Kreiberg 1987 Aquacultural-Engineering

7/28/2019 Kreiberg 1987 Aquacultural-Engineering

1/11

Aq uac ul tura l Engineering 6 (1987) 289-299

A Production-scale Tow able N etpe n for EfficientH igh-volum e Transpo rt of Pacific H erring: D esign andCom parative Perform anceH . K r e i b e r g a n d A . S o l m i e

Department of Fisheries and Oceans, Fisheries Research Branch,Pacific Biological Station, Nanaimo, British Columbia, Canada V9R 5K6

A B S T R A C TA t o w a b l e n e t p e n u n i t b a s e d o n c o m m e r c i a l m a r i n a f l o a t c o m p o n e n t sw a s d e v e l o p e d t o s e r ve d u a l p u r p o s e s o f t r a n s p o r t a n d h o l d i n g o f l iv eP a c i f i c h e r r i n g in i n s h o r e w a t e r s o f B r i t i s h C o l u m b i a . T h e r e c t a n g u l a rn e t pe n u n i t m e a s u r e s a p p r o x i m a t e l y 2 8 x 9 x 7 m d e e p a n d h o l d s 2 5 - 3 0t o n n e s o f h e r r in g a t d e n si ti e s o f 8 - 1 6 k g m - 3. T h e d e s i g n w a s e v a lu a t e du n d e r f i e l d c o n d i t io n s i n c lu d i n g a c o m p a r i s o n w i t h tw o i n d us t ry m e t h o d so f l iv e f i s h t r a n s p o r t. R e s u l t s o v e r 4 y e a r s i n d i c a t e t h e d e s i g n t o b e s e a -w o r t h y a n d f l e x i b l e i n a p p l ic a t io n . A s a m o d e o f f i s h t r an s p o rt , i t o f fe r sh i g h s u r v i v a l ( 9 7 % t o 8 w e e k s ) a n d i m p r o v e d c o s t - e f f i c i e n c y o v e r o t h e rm e t h o d s t es te d . T h e t o w a b l e n e t p e n i s c o n s i d e r e d u s e f u l f o r c u l t u r e a n dt r a n s p o r t o f o t h e r f i s h s p e c i e s s u c h a s s a l m o n i d s a n d g a d id s .

I N T R O D U C T I O NF i s h c u l t u r a l p r a c t i c e s h a v e , i n r e c e n t y e a r s , r e c e i v e d i n c r e a s i n g u s e i nt r a d i t i o n a l c a p t u r e f i s h e r i e s t o p r o l o n g o r e n h a n c e c o m m e r c i a l h a r v e s t s .T r a n sf er s o v e r s o m e d i s ta n c e t o i m p o u n d m e n t s , w i th o r w i t h o u t su p p l e -m e n t a l f e e d i n g , h a v e c o n s t i t u t e d t h e m a i n t r e n d , e . g . f o r p o l l o c k i nN o r w a y ( B r a t l a n d e t a l . , 1 9 7 6 ) , a n d f o r s a b l e f i s h ( B o u r n e a n d B r e t t ,1 9 8 5 ) a n d h e r r in g ( D i c k s o n , 1 9 7 5 ; G i ll is e t a l . , 1 9 8 2 ; B r e tt a n d S o l m i e ,1 9 8 2 ) o n t h e w e s t c o a s t o f C a n a d a . C o n s e q u e n t l y , f i s h h a n d l i n g a n dt ra n s fe r p r o c e s s e s h a v e a s s u m e d a n e w s ig n i fi c a n c e w i t h t h e r e q u ir e m e n tf o r h i g h s u r v i v a l f o r e x t e n d e d p e r i o d s . M e t h o d s o f t r a n s p o r t h a v ee x p a n d e d f r o m u s e o f t h e c a t c h in g g e a r i ts e lf to i n c l u d e s u c h i n n o v a t i o n sa s w e l l - b o a t s ( E g i d i u s e t a l . , 1 9 8 3 ) . H o w e v e r , m o s t m e t h o d s i n v o l v e c o n -s i d e r a b l e h a n d l i n g o f f i s h w i t h b r a i l i n g n e t s, o f t e n l e a d i n g t o i n j u r y a n dmortali ty. 289Aquacul tura l Engineering 0144-8609/87/S03.50-- Elsevier Applied SciencePublishers Ltd. England. 1987. Printed in Great Britain


