c e n t r a l areas, chang ing spec ies compos i t i on i n o t h e rareas, causing some populations t o col lapse o r even ext inct ion o f some species.

The k n o w n f i s h f a u n a o f N e w Zealand, compr i s ing 1 0 0 0 spec ies ( P a u l i n e t a l ,1989), has increased dramatical ly i n recent years (F ig . 1 ) . T h i s does n o t mean tha tclimatic c h a n g e i s a l r e a d y a f f e c t i n g t h e f a u n a : t h e inc reased r a t e o f spec iesrecords i s d u e t o t h e g r e a t e r research e f f o r t o n f i s h s y s t e m a t i c s f o l l o w i n gdeclaration o f the Exclus ive Economic Zone i n 1978 a n d i s n o t a ref lect ion o f thegreater a rea covered a s m o s t species a l s o o c c u r w i t h i n t h e 1 2 m i l e z o n e (Pau l inand Stewart , 1985) . T h e geographical a f f in i t ies o f t h e k n o w n fauna ( F i g . 2 ) s h o wsix m a j o r d iv is ions (Roberts a n d Paul in , i n prep.) :

A s ign i f i can t p r o p o r t i o n o f species a r e v e r y p o o r l y k n o w n a n d h a v e n o tbeen a c c u r a t e l y i d e n t i f i e d , c o n s e q u e n t l y t h e i r g e o g r a p h i c a l a f f i n i t i e s a r eunknown. These w i l l b e o f l i t t l e va lue i n moni tor ing changes i n t h e fauna.

2 A p p r o x i m a t e l y o n e h a l f o f t h e s p e c i e s p r e s e n t i n N e w Z e a l a n d a r ewidespread, t h a t i s , f o u n d i n m o s t oceans. T h e percentage o f these widespreadspecies i n o u r fauna i s greater than f o r many o the r regions a n d ref lects t h e sma l lland mass o f N e w Zealand a n d i t s pos i t ion across a b road la t i tud ina l range. T h i sgroup o f species m a y b e expected t o s h o w l i t t l e change i n compos i t ion s i m p l ybecause the re a r e f e w wide-ranging species n o t a l r e a d y h e r e , a l t h o u g h t h eabundance o f some species w i l l change. A n increase i n temperatures w i l l enablesome migra tory species t o rema in i n o u r northern waters f o r l onge r periods.

3 M a n y o f t h e sou thern species, pa r t i cu la r l y t h o s e w i t h an ta rc t i c a f f i n i t i es ,wi l l disappear. T h e present southern, o f f sho re d is t r ibut ion o f these species makesthem d i f f i c u l t t o s tudy, a n d deta i ls o f t he i r l oss t o o u r fauna w i l l b e d i f f i c u l t t odocument. C o o l e r w a t e r schoo l ing species m a y b e a f fec ted dramat ica l ly a n d the remay b e a col lapse o f t he populat ions a n d associated l oss o f important f isheries. I tw i l l b e d i f f i c u l t , h o w e v e r, t o de termine i f a n y co l lapse i s a r e s u l t o f c l ima techange o r o v e r f i s h i n g . C o a s t a l r e e f f i s h e s w i l l b e s e v e r e l y a f f e c t e d . I ftemperatures increase t h e species m a y n o t b e ab le t o co lon ise n e w areas a s la rgestretches o f sandy a n d m u d d y coast l ine a r e e f fec t ive barr iers t o t h e i r d istr ibut ion.Dispersal t o n e w areas m u s t r e l y o n pelag ic eggs o r juveni les t h a t a r e car r ied i nocean cur ren ts , a n d t h a t movemen t w i l l h a v e t o b e aga ins t p r e v a i l i n g c u r r e n tpatterns i n some areas. Furthermore, t h e r a t e o f change m u s t n o t b e t o o r a p i d t oensure t h a t t h e species c a n con t i nue t o b r e e d successfu l ly w i t h i n t h e i r ex i s t i ngranges w h i l e t h e i r eco log ica l requirements become establ ished i n n e w areas.

