C O N T E N T S
:P a g e
1 .I T I N E R A R Y . . .
12. I N T R O D U C T I O N . . .
13 .
I N I T I A T I N G A N D IN S I T U P R E P A R A T I O N O F T H E C O N S U L T A N C Y .
24 .
A N A L Y S E S O F D A T A
45. C A L I B R A T I O N S U R V E Y . . . * . . .
76 .
R E C O M M E N D A T I O N S . . .
87 .
A C H N O W L E D G E M E N T S . . .
1 6R E F E R E N C E S . . . ~ ~ . m . . .
1 7A P P E N D I X
1 :S c r u t i n i z i n g o f A c o u s t i c D a t a f r o m E c h o I n t e g r a t i o n
A P P E N D I X 2: G T Z - I . N . S . T . O . P . C r u i s e 5 , 2 0 - 2 5 A u g u s t
1 9 8 6 .B r i e f G u i d e l i n e s f o r t h e P r o c e s s i n g o f A c o u s t i c
D a t a .
1 . ITINERARY
5 February 1987;
Trondheim t o Bergen
7 - 8 February 1987:
Bergen to Tunis via Q s l o , Copenhagen, and Geneva.
21-22 February 1987:
Tunis to Bergen via G e n e v a , and Oslo.
23 February 1987:
Bergen to Trondheim.
2. INTRODUCTION
During 1985-86 initial communications took place between the GTZ- I.N.S.T.O.P. project and the Institute of Marine Research ( I M R ) , Bergen, in relation to a consultancy within applied fisheries acoustics.
At the end of 1986 o n e of two scientists of IMR was announced available to the project from the end of January and onwards.
By mid-January t h e inquiry f o r the appointed consultancy was
I
presented to IMR and a preliminary contract w a s agreed upon by end of January - a l l by telexing.The terms of reference were:
1 - formulate and improve the methodology of acoustic data analysis,
2
-
make recommendations for improved survey procedures and acoustic data acquisition.Based on these references a more detailed plan comprising work- ing tasks and schedule was settled for guiding the running acti- vities during the consultancy.
During initiating and terminating phases of the consultancy
period
Ihad discussion on biological and technical matters with members of the "Dr. Fridtjof Nansen" survey team and survey en- gineers at I M R , Bergen.
The main topics of this report will be describing the major ac- tivities and experiences during the stay in Tunis, and making recommendatisns for potential imprsved operations of the hydro- acoustic instruments and optimum survey performance in Tunisian waters .
3.
INITIATING AND SITU PREPARATION OF THE CONSULTANCY
I arrived at Tunis Airport mid afternoon on
8February. There I was met by the project manager G.F. Losse. I got installed in La Marsa, a small village, about
22km from Tunis and about
10km from La Goulette where the I.N.S.T.O.P. was located in near access to the research vessel.
O n 9
February I was presented to the other memberc of the pro-
ject team;
- Abdallah B.M. Hattour, (biology, fisheries acoustics)
-Brahim 8.H. Turki, ( b i o l o g y , fisheries acoustics)
-
Fejri Belhi, (electronics)
- John Nockles, (electronics, technical acoustics)
-Uwe Rowedder-Klatt, ( b i o l o g y , computer science)
-
Winfred Nau (socio-economy, marketing)
and other persons of I.N.S.T.O.P. differentially related to the
pro ject.
I n a d v a n c e o f w o r k i n g o u t p l a n s f o r t h e s p e c i f i c w o r k i n g t a s k s o f my c o n s u l t a n c y we made a g u i d e d t o u r o n b o a r d t h e R I V " T a r e q 1 1 " .
The r e s e a r c h v e s s e l , a p r e v i o u s t r a i n i n g v e s s e l o f a p p r o x . 3 0 m l e n g t h , was e q u i p p e d w i t h t h e f o l l o w i n g h y d r o a c s u s t i c i n s t r u - m e n t s f o r f i s h m o n i t o r i n g and abundance o b s e r v a t i o n :
a
-
S I M R A D E K 4 0 0 , 3 8 kHz e c h o s o u n d e r , t h e m a i n s o u n d e r f o r f i s h a b u n d a n c e o b s e r v a t i o n i n c o n n e c t i o n w i t h t h e e c h o i n t e g r a t o r ,b
-
S I M R A D E K 4 0 0 , 1 2 0 kHz e c h o s o u n d e r , b a c k - u p s o u n d e r f o r f i s h and p l a n k t o n o b s e r v a t i o n as a s t a n d - a l o n e i n s t r u m e n t , o r m i g h t b e c o n n e c t e d t o t h e e c h o i n t e g r a t o r ,c
-
S I M R A D E S 4 0 0 , 3 8 kHz e c h o s o u n d e r , s p l i t - b e a m s o u n d e r f o r e c h o s t r e n g t h c l a s s i f i c a t i o n ,d
-
S I M R A D Q D ; D i g i t a l e c h o i n t e g r a t o r , ande
-
r e l e v a n t t e s t and p e r f o r m a n c e m o n i t o r i n g i n s t r u m e n t s .The i n s t r u m e n t s w e r e m o u n t e d i n a f a i r l y f u n c t i o n a l and w e l l a r r a n g e d manner i n a r a t h e r cramped i n s t r u m e n t r o o m j u s t i n f r o n t o f t h e w h e e l h o u s e .
Upon r e q u e s t s f r o m t h e p r o j e c t t e a m i t was d e c i d e d t h a t t h e
m a j o r a c t i v i t i e s t o g i v e " f l e s h and b l o o d " i n t o t h e t e r m s o f r e - f e r e n c e , w e r e t o w o r k t h r o u g h a l l t h e a c o u s t i c a l d a t a and r e - l a t e d b i o l o g i c a l s a m p l i n g s f r o m c r u i s e n o . 5 o f t h e p r o j e c t . T h i s c r u i s e t o o k p l a c e 2 0 - 2 5 A u g u s t 1 9 8 6 i n t h e N o r t h e r n T u n i s - i a n w a t e r s f r o m t h e A l g e r i a n b o r d e r t o Cape Bon. Members o f t h e p r o j e c t t e a m p a r t i c i p a t i n g i n t h e a n a l y z i n g , e v a l u a t i o n and j u d g i n g o f t h e d a t a s h o u l d a l l t h e t i m e be i n s p i r e d and i n v i t e d t o i n t e r r u p t t h e r u n n i n g j u d g i n g i n o r d e r t o e l u c i d a t e and go d e e p e r i n t o c u r r e n t p r o b l e m s and d i s c u s s r e l a t e d i d e a s and p o - t e n t i a l r e c o m m e n d a t i o n s .
