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L I S T O F F I G U R E S
A map show ing the d i s t r i bu t i on o f t he ca tches o f Pe r thh e r r i n g i n m a r i n e a n d e s t u a r i n e e n v i r o n n e n t s , w i t h t h econ t r i bu t i on made by each exp ressed as a pe rcen tage o fthe to ta l ca tch fo r t he pe r iod be tween Ju l y 1975 and June1 0 4 ?
The re la t i onsh ip be tween (a ) t he number o f days spen tf i sh ing pe r mon th and the number o f boa ts ca tch ing Per thh e r r i n g p e r m o n t h f r o m J u l y l 9 7 I t o J u n e 1 9 8 3 , a n d ( b )annua l va lues fo r t he mean mon th l y number o f boa tsca tch ing Per th he r r i ng and the mean mon th l y number o fboa ts i n t he to ta l Swan Es tua ry f l ee t f o r t he pe r iodL 9 7 L / 7 2 a n d L 9 8 2 / 8 3 .
The annua l ca tch o f Pe r th he r r i ng and the annua l meanmon th l y number o f boa ts i n t he f i sh ing f l ee t o f t he SwanEs tua ry be tween L952 /53 and 1982 /83 . The annua l meanmon th l y ca tch pe r boa t t ak ing Per th he r r i ng (CPUE) i sa l so g i ven . N .B . The va lues fo r t he yea rs be tween1 9 6 7 / / 6 8 a n d L 9 7 O / 7 L r e p r e s e n t e s t i m a t e s ( s e e S e c t i o n
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The rnea n monthlyt h i s s p e c i e s i nJ u n e 1 9 8 3 .
The annua l ca tch( s o I i d l i n e ) a n dbe tween l97 O /71
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The to ta l mon th l y ca tch o f Pe r th he r r i ng by pu rse se ine(above ) and hau l ne t (be low) i n t he i nsho re mar ine wa te rsnear the Swan Es tua ry .
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Dept , F i sh . W i ld l . Wes t . Aus t . Rep t . No 66 1984 , L -17
THE FISHERY FOR PERTH HERRING, NEMATALOSA VLAIV|INGHI (MUNRO)
C . F , C H u s s - , N . G , H A L L - , R . C , J ,LENANToN- & I .C . PoTTER"
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P . 0 . B o xA u s t r a l i a n M a r i n e
2 0 , N o r t h b e a c h ,R e s e a r c h L a b o r a t o r i e sl ^ l e s t e r n A u s t r a l i a 6 0 2 0
S c h o o l o f E n v i r o n m e n t a l a n d L i f e S c i e n c e sM u r d o c h U n i v e r s i t yM u r d o c h , l , l e s t e r n A u s t r a l i a 6 1 5 0
A B S T R A C T
l h e W e s t e r n A u s t r a T i a n c a t c h s t a t i s x i c s f o r t h eP p r l h h F r f i n t f i s h . ' r r t n v a r f h a 7 ^ a f 2 n , , e a r s h a V e
b e e n e x a m i n e d . . W h i f e t h e r e a x e p o c k e t s o f c a t c h e sb e t w e e n B r o o m e a n d B u n b u r g , t h o s e f t o m t h e s w a nE s x u a t g a n d n e a r b g i n s h o t e m a r i n e w a t e t s m a k e b gf a r x h e m o s t i m p o r t a n t c o n t r i b u t i o n t o t h e f i s h e r g .I n t h e S w a n E s t u a x g , t h e c a t c h e s s f a - r t e d r i s i n g i nt h e 1 9 5 0 s i n x e s p o n s e t o a d e m a n d b g t h e r o c kT o b s t e x i n d u s t r g f o t b a i t a n d r e a c h e d p e a k v a T u e si n t h e T a t e 1 9 6 O s a n d e a t T g 7 9 7 0 s . D a t a a r ep r o v i d e d w h i c h d e m o n s t r a t e t h a t c a t c h p e r b o a ti s a g o o d i n d e x o f c a L c h p e r u n i x e f f o r t ( C P U E )