2/11

2 9 0 H. Kre iberg , A . So lmieA t t h e s a m e t i m e , t h e d e v e l o p m e n t o f c o m m e r c i a l a q u a c u l t u r e o fs a l m o n i d s h a s m a d e a v a i la b l e a r a n g e o f f lo a t in g i m p o u n d m e n t d e si gn s ,

a c c o m p a n i e d b y e x p a n d e d r e q u i re m e n t s f o r t h e h a n d l in g a n d t r a n s p o r to f l a rge quan t i t ie s o f l i ve f ish , e .g . fo r t r anspo r t s be tw een f a rm s it es o rr e l ea ses a t s ea o f f ry and smol t fo r ocean r anch ing . Some o f t he serequ i r emen t s have been me t by the use o f l i ve -ba rges , e . g . t o ca r ryjuven i l e s a lm on pas t a s e r i e s o f r ive r dam s (E l li s and No b le , 1960 ;M c C a b e etal., 1979) .I n t h e c o u r s e o f a 4 - y e a r r e s e a r c h p r o g r a m a t t h e P a c if ic B io l o g ic a lS t a t i o n t o d e v e l o p a n i m p o u n d m e n t o p t i o n f o r t h e B r i t i s h C o l u m b i ahe r r ing sac - roe f i she ry , we p e rce ive d a need fo r a com m erc i a l - sca l ei m p o u n d i n g p r o c e s s m o r e e f fi c ie n t t h a n c o m b i n a t i o n s o f e x is ti n g t ra n s -p o r t m e t h o d s a n d f i x e d i m p o u n d m e n t s . A v a i l a b l e t r a n s p o r t t e c h n i q u e se i the r gave good su rv iva l a t h igh cap i t a l cos t o r v i ce ve r sa . He re wed e s c r ib e a n d e v a l u a te a c o m m e r c i a l - s c al e f l o a ti n g n e t p e n u n i t w h i c h w ed e v e l o p e d f o r t h e e f fi c ie n t c o m b i n e d t r a n s p o r t a n d h o l d i n g o f a n i n j u ry -sens i ti ve mar in e f i sh , t he Pac i fi c he r r ing ( C lupea hareng us pal las i ).

M A T E R IA L S A N D M E T H O D STow able netpenT he 30 . 8 x 12 m f loa t we used (F ig . 1 ) was supp l i ed by a com m erc i a lm a n u f a c t u r e r o f f l o a t s y s t e m s f o r m a r i n a s , b u i l t t o a m e d i u m r a n g es t rength spec i f ica t ion (T-23-F, Topper Indus t r ies , Del ta , B.C. ) .* I t con-s i st ed o f a wid e -dec ked su pe r s t ruc tu re o f p re s su re - t r ea t ed f i r i n sec t ionst h r o u g h - b o l t e d t o g e t h e r , w i t h f l o a t a t i o n f r o m c a p p e d f o a m - f i l l e d a u t ot ir e s. F lo a t a t i on was in s t a l led a t t he r a t e o f 57 kg pe r ru nn ing m e te r , w i tha p p r o x i m a t e l y 5 0 0 k g a d d i t i o n a l r e s e r v e a t e a c h c o r n e r ( t o o f f s e tm o o r i n g - c h a i n p u ll ) a n d u n d e r t h e e n d s o f a l a m i n a t e d t r a n s v e r s e s ti ff en -i n g b e a m , a n d 2 7 5 k g c e n t r a ll y o n e a c h e n d o f th e f l o a t ( to c o m p e n s a t ef o r s tr e ss e s w h i l e u n d e r w a y ). T h e n e t p e n m e a s u r e d 2 8 x 9 x 7 m d e e pa n d w a s b u i l t o f w h i t e 2 2 - m m s t r e t c h e d m e s h k n o t l e s s n y l o n . I t w a si n s ta l le d o n t h e f l o a t u s in g s u s p e n d e d 1 0 0 - k g t ri m - a n c h o r s a n d r u n n i n gl i n e s t o t h e p e n - f l o o r v i a a n e y e o n t h e t r i m - a n c h o r t o p e r m i t c o n t r o lf r o m t h e s u r fa c e . A t a u t b o x - li k e s h a p e w i th a h o r i z o n t a l f l o o r c o u l d t h u sb e m a i n t a i n e d . T h e s t r u c tu r e w a s r a t e d c a p a b l e o f w i t h s ta n d i n g w a v e -a m p l i t u d e s o f 3 0 c m f o r s h o r t - w a v e ( c h o p ) a n d 7 5 c m f o r l o n g - w a v e( swe ll) wh i l e m a in t a in in g a f r eeb oa r d o f 38 cm.* I m p l i e s n o o f f i c ia l e n d o r s e m e n t .