A
tentative s c h e d u l e , Table 1 , w a s decided upon.TABLE 1 : Schedule of t h e consultancy periode in Tunis:
1 . A r r i v a l and i n - s t a l l a t i o n
2. I n i t i a t i n g and Y
- -
p r e p a r i n g t h e a c o u s t i c d a t a p r o c e s s i n g and s u r v e y d e s i g n i n g
3. A c o u s t i c d a t a V
p r o c e s s i n g
4. A d v i s i n g o n d a t a a n a l y s e s , s u r v e y p r o c e d u r e s and d a t a a q u i s i t i o n
5. C a l i b r a t i o n sur- V
vey ( 2 4 hrs.)
6. T e r m i n a t i n g a c t i v i t i e s
-
4. ANALYSIS OF ACOUSTIC DATA
To work myself into the position of being able to process the acoustic d a t a , i.e. the echo integrator recordings and related echograms from the EK40O and ES400 echo s o u n d e r s ,
I
had to be informed into the closest details of other relevant and crucial information. From all members of the project teamI
searched for (task 2 ) information through questions and scenarioes about:-
descriptions of the biological and oceanographicalparticulars of the Tunisian coastal w a t e r s , particularily the Northern a r e a s , i . e .
-
s p e c i e s c o m p o s i t i o n s , f i s h a n d p l a n k t o n , by a r e a s , d e p t h s a n d s e a s o n s ,-
m i g r a t i o n ( e . a . s p a w n i n g , f e e d i n g ) o f s p e c i e s by a r e a s a n d s e a s o n s ,-
b e h a v i o u r c h a r a c t e r i s t i c s o f t h e t o p i c a l s p e c i e s , j u v e n i l e s a n d a d u l t s , by d a y a n d n i g h t , d e p t h s a n d s e a s o n s ,-
s p e c i e s a v a i l a b i l i t i e s t o b i o l o g i c a l s a m p l i n g by d i f f e r e n t g e a r l t r a w l s ,-
m a j o r c u r r e n t / w i n d c i r c u m s t a n c e s by a r e a s a n d s e a s o n s , a n d-
m a j o r t e m p e r a t u r e a n d s a l i n i t y d i s t r i b u t i o n s by a r e a s , d e p t h s a n d s e a s o n s .-
d e s c r i p t i o n s o f t h e b o t t o m t o p o g r a p h y i n r e l a t i o n s t o t h e f i s h d i s t r i b u t i o n s a n d t h e o c e a n o g r a p h i c p a r t i c u l a r s .-
d e s c r i p t i o n s o f r e l e v a n t p a r t i c u l a r s o f t h e c r u i s e a n d t h e a c o u s t i c d a t a a c q u i s i t i o n , i . e .-
t h e p r o c e d u r e s a n d w a y s o f l o g g i n g t h e a c o u s t i c d a t a ,-
s e t t i n g o f t h e i n s t r u m e n t s ,-
r u n n i n g c h e c k s a n d c o n t r o l o f t h e p e r f o r m a n c e o f t h e i n s t r u m e n t s ,-
a n y l o g g i n g o f i n s t r u m e n t p e r f o r m a n c e a n o m a l i e s ,- s h o r t - t i m e a i m e d c h a n g e s o f t h e i n s t r u m e n t s e t t i n g s t o i n c r e a s e t h e u n d e r s t a n d i n g o f t h e c u r r e n t d a t a a c q u i s i t i o n d u r i n g f o r i n s t a n c e c h a n g i n g f i s h d i s - t r i b u t i o n p a t t e r n s ,
-
b i o l o g i c a l s a m p l i n g by g e a r , f r e q u e n c e and c a t c h c o m p o s i t i o n ,-
c r u i s e t r a c k s i n r e l a t i o n t o t h e s h e l f and b a n k a r e a s , and-
w e a t h e r c o n d i t i o n s .B a s e d o n p r e v i o u s k n o w l e d g e and e x p e r i e n c e and r e c e n t l y g a i n e d i n f o r m a t i o n
I
f o r m u l a t e d g u i d e l i n e s +'or t h e s c r u t i n i z i n g , e v a - l u a t i o n and j u d g i n g o f t h e e c h o i n t e g r a t o r and t h e e c h o s o u n d e r d a t a i n a m a n n e r t o i n v o l v e and e n g a g e t h e m e m b e r ( s 1 o f t h e t e a m p a r t i c i p a t i n g i n t h e p r o c e s s ( t a s k 2 ) . T h e g u i d e l i n e s f o l l o w e d t h e m a j o r p r o c e d u r e s o f D A L E N and N A K K E N ( 1 9 8 3 ) a d j u s t e d t o t h e p r o c e d u r e s o f a c o u s t i c a b u n d a n c e e s t i m a t i o n by e c h o i n t e g r a t i o n i n t r o p i c a l and s u b t r o p i c a l a r e a s , e - a . , s e e S T R Ø M M E ( 1 9 8 4 ) . T h i s i s s u m m a r i z e d by t h e f l o w c h a r t o f App. 1 and t h e g u i d e - l i n e s o f App. 2.l D u r i n g t h i s p l a n n i n g and f o r m u l a t i n g o f d a t a p r o c e s s i n g g u i d e - l
-
~
l i n e s it b e c a m e d e m o n s t r a t e d t h a t t h e w a y t h e m a n u f a c t u r e r o fl t h e t o p i c a l s c i e n t i f i c a c o u s t i c i n s t r u m e n t s i s t r a i n i n g n e w and
l
not w e l l - e x p e r i e n c e d r e s e a r c h t e a m s in a p p l i e d a c o u s t i c f i s h a b u n d a n c e t e c h n i q u e s i s r a t h e r u n s u f f i c i e n t and t o s o m e d e g r e e
1
m i s l e a d i n g . F a r i n s t a n c e i n a r e a s w h e r e w e h a v e m e r g e d e c h o i n t e g r a t o r c o n t r i b u t i o n s f r o m s e v e r a l d i f f e r e n t s p e c i e s i t i s very d i f f i c u l t and e x t r e m e l y t i m e c o n s u m i n g t o d e a l w i t h t h e" h i g h l y a d v e r t i s e d " m e a s u r e o f m e a n v o l u m e b a c k s c a t t e r i n g s t r e n g t h .