I f i n c r e a s i n g t e m p e r a t u r e s d r i v e s p e c i e s s o u t h w a r d s , t h e i r a b u n d a n c e w i l ldecrease d u e t o reduced hab i t a t ava i l ab i l i t y. Un less t h e r e i s a m a j o r change i noceanic c i r c u l a t i o n pa t te rns , m a n y s p e c i e s c o u l d h a v e t h e i r geog raph ic r a n g enarrowly r e s t r i c t e d b e t w e e n t h e w a r m e r temperatures t o t h e n o r t h a n d c o o ltemperatures t o t h e south. T h u s w e m a y observe a compression o f the central N e wZealand f a u n a l r e g i o n .

Some species a r e dependent u p o n coo le r temperatures f o r successful b reed ing a n dstudies h a v e shown t h a t i n w a r m e r years i n t h e Haurak i G u l f there i s a l ready a

Climate Change and Fish 1 2 9

noticeable d r o p i n breeding success o f f lounder (Co lman, 1973) .

Many species breed i n areas o f coo l a n d w a r m w a t e r convergence a n d these f o r mthe f o c u s f o r several impor tan t f isher ies (Pau l , 1986 ) . I f these convergence zonesdisappear t h e r e w i l l p o s s i b l y b e a s i gn i f i can t decrease i n ocean i c p r o d u c t i v i t yand subsequent decrease i n f i s h n u m b e r s . C o n v e r s e l y n e w convergence z o n e smay f o r m , b u t the re seems l i t t l e chance o f predict ing these a n d o t h e r changes t oexisting c u r r e n t p a t t e r n s .

4 F i s h e s t h a t a r e f o u n d throughout temperate Aus t ra las ia w i l l s h o w changesin abundance i n d i f fe rent regions o f N e w Zealand. W i t h i n t h i s g roup there w i l l b efew i f a n y changes i n ac tua l species, un less t h e r e i s s o m e change i n c u r r e n tpatterns o r o t h e r f a c t o r s i n f l u e n c i n g rec ru i tmen t . R e c r u i t m e n t o f f i s h t o N e wZealand waters i s o f t e n b y dispersal o f eggs a n d la rvae i n ocean currents. M a n yspecies have re la t ive ly sho r t la rva l per iods a n d a r e n o t carr ied t o N e w Zealand b ythe Tasman current . I f t h i s w e r e t h e case there w o u l d a l ready b e several hundredadditional A u s t r a l i a n spec ies h e r e . S c h o o l i n g demersa l f i s h e s o f w a r m e r w a t e r swi l l p r o b a b l y e x p a n d t h e i r r a n g e s f u r t h e r s o u t h . F o r e x a m p l e s n a p p e r m a ybecome commerc ia l l y f i shab le i n Canterbury a n d O t a g o waters . T h e l o w numbersof t h i s spec ies i n t r o p i c a l A u s t r a l i a n w a t e r s (G loe r fe l t -Ta rp a n d K a i Iola, 1 9 8 5 )suggests there m a y b e a decrease i n abundance t o t h e nor th .

Many spec ies o f f i s h e s a r e k n o w n t o under take a n n u a l m ig ra t i ons t o b reed inggrounds (Rober ts , p e r s c o m m ; F ranc is , 1 9 8 1 ) . I f temperatures r i s e a n d b reed ingfails a t these g rounds , t h e popu la t ion m a y co l lapse. Presumably t h e r e a r e o t h e rbreeding g rounds t h a t a r e a t present o f m i n o r impor tance a n d eventua l recoveryof t he populat ion m a y occu r as s tock f r o m these grounds expands.