3/11

Tow able netpen for transport of Pacific herring 291

Fig. 1. Th e tow able netpen. A: To p view showing reinforce m ents and spring l ines; B:Perspective. netpe n u nde r w ay showing dynamic b ow details; C: N etp en und er way, sideview showing trim-anchors in place.

Modif icat ions for t ransport ing l ive f ish consis ted of re inforcing thef loat wi th heavy diagonal angle- i ron braces (Fig. 1A), a t taching a t i re-covered pushing c radle a t the s tem, hanging counterweights midwayacross the bow and s te rn faces of the ne tpen , and s t i t ch ing a very sof tknot less web l iner over the s te rn end-panel . The pen uni t could bemoved empty by pul l ing the web up on the decking and swinging thetr im-anchors up using ret r ieve l ines; this served to prevent foul ing ofthe r igging whi le moving at higher speeds. At the catch s i te , the t r im-anchor s w ere swung dow n in to no rma l pos it ion , and t he ne tpen d ropp edand t r imm m ed squa re, a p rocedure r equ it ing abou t 30 minu t es and twocrewmen . The pen w as b rough t a l ongside and l oaded f rom the cat ch ingse ine us ing a t emporary underwater ga te made by lac ing toge ther wi ththe top edges of the netpen and the seine, and s inking the joint wi th


4/11

2 9 2 H. Kre iberg , A . So lmiecha in . P re - seaso n f i e ld tr ia l s had e s t ab l i shed the b es t con f igu ra t ion fo rt r anspor t , i . e . w i th t he suppor t ves se l push ing r a the r t han towing , andwi th sp r ing l ines a s in F ig . 1A . Un derw ay , t he two fo rw ard co rn e r t r im-l ines were f r eed , a l low ing the com ers t o fo ld back a s i n F ig . 1B , wi th t hed y n a m i c b o w s h a p e b e i n g h e l d b y th e e x t r a w e ig h t h u n g a t t h e m i d p o i n tdeep in s ide the ne tpe n . A t t he ho ld ing si te , t he pe n co u ld e i t he r be o f f -loaded v i a ano the r ' swimming ' t r ans fe r t o a f i xed ho ld ing un i t , o r con-n e c t e d t o p e r m a n e n t m o o r i n g s t o s e r v e a s a h o l d i n g u n i t . F u r t h e rd e s c r i p t i o n s o f t h e p e n u n i t a n d t r a n s p o r t m o d i f i c a t i o n s a r e g i v e n i nK r e i b e r g e t a l . (1982 , 1984) .To w ed-se ine t ransportF i s h e r m e n i n B r i t is h C o l u m b i a ' s sm a l l i m p o u n d m e n t f i sh e r y f o r h e r r in gs p a w n - o n - k e l p h a v e t o t r a n s fe r l iv e g r a v id h e r r i n g f r o m p o i n t o f c a p -t u r e t o a s e a p e n c o n t a i n i n g k e l p h u n g o n r o p e s. T h e p u r s e s e in e s u s ed f o rc a t c h in g a r e a d a p t e d t o m o v e t h e f is h b y m e a n s o f s o m e r ig g in g c h a n g es ,a s shown in F ig . 2 . The se ine i s pu r sed shu t , and the bun t end o f t he

. , t , u -

F i g . 2 . Pe r spec t ive , r igg ing f o r t ow e d- se i ne t r anspor t . I n se t t op show s no r m a l unde r -w a t e r shape o f s t a t i ona r y s ei ne , i n se t bo t t om show s d i s t o r t i on o f shape unde r w ay .


