- ( 1 i I

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G METH ODs USED BY THF: =JACK SURVEY 2 ' U E S C O FOR THE T-AT, PACIFTC

J.-P. Hallier*, R. E. Kearney and R.D. G i l l e t t

Published as Chapter I V i n

mTHODS U SED BY THE S OUTH PA CIFIC COMMISSION FOR ;JACK T S AND BAITFW RESOURCES

R. E. Kearney (Edi tor) Tuna and B i l l f i s h Assessment Programme

Technical Report No.7

South P a c i f i c Commission Nomea, New Caledonia

December 1982

* present address: ORSTOM

5 JANV. 11385 Nomea, New Caledonia

O. R.S.T.0.M. Fonds Documentaire

7 1

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BAITFISHINe; METHODS USID BY -A CK SURUY AND ASSF-NT P R M ATIONS ON-IQUF- TROUCAT. PACIFIC

J.-P. Hallier, R. E. Kearney and R. D. G i l l e t t

CONTENTS

1 .o INTRODUCTION

2.0 THE 2.1 2.2

2.3

2.4

2.5

2.6

2.7

2.8 2.9

USE OF THE BOUKI-AMI The P r inc ip l e of Night B a i t i n g Fishing Gear 2.2.1 The vessels 2.2.2 Attraction l i g h t s 2.2.3 The bouki-ami net 2.2.4 Bait tanks The Bouki-Ami Fishing Technique 2.3.1 Prepara t ion of the net 2.3.2 S e t t i n g t h e a t t r a c t i o n l i g h t s 2.3.3 Checking t h e quant i ty of b a i t 2.3.4 S e t t i n g the net 2.3.5 Concentration of t he b a i t 2.3.6 Hauling of the n e t 2.3.7 Loading of b a i t Additional Modifications Introduced After

2.4.1 Echo-sounder's transducer placed i n t o

2.4.2 New l i g h t manipulation procedures Advantages and Drawbacks of Modifications t o t h e

2.5.1 Advantages of t he modif icat ions 2.5.2 Drawbacks of t he modif icat ions Recommendations f o r the Se lec t ion of a Light

Commencement of t he Programme

the net

Conventional Japanese Technique

At t r ac t ion System According t o Fishing Conditions

The Se lec t ion of Ba i t f i sh ing Areas 2.7. I Occurrence of des i red ba i tf i s h species 2.7.2 Depth and bottom type 2.7.3 Anchoring of vessel 2.7.4 Curren ts 2.7.5 Wind 2.7.6 Swell and wind-chop Recommended Procedures f o r Loading of B a i t f i s h Care of B a i t f i s h Once Loaded

3.0 BAITFISHING WITH A BEACH SEINE NET 3.1 Fishing Gear and C r e w 3.2 Fishing Operations 3.3 The Transfer of B a i t

-€3!32

75

75 75 75 75 76 76 7 8 79 80 80 80 8 2 8 2 82 85

86

86 86

87 87 87

87 88 88 88 88 8 9 8 9 8 9' 8 9 90

9 1 9 1 92 96

72

3.4 Modif icat ions 3.5 Other Considerations 3.6 Drawbacks of Beach Seining

96 96 97 z

4.0 BAITFISH SAMPLING AND DATA COLLECTION 4.1 Sampling Methods and Est imat ion of Total Catch 4.2 4.3 B a i t f i s h I d e n t i f i c a t i o n

Sample Analysis and Est imat ion of Bait Usage

99 99 99

100

1 O0 5.0 SUMMARY AND CONCLUSIONS

102 REFERENCES

APPENDICES A. S p e c i f i c a t i o n s of gear used f o r b a i t f i s h i n g by t h e

B. I n s t r u c t i o n s f o r completing t h e b a i t f i s h l o g Skip jack Programme 103

105

Table

Bai t species captured by Skipjack Programme w i t h beach s e i n e 98

Finur Q

76

77

1 The s t a rboa rd s i d e of t he B a t s u t o r i Maru

2 Plan of t he bouki-ami used on t h e Ha t su to r iMaruNo.5

3 Middeck of t h e Ba t su to r i, Maru No.5 showing s i x o f t h e seven b a i t tanks 78

4 The d i f f e r e n t s t e p s o f t h e c o n v e n t i o n a l b o u k i - ami technique 8 1

5 The d i f f e r e n t s t e p s of t h e bouki-ami t e c h n i q u e a s modified by the s c i e n t i s t s of t h e Skipjack Programme 8 3

8 4

85

90

92

92

6 Crowding t h e b a i t

7 Bucketing b a i t from the bouki-ami t o the b a i t tanks

8

9 The beach s e i n e stacked i n the 5.5 metre s k i f f

Gently crowding b a i t i n t o buckets

10 F i sh ing crew i n search of b a i t w i t h beach s e i n e t t

73

11

12

13

14

15

S e t t i n g t h e beaoh seine a t f u l l speed 93

The beach seine f u l l y set 94

F ina l stages of haul ing t h e beach seine 94

Schematic r e p r e s e n t a t i o n of s e t t i n g and h a u l i n g t h e beach seine

The beach seine p a r t i a l l y set

95

96

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J.-P. H a l l i e r , R.E. Kearney and R.D. Gillett

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Most Japanese-s tyle pole-and-line v e s s e l s based i n t h e t r o p i c a l w e s t e r n and c e n t r a l Pacific (Palau, Papua New Guinea, Solomon I s l a n d s , F i j i , e t c . ) , and t h e two v e s s e l s c h a r t e r e d by t h e S k i p j a c k S u r v e y a n d A s s e s s m e n t Programme, use the same b a s i c "bouki-amitt b a i t f i s h i n g technique. Though t h e n e t d e s i g n i s similar, d i m e n s i o n s v a r y c o n s i d e r a b l y be tween v e s s e l s o f d i f f e r e n t s i z e , as d o e s t h e u s e of b a i t a t t r a c t i o n l i g h t s . From t h e commencement o f t h e Programme, C o m m i s s i o n s c i e n t i s t s m o d i f i e d t h e convent ional Japanese method on t h e b a s i s of trials p r e v i o u s l y conduc ted by s c i e n t i s t s from t h e Department of A g r i c u l t u r e and F i s h e r i e s i n Papua New Guinea (Kearney e t ax, 1972).

I n some f i s h e r i e s , n o t a b l y t h e Hawaiian po le -and- l ine f i s h e r y f o r sk ip j ack , beach s e i n e s are t h e primary method used t o c a p t u r e b a i t f i s h . I n A p r i l 1978, t h e Programme began u s i n g a beach s e i n e t o supp lemen t b a i t . catches made a t night.

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2.0 Y

1 . . 2.1 The PrinciDle of U h t Bai-

The p r i n c i p l e s of n igh t b a i t i n g are the same f o r bouki-ami, l a m p a r a o r purse-seine nets . Powerful l i g h t s are employed e i t h e r above or under-water t o a t t r a c t f i s h . When s u f f i c i e n t f i s h have gathered c l o s e t o t h e l i g h t s , a n e t i s s e t t o ca tch them. This ne t , when pul led , forms a n e n c l o s u r e or bag i n which t h e f i s h are t r a p p e d . D i f f e r e n t t y p e s o f n e t s s u i t d i f f e r e n t f i s h i n g c o n d i t i o n s and p u r p o s e s , t h e end r e s u l t b e i n g t h a t b a i t f i s h are caught and loaded l i v e i n t o b a i t tanks.

2.2 F i s h i r p G ear

Basic gear involved i n t h e bouki-ami f i s h i n g t e c h n i q u e i n c l u d e s t h e v e s s e l , t h e a t t r a c t i o n l i g h t s , t h e n e t and t h e b a i t t a n k s . Appendix A con ta ins t echn ica l s p e c i f i c a t i o n s f o r b a i t f i s h i n g gear u sed by t h e S k i p j a c k Progr amme.

. 2.2.1 .The v e s s e l s

Two Japanese l i v e - b a i t pole-and-line v e s s e l s , t h e 192- tonne B a t s u t o r i Maru No.1 (F igure 1 ) and the 254-tonne h t s u t o r i &aru JQ&, were cha r t e red by t h e Programme from Hokoku Marine Products Company L i m i t e d of Tokyo, J apan . F i e ldwork f o r t h e Programme d u r i n g t h e f irst two IO-month c r u i s e s f rom October 1977 was c a r r i e d out using t h e H a t s u t o r i Maru No.1. During the t h i r d IO-month c r u i s e , November 1979 t o August 1980, t h e B a t s u t o r i J laru 30.5. was used.

76

FIGURE 1. THE STARBOARD SIDE OF THE HATSUTOqI N0.5. On t h i s t y p e of v e s s e l most of t h e sponson a l o n g t h e s t a r b o a r d s i d e i s devoted t o b a i t f i s h i n g . Note t h e bamboo n e t f l o a t wh ich i s l y i n g on t h e sponson from the s t e r n t o t h e f o r e c a s t l e . Also v i s i b l e i s t h e pole f o r t h e ne t l i g h t extending over t h e water from t h e wheel house.

On s tandard Japanese pole-and-line v e s s e l s , most of t h e sponson (a ramp, 50 cm wide, t h a t e n c i r c l e s the s h i p and i s a t t ached t o the outboard and j u s t below t h e s h i p ' s gunwhale) along t h e s t a rboa rd s i d e i s devoted t o b a i t f i s h i n g opera t ions ; t he por t - s ide sponson, as w e l l as the bow and s t e r n , are reserved f o r pole-and-line f i s h i n g (Figure 1 ) .

2.2.2 At t r ac t ion l i g h t s

Most Japanese-s tyle pole-and-line v e s s e l s ope ra t ing i n t h e c e n t r a l and western P a c i f i c u s e unde rwa te r l i g h t s which are c o n s i d e r e d e f f i c i e n t i n a t t r a c t i n g most b a i t species . These l i g h t s are set between t h e s u r f a c e and a normal maximum depth of 20 metres.

B a i t l i g h t s are normal ly powered by AC c u r r e n t of 100 t o 220 v o l t s , according t o a v a i l a b i l i t y . Power can be s u p p l i e d e i t h e r d i r e c t l y f rom t h e v e s s e l ' s main electric system or from independent generators . The Programme i n i t i a l l y used unde rwa te r l i g h t s o f 1000 t o 2000 watts and l a t e r added above-water l i g h t s of 100 t o 1000 watts. During t h e t r a n s f e r of b a i t f rom the bouki-ami ne t i n t o the s h i p ' s b a i t tanks, one or more 40-watt above-water lamps were used t o h e l p con t ro l t h e behaviour of t h e b a i t w i th in t he n e t and t o i l l u m i n a t e p a r t of the deck.

2.2.3 .The bouki-ami n e t

A bouki-ami c o n s i s t s . o f a shee t of f i n e mesh n e t t i n g mounted on a bamboo frame (Figure 2). The ne t used on t h e Hats u t o r i Maru No.1 was 25 metres long a t the top, 27 metres a t the bottom and 23 metres deep, whi le t he one used on

,

,

7 7

1% .