T o t h e m a n u f a c t u r e r : As l o n g a s t h e Q D s a r e " a l i v e " , p l e a s e w o r k o u t and a d v i s e i n h o w t o i n c o r p o r a t e t h e t o p i c a l v a l u e o f C I i n t h e r e c o r d i n g s , f o r i n s t a n c e by m a n i p u l a t i n g t h e e c h o i n t e g r a t o r g a i n . T h u s t h e p r e s e n t m e a s u r e o f t h e " m m d e f l e c t i o n "
c a n be a d j u c t e d t o r e p r e s e n t an a b s o l u t e l i n e a r m e a s u r e o f t h e i n t e g r a t e d b a c k s c a t t e r i n g c o n t r i b u t i o n s f r o m t h e t a r g e t s i n s i d e e a c h d e p t h i n t e r v a l , c o n f . 6 . 2 and 6 . 3 .
The d a t a p r o c e s s i n g w h i c h r e s u l t e d i n d i s t r u b u t i o n maps o f e c h o a b u n d a n c e o f t h e t o p i c a l g r o u p s o f s p e c i e s was f i n i s h e d 1 7
F e b r u a r y ( t a s k 3 ) . The f i n a l e s t i m a t i o n s o f f i s h abundance c o u l d n o t b e c a r r i e d t h r o u g h u n t i l l t h e c o n v e r s i o n f a c t o r ( C ) b e t w e e n a c o u s t i c abundance and f i s h abundance h a s b e e n e s t a b - l i s h e d . T h i s i s t h e i n s t r u m e n t a t i o n f a c t o r C I f r o m s t a n d a r d t a r g e t e c h o i n t e g r a t o r c a l i b r a t i o n and t h e f i s h s p e c i e s f a c t o r C F f r o m t h e e f f e c t i v e t a r g e t s t r e n g t h s r e p r e s e n t i n g t h e t o p i c a l g r e u p s o f s p e c i e s .
5 .
C A L I B R A T I O N
S U R V E YA l r e a d y t h e 9 F e b r u a r y we p l a n n e d t o c a r r y o u t a 2 4 h r s . s u r v e y d u r i n g t h e m i d o f t h e s e c o n d week o f my c o n s u l t a n c y . The s c o p e o f w o r k f o r t h e s u r v e y was as f o l l o w s :
1
-
t o u n d e r t a k e a s t a n d a r d t a r g e t c a l i b r a t i o n o f t h e e c h o i n t e g r a t o r t o e s t a b l i s h t h e i n s t r u m e n t a t i o n f a c t o rC I o f t h e c o n v e r s i o n f a c t o r C .
2
-
t o t r y o u t b a l a n c e d s e t t i n g s o f t h e e c h o s o u n d e r ( E K 4 0 0 ) and o f t h e p a r a m e t e r s o f t h e e c h o i n t e g r a t o r t o g a i nb e t t e r c o r r e s p o n d e n c e b e t w e e n t h e e c h o i n t e g r a t o r r e c o r d - i n g s and t h e a p p e a r a n c e o f p l a n k t o n , m i d w a t e r and b o t t o m l o c a t e d f i s h d i s t r i b u t i o n s o f t h e e c h o g r a m s .
The s u r v e y t o o k p l a c e f r o m 1 1 0 0 h r s 1 8 F e b r u a r y t o 1 3 0 0 h r s 1 9 F e b r u a r y . A l t h o u g h t h e w e a t h e r c o n d i t i o n s w e r e e x c e l l e n t a t d e p a r t u r e t h e y r a p i d l y g r e w b a d ( f r e s h b r e e z e ) so t h e f i r s t a t t e m p t o f c a l i b r a t i o n d u r i n g t h e a f t e r n o o n was r a t h e r u n s u c - c e s s f u l .
F o r some h o u r s d u r i n g t h e n i g h t we c r u i s e d a t 8 k n t s . t o e x a m i n e t h e echograms a t d i f f e r e n t c o n t r o l s e t t i n g s , b u t t h e w i n d and t h e r e b y t h e b u b b l e a t t e n u a t i o n w e r e so h i g h t h a t t h e
f i n d i n g s w e r e o f m i n o r v a l u e .
T h e n e x t m o r n i n g t h e w i n d h a d c a l m e d a n d t h e s t a n d a r d t a r g e t c a l i b r a t i o n w a s r e p e a t e d f r o m 0 6 3 0 h r s . U n f o r t u n a t e l y t h e h i g h s w e l l m a d e i t v e r y d i f f i c u l t t o k e e p t h e c a l i b y a t i o n s p h e r e
s t a b l e i n t h e e c h o s o u n d e r b e a m s o t h e o b t a i n e d r e s u l t s w e r e n o t r e c o m m e n d e d f o r " C I - a p p l i c a t i o n " .
F i s h d i s t r i b u t i o n s d u r i n g d a y t i m e c o n d i t i o n s w e r e n o t f a v o u r a b l e f o r e c h o g r a m e x a m i n i n g s o t h e c r u i s e w a s t e r m i n a t e d a f t e r t h e c a l i b r a t i o n a t 1030 h r s 1 9 F e b r u a r y .
