ISSN: 1693-6
930
¢
139
Swim
bladde
r on Fish T
a
rg
et Strength (Sunardi)
SWIMBLADDER ON FISH TARGET STRENGTH
Sunardi
1
, An
ton Yudha
na
2
, Jafri Din
3
,
Raja Bidin Raja Hassan
4
1, 2, 3
Faculty of Electrical En
ginee
ring,
Un
iversiti Te
knol
ogi Malaysi
a
Skudai 8
131
0
Joho
r, Malay
s
ia
1, 2
Electrical
Enginee
ring
Dep
a
rtme
nt, Universita
s Ahmad Dahla
n
Umbul
ha
rjo 5
5164 Yogya
k
arta, Indone
si
a
4
Marine Fi
sh
ery Re
sou
r
ce
s Devel
opme
n
t and Mana
g
e
ment De
pa
rtment
Kuala Tereng
ganu 2
108
0 Tere
ngg
anu,
Malaysia
e-mail: suna
rgm@ya
hoo.
com
A
b
st
r
a
ct
This pap
er di
scusse
s
of T
a
rget
Stren
g
th
(TS
)
fo
r th
e Sela
r b
oop
s
(O
xe
ye
scad) and
Megala
s
pi
s
cordyl
a (To
r
pedo
scad),
the m
o
st co
m
m
e
rcially
fish in Mala
ysi
a. TS ca
n be
determ
i
ned from
in situ m
easurem
ent
s and
cal
c
ulat
ion u
s
ing a
c
ousti
c fish m
odel. TS val
ue,
depth, a
nd
p
o
sition
(x-y-z) of fish
target
ed
can
be
vi
e
w
ed
from
e
c
h
ogram
u
s
in
g
FQ-8
0 An
alyzer
by in situ m
e
asu
r
em
ent. X-ra
y im
aged
can be de
plo
y
ed to develop
the acou
stic
fish m
odel. The
percenta
ge o
f
length an
d
uppe
r surfa
c
e are
a
for
swim
bladder to
bod
y fish
of Selar b
oop
s
m
o
re
than Meg
a
la
spis cordyl
a can be m
easu
r
ed afte
r
X-ray p
r
o
c
e
ss.
The pe
rcenta
ge of width
a
n
d
volum
e
of
swi
m
bladders to
its ea
ch
bod
y are
no
si
g
n
ificantl
y
differe
nce f
o
r
both fi
sh. Th
ese d
a
ta
of swim
blad
d
e
r ph
ysic
are
sup
port
s
the
result fr
om
in
situ m
easu
r
e
m
ent which
T
S
of Megala
s
pis
cordyl
a ha
ve
m
o
re than Selar boo
ps.
Key
w
ords
: t
a
rget st
ren
g
th, swim
bladd
er, aco
u
sti
c
fish m
odel
1. INTRODUCTION
Sonar
(Soun
d Navigatio
n
and Rangi
n
g
) is
a
gen
eral term ap
pli
ed to equi
p
m
ent and
asso
ciated
software
that
re
ceive
s
a
n
d
po
ssib
ly transmit
s
sou
nd. An e
c
h
o
so
und
er i
s
an
instru
ment u
s
ed by fishe
r
s
and research
ers to t
r
an
smi
t
and re
ceive
sou
nd verti
c
a
lly through th
e
water c
o
lumn
[1].
Size an
d refl
ectivity of sound a
r
e com
b
ined into a
para
m
eter
ca
lled the ba
ckscattering
cro
s
s s
e
ct
io
n
(
σ
bs
), whi
c
h i
s
esse
ntially the
acou
stic si
ze of the obj
e
c
t. The ba
ckscatterin
g
cro
s
s
se
ction
ca
n b
e
expresse
d
as th
e a
m
oun
t of refl
e
c
ted
sou
nd i
n
ten
s
i
t
y measure
d
one m
e
ter a
w
ay
from the ta
rg
et, relative to
the amo
unt
of ene
rgy in
cident up
on th
e targ
et. Thi
s
pa
ram
e
ter
is
calle
d the target stre
ngth (
TS
) and exp
r
essed in dB.
TS = 10 log
10
(
σ
bs
)
(1)
Tran
smitter
of an echo
sou
nde
r or
son
a
r send
s out a beam of sound
through a
transdu
ce
r (a
device whi
c
h
co
nvert
s
o
n
e
type of
ene
rg
y to anoth
e
r, i
n
this
case
el
ectri
c
al
ene
rg
y
to soun
d ene
rgy and vice versa
)
. The p
r
essu
re
wave
radiate
s
sph
e
rically from i
t
s sou
r
ce wit
h
the inten
s
ity
decrea
s
in
g i
n
versely with
the
squ
a
re
of the di
stan
ce t
r
aveled. The stre
ngth
of
sou
nd
so
urce, call
ed
so
urce level
(SL), is
simil
a
rly me
asure
d
a
unit di
st
ance a
w
ay
and
expre
s
sed i
n
units
of lou
d
n
e
ss
relative t
o
sta
nda
rd. I
n
un
derwate
r acou
stic, the
unit of
loud
n
e
ss
is in de
cibel (dB).
Actually, there are two pa
rameters
of sound th
at
rel
a
te to its l
oud
ness. O
ne i
s
pre
s
sure
asso
ciated
wi
th the sou
nd
wave. Soun
d sen
s
o
r
(tra
n
s
ducer) re
sp
o
nds di
re
ctly to pre
s
sure si
nce
the pressu
re
cha
nge
s a
r
e
cau
s
e
d
by th
e pa
rticle
vib
r
ations. T
he o
t
her me
asure
of loudn
ess
is
sou
nd inten
s
ity, or the powe
r
/area a
s
soci
ated wit
h
the so
und
wave. Sou
nd inten
s
ity is
prop
ortio
nal to the squ
a
re
of pressu
re.
Whe
n
the
so
und
wave e
n
c
ou
nters a
de
nsity di
ffere
n
c
e
(i.e. targ
et), an e
c
h
o
p
r
opag
ates
radially o
u
tward from the
target b
a
ck t
o
a re
ceiver. Echoe
s retu
rning
to
th
e
sound so
urce are
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