FIGURE 2. PLAN OF THE BOUKI-AMI USED ON THE HATSUTORI &Q&

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1

16 l i n e s fas tened to vessel t h rough r i n g s '

Power winch i

li Power winch

20 Sinkers: 16 single + 2 double ( i . e . 2 weights at each end)

78

t h e b t s u t w i Both n e t s were made from 4 mm s q u a r e mesh k n o t l e s s n e t t i n g made of brown p o l y a m i d e n y l o n . Desc r ip t ions of t h e use of t h i s type of n e t appear i n many p u b l i c a t i o n s , one

bottom edge of t he ne t was weighted w i t h 20 sinkers, of 3.5 kg each, placed 2 metres a p a r t w i t h two a t each corner. A 20-kg l e a d - l i n e was a t t ached t o the n e t a t h i r d of t he d i s t a n c e from the top edge. T h i s h e l p e d t o keep t h e n e t v e r t i c a l before haul ing and prevented f o l d s from forming i n the bag w h i l e the n e t was being closed. Eighteen 30-metre l i n e s attached from t h e sponson t o the bottom l ead - l ine allowed the n e t t o be hauled. Two l i n e s , a t t ached on t h e f o r e and a f t n e t sides, 2 metres from the bottom of t he ne t , were h a u l e d by power winches and ensured faster c losu re of the net.

Jo.5 was l a r g e r , 27 x 35 x 25 metres.

of t he most r e c e n t by Ben Y a m i ( 1 9 8 0 ) . On t h e B a t s u t o r i Maru No.l, t h e

The n e t , wi th i ts bamboo frame, weights and ropes, was assembled p r i o r t o the beginning of the v e s s e l cha r t e r . The prepared n e t took up most of t h e s t a rboa rd sponson , where i t was s e c u r e l y f a s t e n e d when t h e s h i p was n o t ba i t f i s hing.

2.2.4 B a i t tanks

On Japanese pole-and-line v e s s e l s t he re a re two t y p e s o f b a i t t a n k s : l a r g e tanks on the main deck i n which b a i t f i s h are kep t after t h e i r c a p t u r e , and s m a l l chumming tanks from which b a i t i s thrown when f i s h i n g f o r s k i p j a c k and o the r tunas. On t h e H a t s u t o r i &I.PU No.’l, f i v e l a rge b a i t t a n k s h e l d a t o t a l of 80 cub ic metres of water; o n t h e J I a t s u t o r i Maru No.5 ( F i g u r e 3 ) , seven b a i t tanks contained 116 cubic metres. A l l t anks were r e c t a n g u l a r i n p r o f i l e .

FIGURE 3 . MIDDECK OF THE HATSUTORT MARU N0.5 SHOWING SIX OF THE SEVEN Also v i s i b l e on the r i g h t i s the b a i t t r a n s p o r t e r BAIT TANKS.

(see Sec t ion 3.3)

79

Three types of water c i r c u l a t i o n systems were used:

i

(a> Bottom i s r low and t 0 D 0-

I n t h i s type of tank t h e inf low p i p e (20 t o 30 cm i n d i a m e t e r ) was f i x e d a l o n g t h r e e o f t h e i n s i d e w a l l s o f t h e w e l l , a few cent imet res above t h e bottom. The p i p e was d r i l l e d wi th approximately t h i r t y ho le s (1.4 cm i n diameter) t h a t were r e g u l a r l y d i s t r i b u t e d a l o n g i t s l e n g t h . Water was d r a i n e d o f f a t t h e t o p o f t h e t a n k through an o u t l e t which was covered by a g r i l l t o p r e v e n t b a i t f rom es cap i ng .

(b ) TOD inf low and bottom outflolq

I n t h i s tank, water i n f l o w was t h r o u g h a p i p e similar t o t h a t descr ibed i n (a ) , but t h i s p ipe was s e t a t t h e t o p of t h e t a n k j u s t below the top of t h e w a l l s . The water inf low was directed towards t h e bottom of the tank where t h e water was drained through a g r i l l - cove red o u t l e t . There was a n o v e r f l o w a t t h e t o p o f t h e t a n k f o r t h e d ischarge of excess water, p a r t i c u l a r l y when the bot tom g r i l l became blocked w i t h dead b a i t .

Water inf low f o r t h i s tank was through two v e r t i c a l p i p e s p l a c e d a t oppos i te corners of the tank; h o l e s i n these p ipes were d r i l l e d i n such a way t h a t a c i r c u l a r , a l m o s t h o r i z o n t a l w a t e r movement was created. Outflow was from the s t anda rd g r i l l - c o v e r e d o u t l e t a t the top of t h e tank.

On the Hatsutorj. Maru No.1, three tanks had a bottom inf low sys tem, one a t o p inf low system and one a la teral inf low system. A l l tanks, e x c e p t one , had cool ing c o i l s on t h e bottom and s ides i n order t o s t o r e f rozen f i s h when t h e v e s s e l was f i s h i n g commercially. Five c e n t r i f u g a l H I T A C H I 2.2 Kw pumps, opera t ing a t 1800 rpm, ensured complete water renewal i n every tank w i t h i n 20 t o 30 minutes.

On t h e H a t s u t o r i Maru No.5, t h r e e tanks had a bottom i n f l o w sys t em and f o u r a top inf low system. Five of the tanks could be used as f r e e z e r h o l d s . Five c e n t r i f u g a l NANIWA 3.7 Kw pumps o p e r a t e d a t 1800 rpm and renewed t h e water i n each tank i n 15 t o 30 minutes.

On b o t h c h a r t e r e d v e s s e l s t h e r e were two chumming t a n k s , o n e a t po r t - s t e rn and the o the r a t port-bow. These s m a l l round tanks (265 litres on t h e Batsu tor j . Maru No.1 and 375 l i t r e s on t h e J0.5) had c o n t i n u o u s water turnover approximately every 3 minutes.

2.3 The Bouki-Ami F i s h i m Techlu ‘aue

Nigh t b a i t f i s h i n g w i t h a bouki-ami i s norma l ly a l a b o u r - i n t e n s i v e technique r e q u i r i n g a t leas t 20 crew on v e s s e l s t h e s i z e of t h e B a t s u t o r i, Maru Nos. 2. or 5. The sequence f o r a normal opera t ion c a n be summarised as fol low s.

Once t h e s h i p was anchored a t a s u i t a b l e b a i t f i s h i n g l o c a t i o n , t h e crew un t i ed the bouki-ami and readied the numerous l i n e s . To p o s i t i o n the n e t f o r f i s h i n g , bamboo poles, h e r e a f t e r called cross-poles, were f a s t e n e d a t r i g h t ang le s t.0 each end and t o t h e middle of t h e bamboo f l o a t . T h i s e n a b l e d t h e ne t t o be moved seaward from t h e s t a r b o a r d s i d e of t h e v e s s e l . P r i o r t o s e t t i n g , t he n e t rested on the s t a rboa rd sponson with the cross-poles r e s t i n g on t h e gunwhales (Figure 3). On both cha r t e red v e s s e l s , 12 bamboo po le s were needed: s i x as f l o a t s and s i x ( three jo ined p a i r s ) as cross-poles.

e a t t r a c t i o n (Step 1 of Figure 4) 2.3.2 S e t t i n n t h

Unless the Captain knew t h e b a i t f i s h i n g ground very well, and knew t h a t i t was clear of major obs t ac l e s , t h e v e s s e l was g e n e r a l l y anchored b e f o r e dusk, after echo-sounding f o r a s u i t a b l e bottom. An underwater l i g h t was then suspended from a sk i f f tethered a t a d i s t a n c e of a b o u t 100 metres f rom the s t e r n of t h e vessel . Sometimes a second l i g h t powered by a g e n e r a t o r i n another s k i f f was i n d e p e n d e n t l y moored a t some d i s t a n c e from t h e p a r e n t vessel .

The Programme's research v e s s e l s each ca r r i ed two s t u r d y f i b r e g l a s s s k i f f s . These s k i f f s were 5.5 metres long and 1.5 metres wide and b o t h were a t times used t o s e t u n d e r w a t e r l i g h t s away from t h e main v e s s e l . Both r e sea rch v e s s e l s carried two 1 IO-volt gene ra to r s s p e c i f i c a l l y t o supply power f o r t h e underwater l i g h t s used from t h e s k i f f s ; each generator provided power f o r one 1500-watt underwater l i g h t . Before n i g h t f a l l , t h e 1500-watt l i g h t was immersed 10 metres under t he s k i f f , t h e g e n e r a t o r was s t a r t e d and t h e s k i f f allowed t o d r i f t away from the s t e r n of the s h i p on i t s 100-metre-long towline. A t t h e same time, on the port-s ide near t he bow, a 2000-watt l i g h t was immersed t o a depth of 15 metres. This l i g h t was suspended from a bamboo pole which e x t e n d e d a b o u t 5 metres f rom t h e p o r t - s i d e sponson. A t h i r d underwater l i g h t of between 1000 and 2000 watts was occasional ly s e t 7 t o 10 metres underwater a t the s t e rn . Rheostats enabled t h e l i g h t i n t e n s i t y t o be va r i ed as r e q u i r e d . On t h e research v e s s e l s , two u n d e r w a t e r l i g h t s , i n a d d i t i o n t o t h e s k i f f l i g h t , were c o n t r o l l e d by rheos t a t s .

2.3.3 Checkinn t h e a u a n t i t v of ba i t (S tep 2 of Figure 4)

After the l i g h t s had been ope ra t ing f o r f o u r or f i v e hours, a check f o r the presence of b a i t was made. The s k i f f l i g h t and t h e underwater bow l i g h t were moved along the port-s ide t o midship. A s t h e s k i f f was slowly drawn t o the s t e r n of the ship, and subsequently t o midship, the s t e r n l i g h t , i f used, was g r a d u a l l y dimmed t o z e r o , m e r g i n g t h e t w o s c h o o l s o f b a i t . Simultaneously, the bow l i g h t was brought up from a dep th o f 15 metres t o a d e p t h of a b o u t 7 metres, and was moved from bow t o p o r t m i d s h i p . The q u a n t i t y of b a i t f i s h p r e s e n t was t h e n checked w i t h a n u n d e r w a t e r v i e w i n g g l a s s from t h e s k i f f , and w i t h a n echo-sounder . I f , on i n s p e c t i o n , t h e q u a n t i t y of b a i t was c o n s i d e r e d t o b e i n s u f f i c i e n t , t h e n a l l l i g h t s were s w i t c h e d on a g a i n and moved back t o t h e i r o r i g i n a l p o s i t i o n s . When s u f f i c i e n t b a i t had gathered, b a i t catching ope ra t ions started.

8 1

FIGURE 4. THE DIFFERENT STEPS OF THE CONVENTIONAL B O U K I - A M I TECHNIQUE

1 . A t t r a c t i o n l i g h t s on

2. Checking the b a i t and s e t t i n g the n e t

n

3 . Concentrating t h e b a i t and haul ing the n e t

n

4. Crowding the ba i t (see Figure 6 )

n *

82

2.3.4 t he ne t (SteP 2 off Finure 4). I

Available crew then took up positions on t h e s t a r b o a r d sponson and a t t he ends of t h e three cross-poles. The bamboo f l o a t was t h e n lowered from the sponson i n t o t h e water and gen t ly pushed by t h e cross-poles away from the vesse l . The ne t , which had been l y i n g a l o n g t h e starboard sponson, t h e n gradual ly spread out. When t h e bamboo f l o a t was a b o u t 18 m e t r e s f rom t h e side of t h e sh ip , the ends of t h e cross-poles were s e c u r e l y f a s t e n e d t o t h e s h i p ' s gunwhale and two sp r ing l i n e s were t i e d d iagonal ly a c r o s s t h e n e t t o s t r eng then the framework. The bottom of the ne t , along w i t h the s i n k e r s and connecting l i n e s , were t h e n thrown ove rboa rd from t h e i r p o s i t i o n on t h e sponson. While the n e t was s inking , the fishermen checked the t ens ion on t h e l i n e s t o make s u r e tha t t he n e t was spreading out evenly. The f i sh ing master or the Captain also checked the p o s i t i o n of the ne t from the upper deck. T h e area bound by the bamboo, the ne t and t h e v e s s e l formed a box, which on the b t s u t o r i Maru Bos. 1 and 5, was a p p r o x i m a t e l y 26 metres l o n g by 18 m e t r e s wide. The attracted b a i t had then t o be drawn t o A ca tch ing p o s i t i o n between the n e t and the v e s s e l before the n e t was raised from i t s v e r t i c a l p o s i t i o n under the bamboo f l o a t .