i n t h e p e r i o d s i n c e 1 9 6 7 w h e n m a r k e t d e m a n d h a st e n d e d x o s t a b i l i s e . T h e C P U E i n x h e S w a n E s x u a t gr e a c h e d a p e a k i n A u g u s t a n d s e p t e m b e r a t t h e t i m ew h e n P e r t h h e r r i n g s t a r t m o v i n g f r o m t h e s e at o w a t d s t h e i t s p a w n i n g g r o u n d s i n t h e u p p e re s x u a r g , e x c e p t w h e n I a r g e c a t c h e s w e r e t a k e ni n n e a t b g m a t i n e w a t e r s . e c a s e i s m a d e f o t
c o n s i d . e r i n g t h e P e r t h h e r r i n g f o u n d i n t h e S w a nE s t u a t g a n d T o c a l m a r i n e w a t e r s a s a u n i t s t o c k .D a x a a r e p r e s e n t e d w h i c h i n d i c a t e t h a t , i f t h i sa p p r o a c h i s v a l i d , r e c r u i t m e n t d e c l i n e d i n t h ee a r T g 7 9 8 0 s f o T T o w i n g a p e r i o d o f h i g h c a t c h e si n T o e a i m a r i n e w a t e r s d u r i n g x h e T a t e 1 9 7 0 s .
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T h e e s t u a r i n e a n d s e v e r a L i n s h o r e m a r i n e f i s h e r i e s o f W e s t e r nA u s t r a l i a a r e m u l t i g e a r , m u l t i s p e c i e s a n d m u l t i s t o c kf i s h e r i e s ( L e n a n t o n , I 9 8 4 ) . T h u s , i n t h e S w a n E s t u a r y , w h o s eP e r t h h e r r i n g f i s h e r y i s b y f a r t h e m o s t i m p o r t a n t i n t h eS t a t e ( s e e S e c t i o n I i . B ) , g i l l n e t t i n g , h a u l n e t t i n g , f i s ht rapp ing and hand l i n ing wou ld each tend to ca tch a number o fc o m m e r c i a l l y i m p o r t a n t s p e c i e s . W h i I e t h e r e i s l i t t l ea l t e r n a t i v e - t o L o n s i d e r i n g t h e f i s h i n g b o a t a n d i t s c r e w a n dg e a r a s o n e f i s h i n g u n i t , t h e w o r k o f L e n a n t o n ( 1 9 8 4 )ind i ca tes tha t such an app roach i s va l i d . The Per th he r r j ' ngf i s h e r y i n a l l r e g i o n s i s b a s e d o n g i I I n e t t i n g a n d h a u l .ne t t i n -g , bu t i s somet imes supp lemen ted by pu rse se in ing i nt h e m a r i n e w a t e r s o f s o u t h - w e s t e r n A u s t r a l i a .
Da ta on Per th he r r i ng ca tches were ob ta j ' ned f rom the Wes te rnA u s t r a l i a n D e p a r t m e n t o f F i s h e r i e s f i l e s a n d f r o m t h e c a t c hsummar ies p rov ided by the annua l pub l i ca t i ons o f t heA u s t r a l i a n B u r e a u o f S t a t i s t i c s . T h e s e d a t a a r e b a s e d o nf i s h e r m e n ' s c o m p u l s o r y m o n t h l y c a t c h r e t u r n s f o r e s t u a r i e sa n d m a r i n e w a t e I s , t h e l a t t e r p e i n g d i v i d e d i n t o b l o c k s , e a c he q u i v a l e n t t o I " I a t i t u d e b y I " l o n g i t u d e ( F i g . f ) .