Climatic change w i l l p robab l y h a v e s i m i l a r e f fec ts o n d e e p w a t e r f i shes. T h e s efishes s h o w d i s t i n c t f a u n a l assemblages n o r t h a n d s o u t h o f t h e convergencezones j u s t a s i s seen i n coasta l o r pe lag ic f i shes . M a n y d e e p w a t e r f i s h h a v epelagic e g g s a n d juven i les w h i c h f l o a t t o su r face wa te r s b e f o r e metamorphosingand se t t l i ng t o t h e bo t t om. A l t h o u g h t h e a d u l t popu la t ion m a y n o t b e a f fec teddirectly, t h e species w i l l b e exposed t o c l imate change a t t h e pelagic phase o f thelife c y c l e . A l s o , w a r m i n g o f surface wa te rs a n d m o r e se t t led weather condi t ionsmay reduce t h e amoun t o f m i x i n g o f wa te r layers w i t h a subsequent decrease i nproductivity, resu l t ing i n a general dec l ine i n deep w a t e r f i s h populat ions.

5 M o s t changes t h a t w i l l b e r e a d i l y observed w i l l b e changes i n spec iescomposition a n d abundance o f t h e t r o p i c a l a n d subt rop ica l f i s h e s t h a t p resent lyreach o u r no r the rn wa te rs : w e c a n e x p e c t a n increased d i v e r s i t y a m o n g these.However i t w i l l b e d i f f i cu l t t o determine i f n e w species records a re as a resul t o fglobal wa rm ing e ffec ts o r s imp ly t h e resu l t o f t h e cumulat ive e ffec ts o f increasedcollecting a n d research. T h e increase i n species recorded s i n c e t h e beg inn ing o fthe 1980s i s n o t a resu l t o f g loba l warming , y e t a s ign i f icant p ropor t ion o f t ha tincrease h a s b e e n t r o p i c a l s p e c i e s c o l l e c t e d o r p h o t o g r a p h e d a t n o r t h e r noffshore is lands (Francis, Grace and Paul in, 1987; Francis, i n prep). M a n y o f thesetropical spec ies s t ragg le t o N e w Zea land a t i r r e g u l a r i n te rva l s a n d r e f l e c t t h eongoing, dynamic changes o f o u r environment. O n l y i n t h e l o n g t e r m w i l l w e b eable t o determine w h a t changes h a v e occurred.

Tropical cyc lones h a v e a n in f luence o n dispersal a n d a n increase i n t h e numberof cyclones w i l l a f fec t t h e species composit ion o f the fauna. I t i s possible t ha t t h einfluence o f cyc lones , r a p i d l y b r i n g i n g quan t i t i es o f sub t rop ica l w a t e r t o o u rregion, m a y b e m o r e impor tan t i n t ransport ing eggs a n d l a r vae t h a n t h e v o l u m eof wa te r car r ied b y t h e ocean currents.

The meteoro log ica l r e c o r d s h o w s t h a t t h e m id -1970s w a s unusua l i n t h a t t h e r e

130 C l i m a t e Change and Fish

were t h ree t rop i ca l cyc lones i n o n e summer (Reve l l , 1981 ) . T h i s p e r i o d m a y b eresponsible f o r t h e o b s e r v e d i nc rease i n s u b t r o p i c a l f i s h e s i n n o r t h e r n N e wZealand d u r i n g t h e 1970s . A l t h o u g h 1 9 7 1 w a s recorded a s a pa r t i cu la r l y w a r myear, t h e l a t e r years w e r e c o o l (Pau l , 1978) , a n d t h e observed increase i n t rop ica lspecies occur red f r o m t h e mid -1970s onwards. T h e 1 9 8 0 s h a v e b e e n w a r m , b u tthere has been a dec l ine i n t h e abundance o f t ropical species, a l though the re a r eindications o f a n increase i n t rop ica l species f o l l ow ing cyc lone B o l a i n 1988 . T h edecline o b s e r v e d i n t h e e a r l y 1 9 8 0 s m a y b e t h e r e s u l t o f t h e p o p u l a t i o n sestablished i n t h e m id -1970s m a t u r i n g a n d d y i n g , b u t , because o f unfavourableenvironmental cond i t ions , t h e y w e r e unab le t o breed.