).

2.3.5 G & U W I ~ (S tep 3 of F igure 4)

A t t h i s stage, under the conventional J a p a n e s e sys tem, two men d i r e c t the s k i f f and i ts l i g h t , a round which t h e b a i t h a s gathered, towards t h e s ta rboard s i d e of t h e ship. The s k i f f passes under t he s t e r n c ros s -po le and i s moved forward t o the middle of t h e r e c t a n g l e formed by t h e bamboo frame and t h e ship. A l l movements of the skiff and t h e attached l i g h t must be very slow s o t h a t the b a i t f i s h fol low t h e l i g h t and do not panic. When the s k i f f reaches t h e middle cross-pole, the l i g h t i n t e n s i t y i s reduced. The degree of dimming depends upon the b r igh tness of the moon, the' water c l a r i t y and t h e s p e c i e s of b a i t present . I n add i t ion , t he l f g h t i s brought up slowly from a depth of 10 metres t o w i t h i n 1 metre of t h e s u r f a c e . The pu rpose of these two simultaneous opera t ions i s t o aggregate t h e b a i t f i s h and br ing them c l o s e t o the s u r f a c e where they are more vu lne rab le t o t he net. B a i t f i s h behaviour i s monitored wi th an underwater viewing glass and a n echo-sounder . If t h e b a i t does not gather s a t i s f a c t o r i l y around the l i g h t , f u r t h e r a d j u s t m e n t s of t h e l i g h t are made. If a l l is w e l l , the n e t i s hauled.

%

S c i e n t i s t s on board t h e surveyl v e s s e l s found t h a t t h e cumbersome ope ra t ion of br inging the s k i f f wi th t h e underwater l i g h t i n t o the framework of t he n e t could e a s i l y be replaced by suspending a n underwater l i g h t i n t h e cen t r e of the n e t ' s frame. This modi f ica t ion was first made a t t h e beginning of t he Programme i n October 1977, and was,used wi th few except ions during t h e three y e a r s of the Programme's fieldwork. A 2000-watt l i g h t w a s a t t a c h e d t o a r o p e which s l i d on a p u l l e y a t t h e e n d o f a n 8 - m e t r e bamboo p o l e overhanging the bouki-ami. These f i t t i n g s a l lowed bo th t h e d e p t h of t h e l i g h t and its d i s t ance from the s h i p ' s side t o be addusted as requ i r ed . The l i g h t was normally set about 6 metres below the surface. After t h e b a i t had been gathered around t h e underwater l i g h t a t port midship (Sec t ion 2.3.2) and the n e t had been set, the 2000-watt underwater light between the n e t and t h e v e s s e l was switched on, and t h e p o r t l i g h t dimmed t o effect t r a n s f e r of b a i t t o t h e l i g h t between the n e t and the v e s s e l ( s t e p 3 of Figure 5).

i

2.3.6 &gJ&g of t h e n e t (S teps 3 and 4 of Figure 5)

When t h e Captain and s c i e n t i s t s agreed t h a t t h e b a i t had c o n c e n t r a t e d around t h e l i g h t between t h e v e s s e l and t h e bamboo f l o a t , t h e s i g n a l was

I

P

83

FIGURE 5. THE DIFFERENT STEPS OF THE BOUKI-AMI TECHNIQUE AS MODIFIED BY THE SCIENTISTS OF THE SKIPJACK PROGRAMME

1. Att rac t ion . l i g h t s on . . I .

. ( . .. . ’

2. Checking t h e b a i t and setting t h e net

3 . Concentrating t h e b a i t and haul ing t h e ne t

4. Crowding the b a i t (see Figure 6 )

n

84

given f o r t he crew t o begin p u l l i n g t h e r o p e s . The two s i d e r o p e s , which were under cons iderable tens ion , were hauled by power winches l o c a t e d a t t h e bow and a t the s t e r n of t he sh ip . These closed the f o r e and a f t s i d e s of t he ne t wh i l e t h e ropes a t t ached t o the bottom of the n e t were pu l l ed more slowly by hand.

With a l l ne t edges a t t he su r face , the e n c l o s u r e , or bag, t h u s formed t rapped the b a i t . As soon as t h i s bag was p r o p e r l y c l o s e d , t h e unde rwa te r l i g h t i n t h e ne t was switched o f f and removed from the water. The s k i f f was then moved out of the n e t by the same r o u t e as i t was entered.

The s i z e of t h e bag was gradual ly reduced by h a u l i n g t h e n e t on board and p u l l i n g i n t he bamboo cross-poles. Th i s work was c a r r i e d o u t w i t h t he h e l p of t h e two men i n t h e s k i f f . Dur ing t hese o p e r a t i o n s , a imed a t concent ra t ing the b a i t f i s h , t he l e a d - l i n e incorpora ted i n t o t h e mid- s e c t i o n of t h e ne t he lps t o keep f o l d s from forming i n t h e n e t , t h e r e b y p r e v e n t i n g l i v e b a i t from being trapped i n small pocke t s . However, when c u r r e n t s or winds are s t r o n g , t h i s l e a d - l i n e i s o f t e n n o t s u f f i c i e n t and a d d i t i o n a l weights, which are a t t ached t o l i n e s connected i n board of t h e sponson, are thrown i n t o the bottom of t h e net. These we igh t s a re g r a d u a l l y removed a s t h e size of the bag i s reduced. The f i n a l s i z e of t he bag depends o n t h e s i z e of t h e catch, but gene ra l ly the depth i n t h e bag i s k e p t t o between 1 and 2 metres t o assist loading , and the w i d t h is usua l ly reduced t o about 2.5 metres. A t t h i s stage, s m a l l deck l i g h t s a r e switched on over the ne t and on the deck t o i l l u m i n a t e t h e loading operat ion, or the ne t i s l e f t as i t is and t h e b a i t loaded after daybreak, as shown i n F igure 6.

FIGURE 6 .

'

CROWDING THE BAIT (S tep 4 of F igures 4 and 5 )

I

85

2.3.7 Loadim of b a i t

The f i n a l crowding of the b a i t i n t h e n e t t o o k p l a c e a t t h e m i d d l e of the s t a rboa rd s ide of t h e f i s h i n g v e s s e l where t h e sponson i s l o w e s t ; t h i s made i t easier t o t r a n s f e r the buckets of b a i t f i s h and water from t h e n e t t o the b a i t tanks. When the b a i t was crowded i n t o t h i s r e s t r i c t e d area, o n l y l imi t ed e f f o r t was needed t o c o n t i n u e a d j u s t i n g t h e n e t , t h e r e f o r e most f ishermen were free t o assist wi th load ing the b a i t i n t o t h e b a i t tanks.

A plank was then placed a c r o s s t he ne t , one end resting on t h e s k i f f and t h e o the r suspended from a s t rong r o p e a t t ached t o t h e gunwhale. Two men were posi t ioned on t h e plank; one g u i d e d o r scooped t h e b a i t i n t o b u c k e t s f i l l e d w i t h water and the o t h e r l i f t e d the f u l l b u c k e t s and handed them t o the fishermen s tanding on t h e s h i p ' s sponson, who then passed them from haLnd t o hand (Figure 7) and emptied them gen t ly i n t o the b a i t tanks. The s i z e of t h e bag formed by the n e t was reduced as t h e load ing of b a i t proceeded.

FIGURE 7. BUCKETING BAIT FROM THE BOUKI-AMI TO THE B A I T TANKS

When a l l t h e b a i t had been t r a n s f e r r e d t o t h e b a i t t a n k s , t h e l a s t p o r t i o n of the n e t and t h e bamboo f l o a t were p u l l e d o n t o t h e sponson by means of the bamboo. cross-poles. The n e t was l e f t r e a d y t o be used a g a i n la ter t h e same night , o r was t i e d up u n t i l t h e n e x t b a i t f i s h i n g o p e r a t i o n . I n t h e l a t te r case the cross-poles were removed and s to red , and t h e remainder of the n e t and the bamboo f l o a t s simply f a s t ened t o the sponson.

Y

P r i o r t o loading b a i t onto the research v e s s e l s , a n estimate was made of the amount of b a i t i n the ne t bag. Th i s estimate was u s e d t o d e c i d e which b a i t tanks t o f i l l wi th water, and how t o a p p o r t i o n b a i t amongst p a r t i a l l y loaded and newly f i l l e d tanks. T h i s estimate was made w e l l b e f o r e l o a d i n g began so tha t s u f f i c i e n t tanks would be f i l l e d wi th water (15-30 m i n u t e s t o

86

fill) r"eladJr fior The beading of b a i t tanka wila r o t a t e d a f t e r e v e r y 20 busketa o f bat (aPProx$mat@J.y 30 kg of b a i t ) so thilt b a i t f i a h would baye w chasse ts settle d~ws and form alswly moying acboola around t h e u n d e r w a t e r l ights i n the tankac Mast ~f t h e b a i t tank8 were loaded t o a maximvm of 100 b u c k e t a S o r t r o p i o a l ba l l ; a p e c i a s , and t o a plaxiplupl QS 400 buckets, f o r temperate snd w l t u m d b a i t s p e ~ i e s , HoweyeF1 bheae l e v e l 8 d i d f l u c t u a t e depending o n auah f a c t o r s as amount of b a i t a a p t u r e d , w e a t h e y , y a t e r teDperature, b a i t a p e c i e s and t h e i r c o n d i t i o n i m w e d i a t e l y a f t e r c a p t u p e , water flow rake and capaci ty of p a r t i c u l a r tanks.

2.4 2 d O e of the Programm e,

2.4.1 -Echo- sounder s t ransducer DJ aced i n t o t h e n e t

During b a i t f i s h i n g operat ions, as b a i t moved ou t from m d e r t h e v e s s e l and i n t o t h e n e t t i n g area, t h e i r t race d i s a p p e a r e d f r o m t h e v e s s e l ' s echo-sounder. The t ransducer of t h e echo-sounder was permanent ly l o c a t e d near t he keel and t h e r e f o r e i t s beam d i d not cover the s u r f a c e area between t h e v e s s e l and t h e n e t where b a i t gathered. I n order t o fol low b a i t movement a t t h e f i n a l s t a g e of t h e i r c a p t u r e , Programme s c i e n t i s t s u s e d a small po r t ab le echo-sounder (see Appendix A ) t o which the t r a n s d u c e r was a t t a c h e d by 18 metres of coax ia l cable and support ing rope. The s u p p o r t i n g r o p e was a t t ached t o t h e middle of t he c e n t r a l cross-pole so t h a t t he t r a n s d u c e r hung 50 cm below the water su r face , i n t h e c e n t r e of t h e bamboo frame and v e r y c l o s e t o where t h e b a i t was g a t h e r e d . I n t h i s manner i t was p o s s i b l e t o fol low b a i t movement during the e n t i r e capture process.