5/11

Tow able netpen for transport of Pacific herring 293c o r k l i n e is a t t a c h e d t o t h e b o w o f t h e m a i n v e s se l. G a t h e r s a r e m a d e a tseve ra l po i n t s a l ong t he l eng t h o f t he ves se l to d i s t r ibu t e t he excess ne t -m a t e r i a l even ly . T he aux i l i a ry pow er - sk i f f , a t t ached by a b r id l e , t ow s t hes e i n e r b r o a d s i d e . H e a v y c o u n t e r w e i g h t s a r e o f t e n s u s p e n d e d f r o m t h ese i ne r i n t o t he ne t , t o coun t e r p rope l l e r -w ash and d rag e f f ec t s w h i cht e n d to c o l l ap s e t h e se i ne . S t a n d a r d p u r s e s e in e s c a r r ie d b y 1 8 - 2 0 - mc o m m e r c i a l s e i n e r s w e r e u s e d i n th e p r e s e n t w o r k ( a p p r o x i m a t e d i m e n -s i ons 400 50 m , 25 m m m esh).T o w e d s e m i - s u b m e r s i b l e l i v e -b a r g e t r a n s p o r tA d i sp l acem en t hu l l o f up t o 75 t onnes g ross i s m od i f i ed w i t h ba l l a s tt a n k s a l lo w i n g i t to b e s u b m e r g e d a fu r t h e r 2 - 4 m w i t h t h e m a i n h o l d sf l ooded . O pen i ngs a re m ade i n t he s t e rn fo r a f l anged l oad i ng ga t e , anda l o n g th e s i d e s fo r s c r e e n e d w a t e r - e x c h a n g e p o r ts . T h e f l o o d e d b a r g e i sl oaded f rom a se i ne a s show n i n F i g . 3 , and no rm a l l y t ow s a s t e rn . Fo ro f f - load i ng , the t op edge o f a r ece iv i ng ne t p en i s f i tt ed a rou nd t hef l anged ga te and t he ba l l a s t t anks pu m ped d ry . A sm a l l nu m ber o f l ive -ba i t w ho l e sa l e r s i n Br i t i sh Co l um bi a u se l i ve -ba rges fo r t r anspor t o fse i ne -caugh t juven i l e he r r i ng . Tw o suc h l ive -ba rges w ere ch a r t e red i n t hep r e s e n t w o r k , o n e m e a s u r i n g 1 8 4 1 m d r a f t ( a p p r o x i m a t e 4 - t o n n ef ish capac i t y ) , t he o t he r m easu r i n g 20 5 -5 1 m d ra f t ( app ro x i m a t e6 - t on ne f i sh capac it y ).E v a l u a t i o nT h e t o w a b l e n e t p e n u n i t w a s t e s t e d a s a f i x e d i m p o u n d m e n t f o r h e r r i n gdur i ng f i e ld sea sons i n sp r i ng 1982 t o 1985 , bo t h s i ng l y and i n m u l ti p l e s ,a t the Pac i fi c B i o l og i ca l S t a t i on ' s r e sea rch f i sh f a rm a t N an a i m o , B r i t i shC o l u m b i a a n d a t a f ie l d s it e i n th e n e a r b y G u l f Is la n d s . D u r i n g i n t e r i mper i ods , s l i gh t m od i f i ca t i ons pe rm i t t ed su bd i v i s i on o f t he pen un i t toa c c o m m o d a t e g r o u p s o f s a l m o n i d s . T h e n e t p e n w a s t e s te d a s a t r a n s p o r tdev i ce u s i ng adu l t he r r i ng caugh t by cha r t e red se i ne r i n l a t e J anua ry1 9 8 4 , u p p e r G u l f I s la n d s , w h i c h w e r e t r a n s f e r r e d d i r e c tl y f r o m t h e p o i n to f cap t u re t o a ho l d i ng s i te u s i ng t he t ow ab l e ne t pen . A dd i t i ona l ca t cheso f h e r r i n g m a d e w i t h in 2 4 h f r o m t h e s a m e b o d y o f w i ld f is h w e r e t r a n s -fe r r ed t o t he ho l d i ng s i te by tow ed se i ne and by l ive -ba rge . H o l d i n g con -d i t i o n s w e r e s t a n d a r d i z e d f o r h a n d l i n g a n d d e n s i t y ( 8 k g m-3) . T h et h r e e g r o u p s o f h e r r i n g w e r e m o n i t o r e d f o r s u r vi v a l a n d n o r m a l m a t u r a -t i o n o v e r t h e n e x t 8 w e e k s , a n d w e r e r e l e a s e d o n 2 2 M a r c h 1 9 8 4 . T h et o w a b l e n e t p e n w a s te s t e d a g a i n i n M a r c h 1 9 8 5 f o r t r a n s p o r t a n d h o l d -


6/11

b~

\%

a

-

).

"

,-~:>

-~

'."~%;~~;

"

,~

,"e#J~,-~

"

".

"~-~>~

Z >

Fg3Ppvtrensnuohntofodlvb

Inshwfadlongeacknisbnfed


7/11

Tow able netpen for transport of Pacific herring 295i ng o f he r r ing . W e as sessed co s t - e ff i c iency based on ou r ow n budg e t ingd a t a a n d i n f o r m a t i o n g a th e r e d f r o m c o m m e r c ia l f i sh e r m e n o n c h a rt er .