6. R E C O M M E N D A T I O N S
6.1. P r e ~ a r i n q c h a r t s o f r e l a t i v e a n d a b s o l u t e f i s h a b u n d a n c e
I n o r d e r t o c l a s s i f y a n d d e m o n s t r a t e t h e p a r t i c u l a r s o f t h e o c c u r r i n g g r o u p s o f s p e c i e s i t i s r e c o m m e n d e d t o e s t a b l i s h i s o - l i n e c h a r t s b o t h f o r r e l a t i v e i.e. a c o u s t i c f i s h a b u n d a n c e a n d a b s o l u t e f i s h a b u n d a n c e i n s t e a d o f a n y s y s t e m o f g e o g r a p h i c a l l s t a t i s t i c a l s q u a r e s w i t h a t t a c h e d a v e r a g e d e c h o a b u n d a n c e s . T h e a p p l i e d " g r o u p o f p e l a g i c s p e c i e s " w h i c h c o m p r i c e s a c o n s i d e r - a b l e n u m b e r o f s p e c i e s c a n e f f e c t f u l l y b e d e v i d e d i n t o s u b g r o u p s e a c h c o m p r i c i n g f e w e r s p e c i e s by s t r a t i f y i n g t h e s u r v e y e d a r e a by d e p t h .
W h e n c o m p a r i n g d a t a a n d r e s u l t s f r o m s e v e r a l s u c c e e d i n g s u r v e y s t h i s d e p t h s t r a t i f i c a t i o n a n d a b u n d a n c e i s o l i n i n g m a y p r o v i d e u s e f u l i n f o r m a t i o n a b o u t s e a s o n a l s p e c i e s m i g r a t i o n a n d c h a n g e s o f a b u n d a n c e .
W h e n d e c i d i n g o n w h a t s p e c i f i c i n t e g r a t o r v a l u e t o a t t a c h t o e a c h i s o l i n e t h i s s h o u l d b e b a s e d o n t h e t o t a l d y n a m i c r a n g e o f t h e j u d g e d i n t e g r a t o r r e c o r d i n g s a n d a r a t i o n a l d i v i s i o n o f t h i s r a n g e i n t o s u b r a n g e s i.@. q u a n t i t a t i v e a b u n d a n c e r a t i n g s o f l o w , m e d i u m , h i g h a n d v e r y h i g h a b u n d a n c e . T h e s e n o t a t i o n s a r e p r e -
f e r r e d t o e l s e w h e r e a p p l i e d n a t a t i o n s o f v e r y s c a t t e r e d , s c a t - t e r e d , d e n s e a n d v e r y d e n s e r e c o r d i n g s .
A particular data processing journal for estimating absolute fish abundances from isoline charts of echo abundances w a s work- ed out during the consultancy. This journal is not presented in t h e report.
6.2. Estimation of the convertion factor ( C ) in relation to echo intearation
When applying echo sounder and echo integrator f o r absolute fish abundance estimation the succeeding equation is eommonly used:
where
e A -
area fish d e n s i t y , i.e. numberslweight of fish per unit area ( e - a . square nautical mile),C F
-
fish (speciesl f a c t o r , part of the conversionfactor C = C F C I ,
C I
-
instrumentation f a c t o r ,M
-
echo integrator recording ( " m m d e f l e c t i o n " ) with- out adjustment d u e to the instrumentation factor.The integrator recording M is n o w a measure of t h e relative acoustic abundance of fish. In order to adjust the integrator recording to become an absolute measure o f the acoustic abund- ance of fish w e w i l l d o this by taking account of the perform- ance o f the echo sounder and echointegrator, i.e. establish a certain value of CI by a standard target calibration. The procedure 07 this i s described in detail by
F O O T E
et al. 1 9 8 7 ,and is recommended to be followed during the calibration.
We want the integrator recordings to be of the form:
where s is the area backscattering coefficient related to the A
area backscattering strength, S A , by the equation (URICK 1 9 7 7 1
'
A
= 1 0 l o g s AT h e i n s t r u m e n t a t i o n f a c t o r C I i s r e p r e s e n t e d by:
w h e r e
" 3 . 4 3
lo6'' -
n u m b e r o f m2 o f o n e s q u a r e n a u t i c a l m i l e , a-
b a c k s c a t t e r i n g c r o s s - s e c t i o n Cm 2I
o f t h eb s , S P
s t a n d a r d t a r g e t / t h e s p h e r e ,
k
-
c o r r e c t i o n f o r p o t e n t i a l T V G - d e v i a t i o n at t h e d e p t h o f t h e s t a n d a r d t a r g e t ,M
-
i n t e g r a t o r r e c o r d i n g f r o m t h e s t a n d a r d t a r - S P g e t , [ m m d e f l e c t i o n l ,D s P
-
d e p t h o f t h e s t a n d a r d t a r g e t , a n d-
t h e e q u i v a l e n t b e a m a n g l e o f t h e t o p i c a l e c h o s o u n d e r t r a n s d u c e r .T h e b a c k s c a t t e r i n g c r o s s - s e c t i o n , a b s , s p , o f t h e s p h e r e i s r e - l a t e d t o t h e t a r g e t s t r e n g t h ( C L A Y & M E D W I N 1 9 8 7 ) o f t h e s p h e r e b y :
T S = 1 0 l o g a
S P b s , s p l A r e f CdBl w h e r e
A r e f = 1 rn2 i s t h e r e f e r e n c e a r e a . W h e n a p p l y i n g t h e p r e v i o u s d e f i n i t i o n ( e . a . U R I C K 1 9 7 7 ) o f t h e t a r g e t s t r e n g t h
T S = 1 0 l o g a / 4 a CdBl
b s , S P S P
C I O: c q . ( 4 ) h a s t o b e m u l t i p l i e d by 4 R .
T h e f i s h ( s p e c i e s ) f a c t o r C F i s r e p r e s e n t e d by
where < a b s l i
>
i s the effective backscattering cross-section o f the species " i " / g r o u p of species " i " , o f which w e w a n t to esti- mate absolute abundance of fish. The effective target strength<TSi> is similarely related to t h e effective backscattering cross-section < o
bs
.
i>
b y ;If t h e previous definition of target s t r e n g t h , Eq. ( 6 ) is app- l i e d , C F of % q . ( 7 ) has to be devided by 47r.