2.4.2 New li-mniDulation D r o c e d u m S

A s mentioned i n S e c t i o n 2.3.5, t h e c o n v e n t i o n a l J a p a n e s e method o f mooring the s k i f f and underwater l i g h t between the n e t frame and v e s s e l was replaced by using a n underwater l i g h t , suspended from a pole on the s t a rboa rd s i d e . The p o r t u n d e r w a t e r l i g h t was g r a d u a l l y dimmed by m e a n s o f t h e rheos t a t . Then t h e deep b a i t moved under the v e s s e l and gathered a round t h e s t a rboa rd l i g h t . The vo l t age of t h i s l i g h t was then v e r y s l o w l y r e d u c e d t o approximately one-third of maximum i n t e n s i t y , and t h e l i g h t was ra ised t o about 1 metre below the surface. T h i s c o n c e n t r a t e d t h e b a i t c l o s e t o t h e su r face where i t was most v u l n e r a b l e t o t h e n e t . The n e t was t h e n h a u l e d (Figure 5).

I n some c o u n t r i e s s u r v e y e d by t h e S k i p j a c k Programme, s u r f a c e b a i t s p e c i e s were more abundant than the gene ra l ly more common mid-water or bottom species. I n such circumstances, above-water l i g h t s were tested and found t o a t t ract more b a i t f i s h than underwater l i g h t s . I n J u l y 1978 i n K i r i b a t i , a 300-watt above-water l i g h t was suspended 5 metres above t h e water s u r f a c e from a 3-metre bamboo pole p r o j e c t i n g from t h e s h i p ' s bow. From December 1978, t h i s l i g h t was replaced by a 1000-watt l i g h t . When t h e above-water l i g h t was used i t was slowly walked around from t h e bow a l o n g t h e s t a r b o a r d sponson t o a midship p o s i t i o n and switched o f f j u s t p r i o r t o h a u l i n g o f t h e n e t ( S t e p 3 of F i g u r e 5 ) . N o r m a l l y , t h e s u r f a c e b a i t f o l l o w e d t h e above-water l i g h t from the bow i n t o the n e t t i n g area and remained g a t h e r e d around the glow of the underwater l i g h t .

D i f f e ren t l i g h t combinations were sometimes used on a trial b a s i s . For i n s t ance , on occasions when b a i t was scarce, a t t empt s t o o f f s e t t h e v e r y low b a i t dens i ty were made by inc reas ing the number of l i g h t s and by m o n i t o r i n g

,

,

b a i t f i s h movements even more c l o s e l y . I n t h e l a g o o n s o f some a t o l l s , two s k i f f s were used, each ca r ry ing a generator providing power t o an u n d e r w a t e r l i g h t , One s k i f f was kept t i e d up t o t h e s te rn of t h e vessel as p r e v i o u s l y descr ibed, w h i l e t h e o t h e r was moored 100 t o 200 metres upwind from t h e vessel. This enabled t h e moored s k i f f t o be paddled back downwind t o t h e vessel after b a i t had gathered around it. I n a number of i n s t ances , a n extra underwater l i g h t was se t immediately below t h e s t e r n of t h e vessel .

2.5 Advantane s and Drawba cks of I$&g ' f i c a t i o n s t Q t h e Conventional J aaanese T e c h n u

2.5.1' Advantaa es of t h e modif icat ions

( i ) The use of underwater l i g h t s on both sides of t he v e s s e l , i n c o m b i n a t i o n w i t h t h e s h i p ' s echo-sounder and t h e p o r t a b l e sounder a d j a c e n t t o t h e s t a rboa rd underwater l i g h t , makes i t p o s s i b l e t o monitor more a c c u r a t e l y t h e movement of b a i t under t he v e s s e l and i n t o the n e t t i n g area.

(ii) By e l i m i n a t i n g t h e u s e of t h e g e n e r a t o r and s k i f f d u r i n g t h e f i n a l s t a g e s of b a i t i n g , n o i s e l e v e l s are minimised. T h i s was c o n s i d e r e d t o i n c r e a s e the o v e r a l l e f f e c t i v e n e s s of t he l i g h t s f o r a t t r a c t i n g and h o l d i n g b a i t f i s h , p a r t i c u l a r l y those s p e c i e s t h a t normally occupied lower s e c t i o n s of t h e water column and were d i f f i c u l t t o at tract t o the surface.

(iii) The a d d i t i o n of an above-water l i g h t g r e a t l y improves t h e a t t r a c t i o n of s u r f a c e b a i t spec ie s , t h u s i n c r e a s i n g the amount of b a i t f i s h caught.

2.5.2 Drawbacks of t he modif icat ions

(i) When the moon was very b r igh t , p a r t of t h e b a i t at tracted around t h e p o r t and s t e r n l i g h t s was l o s t during t r a n s f e r from the p o r t u n d e r w a t e r l i g h t t o the s t a rboa rd underwater l i g h t . I n these circumstances, it i s more e f f i c i e n t t o use a s k i f f ca r ry ing an underwater l i g h t i n order t o t r a n s f e r b a i t t o t h e s t a rboa rd side.

(ii) When t h e s k i f f i s used i n s i d e t h e n e t , b a i t f i s h b e h a v i o u r c a n b e v i s u a l l y moni tored from t h e s k i f f d u r i n g t h e n e t h a u l i n g p h a s e u s i n g a n underwater viewing g l a s s . This i s not poss ib l e when t h e s k i f f w i t h its l i g h t i s replaced by a n underwater l i g h t con t ro l l ed from the vesse l . This drawback was l a r g e l y overcome by t h e u s e of a p o r t a b l e e c h o - s o u n d e r w i t h i t s transducer se t i n the n e t t i n g area.

(iii) The modif icat ions discussed r equ i r ed t h e fol lowing e x t r a materials: one underwater l i g h t , one r h e o s t a t , one pul ley, s eve ra l bamboo poles, e l e c t r i c a l cable; however, t h e e x t r a c o s t of these materials i s not great (approximately US$450 i n 1982).

2.6 Recommendations f o r t he S e l e c t i o n of a J . i g h t A t t r a c t i o n Svstem Ac cordinn t o F ishine: Cond i t i o n s

Trials over the three y e a r s of f ieldwork of t he S k i p j a c k Programme l e d t o t he fol lowing recommendations f o r l i g h t a t t r a c t i o n systems.

When f i s h i n g i n a new b a i t f i s h i n g ground where spec ie s c o m p o s i t i o n i s unknown, or i n a n ' a r e a where s u r f a c e b a i t i s a b u n d a n t , t h e a d d i t i o n of a n above-water l i g h t i s recommended. If i t i s used i n a s s o c i a t i o n w i t h t h e conventional Japanese method, t h e procedure i s as f o l l o w s : a f t e r t h e s k i f f

When weather oond i t i sns are poor (rough sem1, heavy r a i n ) a n d / o r when benthic or mid-water b a i t s p e c i e s ape p r e s e n t , i t i s more e f f i o i e n t t o use t h e f i x e d underwater l i g h t between t h e vessel and net.

At o t h e r times, and p a r t i c u l a r l y d u r i n g p e r i o d s of f u l l moon, t h e conventional method i s recommended with the a d d i t i o n of an above-water l i g h t ' i f surface b a i t s p e c i e s are present.

The s e l e c t i o n of a b a i t f i s h i n g ground i s governed no t only by abundance of t he desired b a i t spec ie s , but a l s o by physical l i m i t a t i o n s of t h e f i s h i n g gear. Major f a c t o r s t o be considered are:

2.7.1 Oc currence of des i r ed ba i t f i s h species

S u i t a b l e b a i t s p e c i e s are mostly coastal . Popu la t ions may be r e s i d e n t or temporary. High abundance i s o f t e n a s s o c i a t e d w i t h p r e s e n c e o f l a r g e shallow expanses of water, e.g. bays and lagoons, w i t h depths ranging from a f e w metres t o a b o u t 20 metres (Kearney d. 1 9 7 8 ) . I n t h e waters s u r r o u n d i n g i s l a n d s w i t h mounta inous t o p o g r a p h y , r i v e r s e d i m e n t s a n d e x t e n s i v e mangrove swamps h e l p t o p r o v i d e a f a v o u r a b l e envi ronment f o r b a i t f i s h . For a t o l l s , the s i z e of t h e lagoon i s o f t e n a good i n d i c a t o r , t h e larger lagoons being better.

Water c l a r i t y , which v a r i e s a c c o r d i n g t o t h e p r o x i m i t y of r i v e r s , mangrove swamps, cu r ren t s , swell, e t c . , a l s o a f fec ts b a i t abundance. For example, s p r a t s are gene ra l ly found i n very clear waters, while anchovies are of t e n a s soc ia t ed w i t h more cloudy waters.

2.7.2 Der>th and bottom tvD e

The d e p t h of t h e n e t o f t e n l i m i t s t h e a r e a s t h a t c a n b e f i s h e d . Nevertheless, i f the bottom is sand o r mud, and c l ea r of o b s t r u c t i o n s , t h e n e t can be set i n p l aces where t h e water d e p t h i s l e s s t h a n t h e n e t f a l l . During the t h r e e y e a r s of S k i p j a c k Programme f i e l d w o r k , t h e m a j o r i t y o f b a i t f i s h hauls were made i n waters between 25 and 35 metres deep ; however, some sets were made i n depths of 20 metres or less. On a few o c c a s i o n s t h e n e t was purposely set i n shallow water t o capture p a r t i c u l a r s p e c i e s such as Marquesan s a r d i n e s ( G i l l e t t and Kearney 1980). Good q u a n t i t i e s of b a i t are more o f t e n found on mud or muddy-sandy bottoms than i n areas w i t h pure sand.

2.7.3 Anchorim of v e s s e l

When a n c h o r i n g t h e s h i p , care must be t a k e n t o check t h a t t h e area l i a b l e t o be covered by t h e s h i p as i t swings on i t s a n c h o r i s f r ee of a l l o b s t a c l e s such as ' large rock outcrops, co ra l patches, wrecks or sunken l o g s . The bottom should a l s o be r e l a t i v e l y f l a t as sudden v a r i a t i o n s i n d e p t h t e n d t o make handling of t he bouki-ami d i f f i c u l t , and can damage it.

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On both &&sutor i Maru JO. and jIo.5, l i m i t a t i o n s of t he anchor windlass r e s t r i c t e d t h e maximum depth f o r anchoring t o about 45 metres.

2.7.4 Curr en t s

Where c u r r e n t s a r e p r e v a l e n t , i t i s sometimes e f f e c t i v e f o r s m a l l v e s s e l s t o anchor "across current11 w i t h bow and s t e r n a n c h o r s s o t h a t t h e cu r ren t w i l l push the ne t away from t h e ship. This type of anchoring was not a t tempted wi th the l a r g e v e s s e l s char te red by the Programme. Consequen t ly , t h e r e were i n s t a n c e s where cu r ren t decreased b a i t ca t ches by causing t h e n e t t o bi l low or f o l d and f i s h a t a shallower depth than normal.