I I . T H E F I S H E R Y
A . F I S H I N G T E C H N I Q U E S A N D S O U R C E S O F D A T A
B . D I S T R I B U T I O N O F ' C A T C H E S A N D T H E I M P O R T A N C E O F T H E
SWAN RIVER REGION
N e m a t a l o s a v l a m i n g h i i s f i s h e d c o m m e r c i a l l y a t l o c a l i t i e s o fE r l rnan se tE femen t be tween Broome and Bunbury . I n morenor the rn a reas , t he ca tches o f Pe r th he r r i ng tend to bere la ted to seasona l ava i l ab i l i t y and the demands o f t he rocklobs te r i ndus t r y . E igh ty two pe rcen t o f t he to ta l ca tchb e t w e e n 1 9 7 5 a n d 1 9 8 3 w a s t a k e n i n e s t u a r i e s a n d m a r i n ee n v i r o n m e n t s b e t w e e n P e r t h a n d B u n b u r y ( F i g . f ) . T h e g r e a ti m p o r t a n c e o f t h e f i s h e r y i n t h e s w a n E s t u a r y i s i l l u s t r a t e dby the fac t t ha t on ave rage i t con t r i bu tes 35? to the S ta te ' sto ta l - annua t ca tch o f app rox ima te l y I 92 .8 tonnes pe r annum.D i s c u s s i o n s w i t h m a j o r b a i t s u p p l i e r s t o t h e r o c k l o b s t e ri ndus t r y i nd i ca te tha t t he demand fo r Pe r th he r r i ng f rom theSwan Es lua ry has tended to rema in h igh and re la t i ve l y s tab les i n c e 1 9 6 6 .
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L 9 6 8 / 6 9 ( F i g . 3 ) . A f t e r a s u b s e q u e n t m a r k e d d e c l i n e t oa p p r o x i m a t e l y 5 0 - 5 5 t o n n e s i n 1 9 6 9 / 7 0 a n d 1 9 7 0 1 7 I , t h ec a t c h e s r o s e s h a r p l y a g a i n b e f o r e f a l l i n g s t e a d i l y t o v a l u e so f b e t w e e n 4 5 a n d 6 5 t o n n e s a f t e r 1 9 7 8 ( F i g . 3 ) . W h i l e t h et rends shown by the CPUE fo l l owed qu i te c lose l y thoseexh ib i t ed by ca tch du r ing the l a te 1960s and ea r l y 1970s , t heca tch , i n con t ras t t o t he CPUE, has dec l i ned du r ing morerecen t yea rs . I t i s a l so impor tan t t o recogn ise tha t as aresu l t o f managemen t dec i s ions imp lemen ted i n 1969 by theW.A . Depar tmen t o f F i she r ies to reduce f i sh ing e f fo r t i n t hecommerc ia l f i she ry , t he number o f boa ts f i sh ing , and hencethose ca tch ing Per th he r r i ng , i n t he swan Es tua ry hasd e c l i n e d p r o g r e s s i v e l y o v e r r e c e n t y e a r s ( F i g . 3 ) .
P r io r t o 1975 , t he mon th l y va lues fo r CPUE showed a markedtendency to va ry seasona l l y , w i th max imum va lues be inga t t a i n e d i n t h e S w a n E s t u a r y i n A u g u s t a n d S e p t e m b e r ( F i g . 4 ) .These mon ths co r respond to the t ime when a comprehens iveresearch p rog ranune o f g i I l ne t t i ng th roughou t t he sys tems ta r ted to y ie ld l a rge Per th he r r i ng , wh ich be long to a g roupwh ich subsequen t l y accumu la tes and b reeds i n the upperes tua ry i n December and ea r l y January (Chubb and po t te r , i np r e s s ) . I t i s t h u s r e a s o n a b l e t o a s s u m e t h a t t h e g r e a t l yi nc reased co rnmerc ia l ca tches i n Augu s t /S ep tember , wh ich weretaken i n the commerc ia l l y open f i sh ing wa te rs o f t he m idd lees tua ry , re f l ec t t he en t rance o f l a rge numbers o f Pe r thhe r r i ng on the i r spawn ing run f rom the mar ine env i ronmen t .I t i s a l so wor th no t i ng tha t a second bu t sma l l e r peak i nabundance i s f requen t l y ev iden t be tween Februa ry and May( F i g . 4 ) . T h i s c o u l d r e p r e s e n t f i s h t h a t w e r e c a u g h t o n t h e i rway out of the system.