A weight normalized efoective backscattering cross-section,
< a
b s , i , w
>
might as w e l l be applied in Eq. ( 7 ) . This normalized version i s obtained bywhere
w
is the weight of the specimen of species " i " having the backscattering cross-section ob s , i' The corresponding weight normalized target strength < T S i > w has the denomination
CdBlkgl and is related t o
>
by an equation equivalent to Eq. ( 8 ) .By
applying the specimen related effective backscattering cross- section, Eq. ( 8 1 , the absolute fish estimate w i l l be in number of fish per square nautical mile w h i l e t h e weight normalized o n e ,Eq. ( 9 1 , yields weight of fish per square nautical mile.
T h e integrator recording, s represents the accumulated back- A '
scattering cross-sections exceeding a controlled threshold o f a l l the targets, i.e. fish and plankton, of the integrated depth interval over the integrated distance. The area backscattering coef f icient , s Eq. ( 2 , has now dimension m2 per square
A ' nautical mile.
6 . 3 . B a l a n c e d s e t t i n g s o f t h e e c h o s o u n d e r c o n t r o l s and t h e s y s t e m v a r i a b l e s o f t h e e c h o i n t e g r a t o r
The p r o j e c t t e a m e x c e l l e n t l y r e p r e s e n t e d b y t h e i r e l e c t r o n i c s e n g i n e e r , M r . J . N o c k l e s , had a h i g h l y q u a l i f i e d u n d e r s t a n d i n g and k n o w l e d g e a b o u t t h e t e c h n i c a l d e t a i l s and f u n c t i o n i n g o f a l l t h e i n s t r u m e n t s . B u t d u e t o f e w and t o some e x t e n t s h o r t s u r v e y s t h e t e a m had u n f o r t u n a t e l y n o t g o t t h e r e q u i r e d o p p o r t u n i t i e s t o a d a p t a l l t h e t e c h n i c a l s k i l l and b i o l o g i c a l k n o w l e d g e i n t o
q u i t e s a t i s f a c t o r y a p p l i e d s u r v e y t e c h n i q u e s .
On t h e b a s i s o f t h e e x p e r i e n c e d u r i n g t h e a c o u s t i c d a t a p r o c e s s - i n g f a v o u r a b l e c h a n g e s o f t h e a p p l i e d s e t t i n g s o f t h e e c h o
s o u n d e r ( E K 4 0 0 ) c o n t r o l s i n r e l a t i o n t o t h e d y n a m i c s o f t h e e c h o i n t e g r a t o r r e c o r d i n g s , s h o u l d be d i s c u s s e d and p r o s p e c t i v e d e c i - s i o n s o f new s e t t i n g s s h o u l d be made. The o v e r a l l o b j e c t i v e s o f t h i s was t o g a i n b e t t e r c o r r e s p o n d e n c e b e t w e e n t h e e c h o i n t e - g r a t o r r e c o r d i n g s and t h e a p p e a r a n c e o f f i s h and p l a n k t o n o f t h e e c h o g r a m s , and t o r e l a t e t h e a v a i l a b l e t o t a l d y n a m i c r a n g e o f t h e e c h o s o u n d e r and i n t e g r a t o r t o t h e a c o u s t i c d y n a m i c r a n g e o f t h e f i s h ( a n d p l a n k t o n ) t a r g e t s .
The m a i n p a r a m e t e r s c o n s i d e r e d w e r e t h o s e r e l a t e d t o g a i n / a t t e n - u a t i o n o f b o t h t h e e c h o s o u n d e r and t h e i n t e g r a t o r .
Echo s o u n d e r t i m e v a r i e d s a i n ( T V G ) :
A l t h o u g h t h e 4 0 l o g R may be u s e d f o r c e r t a i n s t u d i e s d u r i n g o r d i n a r y e c h o i n t e g r a t i o n s u r v e y s ( 2 0 l o g R on t h e i n t e g r a t o r ) i t i s recommended t o r u n t h e e c h o s o u n d e r on 2 0 l o g R t o o f o r sake o f c o r r e s p o n d e n c e .
Echo s o u n d e r a t t e n u a t i o n ( A ) :
When a p p l y i n g a h i g h p o w e r e d t r a n s m i t t e r i t i s recommended t o r u n t h e a t t e n u a t i o n on 1 0 o r 2 0 d B / / l V a t 3 8 k H z . Based on
t h e p e r f o r m a n c e o f t h e t o p i c a l e q u i p m e n t t h e a l r e a d y a p p l i e d a t t e n u a t i o n o f A = 1 0 dB s e e m e d t o b e c o r r e c t . T h e a v a i l a b l e a t t e n u a t i o n l e v e l s o f E K 4 0 0 i n s t e p s o f 1 0 di3 a r e o f t e n t o o r o u g h . I t s h o u l d b e f a v o u r a b l e t o h a v e t h e s t e p s i n c h a n g e s o f 5 d B .
F c h o s o u n d e r a a i n ( r e c o r d e r ) :
T h e v a l u e s o f t h e r e c o r d e r g a i n s h o u l d b e e v a l u a t e d a n d d e c i d e d upon i n r e l a t i o n t o t h e T V G a n d a t t e n u a t i o n . Due t o t h e g r e a t d i f f e r e n c e s b e t w e e n t h e d a y t i m e ( d a w n - d u s k ) a n d n i g h t t i m e
( d u s k - d a w n ) f i s h r e c o r d i n g s t h e r e c o r d e r g a i n may w e l l b e d i f f e - r e n t f o r t h e t w o p e r i o d s ( a s i s a l r e a d y a p p l i e d ) .