The bouki-ami, because of i t s f i n e mesh ( 4 mm) and its bamboo frame, i s s e n s i t i v e t o even t h e weakest c u r r e n t . On s e v e r a l o c c a s i o n s , bamboo cross-poles were broken by s t rong c u r r e n t s . The e f f e c t s of c u r r e n t c o u l d o f t e n be minimised by haul ing the ne t dur ing per iods of slack tide.

2.7.5 Wind

If winds are s t r o n g a t t h e time t h e h a u l i s concluded , t h e f o r w a r d (windward) end of the bouki-ami w i l l occas iona l ly ca tch t h e wind and b i l l o w l i k e a sail . On t h e char te red vesse l s , a t such times, 3.5-kg s i n k e r s ( t h e same as t h o s e t i e d a l o n g t h e bot tom of t h e n e t ) were p i t c h e d i n t o t h e bi l lowing net . When winds were except iona l ly s t r o n g , a c h a i n was at tached between t h e forward end of the bamboo f l o a t n e a r e s t t h e bow c r o s s - p o l e and t h e sponson. When the ne t was i n pos i t i on , t h i s chain acted as a l e a d - l i n e t o prevent the n e t from billowing.

2.7.6 Swell an d wind -choD

Rough seas hinder bouki-ami f i s h i n g ; f i r s t l y , because of t h e v e r y great s t r a i n p laced o n t h e bamboo p o l e s and t he r o p e s t h a t h o l d t h e n e t i n p o s i t i o n ; s e c o n d l y , because t h e s k i f f becomes d i f f i c u l t t o h a n d l e ; and t h i r d l y , because of i n j u r y t o the b a i t f i s h during crowding and loading.

2.8 Recomende d Procedur e s f o r L oading of B a ' tf i s h

Once b a i t f i s h are trapped i n the ne t , they must be crowded t o g e t h e r f o r bucketing and loading. Care must be taken during t r a n s f e r t o keep m o r t a l i t y t o a m i n i m u m . I n t h i s r e s p e c t time is a c r i t i c a l f ac to r . When b a i t f i s h are severely crowded they can be loaded much f a s t e r , b u t some s p e c i e s t e n d t o panic more and consequently mor t a l i t y is higher. On the o ther hand, l o a d i n g time i n c r e a s e s as crowding decreases , and increased time i n the n e t c a n a l s o r e s u l t i n a high incidence of i n j u r i e s .

Once the b a i t i s adequately crowded, it i s bucke ted on board. Scoops are used t o crowd b a i t i n t o buckets f i l l e d w i t h water ( F i g u r e 8 ) . If f l a t scoops are used t o f i l l the buckets, loading takes l o n g e r . If deep s c o o p s are used, crowding i n the bouki-ami can be l e s s s e v e r e and l o a d i n g t ime i s kept s h o r t ; however, such scoops r e s u l t i n more abras ion t o the b a i t t han t h e f l a t ones, which tend t o d i r e c t the b a i t f i s h i n t o t h e b u c k e t s , r a the r t h a n force them in .

The Skipjack Programme 'used two s c o o p s of d i f f e r e n t d e p t h s ; a 40-cm diameter f la t scoop wi th a s t r e t c h e d d e p t h o f 10 cm, and a 40-cm d i a m e t e r scoop w i t h a stretched depth of 25 cm. The n e t t i n g i n both scoops was of t h e same material and mesh size as the bouki-ami. Loading techniques were v a r i e d

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according t o t h e b a i t spec ie s captured and t h e weather condi t ions a t t h e time of capture. For example, i n t h e lagoon a t Wallis I s l and , t h e only access ib l e b a i t f i s h i n g ground f o r t h e Programme's ves se l was open t o s t r o n g s o u t h - e a s t winds and sea c o n d i t i o n s were o f t e n rough d u r i n g l o a d i n g . The dominant spec ies , a d e l i c a t e anchovy, StoleDho rus d e v i s i , would no rma l ly have been loaded i n t h e most g e n t l e manner p o s s i b l e . However, i n t h i s i n s t a n c e bad weather requi red r a p i d loading, hence t h e anchovies were t i g h t l y crowded and the deep scoop used.

FIGURE 8. GENTLY CROWDING BAIT I N T O BUCKETS

2.9 Care of Ba i t f i s h On ce J , oaded

A s ba i t captured by t h e S k i p j a c k Programme was norma l ly u s e d w i t h i n h o u r s of c a p t u r e , t he re was l i t t l e n e e d f o r b a i t f i s h h u s b a n d r y , a n d consequently improvements t o conventional b a i t handling techniques were f e w ; there were some excep t ions , however. Whenever t h e v e s s e l t r a v e l l e d l o n g d i s t a n c e s between coun t r i e s w i t h b a i t on board, p a r t i c u l a r l y c u l t u r e d b a i t ( J o e c i l l i a mexicana and Chanos chanos) or b a i t purchased i n Japan (m

9aDonicus and Sa rd inoDs m e l a n o s t i c t a ) , a f e e d i n g regime was i n i t i a t e d . E i t h e r prepared f i s h food o r f i n e l y ground s k i p j a c k gonads and f l e s h was o f fe red seve ra l times da i ly . A t times, an a n t i b i o t i c (Furacin) was i n c l u d e d w i t h f o o d , a n d i n o n e i n s t a n c e a p r e - t r e a t e d f i s h f o o d c o n t a i n i n g t e t r a c y c l i n e was used t o good effect.

The incidence of disease was found t o inc rease when dead b a i t f i s h were allowed t o accumulate i n the tanks f o r l ong p e r i o d s . Thus, a s a matter of course, all crew members p a r t i c i p a t e d i n removing accumulated dead b a i t f rom the g r i l l s over the su r face o u t l e t s . This dead b a i t was e i t h e r accumula ted i n p l a s t i c buckets p laced b e s i d e t h e t a n k s , which were t h e n p e r i o d i c a l l y weighed before the b a i t was discarded, or, when m o r t a l i t y was low, t h e dead b a i t was simply allowed t o pass through t h e d r a i n by removing and shaking t h e g r i l l . I n t h i s case, the s c i e n t i s t i n charge of preparing the b a i t l o g made

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a sub jec t ive estimate of t h e amount of b a i t dying over a 24-hour per iod based on v i s u a l o b s e r v a t i o n s o f d e a d b a i t o n t h e g r i l l s , When d e a d b a i t accumulated on t h e bottom of t h e tanks, an e lectr ical water pump was used t o remove i t and the b a i t s o accumulated was weighed before being discarded.

3.0 BAITFISHING WITH A BEACH SEINE NE T

Most of t he sk ip j ack f l e e t s b a s e d i n t h e i s l a n d s o f t h e c e n t r a l and western Pacific use the bouki-ami technique as t h e s o l e means of c a p t u r i n g b a i t f i s h . S k i p j a c k Programme s c i e n t i s t s a p p r e c i a t e d t h e v a l u e o f t h e bouki-ami t e c h n i q u e , b u t f e l t t h a t , as b a i t was f r e q u e n t l y t h e l i m i t i n g f a c t o r f o r s k i p j a c k f i s h i n g , i n c r e a s i n g b a i t catches by u t i l i s i n g a n y a l t e r n a t i v e capture techniques would r e s u l t i n i n c r e a s e d t u n a c a t c h e s . :In March 1978, t h e Programme began u s i n g a beach s e i n e t o supplement b a i t catches made a t night.

The bas ic p r i n c i p l e of t h i s method i s t o s p o t a b a i t f i s h s c h o o l i n shallow water during day l igh t hours and then e n c i r c l e t h e s c h o o l w i t h a n e t set from a fast-moving s k i f f . Beach se in ing techniques used by the Programme were based on the Hawaiian anchovy (StoleDhorus D u r D ureus) f i s h e r y ; however , i n response t o v a r i a b l e l o c a l condi t ions and t h e need t o capture a v a r i e t y of b a i t f i s h species, techniques evolved considerably.

3.1 F i s h i m G ear and Crew

Spec i f i ca t ions f o r the rec tangular 148 x 7-metre beach ne t , made of 4-mm k n o t l e s s n e t t i n g , and t h e 80-metre e x t e n s i o n , t o g e t h e r w i t h a l i s t o f a s soc ia t ed gear, appear i n Appendix A. T h i s r e l a t i v e l y deep beach s e i n e was used i n condi t ions ranging from s h a l l o w a t o l l l a g o o n s ( K i r i b a t i ) t o s t eep h igh i s l a n d s without reefs (Marquesas I s l a n d s ) . It was found t h a t , w i t h experience, t he 7-metre ne t was only a minor disadvantage i n water s h a l l o w e r than one metre, and enabled many sets t o be successfu l i n deep water. Well over a h a l f of a l l b a i t beach-seined by the Skipjack Programme came from sets where the water depth was greater than 4 metres.

The optimum leng th of t h e n e t s h o u l d be de t e rmined a c c o r d i n g t o t h e target species. For b a i t f i s h t h a t are t i g h t l y schooled, such as h a r d y h e a d s and goldspot her r ing , a s h o r t ne t may be a n a d v a n t a g e as i t c a n be s e t and hauled quickly. For f i s h t h a t are d i s p e r s e d o r i n s e v e r a l small s c h o o l s s t r u n g o u t o v e r a l a r g e area, a l o n g n e t g i v e s a b e t t e r c a t c h r a t e . Marquesas sard ine , g o a t f i s h and m u l l e t a re examples o f s p e c i e s which are f requent ly dispersed. A s t he Skipjack Programme f requent ly had t o opera te i n areas of extreme b a i t scarcity, where these d ispersed species were preva len t , an 80 x 2-metre e x t e n s i o n was added t o t h e l a r g e r n e t . T h i s a d d i t i o n a l n e t t i n g was set after the main n e t had been p a i d o u t , and t h e n o n l y o n a n o p t i o n a l bas i s when n e c e s s a r y t o c a p t u r e t h e r e m n a n t s o f a s c h o o l o r dispersed groups of f i s h . A s i t was o n l y 2 metres deep , i t was t h e l a s t s e c t i o n set and t h e first s e c t i o n hauled, se rv ing only t o r e t a i n t h e f i s h f o r a f e w minutes u n t i l the school was s e c u r e l y su r rounded by t h e d e e p e r main net. The very l i g h t weight of t he s m a l l s e c t i o n de t rac ted l i t t l e f rom t h e speed of the s k i f f wh i l e i n the process of s e t t i n g . .

Additional gear used w i t h the beach se ine included a s k i f f l a rge enough t o hold the ne t and seve ra l fishermen, a 25-hp o u t b o a r d e n g i n e , s c u b a gear f o r two d ive r s , and a b a i t t ranspor te r . A second s k i f f was used but w a s n o t absolu te ly necessary. The ne t could be set w i t h as few as 6 f i s h e r m e n , b u t up t o 1 4 were usua l ly involved.

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3.2 p i s h i m Oper a t i o n s

The net was s tacked n e a t l y i n t o t h e outboard-powered s k i f f w i t h t h e l ead - l ine forward and t h e cork- l ine aft (F igure 9 ) . Wett ing t h e n e t w i t h a deck hose whi le s t ack ing proved u s e f u l as t h e wet ne t sank f a s t e r . Four t o e i g h t f i she rmen were i n v o l v e d i n t h e s e a r c h f o r b a i t f rom t h e n e t s k i f f (F igure IO).