The fac t t ha t seasona l t rends become less consp icuous i n thela te 1970s may be a re f l ec t i on o f t he e f fec ts o f t heunusua l l y l a rge ca tches ob ta ined f rom loca I mar ine wa te rs i nt h e s u m m e r s o f 1 9 7 6 / 7 7 , L 9 7 7 / 7 8 a n d 1 9 7 8 / 7 9 ( F i g . 5 ) .Moreove r , a marked seasona l peak was ev iden t aga in a f te r I 980fo l l ow ing reduced mar ine ca tches i n t he sunmer o f 1979 /80 ands u b s e q u e n t y e a r s ( F i 9 , 4 ) .
III. CURRENT STATUS OF THE FISHERY
A . CONCEPT OF THE SWAN ESTUARY STOCK
Whi le emphas is has been p laced on the l ong te rm and seasona lt rends i n t he f i she ry fo r Pe r th he r r i ng i n t he Sv ran Es tua ry ,l a rge ca tches were a l so taken i n nea rby mar ine wa te rs be tween1 9 7 6 a n d I 9 8 0 ( F i g . 5 ) . T h e f o l l o w i n g c h a r a c t e r i s t i c s o fthese ca tches i nd i ca te tha t t hey were based on f i sh tha t hadmoved in o r ou t o f t he Swan Es tua rv .
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A S S E S S M E N T O F T H E F I S H E R Y
T h e t o t a l c a t c h o f P e r t h h e r r i n g i n t h e S w a n E s t u a r y s t o c k ,i . e . f r o m t h e S w a n E s t u a r y a n d n e i g h b o u r i n g c o a s t a l w a t e r sb e t w e e n L 9 7 5 / 7 6 a n d 1 9 8 2 / 8 3 r e a c h e d a p e a k o f 2 3 7 t o n n e s i nL 9 7 1 / 7 8 ( F i g . 7 ) , a f e a t u r e r e f l e c t i n g e x c e p t i o n a l l y l a r g ec a t c h e s i n t h e m a r i n e e n v i r o n m e n t i n t h i s y e a r ( F i g . 5 ) .W h i l e t h e t o t a l c a t c h o f P e r t h h e r r i n g f r o m t h i s s t o c kd e c l i n e d o v e r t h e n e x t t w o y e a r s , i t h a s s u b s e q u e n t l yr e m a i n e d b e t w e e n 6 0 a n d l l 0 t o n n e s . D e s p i t e m a r k e dv a r i a L i o n s i n t h e t o t a l c a t c h o v e r L h e e i g h t y e a r p e r i o d , t h eC P U E , a s m e a s u r e d b y t h e g i l l n e t c a t c h o f P e r t h h e r r i n g p e . rb o a t i n t h e S w a n ( s e e S e c t i o n I I I B ) , s h o w e d n o o b v i o u st e n d e n c y t o r i s e o r f a l l ( F i g . 7 ) . H o w e v e r , t h e a b s e n c e o f ar i s e i n C P U E o v e r t h i s p e r i o d w h e n t h e c a l c u l a t e d e f f o r t h a sf a l l e n c o n s i s t e n t l y i n d i c a t e s t h a t r e c r u i t m e n t i n t o t h ef j . s h e r y m a y h a v e d e c l i n e d .