6 E n d e m i c mar ine f ishes, w i t h a f e w exceptions, a r e genera l ly p o o r l y k n o w nand a r e restr ic ted i n d is t r ibut ion. Changes i n abundance a n d ranges o f these w i l lbe impor tan t ind ica tors o f chang ing condi t ions. T h e r e a r e a b o u t 1 3 0 species o ffish tha t a re endemic t o N e w Zealand (Paul in e t a l . , 1989). Some o f those restrictedto c o o l e r southern w a t e r s m a y become e x t i n c t i f temperatures r i s e , s i n c e t h e r eare n o m o r e i s lands t o t h e s o u t h w h e r e populat ions c o u l d ex i s t . O t h e r endemicspecies h a v e v e r y rest r ic ted ranges, a n d populat ions m a y n o t b e l a r g e enough t oensure t h e species s u r v i v a l i f condi t ions change t o o r ap id l y.

Only one species o f N e w Zealand f i s h i s known t o have become ex t inc t i n histor ictimes: t h e N e w Zealand gray l ing (McDowal l , 1978). T h e nex t century m a y witness aperiod du r i ng w h i c h o u r endemic f i shes w i l l b e depleted i n number a n d d ivers i tyas severely a s o u r endemic b i r d fauna has been o v e r t h e l a s t century. T h i s w o u l dbe a ser ious s i tuat ion, b u t w e d o n o t a s y e t k n o w h o w dramat ic t h e e f fec ts o fclimate change a re g o i n g t o be .

Re fe rences

Colman, J A, 1973. Spawning and fecundity o f two flounder species i n the Hauraki Gulf, NewZealand. New Zealand Journal o f Marine and Freshwater Research 7: 21-43.

Francis, M P, 1981. Spawning migration o f mok i (Latr idopsis c i l i a r i s ) o f f eastern N e wZealand. New Zealand Journal o f Marine and Freshwater Research 15: 267-273.

Francis, M P i n prep. Additions t o the f i sh faunas o f Lord Howe, Norfo lk and KermadecIslands, South-west Pacific Ocean.

Francis, M P; Grace, R V; Paulin, C D , 1987. Coastal fishes o f the Kermadec Islands. N e wZealand Journal o f Marine and Freshwater Research 21: 1-13.

Gloerfelt-Tarp, T; Kailola, P J, 1985. Trawled fishes o f Southern Indonesia and NorthwesternAustralia. Australian Development Assistance Bureau. 406 pp.

McDowall, R M, 1978. New Zealand Freshwater Fishes, a guide and natural history. HeinemannEducational Books, Auckland. 230 pp.

Paul, L J, 1978. Historical trends i n New Zealand's sea temperatures. pp 70-74 i n : Habib, G ;Roberts, P E R (comps). Proceedings o f the pelagic fisheries conference July 1977. Fisher iesResearch Division Occasional Publication 15: 102 pp.

Paul, L J, 1986. New Zealand Fishes, an identification guide. R e e d Methuen, Auckland. 184PP.

Paulin, C D; Stewart, A L, 1985. A l i s t o f New Zealand teleost fishes held i n the NationalMuseum of New Zealand. National Museum o f New Zealand Miscellaneous Series N o 12.

Climate Change and Fish 1 3 1

Paulin, C D; Stewart, A L; Roberts, C D; McMillan, P J, 1989. New Zealand Fish, a completeguide. National Museum o f New Zealand, Government Print Books, Wellington.

Revell, C G, 1981. Tropical cyclones i n the south-west Pacific, November 1969-April 1979.New Zealand Meteorological Service Miscellaneous Publication 170.

Roberts, C D; Paulin, C D, i n prep. Biogeographic affinities o f the New Zealand fish fauna.

Figure 1 N u m b e r o f species o f f i sh recorded f r o m N e w Zealand

Paufin et at1000

500

Unknown

0

Endemic

Forster

—co c oYEAR o C P0 0

Hutton

WaiteSherrin

Philipps W h i t l e y

Co

Graham

Figure 2 N e w Z e a l a n d Ich thyofauna: geograph ica l a f f i n i t i e s

Paulin&Stewart

Indo-PacificAustralian

subtropical t r o p i c a l w a r m temperatecool temperate

Southernklemisphere

subantarctic

Widespread

AYling

No. OF SPECIES