FIGURE 9. THE BEACH SEINE STACKED I N THE 5.5 METRE SKIFF. The cork-l ine i s stacked a f t and t h e l e a d - l i n e fo rward . I n a d d i t i o n , t h e p h o t o g r a p h s h o w s b a i t b e i n g t r a n s f e r r e d f r o m t h e ba i t - t r anspor t e r t o t h e survey vessel ( see S e c t i o n 3 . 3 ) .

FIGURE 10. FISHING CREW I N SEARCH OF B A I T W I T H BEACH SEINE. When t h e d e c i s i o n i s made t o set the net , a l l f i v e of t he crew who a re s tanding w i l l d i v e i n t o t h e water.

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B a i t f i s h were found by looking for b i r d s , s p o t t i n g bubbles or r i p p l e s on the s u r f a c e , d i r e c t o b s e r v a t i o n ( i n which case p o l a r o i d s u n g l a s s e s were h e l p f u l ) , or by d iv ing with a f a c e mask. After b a i t had been l o c a t e d , t h e d e c i s i o n t o s e t t h e n e t was based o n t h e a b s e n c e o f l a r g e q u a n t i t i e s of c o r a l , and t h e water being deep enough f o r t h e o u t b o a r d b u t s h a l l o w enough f o r t h e net.

Immediately upon s i g h t i n g b a i t f i s h t h a t were judged t o , be v u l n e r a b l e , one fisherman, holding the tow-line of the n e t , jumped i n t o t h e water f rom the s k i f f as i t was t r a v e l l i n g a t f u l l speed. A second fisherman t o s s e d t h e cork-line overboard i n bunches of about 2 metres, w h i l e a t h i r d t o s s e d t h e l ead - l ine i n a s i m i l a r f a sh ion (Figure 11 ) . O t h e r s i n t h e n e t s k i f f d i v e d overboard ready t o assist w i t h haul ing the net. Th i s decreased the weight i n t he s k i f f and hence increased the s e t t i n g speed. The s k i f f o p e r a t o r p a i d c l o s e a t t e n t i o n t o the movements of t h e b a i t f i s h , d e p t h of t h e water, t he speed a t which t h e n e t was b e i n g thrown, t h e amount o f n e t r e m a i n i n g on board, and any c o r a l patches. Depending on underwater topography, d i s t a n c e from the beach, behaviour of t he b a i t and s u r f c o n d i t i o n s , t h e n e t was s e t e i ther i n a complete c i rc le (Figure 12), or between two p o i n t s on t h e beach. The e n c i r c l i n g method r e s u l t e d i n a fas ter haul , w h i l e s e t t i n g from beach t o beach covered a g r e a t e r l e n g t h of beach. If the l a t te r t e c h n i q u e was u s e d , t he ends of the ne t were walked t o g e t h e r a l o n g t h e beach. After t h e n e t formed a complete c i rc le , h a u l i n g p r o c e d u r e s f o r the two t e c h n i q u e s were i d e n t i c a l .

FIGURE 11. SETTING THE BEACH SEINE AT FULL SPEED

The cork-line from the s e c t i o n of t h e n e t first set was t i e d t o t h e bow of the s k i f f . A d ive r , using scuba gear , was posi t ioned d i r e c t l y under t h e sk i f f t o hold t h e two s e c t i o n s of t h e l ead - l ine toge the r as t h e n e t was being hauled. Two t o fpu r men hauled and re-stacked t h e n e t i n t he s k i f f w h i l e o t h e r crew members c o n s t a n t l y d i v e d t o c l e a r t h e l e a d - l i n e f r o m a n y obs t ruc t ions such as rocks or coral. An a d d i t i o n a l man, a second s k i f f , o r an anchor was used t o keep t h e n e t s k i f f i n proper p o s i t i o n w i t h r e s p e c t t o

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t h e n e t f o r ease af' h a u l i n g . Dur ing t h e f i n a l s tages o f t h e h a u l , t h e l ead - l ine was brought toge ther on the bottom and the n e t was p u r s e d ( F i g u r e 13). Most of t h e remaining n e t was d r i e d - u p t o crowd t h e b a i t t o g e t h e r . Care was t a k e n t o e l i m i n a t e f o l d s i n t h e n e t i n which b a i t f i s h cou ld b e trapped. Figure 14 is a schematic r e p r e s e n t a t i o n of t h e s e t t i n g and h a u l i n g process.

FIGURE 12. THE BEACH SEINE FULLY SET (Step 2 of Figure 13)

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FIGURE 13. FINAL STAGES OF HAULING THE BEACH SEINE. A t t h i s stage t h e - ne t has been pursed on the bottom by br inging t h e two s e c t i o n s of t h e lead- l ine together. Shor t ly h e r e a f t e r , b o t h s e c t i o n s of cork-line, both s e c t i o n s of l ead - l ine and n e t t i n g w i l l be simultaneously hauled on board t h e s k i f f .

FIGURE 14. SCHEMATIC REPRESENTATION OF SETTING AND HAULING THE BEACH SEINE

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3 . 3 The Transfer of Bait

A s t h e research v e s s e l s drew nearly 4 metres of water, they o f t e n cou ld n o t g e t c l o s e t o t h e beach s e i n i n g s i t e , t h u s r e q u i r i n g t h e b a i t t o b e t ranspor ted cons iderable d is tances . A. box-type b a i t - t r anspor t e r , as p i c tu red i n F igures 3 and 9 and descr ibed i n Appendix A, was considered t o be the most successfu l arrangement f o r b a i t t ranspor t . If t h e sea c o n d i t i o n s were calm and the v e s s e l was n o t t o o f a r from t h e b a i t i n g area, i t was o f t e n more e f f i c i e n t t o crowd the b a i t i n t o a s e c t i o n of t h e n e t , and t h e n s l i n g t h i s s e c t i o n between the two s k i f f s f o r t r anspor t t o t h e f i s h i n g vesse l .

3.4 Modif icat ions

Numerous v a r i a t i o n s t o t h e a b o v e t e c h n i q u e s were c a r r i e d o u t : ( 1 ) Valuable b a i t species were o f t e n found i n and around l a r g e o b j e c t s s u c h as o l d wrecks. The se ine was p a r t i a l l y s e t a d j a c e n t t o a wreck, o r o t h e r obs tac le , and b a i t scared i n t o the net . (2) S e t t i n g t h e beach n e t a t n i g h t i n c o n j u n c t i o n w i t h a n e l e c t i c a l g e n e r a t o r a n d u n d e r w a t e r l i g h t was occas iona l ly successfu l a t the same l o c a t i o n where r e g u l a r day b a i t i n g had failed. (3) I n shallow water, i t was p o s s i b l e t o s e t h a l f of t h e n e t and then walk the remaining ne t s eve ra l hundred metres p a r a l l e l t o t h e beach t o inc rease the area of coverage (Figure 15). ( 4 ) When there was s u r f , t h e s e t was usua l ly made i n deepe r water t o a v o i d h a v i n g t h e s k i f f i n t h e impac t zone.

FIGURE 15. THE BEACH S E I N E PARTIALLY SET. The f i s h e r m e n have wa lked seve ra l hundred metres a l o n g t h e s h o r e t o i n c r e a s e area of coverage.

3.5 Other Con s idera t i ons

A scuba-equipped d ive r i s considered he lp fu l when water under t h e s k i f f i s deeper t h a n 1 metre, and n e c e s s a r y i n water more t h a n 2 metres deep. There were usua l ly two d i v e r s using scuba, one d i r e c t l y under t h e s k i f f t o haul the ne t and the o ther t o s w i m t he perimeter of the ne t i n o rde r t o f r e e the lead- l ine from obs t ruc t ions and then t o assist i n h a u l i n g t h e n e t . The

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e n t i r e hau l ing ope ra t ion was s i g n i f i c a n t l y f a s t e r u s i n g d i v e r s w i t h s c u b a gear. On occasions, the e n t i r e 228-metre n e t was set and hauled i n less than 22 minutes.

Net maintenance was very important. Only r a r e l y was t h e beach n e t u s e d without a t least a few minor r i p s i n the ne t t i ng , u sua l ly caused by c o r a l o r r o c k o b s t r u c t i o n s . A t t h e f i rs t o p p o r t u n i t y a f t e r each b e a c h s e i n i n g operat ion, t h e n e t was inspec ted and repaired. As t h e mesh was of s q u a r e k n o t l e s s material , p a t c h e s c o u l d be sewn o v e r t h e h o l e s , a p r o c e d u r e r e q u i r i n g l i t t l e net-mending expe r t i s e .

The stage of t h e t i d e a f f e c t e d t h e success of beach se in ing i n two ways. F i r s t l y , i n areas where t h e bottom was g e n e r a l l y u n f a v o u r a b l e , due t o t h e presence of c o r a l , s e in ing was sometimes p o s s i b l e i n t h e sandy i n t e r - t i d a l area during per iods of high t i de . T i d a l ranges are g r e a t e s t du r ing new moon and f u l l moon per iods and t h e area a v a i l a b l e f o r beach s e i n i n g i s t h e n a t a maximum. It i s t h e r e f o r e c o n v e n i e n t t h a t d u r i n g f u l l moon, when n i g h t b a i t i n g is poor, o p p o r t u n i t i e s f o r beach s e i n i n g are g rea t e s t .

Tidal s t a g e a l s o affects v u l n e r a b i l i t y of c e r t a i n species. For example, i t was t h o u g h t t h a t t h e Marquesan s a r d i n e was most v u l n e r a b l e t o b e a c h se in ing a t low t ide .

The e f f e c t i v e n e s s of t he beach s e i n e technique i s g r e a t l y , i n f l u e n c e d by t h e h a b i t a t and b e h a v i o u r of t h e s p e c i e s b e i n g pursued . N o t e s o n t h e habi ta t , school type and behaviour of t h e most common s p e c i e s e x p l o i t e d by .the Skip jack Programme are given i n t he Table. Despite the o f t e n rough beach seining cond i t ions (wind chop, s u r f , e tc . ) and f r e q u e n t l y l o n g t r a n s p o r t distan.ces t o the f i s h i n g v e s s e l , b a i t f i s h m o r t a l i t y was s u r p r i s i n g l y ' low. For in s t ance , SDratel loidea d e l i c a t u l u s , considered by some f ishermen t o be t o o f r a g i l e f o r u se as b a i t , was beach seined and kep t on board f o r f i v e days d u r i n g a t r i p f rom Truk I s l a n d t o Sa ipan . I n t h e M a r q u e s a s I s l a n d s ,

' m o r t a l i t y f o r l a r g e q u a n t i t i e s of beach-se ined Marquesan s a r d i n e was no higher t han t h a t f o r the same s p e c i e s caught a t night by bouki-ami.