W h i I e e m p h a s i s h a s p r e v i o u s l y b e e n p l a c e d o n t h e r e l a t i o n s h i pb e t w e e n c a t c h a n d C P U E a n d t h e f i s h i n g e . [ f o r t , t h e p o s s i b l er o l e o f e n v i r o n m e n t a l f a c t o r s o n P e r t h h e r r i n g p o p u l a t i o n ss h o u l d n o t b e o v e r l o o k e d . T h u s , w h i l e t h e m a r k e d d e c l i n e i nc a t c h a n d a l s o C P U E w h i c h o c c u r r e d i n t h e S w a n E s t u a r y i nL 9 6 9 / 7 0 c o u l d h a v e b e e n t h e r e s u l t o f t h e h i g h c a t c h e s t a k e nd u r i n g t h e p r e v i o u s t w o y e a r s ( F i g . 3 ) , t h e y c o u l d a l s or e f l e c t f e a t u r e s w h i c h a f f e c t e d t h e m o r t a l i t y o f t h e y o u n g o rt h e b r e e d i n g s t o c k j n e a r l i e r y e a r s . I t i s a l s o p o s s i b l et h a t t h e v e r y h i g h c a t c h e s i n L 9 6 9 / 7 0 r e f l e c t g o o d c o n d i t i o n sf o r s p a w n i n g a n d / o r g r o w t h e a r l y i n l i t e d u r i n g e a r l i e ry e a r s . C e r t a i n l y , c o n d i t i o n s i n t h e e s t u a r y , w h e r e s p a w n i n go c c u r s a n d t h e y o u n g s u b s e q u e n t l y s p e n d m a n y m o n t h s , a r el i k e l y t o b e m u c h m o r e v a r i a b l e t h a n i n l o c a l r n a r i n e w a t e r s .W h i l e t h e u n u s u a l l y h i g h c a t c h e s i n t h e c o a s t a l w a t e r s i n1 9 7 6 / 7 7 , 1 9 7 7 / 7 8 a n d L 9 7 8 / 7 9 ( F i q . 5 ) m a y h a v e b e e n a t l e a s tp a r t l y d u e t o a c h a n g e i n t h e p r e l e r r e d t a r g e t s p e c i e s o ff i s h e r m e n a t t h e t i m e o f t h e y e a r w h e n N . v l a m i n g h i i s f o u n di n t h e r e g i o n , i t i s a l s o p o s s i b l e t h a t - E i i - i r o n m e n t a l f a c t o r si n t h e s e y e a r s r e s u l t e d i n t h e f i s h b e c o m i n g m o r e a c c e s s i b l - e .I f e n v i r o n m e n t a l f a c t o r s w e r e i m p o r t a n t i n p r o d u c i n g h i g h e rm a r i n e c a t c h e s i n t h e s e t h r e e y e a r s , i t m a y b e r e l e v a n t t h a tt h e y w e r e t a k e n w h e n a i r t e m p e r a t u r e s w e r e a t t h e i r h i g h e s ta n d e x c e e d e d b y 2 - 3 " C t h e a v e r a g e v a l u e a t t h a t t i m e o f t h ey e a r ( J . P e n n , p e r s . c o m m . ) .
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ACKNOISEEDGET{ENTS
Our g ra t i t ude i s exp ressed to Mr K .Carha r t f o r ex t rac t i ng theh i s t o r i c a l d a t a a n d t o M r N . C a p u t i f o r s t a t i s t i c a l h e l p .Thanks a re a l so due to many p ro fess iona l f i she rmen whoprov ided obse rva t i ons based on ex tens i ve expe r ience o fca tch ing Per th he r r i ng .
REFERENCES
B a k e r , C . D . a n d S c h n i t z , E . H . ( I 9 7 1 ) . Food hab i t s o f adu l tO z a r k r e s e r v o i r s . I n( H . E . H a l I , e d . ) , p p .
Amer i can F i she r i es
C a r s c a d d e n , J . E . a n d L e g g e t t , W . C . ( 1 9 7 5 ) . M e r i s t i cd i f f e rences i n spawn ing popu la t i ons o f Amer i can shad ,A l o s a s a p i d i s s i m a : e v i d e n c e f o r h o m i n g t o t r i b u t a r i e s i nt h e S t . J o h n R i v e r , N e w B r u n s w i c k . J . F i s h . R e s . B d C a n .3 2 , 6 5 3 - 6 5 0 .