R E S U L T S A N D D I S C U S S I O NFixed imp oundm ent phaseT h e t o w a b l e n e t p e n w e d e s c r i b e h e r e w a s u s e d s u cc e ss fu l ly a l o n g si d eo th e r sm a l l e r f ixed ne tpe ns fo r ov e r 4 yea r s , i nc lud ing seve ra l 2 -m on thpe r io ds i n f ie ld l oca tions . Pac i fi c he r r ing in qu an t i t ie s o f up to 30 tonn esw e r e h e l d f o r p e r i o d s o f u p t o 4 m o n t h s w i t h n o e v i d e n t d e s i g n p r o b -l em s . H a n d l i n g o f t h e n e t p e n f o r s a m p l in g , r e m o v a l o f d e a d , a n d t r an s -f e rs t o o t h e r n e t p e n s w a s e a s il y d o n e m a n u a l l y b y a s m a l l c r e w o f t w o o rt h r e e p e r s o n s . T h e s i m p l e c o n s t r u c t i o n p e r m i t t e d b r e a k d o w n i n t o s ec -t i o n s w h i c h c o u l d b e r a f te d t o g e t h e r f o r c o n v e n i e n t t o w i n g t o a d i s t a n ts it e. T he long r ec t angu la r p l an o f the f l oa t was we l l su i t ed fo r subd iv i s iont o h o u s e a n u m b e r o f g r o u p s o f h e r r i n g o r s a l m o n i d s in s e p a r a t e s m a l le rpens . T h e fuU-size ne tpe n w as espec ia l ly su i ted to a scho ol ing f i sh l iket h e h e r r in g , a l lo w i n g g r o u p s o f m a n y t o n n e s o f f is h to s c h o o l n a t u r a l lya n d t o s o u n d i n r e s p o n s e t o s u r fa c e d is t u rb a n c e s . S o m e o f o u r t o w a b l en e t p e n s h a v e b e e n i n s al t w a t e r s in c e 1 9 8 2 , a n d i n d i c a t io n s a r e t h a t t h eexpec ted 7 -10 yea r f i f e - span wi l l be me t . De ta i l s on expe r i ence in r i g -g ing , hand l ing and se rv i c ing th i s l a rge ne tpen des ign a re g iven inK r e i b e r g e t a l . (1982) .Live transport phaseT h e t o w a b l e n e t p e n g a v e e x c e ll e n t p e r f o r m a n c e a s a h i g h - c a p a c it y t r a n s -p o r t m e t h o d , w h e n c o m p a r e d t o o t h e r e s ta b l is h e d m e t h o d s u n d e r p r a c ti -ca l ly iden t i ca l cond i t i ons . Su rv iva l o f he r r ing t r an spo r t ed in t he t ow ab len e t p e n w a s 9 7 % t o 8 w e e k s, c o m p a r e d t o 1 0 0 % f o r t h e li v e -b a r g e a n d79% fo r t he t owe d se ine (F ig . 4 ). T he l a t t e r two su rv iva l s a r e t yp i ca l o fthe r e spec t ive me thods , a l t hough fo r s e ine - towing , t he su rv iva l o f t endrop s a s l ow as 60% desp i t e sho r t e r ho ld ing pe r iods (Sh ie lds e t a l . ,1 9 8 5 ) . T h e i m p r o v e m e n t i n s u r v i v a l o v e r t h e t o w e d - s e i n e m e t h o d i ss ign i fi can t a t t he p ro bab i l i t y l eve l P < 0 . 001 ( s lope com par i son s , l og -t r a n s f o r m e d m o r t a l it y c u rv e s) .

C o n v e r t i n g a f i xe d n e t p e n f o r t o w i n g c o n s i s te d i n p r a c ti c e m e r e l y o fs t i tch ing in t he so f t end - l i ne r , hang ing the bo w and s t e rn coun te rwe igh t sa n d r e le a s in g a p p r o p r i a t e l in e s. T h e e x t ra c o m e r b r a c e s, c o u n t e r w e i g h t sa n d t o w i n g f e n d e r w e r e n o r m a l l y l e ft i n p l a c e o n c e i n st a ll e d . T h e t o t a l


8/11

2 96 H. Kre iberg , A . So lmie

Fig . 4 .

25"

> -p . . 2 0D. JI v0 15

I-- I0. . . I

S E I N E,~1~41- . . .. - - . . . . . . . . . . . . . . . . . . . . .,.