A major problem w i t h beach s e i n i n g i s t h a t o b s t r u c t i o n f ree , sandy areas, of p r o p e r d e p t h , where b a i t f i s h spec ies c o n g r e g a t e a r e r a r e or non-existent around many is lands. Another l i m i t a t i o n i s t h a t t h e c a p t u r e of q u a n t i t i e s of f i s h c l o s e t o shore during day l igh t hours could cause c o n f l i c t wi th l o c a l t r a d i t i o n a l f i s h i n g r i g h t s . Furthermore, t h e e f f i c i e n c y of t h e beach s e i n i n g technique i n terms of catch per se t or catch p e r u n i t o f t ime was usua l ly considerably less than f o r t he bouki-ami. Over a per iod of three

' y e a r s , t he Skipjack Programme caught a n average of 45 kg of b a i t p e r h a u l o f t h e beach n e t (74 hau l s ) , compared t o 122 kg pe r haul f o r the bouki-ami (561 hauls) .

t

There are othe ' r d i s a d v a n t a g e s which a re a p p l i c a b l e o n l y i n c e r t a i n s i t u a t i o n s . For in s t ance , time spent i n day b a i t i n g a c t i v i t i e s i s normal ly time l o s t f o r t u n a f i s h i n g . Beach s e i n i n g i s e x h a u s t i n g , p h y s i c a l l y demanding work that could be a n a d d i t i o n a l h a r d s h i p o n t h e crew i f o t h e r i n t e n s e a c t i v i t i e s ( n i g h t b a i t i n g , v e s s e l main tenance , s u c c e s s f u l t u n a f i s h i n g ) are pursued during the same 24-hour period.

i

TABLE. BAIT SPECIES CAPTURED BY SKIPJACK PROGRAMME WITH BEACH SEINE

Species Depth Captured School Type Behaviour and Comments

Hardy heads . (S i lve r s ides )

Marquesan sardine

Blue s p r a t

Sead

Goatfish

Mull e t s

Bone f i s h

Atherinidae: HvDoatherina ovala ua Pranesus ~ i m

Berk los i ch thvs Dunc t a t u s

0.1 - 3 metres

0.3 - 3 metres

Sard,&g&La marauiensis

Smatell o ides d e l i c a t u l u s

Muligidae

Albula vulDes

0.8 - 7 metres

1.5 - 10 metres

2 - 5 metres

1.3 - 3 metres

0.1 - 2 metres

0.3 - 4 metres

S m a l l t o medium, dense c lose t o beach.

Slow, easy t o spot , easy t o catch.

Medium t o very large, dense, c l o s e and far from shore. Frequently mixed w i t h Atherinids.

Small t o medium, medium dens i ty , f a i r l y c lose t o beach. Fre- quent ly many small schools i n one area.

Dispersed school. Frequently on edge of drop o f f . Frequently around p i e r s and wharfs.

Dense, moving

Very dispersed. Sandy area near beach. S m a l l school s.

Dispersed, near shore

Dispersed, on bottom

Fas t , i f escape i s found from ne t most b a i t w i l l follow. Important t o keep n e t on bottom. D i f f i c u l t t o estimate amount and overcrowd. B i r d s f requent ly i n d i c a t e posi t ion.

Long n e t useful . Can be spot ted by s m a l l bubbles on su r face or by diving. Eas i ly escape from net.

Often i n deep water adjacent t o shallow area and may be scared t o catchable loca t ion . D i f f i c u l t t o s p o t without div- ing. Leap when chased by predators.

Very fast, w i l l t r y t o out race s k i f f , jumping i n process.

On bottom. Hard t o see. Often i n shade of overhanging trees.

Not usua l ly found i n concentra- t ions. Net walked for seve ra l hundred metres t o inc rease area of coverage.

W cx,

1 . - 1 ’ I

.-

99

Detailed data on ca t ches of a l l b a i t f i s h spec ie s , and t h e i r s u b s e q u e n t use, were c o l l e c t e d and recorded r e g a r d l e s s o f which b a i t f i s h i n g t e c h n i q u e was used.

4.1 S a m ~ l i m Me thods and Estimat i o n of Total Catch

While t h e b a i t was b e i n g l o a d e d i n t o t h e b a i t t a n k s f o l l o w i n g each b a i t f i s h haul , a sample of one bucket was taken from a p p r o x i m a t e l y e v e r y 20 buckets of b a i t loaded. T h i s sample r a t i o was reduced f o r very l a r g e h a u l s , and r a r e l y were more than three buckets taken even when t h e t o t a l catch was more than 60 buckets. The wet weight of t he b a i t f i s h i n the samples was t h e n taken t o the nea res t 1/10 kg using a s p r i n g b a l a n c e . T o t a l w e i g h t of b a i t loaded was then estimated from the product of average sample-weight and t o t a l catch i n buckets. When the hau l was l e s s than 20 buckets, a sample was taken from s e v e r a l buckets w i t h a s m a l l n e t scoop and t h e a v e r a g e w e i g h t of b a i t per bucket was estimated v i sua l ly .

Sometimes the amount of b a i t caught exceeded t h e c a p a c i t y o f t h e b a i t tanks, and occasional ly a s i g n i f i c a n t amount of b a i t d i e d i n t he n e t b e f o r e loading. I n both these s i t u a t i o n s t h e b a i t was discarded d i r e c t l y from t h e n e t and the amounts discarded a l i v e or dead were estimated v i sua l ly .

4.2 e S e ' O ' s e

B a i t f i s h s p e c i e s m a k i n g up more than one per cent of t h e catch, o r which had p o t e n t i a l as tuna b a i t , were i d e n t i f i e d t o t he l e v e l o f s p e c i e s ; o t h e r s were i d e n t i f i e d t o f a m i l y o r genus. P e r c e n t a g e n u m e r i c a l abundance was determined from counts of each s p e c i e s making up more t h a n f i v e p e r c e n t of the sample. For each o f these s p e c i e s , a subsample of 10 spec imens was measured f o r s tandard l e n g t h t o the nea res t idillimetre w i t h a stainless steel micrometre r u l e . During t h e c o u r s e o f t h e Programme, e x a m p l e s o f t h e dominant spec ie s , s p e c i e s whose i d e n t i f i c a t i o n was d i f f i c u l t , and s p e c i e s o f p a r t i c u l a r s c i e n t i f i c i n t e r e s t were preserved i n 10 per c e n t f o r m a l i n o r 80 per cen t a lcohol f o r the refer.ence c o l l e c t i o n on board the vessel .

The weight of bait used f o r f i s h i n g each day was g e n e r a l l y es t imated from the number of b u c k e t s of b a i t t a k e n from t h e t a n k s d u r i n g f i s h i n g operat ions, and a v i s u a l estimate of t he average weight of b a i t p e r bucke t . I n the middle of a "good b i t i n g " school, however, these estimates would o f t e n be inaccura t e s i n c e the amount of b a i t per bucket was highly v a r i a b l e a t such t imes , a n d t h e number o f b u c k e t s u s e d was s o m e t i m e s m i s r e c o r d e d . Consequent ly , t h i s estimate of t h e amount of b a i t u s e d f o r f i s h i n g was cross-checked a g a i n s t the,amount of b a i t estimated t o have d i e d d u r i n g t h e day, and a v i s u a l estimate of t he amount of b a i t remaining i n the b a i t t a n k s a t the end of the f i s h i n g day. Dai ly b a i t usage, i n standard 1.5 kg buckets, was t h e r e f o r e monitored on the basis o f f o u r o b s e r v a t i o n s r e c o r d e d i n t h e d a i l y log : (1 ) b a i t carried a t the beginning of the d a y l s f i s h i n g ; ( 2 ) b a i t used during t h e day f o r f i s h i n g ; (3) b a i t m o r t a l i t y during the 24-hour period p r i o r t o commencement of f i s h i n g (Sec t ion 2.9); and ( 4 ) a v i s u a l es t imate of species composition of t h e b a i t on hand a t Commencement of f i s h i n g ( o n l y t h e dominant three o r f o u r spec ie s ) .

I n a d d i t i o n $0 t he above information, the fol lowing data were r e c o r d e d f o r each b a i t f i s h haul: date, time and p o s i t i o n of t he haul , depth o f water, type of bottom, and l i g h t combinations used. For most bouki-ami h a u l s , t h e t r a c e o b t a i n e d from t h e Programme's echo-sounder was a t t a c h e d t o t h e

100

log-sheet. Each day, data from ind iv idua l b a i t h a u l s were e n t e r e d o n t o t h e b a i t f i s h computer log-sheets , f o l l o w i n g the c o d i n g i n s t r u c t i o n s l i s t e d i n Appendix B.

4.3

I d e n t i f i c a t i o n o f t r o p i c a l b a i t f i shes i n t h e f i e l d i s d i f f i c u l t . S e p a r a t i o n of t h e more common s p e c i e s w i t h i n t h e b a i t f i s h g e n e r a i s p a r t i c u l a r l y troublesome, o f t e n r e q u i r i n g the use of a dissecting mic roscope f o r c a r e f u l a n a t o m i c a l e x a m i n a t i o n s . The task i s c o m p l i c a t e d b e c a u s e c l a s s i f i c a t i o n s of many b a i t f i s h are b e i n g r e v i s e d as a r e s u l t o f c u r r e n t taxonomic s t u d i e s , r e q u i r i n g cons tan t up-dating of f i e l d keys. A d raf t f i e l d guide, prepared by s c i e n t i s t s of t he Programme, was used e x t e n s i v e l y by t he Skipjack Programme t o separate b a i t s p e c i e s i n t h e families E n g r a u l i d a e , D u s s u m e r i i d a e , C l u p e i d a e , A t h e r i n i d a e , C a r a n g i d a e , L e i o g n a t h i d a e , Caesiodidae, Apogonidae, and Scombridae. Keys i n t h e g u i d e were based o n pub l i ca t ions by Schul tz J& a. (1953), Chan (1965), Ronquillo (1 965) Munroe (1967) Berry and Whitehead ( 1 968) , Paxton ( 1 9 7 2 ) , Whitehead (1 972) , and F i she r and Whitehead (1974). A r ev i sed key f o r A t h e r i n i d s was s u p p l i e d i n September 1979 i n p r e - p u b l i c a t i o n form by D r W. I v a n t s o f f , M a c q u a r i e Universi ty , Austral ia . Throughout t he Programme, f i e l d personnel m a i n t a i n e d a b a i t f i s h r e fe rence c o l l e c t i o n and recorded v i s u a l features that assisted i n r ap id c l a s s i f i c a t i o n under f i e l d c o n d i t i o n s . Specimens t h a t c o u l d n o t be i d e n t i f i e d , b u t were common i n t h e catch, were fo rwarded t o s p e c i a l i s t taxonomists f o r d e t a i l e d examination.

The f i e l d g u i d e , t o g e t h e r w i t h t h e b a i t f i s h r e f e r e n c e c o l l e c t i o n ' . accumulated dur ing the s u r v e y , were i n v a l u a b l e aids t o c l a s s i f i c a t i o n of b a i t f i s h species . An updated ve r s ion of t h i s f i e l d guide, i nc lud ing d e t a i l s on d i s t r i b u t i o n and o c c u r r e n c e of t h e i m p o r t a n t b a i t f i s h s p e c i e s , i s cu r ren t ly i n pre-publ icat ion form ( L e w i s e t a. MS).

- --

5.0

During the three y e a r s of the Skipjack Programme, night b a i t i n g wi th the bouki-ami and day b a i t i n g wi th the beach s e i n e l e d t o a t o t a l catch of more t h a n 68,000 kg o f b a i t i n t h e waters of 25 c o u n t r i e s and t e r r i t o r i e s . Catches wi th the bouki-ami exceed 65,000 kg, whi le day b a i t i n g w i t h a beach s e i n e i n the waters of eight; c o u n t r i e s accounted f o r o v e r 3,200 kg. These techniques produced large catches under a wide v a r i e t y of c o n d i t i o n s . Many b a i t spec ie s wi th d i f fe ren t b e h a v i o u r p a t t e r n s were v u l n e r a b l e t o one o r o the r , o r both methods of capture.