C h u b b , C . F . , H u t c h i n s , J . 8 . , L e n a n t o n , R . C . J .I . C . ( 1 9 7 9 ) . A n a n n o t a t e d c h e c k l i s t o f t h eSwan-Avon r i ve r sys tem, Wes te rn Aus t ra l i a .A u s t . M u s . 8 , 1 - 5 5 .
a n d P o t t e r ,f i shes o f t heR e c . W e s t .
Chubb C . F . andb io logy andNemata losa
G u l l a n d , J . A . ( I 9 6 9 ) .assessmen t . Pa r tF i s h . S c i . N o . 4 .
P o t t e r f I . C . ( i n p r e s s ) . T h ee s t u a r i n e m o v e m e n t s o f t h e
v l a m i n g h i ( M u n r o ) . J . F i q b .
rep roduc t i veg i z z a r d s h a d ,B i O I .
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J h i n g r a n , V . G , a n d G o p a l a k r i s h n a n ,f i s h e r i e s r e s o u r c e s o f I n d i a i ns e a s . J . m a r . b i o I . A s s . I n d i a
V . ( f 9 7 3 ) . E s t u a r i n ere la t i on to ad j acen t
1 5 , 3 2 3 - 3 3 4 .
J o n e s , S . a n d S u j a n s i n g a n i , K . H . ( I 9 5 4 ) .o f t h e C h i l k a L a k e w i t h s t a t i s t i c s o ft h e y e a r s 1 9 4 8 - I 9 5 0 . I n d i a n J . F i s h .
F i s h a n d f i s h e r i e sf i sh ca tches fo r
L , 2 5 6 - 3 4 4 .
L e n a n t o n , R . C . J . ( 1 9 8 4 ) . T h e c o m m e r c i a l f i s h e r i e s o ftempera te Wes te rn Aus t ra l i an es tua r ies , ea r l y se t t l emen tt o 1 9 7 5 . D e p t . F i s h . W i l d t . W e s t . A u s t . R e p t . N o . 6 2 .
g i zza rd and th read f i n shad i n twoReservo i r F i she r ies and L imno loq3 - l L S p e c i a I P u b l i c a t i o n U o . B .S o c i e t y : W a s h i n g t o n D . C .
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TOTAL CATCH1975 -1 983 : 1 5 t 2 .779 t onn es
12o"M E T H O D C O O E :
G G ILL NETH HAUL NETP PURSE SE INET TRAPPING
z o "
Figure 1- Distr ibut ion of the catches of Perth herr ing in marineand estuarine environments r with the contribution made by eachexpressed as a percentage of the total catch for the periodbetween JuIy 1975 and June 1983.
BROOME
PORT HEDLAND
EXMOUTH
CARNARVON
PERTH - FREMANTLE: SWAN ESTUARY- GH 3S.OCOCKBURN SOUNO - GHP I I ,O
MANDURAH: PEEL . HARVEY ESTUARY-GH 2 .7
AUNBURY: LESCHENAULT INLET. GH 12.I
GERALDTON
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PERTHFREMANTLE
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BUNBURY
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Figure 5 - The annual catch of Perth herring in the Swan Estuary(sol id l ine) and loca1 marine waters (dashed l ine) between I97Q/7Ia^d . J -982 /83 .
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Figure 7 - The total catch of Perth herring in the Swan Estuaryand local marine waters taken by al-l- methods, the mean monthlygi lJ- net catch of Perth herr ing per boat taking this species(CPUE) , anil the estimated effort required with this CPUE to catchall the Perth herring taken in the S\^ran Estuary and l-oca1 marinewa te rs .
TO,TALCATCH
GILL NETCATC H RATE
36736/10/84 1M BKS L/3794 I 7
