Abstract:
Five demersal trawl surveys were conducted in the P
akistani waters in October,
November 2009 and August, October, November 2010. A
total of 819 length-weight and
7,240 length-frequency data of
Atrobucca alcocki
were collected, the length ranged from
10 cm to 45 cm with the dominant length group from
19 to 29 cm. The total weight ranged
from 14 to 928 g. The length-weight relationship ca
n be expressed as
W
= 0.012*
L
2.925
(R
2
=
0.972). Using the ELEFAN program in FiSAT computer
package, the calculated von
Bertalanffy growth function parameters were
L
∞
= 47.25cm,
K
= 0.180 yr
-1
. Total mortality
(
Z
) was computed using the length-converted catch cur
ve analysis at
Z
= 1.07 yr
-1
. Natural
mortality was computed as
M
= 0.494 yr
-1
at an annual average sea surface temperature of
26°C, hence, the fishing mortality was computed as F
=Z-M= 0.576 yr
-1
. The Exploitation
ratios (E) were computed as
E
max
= 0.421,
E
10
=0.355,
E
50
=0.278. Yield per recruit
analysis revealed that when
t
c
was assumed to be 2,
F
max
was calculated at 0.75 and
F
0.1
at
0.6. When
t
c
was assumed to be 1,
F
max
was calculated at 0.55 and
F
1.0
at 0.45. Current age
at first capture was about 1 year and
F
current
was 0.576, therefore,
F
current
was larger than
F
0.1
and
F
max
. When biological reference point was
F
opt
equal to
M
(0.494), current fishing
mortality rate of 0.576 was larger than the target
biological reference point.
Keywords
:
Biological reference points, Bertalanffy growth fun
ction,
Length-converted
catch curve,
Natural mortality.