Both techniques we labour i n t e n s i v e ; however, t h i s i a nc?t g e n e r a l l y regarded as a handicap by most P a c i f i c I s l a n d c o u n t r i e s . The equipment i s comparatively simple and resistant t o t h e rough h a n d l i n g on board f i s h i n g v e s s e l s . Both t e c b n i q u e e , when p r o p e r l y e x e c u t e d , a r e g e n t l a o n t h e b a i t f i s h , which is a v a l u a b l e q u a l i t y when h a n d l i n g t he d e l i c a t e species common i n the South P a c i f i a Commission area.

T r i a l s conduc ted d u r i n g t h e Programme showed t h a t w h l l e u n d e r w a t e r l i g h t s are g e n e r a l z y aQpe e f f i c i e n t , a n above-water l i g h t c m b e m o r e e f f e c t i v e f o r attracting c e r t a i n species of surface b a i t . The p r a c t i c a l i t y of combining both t y p e s ~f l i g h t s was demonstrated.

When using the bouki-ami, replacement of t h e s k i f f and I t s underwa te r l i g h t by an underwater l i g h t c o n t r o l l e d from t h e ves se1 f ;g deck , improved

4

B

101

f l e x i b i l i t y of t h e f i s h i n g o p e r a t i o n s . P l acemen t o f a n e c h o - s o u n d e r transducer between the ne t and the ves se l enabled improved monitor ing of t h e b a i t and t h e net a t the f i n a l stage of t h e f i s h i n g operation.

I n addi t ion t o work on b a i t capture, severa l methods of loading b a i t f i s h f rom t h e n e t t o t h e b a i t t a n k s were t r i e d , p a r t i c u l a r l y t e c h n i q u e s f o r scooping and bucketing l i v e b a i t from the net. It was p o s s i b l e t o improve su rv iva l considerably by gent ly scoop ing and b u c k e t i n g b a i t i n t o t he b a i t tanks.

Details of r e s u l t s from these b a i t f i s h methods and r e s u l t i n g r e s o u r c e assessments f o r each of t he 25 coun t r i e s surveyed by t h e S k i p j a c k Programme are presented i n the Fina l Country Report series.

J

102

REFERENCES

BEN YAMI, M. (1980). hci,th Dole - - . London : Fishing News Books Limited.

BERRY, F.H. and P.J .P . W H I T E H E A D ( 1 9 6 8 ) . A new s p e c i e s o f s a r d i n e (Sard ine l la , Clupeidae) from the Marquesas Is lands. p r o ceedinqg a m Biolost icsrl. Societv -ton 81: 209-22.

CHAN, W. Lae-Yei (1965). A systematic r e v i s i o n of t he Indo-Pacific c l u p e o i d f i s h e s of the genus Sa rd ine l l a (Family Clupeidae). JaDane se .Journal Ich t hv o1 ogy 12:104-18, 13:1-39.

. . FISHER, W. and P. J.P. WHITEHEAD (eds.) (1974). E9Q mecies i d e n t i f i c a t i o u

P a c i f i c ( F i s u Area a, Volumes I t o IV. Rome : Food and Agricul ture Organization of t he United Nations.

s h e e t s f i she ry mrDose S. - n Qcean arid Wester n C e n t r a l

GILLETT, R.D, and R,E. KEARNEY (1980) . Second i n t e r i m r e p o r t o f t h e a c t i v i t i e s of t he Skipjack Survey and Assessment Programme i n the waters of French P o l y n e s i a (13 December 1979 - 2 F e b r u a r y 1980 and 5-17 February 1980). SkiD.iack Survey u Assessmen t p r o m m e

ReDort No.21, South Pacific Commission, Noumea, New Caledonia.

KEARNEY, R.E., A.D. LEWIS and B.R. .SMITH (1972). Survey of sk ip jack tuna and Cruise Repor t Tagula 71-1. b a i t resources i n Papua New Guinea waters.

DeDartmea a AFricul tur e. Stock and F i s h e r i e s R esearch Bu l l e t i n 8.

KEARNEY, R.E., A.D. LEWIS and J-P. HALLIER (1978) . I n t e r i m r e p o r t of t h e a c t i v i t i e s of t he Skipjack Survey and Assessment Programme i n the waters of t h e New Hebr ides (5-13 December 1977 and 20-23 J a n u a r y 1 9 7 8 ) .

IkwLLLY Sk iD. i ack S u r v e y u Asses s m e n t progr- - e P r e l i m i n a r v ReDort No. 4, South Pacific Commission, Nomea, New Caledonia.

. .

LEWIS, A.D., B.R. SMITH and C.P. ELLWAY (Manuscript). A guide t o t h e common tuna b a i t f i s h e s of t he South P a c i f i c Commission area. South P a c i f i c Commission, Nomea, New Caledonia.

MUNROE, I.S.R. (1967). JJg f ishes of m. Port Moresby : Department of Agricul ture , Stock and Fisher ies .

PAXTON, John R. (1972). Osteology and r e l a t i o n s h i p s o f t h e l a n t e r n f i s h e s (Family Myctophidae), me T,OS Angeles mseurq Bulletin. m e n c e 13.

RONQUILLO, I .A. (1965). A review of t h e genus S t o l e D h o r u w i t h a key t o species. (Manuscralpe FAO, Andre Mayer Research Fellow r e p o r t )

SCHULTZ, L.P. , E.S. HERALD, E.A. LACKNER, A.D. WELANDER and L.P. WOODS (1953). F ishes of the Marshall and Mariana Is lands. Volume 1 (Famil ies from Asymmet reabidae through Siganidae) . Nat- Museum Bul l e t i n 202.

WHITEHEAD, P. J. P. (1972) . A s y n a p s i s o f t h e c l u p e o i d f ishes of I n d i a . Journal of' t he KErine Biolo= ' a t i on , India 14(1):168-256.

103

,

4 .

.I '

"

APPENDIX A. SPECIFICATIONS OF GEAR USED FOR BAITFISHING BY THE SKIPJACK PROGRAMME

- Underwater l i g h t s : 2000 watts - 200 v o l t s 1500 watts - 110 v o l t s 1000 watts - 110 v o l t s

- Above-water l i g h t s : 100 watts - 110 v o l t s 300 watts - 200 v o l t s

1000 watts - 200 v o l t s

- Portable generator : YANMAR - 3000 watts - 100 v o l t s

- Bouki-ami : Hatsu tor i Maru No.1 : 25 metres ( f l o a t - l i n e length)

27 metres ( lead- l ine length) 23 metres (depth)

b t s u t o r i Maru No.5 : 27 metres ( f l o a t - l i n e length) 35 metres ( lead- l ine length) 25 metres (depth)

- Bamboo : Length : 11 metres Diameter : 12 cm

- S k i f f s (two per ves se l ) : Length : 5.5 metres Width : 1.5 metres Material : f ibre-g lass Design : bottom f l a t

- Underwater viewing g l a s s : Height : 42 cm Diameter a t the bottom : 30.5 cm Diameter a t the top : 26 cm

- Echo-sounders : J a t s u t o r i Maru No.1 : SANKEN TS-16 0-1600 metres (4 scales - wet paper)

Flying Bridge

SANKEN NSS 1300 0-1320 metres (wet paper) Wheel House

Hatsutor i Mar u No.5 : SANKEN TL-32 0-3200 metres ( w e t paper), 2 f requencies 28 KHz-200 KHz. Flying bridge.

SANKEN NSS-1300 0-1320 metres (wet paper) , frequency 28 KHz. Wheel house.

104

Por tab1 e : J A P A N MARINA, JMF-707AB-1 e 2 Volts DC, echo- sounder frequency 50 KHz

- Scuba Gear : A i r tank : 80 cubic f o o t aluminium SCUBA tanks - max. PSI 3000 Double stage regula tor : Sherwood Octopus pressure gauge : 0-3500 PSI, USD Backpack : U.S. Divers A i r compressor : Luchard tlPorpoiself, 6.7 cubic metres per hour Weights : 2 l b s , 1.5 l b s , 0.75 l b s Weight b e l t : Sextec Diving masks, f i n s and snorkels

- Buckets : ' Volume : 13 and 15 litres

Material : Blue plast ic

- scoops : Bait-loading scoops Bait-chumming scoops

Diameter 40 cm 40 cm Depth 27 cm 12 cm Handle length 80 c m 41 cm Mesh size 4 " 4 "

24 cm 10 cm 40 cm

4 "

- Beach se ine : Material suppl ie r : K. Kida Fishing Suppl ies

212 Kamani Street HONOLULU, H a w a i i 96813

Dimensions : 148 x 7 metres Type of mesh : 4 mm, square mesh kno t l e s s F l o a t s : egg shaped, 12 x 6.5 om, spaced every 24 cm

- Beach se ine extension : Dimensions : 80 x 2 metres Mesh s i z e : 5 mm (bar length) lJlycle kno t l e s s F l o a t s : round, 3.5 x 5.5, spaced every 42 cm Leads : 4.5 x 2.0 cm, 100 g, spaced 1 metre apart Dry weight : 40 kg

- B a i t t r anspor t e r : Length : 2.45 metres Width : 1.22 metres Height : 1 metre

105

. O'

i(

Heading i n Log

AREA

RECORDER

YYmmdd

h t

c t r y

no

l a t

1 ong

S

sst

d

b

1

It on

n

b l

bw

s b l

bda

bdd

comment

f /gen

APPENDIX B.

Column Number

- -

5-10

11-14

15-18

19-20

22-27

28-34

38

41 -44

45-46

47-48

51-52

53-56

57-58

60-62

63-54

65-67

6 8-70

71-73 '

15-80

15-19

INSTRUCTIONS FOR COMPLETING THE BAITFISH LOG

Data Entered

General desc r ip t ion of area

Person recording data

Date i n year/month/day format

T i m e of haul of b a i t ne t

Three-letter country code p lus v i s i t number

Sequent ia l haul number f o r country

Lat i tude of pos i t i on of haul t o 1/10 of minute

Longitude of p o s i t i o n of haul t o 1/10 of minute

Surface condi t ions, i. e. p l ac id , rough

Sea sur face temperature

Depth of water i n metres

Composition of bottom, e.g. sand, mud

Code number f o r l o c a t i o n a n d number o f b a i t a t t r a c t i o n l i g h t s used

Time when l i g h t s switched on

Type of ne t used, e.g. bouki-ami, beach se ine

Number of buckets of b a i t l o a d e d o n t o t h e research vesse l

Average dry weight of a bucket of b a i t

Number of s tandard (1.5 kg) buckets of b a i t loaded

Number of s tandard buckets of b a i t discarded a l i v e

Number of s tandard buckets of b a i t discarded dead

Comment on unusua l c i r c u m s t a n c e s , e.g. moon v e r y b r igh t , s t rong cur ren t

F i v e - l e t t e r a b b r e v i a t i o n s of f a m i l y or g e n u s o f b a i t f i s h , e.g. SDrat e l l o i d e s (SPRAT)

Heading Column i n Log Number

106

Data Entered

SP 21-25 Five - l e t t e r abbrevia t ion of spec ie s of b a i t f i s h , e.g. i%wUml& (SARDI) (A separate l i n e f o r each species)

% 26-28 Numerical percentage occurrence i n ne t haul

1 cf 30-68 Standa rd l e n g t h t o n e a r e s t mil l imetre o f random sample of t e n f i s h of each species

* Columns not l i s ted were l e f t blank.

,

d

B A I T F I S H L O G

c o m m e n t