// /o

I

// .5 N E T P E NI 0 ~ 0 ~ 0

. . . . . . . . . . . . . . . . . . . . . .0 , o 2 '0 g o, - F E B = ' , = , , / I A R r I

D A Y S O F I M P O U N D M E N TCum ula t ive mor ta l ity o f he r r ing in th ree ho ld ing pens a f t e r t r anspor t f rom cap-

tu re po in t to ho ld ing si te . Im pou ndm en t t e rm 53 days .

c o s t o f t h e a l t e r a t i o n s a m o u n t e d t o l e s s t h a n 8 % o f a n e t p e n ' s c a p i t a lc o s t ( 1 9 8 3 ) o f $ 2 5 0 0 0 C a n a d i a n . T h e a u d i b l e p r e s e n c e o f t h e p u s h i n gv e s se l a t t h e s t e r n o f t h e n e t p e n k e p t f i sh c o n c e n t r a t e d i n th e b o w z o n e ,sw im m ing read i ly . A n un derw a te r l igh t hung o f f t he vesse l w as used toaug m ent th i s e f f ec t a t t im es ; it w as foun d tha t he r r ing w ere t r an spo r t edles s s t r e s s fu l ly by n igh t t han by day . The long r ec t angu la r geom et ry o ft h e n e t p e n p e r m i t t e d b e t t e r h a n d l i n g o f b o w - e n t r y d r a g t h a n w o u l d as q u a r e o r c i r c u l a r n e tp e n .Implications for fish cu ltureO u r o b j e c t iv e i n th i s w o r k w a s t o i m p r o v e t h e o v e r a l l e f fi c ie n c y o f o p e r a -t i o n s r e q u i ri n g b o t h o c c a s i o n a l li ve tr a n s p o r t a n d s u s ta i n e d h o l d i n g o fl a rg e q u a n t i t ie s o f fis h . T h e d e v e l o p m e n t o f t h e t o w a b l e n e t p e n y i e l d e dthe des i r ab le b io log ica l e f f ic i ency o f exp ens ive l i ve -ba rges w hi l e m a in -t a in ing the cos t - e f f i c iency typ ica l o f t ow ed-se ine t r anspo r t . Th e m a insav ing i s i n the du a l pu rpose s to w h ich a s ing le cap i t a l expe nd i tu re fo r an e t p e n c a n b e p u t. F o r a n y o p e r a t i o n i n v o l v in g f is h h o ld i n g , a n e n c l o -s u r e i s a n u n a v o i d a b l e e x p e n s e. T h e i n e x p e n s iv e t o w i n g - m o d i f ic a t io n s t oo u r n e t p e n r e s u lt i n a c o m p a r a t i v e l y l o w t r a n s p o r t c o s t, a s i n d i c a te d i nthe cos t - e f fi c i ency sum m ary (Tab le 1 ). W e fee l t ha t t he cap i t a l cos t o f ou r


9/11

Towable netpen for transport of Pacific herring 2 9 7T A B L E 1

C o s t -e f fi c ie n c y C o m p a r i s o n o f T o w a b l e N e t p e n t o T w o O t h e r L i v e - t ra n s p o r t M e t h o d sSeine Barge Netpen

S u r v i v a l to 8 w e e k s ( % )L o a d c a p a c i t y p e r d e l iv e r3, ( t on ne s)T o p s p e e d ( k m h - J )H a n d l i n g t im e p e r d e l i v e r y

( p e r s o n - h o u r s )R a n g e ( k i n)

7 5 1 0 0 9 77 0 6 3 0

0.4 6"5 0"96 6 93 1 5 0 3 0 - 5 0 a

Own Lease Own Lease OwnC a p i t a l c o s t ( S 0 0 0 ) 5 0 0 ~ - - 7 5 - 2 5 bC a p i t a l c o s t , a l t e r a t i o n s f o r 3 0 0 - - 0 - 2 0 0 0

t r a n s p o r t ( S)E x p e c t e d l if e o f a l t e r a t i o n s ( y e a rs ) 1 0 - - 2 0 - - 7O p e r a t i n g c o s t: d a i l y r e n t a l ( S) - 2 2 0 0 ' - 5 0 0 -

o r a n n u a l d e p r e c i a t i o n o n 3 0 - - 0 - - 3 0 0a l t e r a t i o n s ( S)

T r a n s p o r t c o s t p e r t o n n e o f s u r v i v o r s , N/A ~ 4 5 N / A a 8 3 1 0m a x i m u m l o a d (S )

G e a r - c o s t t o d e l i v e r 5 0 t o n n e s w i t hi n N / A a 1 3 5 0 N / A d 2 5 0 0 5 0 0t r a v e l r a n g e ( S) "

