128 W e a t h e r and Climate (1991) 11: 128-131 CLIMATIC WARMING AND NEW ZEALAND MARINE FISH C D Paulin National Museum of New Zealand Climatic warming in the New Zealand region will affect the fish fauna, increasing diversity in the north and central areas, changing species composition in other areas, causing some populations to collapse or even extinction of some species. The known fish fauna of New Zealand, comprising 1000 species (Paulin et al, 1989), has increased dramatically in recent years (Fig. 1). This does not mean that climatic change is already affecting the fauna: the increased rate o f species records is due to the greater research effort on fish systematics following declaration of the Exclusive Economic Zone in 1978 and is not a reflection of the greater area covered as most species also occur within the 12 mile zone (Paulin and Stewart, 1985). The geographical affinities o f the known fauna (Fig. 2) show six major divisions (Roberts and Paulin, in prep.): A significant proportion of species are very poorly known and have not been accurately identified, consequently their geographical affinities are unknown. These will be of little value in monitoring changes in the fauna. 2 Approximately one half of the species present in New Zealand are widespread, that is, found in most oceans. The percentage o f these widespread species in our fauna is greater than for many other regions and reflects the small land mass of New Zealand and its position across a broad latitudinal range. This group of species may be expected to show little change in composition simply because there are few wide-ranging species n o t already here, although t h e abundance o f some species will change. A n increase in temperatures will enable some migratory species to remain in our northern waters for longer periods. 3 M a n y o f the southern species, particularly those with antarctic affinities, will disappear. The present southern, offshore distribution o f these species makes them difficult to study, and details of their loss to our fauna will be difficult to document. Cooler water schooling species may be affected dramatically and there may be a collapse o f the populations and associated loss o f important fisheries. I t will be difficult, however, to determine i f any collapse is a result of climate change or overfishing. Coastal reef fishes will be severely affected. If temperatures increase the species may not be able to colonise new areas as large stretches of sandy and muddy coastline are effective barriers to their distribution. Dispersal to new areas must rely on pelagic eggs or juveniles that are carried in ocean currents, and that movement will have to be against prevailing current patterns in some areas. Furthermore, the rate of change must not be too rapid to ensure that the species can continue to breed successfully within their existing ranges while their ecological requirements become established i n new areas. If increasing temperatures drive species southwards, their abundance will decrease due to reduced habitat availability. Unless there is a major change in oceanic circulation patterns, many species could have their geographic range narrowly restricted between the warmer temperatures to the north and cool temperatures to the south. Thus we may observe a compression of the central New Zealand faunal region. Some species are dependent upon cooler temperatures for successful breeding and studies have shown that in warmer years in the Hauraki Gulf there is already a
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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
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