Echo i n t e g r a t o r q a i n ( G ) :
T h i s g a i n , G C d B / / l V ] , s h o u l d b e c o n s i d e r e d i n r e l a t i o n t o t h e a t t e n u a t o r s e t t i n g o f t h e e c h o s o u n d e r :
I : When t h e t o p i c a l v a l u e o f C I i s d e c i d e d t o b e i n c o r p o r a t e d ( i n t o t h e i n t e g r a t o r ) b e f o r e p r i n t i n g o u t t h e e c h o i n t e g r a t o r r e c o r d i n g s , a n e a t a n d f a v o u r a b l e way i s t o o p e r a t e t h e e c h o s o u n d e r
-
e c h o i n t e g r a t o r c h a i n a t a 1 : l l e v e l t r o u g h o u t . T h i s m e a n s t h a t f o r A = X d 8 p u t G = - X d 8 . Then t h e e c h o i n t e - g r a t o r r e c o r d i n g s w i t h C I i n c l u d e d w i l l e x a c t l y r e p r e s e n t sA ' t h e a c c u m u l a t e d a r e a b a c k s c a t t e r i n g p e r s q u a r e n a u t i c a l m i l e , c o n f . 6 . 2 . P l e a s e n o t e t h a t i n t h i s c a s e t h e "
S v
- r e c o r d i n y s W w i l l b e i n c o r r e c t ( d u e t o t h e i n t e r n a l h a n d l i n g o f G i n t h e Q 0 ) .1 1 : I f C I i s n o t t o b e i n c o r p o r a t e d b e f o r e p r i n t i n g o u t t h e i n t e g r a t o r r e c o r d i n g s b u t t a k e n i n t o a c c o u n t l a t e r i n t h e d a t a p r o c e s s i n g , t h e n we may p u t G = - ( X + 1 0 o r 2 0 ) d 8 . T h e s e 1 0 o r 2 0 d 8 a d d i t i o n a l g a i n i s t o p r o d u c e a c o n v e n i e n t d y n a m i c r a n g e o f t h e e c h o i n t e g r a t o r r e c o r d i n g s f o r d a t a e v a l u a t i o n a n d j u d g i n g . N B ! I f t h i s l a s t p r o c e d u r e i s a p p l i e d , p l e a s e r e m e m b e r t o d e v i d e t h e a c o u s t i c f i s h a b u n d a n c e ( e c h o a b u n d a n c e ) by t h e r e a l n u m b e r c o r r e s p o n d i n g t o ( 1 0 o r 2 0 - X ) dB d u r i n g t h e a b s o - L u t e f i s h a b u n d a n c e e s t i m a t i o n .
A f e w e x a m p l e s o f g a i n s e t t i n g s d u r i n g d i f f e r e n t k i n d s o f o p e r a - t i o n s h a l l b e c o n s i d e r e d :
S t a n d a r d t a r n e t c a l i b r a t i o n :
As p r e v i o u s l y m e n t i o n e d t h i s i s t o e s t a b l i s h t h e CI. The e c h o s o u n d e r a t t e n u a t i o n s h o u l d be t h e one a p p l i e d d u r i n g s u r v e y s , e . a . A = 10 dB. D u r i n g t h e c a l i b r a t i o n p u t G = - 1 0 dB. The o b t a i n e d i n t e g r a t o r r e c o r d i n g o f t h e s t a n d a r d t a r g e t i s now t h e v a l u e o f M t o p u t i n t o E q . ( 4 ) . C a l c u l a t e CI f r o m E q . ( 4 ) a f t e r h a v i n g r e c o r d e d / c a l c u l a t e d t h e o t h e r p a r a m e t e r s o f t h i s
e q u a t i o n . F o r i n s t a n c e l e t u s assume t h i s y i e l d s CI = 5 0 . ,
l
l l
l
I
I: From o u r e x a m p l e we h a v e C p = 50 w h i c h y i e l d s 10 l o g C p = 1 7 . 0 dB. The a d j u s t e d e c h o i n t e g r a t o r g a i n w h i c h we now e n t e r s h o u l d be
G c I
= - ( l 0 + 1 7 ) d6 = -27 d 8 . The i n t e g r a t o r r e c o r d - i n g s w i l l now r e p r e s e n t s A o f E q . ( 2 ) .
11: W i t h A = - 1 0 d B e n t e r G = - 1 0 o r - 2 0 d B . I f G = - 2 0 d B i s a p p l i e d , d e v i d e t h e e v a l u a t e d and j u d g e d e c h o abundance b y 10 d u r i n g t h e f i n a l f i s h abundance e s t i m a t i o n .
Echo i n t e q r a t o r t h r e s h o l d ( u t r l :
F i g u r e 1 shows a c o p y o f t h e h e a d i n g o f t h e C D - j o u r n a l . T h i s c o p y i s f r o m t h e f i r s t shakedown c r u i s e w h i c h means t h a t s e v e - r a 1 p a r a m e t e r s w h i c h a r e b e i n g e n t e r e d m a n u a l l y ( n o t m e a s u r e d and c a l c u l a t e d b y t h e UD i t s e l f ) h a v e been a d j u s t e d t o m o r e p r o - p e r v a l u e s d u r i n g t h e l a t e r c r u i s e s .
CCIMMRND : STHRT
---.---
Plsca: TUPtISXA N D U f H
Cornments: SHYKEBOWN C R U I S E tiOs 01
P a g r 1 Date: 86,4,%!5
c o u n d e r 144. : h F r e q u e n c y : 353.0 i+=tz P u l s e D u r a t l o n : 0.40 ~ n s T r a n s d u c e r 3 - 2 0 . 3 d B P u l s e R e p . F r e ~ . : $ 3 o,'iit T V G r 6 4 . 6 rJB Plax. R a n g e : '5113 181 S I J - S u p p r e a s : - 1 0 8 dB
---
L a y e ~ O I 1 1 1 1 1 I I/ 'l 'I I
C i p p z r - L i i ~ , 5 . ?i LI?. I) 411. O bit. O 81). 0 12.0, Ci b o w e r - L i i n 20.13 4 0 . (1 b 0 . O $ 8 . O 120.11 1 8 0 . O
2 o
T h r e s . wVp 3 1.1 2 0 2 O 2 0 2 O
Ccee.Ch. 1
< c a l e l 0
S o u r c e L e v e l 8 13%,7 dB V o l t a g e k e s g o n s e : 8.0 dB
G a i n: 0.0 dB
C - E e h o s o u n d e r : -42.6 dB
.oi---i--,eoPP----~-~-
V I 1 V P I I I X X
1 8 0 . 0 250.OB4 6.2B4 3.2
250.0 350.OB+ 3.2B9 0.2
2 O % O
2 1 0 0 e 00
L o g . T o t a l
a
7C.