" T r a v e l l i n g f o r 3 - 4 n i g h ts a c c e p t a b l e w e a t h e r , t id e s .h F o r i n f o r m a t i o n o n l y . S in c e t h e g e a r w i ll b e u s e d a l s o f o r a n o t h e r n e c e s s a r y o p e r a t i o n ,t h is e x p e n s e i s c o m m o n t o al l t h r e e m e t h o d s .' I n c l u d e s c r e w e d s e i n e r w h i l e i n t r a n s i t .' ~V a ri es e x t r e m e l y w i t h n u m b e r o f o t h e r t a s k s g e a r is d e p r e c i a t e d a g a i n s t." F u e l . c r e w c o s t s f o r t r a v e l a d d i t i o n a l , s l i g h tl y h i g h e r c o s t f o r l o n g e r r u n s w i t h b a r g e o rn e t p e n .

des i gn , a l t hough ce r t a i n t o be h i ghe r t han such a l t e rna t i ves a s t he l og -b o o m a n a l o g u e s p e c u l a t e d u p o n ( B a rb e r , 1 9 8 0 ), w ill b e f u ll y c o m p e n -sa ted by i t s su i t ab i l i t y as a w ork p la t form . S ea- l ions a re ab le to c l imbo v e r l o g - b o o m s w i t h m u c h g r e a t e r e a s e t h a n o v e r a h i g h r a i s e d - d e c kf loa t. T he deck i ng a l so i nc reases c rew sa fe t y a t n i gh t and i n bad w ea t he r ,a n d c a n e l im i n a t e s o m e r e q u i r e m e n t s f o r a s u p p o r t v e s s el .S o m e c o m p r o m i s e s w e r e n e c e s s a r y ; f o r e x a m p l e , t h e t o w a b l e n e t p e ns a c r i f i c e s h i g h s p e e d t o p e r m i t c h e a p h i g h - v o l u m e t r a n s p o r t . H o w e v e r ,f o r a n y t r a n s p o r t m e t h o d w h i c h r e q u i r e s f is h t o s w i m to t h e d e s t i n a ti o n ,t h e m a x i m u m c r u i si n g s p e e d o f t h e fi s h c a n n o t b e e x c e e d e d . T h i s m e a n sl ow t r a n s p o r t s p e e d s o f 1 - 3 k m h - 1 f o r m a n y f is h . T h e t o w a b l e n e t p e n ' sr ange i s g rea t l y ex t en ded ove r t he t ow ed se i ne (o r o t he r ca t ch i ng gea r ) byv i r t ue o f t he s t ruc t u re and de f i ned shape o f t he enc l osu re . Th i s has t he


10/11

298 H. Kreiberg, A . Solrniee f f ec t o f m i n i m i z i n g h a r m f u l c o n t a c t b e t w e e n n e t t in g a n d f is h, a n d a l lo w st h e u n i t t o b e l e ft s a f el y a t a n c h o r o r a d r i f t i f c i r c u m s t a n c e s r e q u i r e . T h eb o x - l i k e s h a p e a l s o m i n i m i z e s l ik e ly p r e d a t o r d a m a g e t o f i sh i n c u r r e d e nr o u t e . O u r e x p e r i e n c e w i t h h e r r i n g a n d s a l m o n i d s le a d s u s t o f a v o r t h em e t h o d o f 's w i m m i n g ' f is h f r o m p e n t o p e n v ia t e m p o r a r y l in k - up s . T h et o w a b l e n e t p e n p e r m i ts t h is m e t h o d o f t r an s fe r, a s d o t h e o t h e r m e t h o d sw e u s e d , b u t i n c l u d e s t h e o p t i o n o f n o t r a n s f e r r e q u i r e d , if a n o p e r a t o rc h o o s e s s i m p l y t o u se t h e n e t p e n a s a f ix e d i m p o u n d m e n t u p o n r e a c h in gt h e d e s t i n a ti o n .

T h e f lo a t d e s ig n w e u s e d w a s b a s e d o n c o m m e r c i a l ly av a il ab le m a r i n ac o m p o n e n t s . I t i s c o m p a t i b l e w i t h a w i d e r a n g e o f i n s h o r e c o a s t a l s e ac o n d i t i o n s , a n d w e b e l i e v e th a t t h e t o w a b l e n e t p e n d e s i g n w e d e s c r ib eh a s p o t e n t i a l l y w i d e a p p l i c a ti o n t o f i s h c u l tu r e o p e r a t i o n s u s i n g v a ri o u sn o n - b e n t h i c m a r i n e a n d a n a d r o m o u s f ish .