AA.(T."R):;€MI-AIJTOIlHT IC LOG PICIDE > 5 \'ESSELSPEED= 3.6 t:ll(3TS
F i g u r e 1 . H e a d i n g o f t h e Q 0 - j o u r n a l .
C o n c e r n i n g t h e e c h o i n t e g r a t o r t h r e s h o l d ,
u t r
C m V l , t h i s s h o u l d be m a n i p u l a t e d t o a v o i d c o n t r i b u t i o n s f r o m s y s t e m g e n e r a t e de l e c t r o n i c n o i s e , v o l u m e r e v e r b e r a t i o n , e c h o e s f r o m very s m a l l o r g a n i s m s / p a r t i c l e s and v e s s e l g e n e r a t e d n o i s e . S i n c e t h e s e n o i s e c o n t r i b u t i o n s a r e b e i n g a m p l i f i e d by t h e T V G , t h e u t r s h o u l d be i n c r e a s e d by i n c r e a s i n g d e p t h . Based on e x p e r i e n c e f r o m N o r w e g i a n r e s e a r c h v e s s e l s t h e s u c c e e d i n g r e l a t i o n s h i p has b e e n f o u n d t o w o r k w e l l .
U = u + 0 . 2 R
m
t r O CmVl ( 1 0 )
w h e r e
u - t h r e s h o l d v o l t a g e o f t h e u p p e r i n t e g r a t i n g i n t e r v a l
O
( l a y e r ) . u = 1 0 - 1 5 mV i s r e c o m m e n c e d f o r m o s t O
a p p l i c a t i o n .
R
-
m e a n d e p t h o f an i n t e g r a t i n g i n t e r v a l l .I n t e a r a t i n g d e p t h i n t e r v a l s :
W h e n c o n s i d e r i n g t h e i n t e g r a t i n g d e p t h i n t e r v a l s ( l a y e r l i m i t s ) t h e i n t e r v a l s s h o u l d b e d i r e c t e d t o t h e m o s t i m p o r t a n t w a t e r c o l u m n s , i . e . w h e r e t h e i m p o r t a n t f i s h d i s t r i b u t i o n s a p p e a r . T a k e a l c o i n t o a c c o u n t t h e e x p e c t e d t o t a l d e p t h e x t e n s i o n s o f t h e s u r v e y a r e a d u r i n g t h e l a y e r l i m i t s e n t e r i n g . T h e u p p e r l i m i t o f t h e f i r s t l a y e r s h o u l d n o t b e l e s s t h a n 4 o r r a t h e r 5 m d u e t o s y s t e m g e n e r a t e d n o i s e w h i c h o t h e r w i s e w i l l b e i n t e g r a t e d i n l a y e r 1 . T h e b o t t o m r e l a t e d i n t e r v a l s ( l a y e r I X a n d X )
s h o u l d b e d e c i d e d u p o n f r o m f i s h d i s t r i b u t i o n s , i f t h e e c h o a b u n d a n c e o f t h e s e i n t e r v a l s i s t o b e c o r r e l a t e d t o t h e b o t t o m t r a w l c a t c h e s o r t o o t h e r p a r t i c u l a r c o n s i d e r a t i o n s .
B a c e d o n t h e t o p i c a l r e q u i r e m e n t s o f t h i s p r o j e c t l a y e r I X s h o u l d b e 1 0 - 2 0 m , l a y e r X 3 - 5 m , a n d t h e b o t t o m o f f s e t s h o u l d b e d e c i d e d u p o n d u e t o b o t t o m r o u g h n e s s a n d w e a t h e r c o n - d i t i o n s . L o w b o t t o m o f f s e t v a l u e , 0 . 1 - 0 . 2 , f o r s m o o t h b o t t o m a n d g o o d w e a t h e r a n d h i g h e r v a l u e s f o r r o u g h b o t t o m a n d w i n d y w e a t h e r .
7 . A C K N O W L E D G E M E N T S '
I a m v e r y g r e a t e f u l t o t h e P r o j e c t M a n a g e r G e o r g e
F.
L o s s e f o rl
I h i s f r i e n d l y a n d s t i m u l a t i n g s u p p o r t a n d a c t i o n s d u r i n g t h e c o n - s u l t a n c y . T h e e n t h u s i a s t i c e f f o r t s a n d i n v o l v e m e n t s o f J o h n N o c k l e s , U w e R o w e d d e r - K l a t t , A b d a l l a h B . M . H a t t o u r , a n d B r a h i m B.H. T u r k i a r e g r e a t l y a p p r e c i a t e d . T h e y m a d e i t p o s s i b l e o b - t a i n i n g g o o d p r o g r e s s d u r i n g t h e d a i l y w o r k a n d by f e e d b a c k
s h o w i n g g a i n e d c o m p e t e n c e f o r f u t u r e a c o u s t i c s u r v e y i n g a n d d a t a p r o c e s s i n g .
I w i l l a l s 0 t h a n k t h e D i r e c t o r o f t h e I n s t i t u t N a t i o n a l S c i e n t i - f i q u e e t T e c h n i q u e d l O c e a n o g r a p h i c e t d e P e c h e f o r l e a v i n g t h e i r w h o l e l i b r a r y a t o u r d i s p o s a l d u r i n g t h e c o n c u l t a n c y .
T h e C a p t a i n a n d t h e c r e w o f R / V " T a r e q 1 1 " a r e a c k n o w l e d g e d f o r t h e i r f r i e n d l y a n d p r o p e r c o o p e r a t i o n d u r i n g o u r m i n i - s u r v e y .
REFERENCES
C L A Y , C . S . a n d MEDWIN, H. A c o u s t i c a l O c e a n o g r a p h y . P r i n c i p l e s a n d A p p l i c a t i o n s . W i l e y - I n t e r s c i e n c e 1 9 7 7 .
D A L E N , J . a n d NAKKEN, 0 . 1 9 8 3 . O n t h e a p p l i c a t i o n o f t h e e c h o i n t e g r a t i o n m e t h o d . I C E S CM 1 9 8 3 / 8 : 1 9 : 3 0 p . ( M i m e o ) .
FOOTE, K . G . , KNUDSEN, H . P . , V E S T N E S , G . , MACLENNAN, D . N . a n d SIMMONS, E . J . C a l i b r a t i o n o f A c o u s t i c I n s t r u - m e n t s f o r F i s h B e n s i t y E s t i m a t i o n . A P r a c t i c a l G u i d e .
I C E S C o o p e r a t i v e R e s e a r c h R e p o r t ( i n p r e s s ) .
STRØMME, T . 1 9 8 4 . R e p o r t o n t h e R / V " D r . F r i d t j o f N a n s e n "
F i s h R e s o u r c e S u r v e y s o f f W e s t - A f r i c a , M a r o c c o t o G h a n a a n d C a p e V e r d e . M a y 1 9 8 1
-
M a r c h 1 9 8 2 . S e c a f / E c a f S e r i e s 8 4 / 2 9 E n . FAD Rome 1 9 8 4 .U R I C K , R . J . P r i n c i p l e s o f U n d e r w a t e r S a u n d . M c G r a w - H i l l C o m p . 1 9 7 7 .
A l . 1
A P P E N D I X 1 : S c r u t i n i z i n g o f A c o u s t i c Data f r o m E c h o I n t e g r a t i o n
A l . 1
F l o w C h a r t o f t h e e v a l u a t i o n and 9 u d a i n a ~ r o c e s sS T A R T
W r i t e
'-i
t h e i n t e g r a t o r r e c o r d i n g s o n t h e e c h o g r a m i n t h e d e p t hi n t e r v a l s f o r t h e i n t e g r a t i n g d i s t a n c e *
C o r r e c t t h e a f f e c t e d r e c o r d i n g s by a l l a- v a i l a b l e i n f o r m a t i o n *
I
*
i n t e g r a t i n g d i s t a n c e : e i t h e r 1 m i l e - v a l u e s o r a v e r a g e d 2 o r 5 m i l e s - v a l u e s ( y o u r c h o i c e ) d e c i d e d u p o n f r o m p a r t i c u l a r s o f t h e f i s h d i s t r i b u t i o n p a t t e r n s and b o t t o m t o p o g s a p h y .*
n o n - b i o l o g i c a l c o n t r i b u - t i o n s :i n s t r u m e n t - n o i s e i n t h e u p p e r c h a n n e l , b u b b l e c o n t r i b u t i o n s i n t h e u p p e r c h a n n e l , b o t t o m c o n t r i b u t i o n s i n t h e b o t t o m c h a n n e l .
*
a v a i l a b l e i n f o r m a t i o n : r i n g i n g o f t h e t r a n s - d u c e r , T V G - g e n e r a t o r n o i s e , w e a t h e r d a t a / b u b b l e s i n t h e s u r f a c e l a y e r , c o m p a r e w i t h p r e v i o u s / s u c c e e d i n g m i l e s , r o u g h b o t t o m ,s t e e p s e a b e d .
Correctlincrease the affected values by certain ratios estab- lished from all avail
able information*
*
available information:cdmpare with correctly integrated consentra- tionslschools, area- ratioes of correctly and non-correctly integrated parts of each school (multiply by the inverse ratioes), information from the litterature.
Yes
Establish reduction/
correction figures of the integrator values from topical1"constant"
fishlplankton disbribu- tions from good vs. bad
weather conditions
I
Correct all the inte- grator values by the topical correction
factor
l
/ D e v i d e and d i s t r i b u t e t h e i n t e g r a t o r v a l u e s o n o c c u r r i n g g r o u p s
o f s p e c i e s i n a l l d e p t h c h a n n e l s f r o m a l l a v a i l a b l e i n f o r -
m a t i o n *
i
S u m t h e v e r i f i e d / j u d g e d i n t e g r a t o r v a l u e s f r o m a l l d e p t h
c h a n n e l s o n t h e s p e c i f i c g r o u p s o f
s p e c i e s
*
a v a i l a b l e i n f o r m a t i o n : f r o m r e l a t i v e and a b s o - l u t e a p p e a r a n c e / s t r e n g t h s on t h e e c h o g r a m s , f r o m t r a w l c a t c h e s , f r o m p r e - v i o u s / s u c c e e d i n g m i l e s , f r o m t o p i c a l s e a s o n , t o p i c a l a r e a , f r o m o c e - a n o g r a p h i c o b s e r v a t i o n s / m e a s u r e m e n t s .T u n i s 1 9 0 2 8 7
APPENDIX 2 : GfZ-I.N.S.T.O.P. Cruise 5 , 2 0 - 2 5 August 1 9 8 6 .
7 Brief Guidelines for the Processing of Acoustic Data.
1 ) Concentrate t h e processing of data on the observations
during dusk t i l l dawn i.e. 1 6 0 0 / 1 7 0 0 hrs. till
0 7 0 0 / 0 8 0 0 hrs. when most of the fish is off bottom.
2 1 Bue to l o w contsibutions from typical demersal fish species in the northern areas d o n ' t separate t h e re- cordings of pelagig ssp. and demersal ssp. but only apply the group of pelagic spp. and make remarks when demersal ssp. may clearly be present.
3 ) Contributions from planktonic organisms may be con- siderable parts of the total integrator recordings in certain depth intervalls in some areas. Mostly for instructive reasons the integrator values of plankters w i l l be judged and recorded in the journal.
4 For pelagic spp. the judged integrator recordings of both the total water column (Ch.