A C K N O W I . E D G E M E N TT h i s w o r k w a s c a r ri e d o u t w i t h f u n d i n g s u p p o r t f r o m t h e F is h e r ie sD e v e l o p m e n t P r o g r a m o f t h e C a n a d a D e p a r t m e n t o f F is h e ri es a n dO c e a n s . D r s J . R . B r e t t a n d C . C l a r k e k i n d l y r e v i e w e d t h e m a n u s c r i p t .

R E F E R E N C E SBarber , E G. (1980) . Pink sa lmon dispar i ty: toward def ini t ion. C a n . M S R e p.Fish. Aquat. Sci. , No. 1594 , 20 pp .Bo urne , N. & B re t t, J. R . (1985) . Aq uacu l ture in Bri t ish Colum bia . Spec. Publ.Can. Fish. A qu at. Sci., 7 5 , 2 8 - 4 5 .Bra t land, P ., Kri shnan , S . & Sun dnes , G. (1976) . S tudies on the lon g te rm s tor-age of l iving sai the, Pollachius viren s. FiskDir. Skr. S er . HavU nders., 16,2 7 9 - 3 0 0 .Bre t t, J. R . & Solmie , A . (1982) . Ro e he r r ing impo un dm ent re sea rch - - r epor ton t he 1980 /81 s tud i e s. Can. Tech. Rep. Fish. Aquat. Sci. , No. 1061, 51 pp.Dickson , F . V . (1975) . Sum mary o f t he 1975 t ri a l he r ri ng spawn o n ke lp f ishe ryin Br it ish Co lumbia . F ish . Mar . Se rv . , Canad ian D epa r tm ent o f the E nvi ron -ment .Egidius , E . , Braa ten, B . , Andersen, K. & Gokstad, S . L . (1983) . Vibr ios i s insai the (Pollachius virens) popula t i ons o f t he Norwegian coas t . Rapp. P.-v.Reu n. C ons. Int. Explor. M er, 182 , 103 - 105 .El li s, C . H . & N oble , R . E . (1960) . B arging an d haul ing exper im ents wi th fallchin oo k sa lmon o n th e K l icki ta t River to tes t e ffec ts on surviva ls . Wash. D ep tF i sh ., 70 t h A nn ua l R e po r t, 5 7 - 71 .Gii l is , D. J . , Whit ing, C. A., Radley, R. A., Wilcox, J . E. S. , Ross, M. D. &Jackson , K. (1982) . H e r r ing imp ou nd m ent and pum ping ope ra ti ons . Fac tors


11/11

Towable netpen or transport o f Pacific herring 299a f f ec t in g t h e q u a l it y o f r o e h e r r i n g p ro d u c t s . Ca n. Ind. Rep. F ish. Aq ua t . Sci. ,N o . 1 3 0 , 6 1 p p .K re i b e rg , H . , B re t t , J . R . & So l m i e , A . (1 9 8 2 ) . Ro e h e r r i n g i m p o u n d m en tr e s e a r c h r e p o r t o n t h e 1 9 8 1 / 1 9 8 2 s t u d i e s . Ca n. Te ch. Rep. F ish. Aq uat . Sci. ,N o . 1 1 4 9 , 4 5 p p .K r e i b e rg , H . , B r e tt , J. R . & S o l m i e, A . ( 1 9 8 4 ). R o e h e r r i n g i m p o u n d m e n tr e s e a rc h r e p o r t o n th e 1 9 8 3 - 1 9 8 4 s tu d ie s. Ca n. T ech. Rep. Fish. Aq ua t . Sci. ,N o . 1 3 2 9 , 3 1 p p .M cC ab e , G . T ., L o n g , C . W . & P a rk , D . L . ( 1 9 7 9 ) . Ba rg e t r an s p o r t a t i o n o f j u v e -n il e s a l m o n i d s o f th e C o l u m b i a a n d S n a k e R i v e rs , 1 9 7 7 . M ar. Fish. Rev., 41(7) , 2 8 -3 4 .Sh ie lds , T . , J am ieson , G . S . & Sp rou t , P . E . (1985) . Sp aw n-o n-k e lp f i sher i es int h e Q u e e n C h a r l o t t e Is l an d s a n d N o r t h e r n B r i ti sh C o l u m b i a c o a s t - - 1 9 8 2a n d 1 9 8 3 . Ca b. T ech. Rep. Fish. Aq ua t . Sci. , N o . 1 3 7 2 , 5 3 p p .

Kreiberg 1987 Aquacultural-Engineering

Documents