Hallier, Jean-Pierre

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c 
L 
WORKSHOP ON STOCK ASSESSMENT OF YELLOWFIN TUNA IN 
THE INDIAN OCEAN 
(Colombo, Sri Lanka 7-12 October, 1991) 
YELLOWFIN LENGTH-WEIGHT RELATIONSHIPS FROM 
WESTERN INDIAN OCEAN PURSE SEINE FISHERIES 
by J.P. HALLIER* 
RESUME : Les derniers résultats sur les relations longueurs-poids 
pour l'albacore (Thunnus albacares) avaient été présentés en 1990 
lors du comité d'expert qui s'était tenu à Bangkok en juillet 
1990. L'échantillonnage était alors insuffisant pour les petits 
albacores (poissons inférieurs à 22 cm de LD1). La serie de 
données a été complétée et les analyses ont conduit à plusieurs 
relations qui sont donnees ici avec les tableaux correspondants 
longueurs-poids. 
SUMMARY: The last informations on yellowfin length-weight 
relationships- (Thunnus albacares) have been issued during the 
Expert Committee which took place in Bangkok in July 1990. At 
that time, sampling data on small yellowfin (fish less than 22cm 
in FLD) were insufficient. Since then, data have been updated 
and new relationships are given thereafter with the corresponding 
length-weight tables. 
* .  ' 
1. DATA AVAILABLE 
To data previously collected at the Victoria cannery wk added 
data collected in Port during transhipment operations and a few 
more made at the cannery. They all were collected on small 
yellowfin in order to complete the series already in hands. 
I 
t 
Altogether the samples reach now 2393 yellowfins for Fork Length 
(FL) and First Dorsal Length (FDL); 2242 for FL and Weight (WT) 
and 2228 for FDL and WT. 
>, i: i . I .  
* ORSTOM biologist, SFA BP 449, Victoria, SEYCHELLES 
2. STATISTICAL METHODS 
Relationships are calculated. using linear regression (least 
square method), and different models are tested (exponential. 
logarithmic, power), after having converted data. In order to 
detect uncertain plots, an analysis of standardized residual was 
made. If data fit properly with the model..standardized residual 
values must be approximately between -2 and +2. Every plot 
beyond these values can be suspected and has to be checked and 
thgn be deleted from the sample. Residuals are. reported in 
accordance with independant variable and if they show a 
particular tendency structure. that means there is a link between 
residuals and independant variable, therefore, regression 
equation must be rectified (Sherrer, 1984). Regression lines are 
compared by using a covariance analysis. 
3. RESULTS AND. DISCUSSIONS 
3.1 Analysis of data collected 
Among the different relationships. calculated, the best 
correlation was obtained with an equation of the type y = ax+b 
after a log to log transformation of %he variables. However, as 
previously noted (de MONTAUDOUIN &..-al, 1991) relationships are 
more properly described when samples are separated between small 
size fish on one side and medium size and large size fish on the 
other side. 
3.2 Relationships FL - FDL 
The general relationship, described by figure 1, responds to the 
equation : 
! _. 
Y = 1.1477 x + 0.3195 (n = 2393) 
y = Log FL in ,cm 
I 
e x = Log E'DL in cm 
When data ..are I separated in the two data groups easily 
recognizable -from figure 1, we obtain the two following 
equations: 
. .. 
(1) yi = 0.9899 xi + 0.5113 (n = 679) 
yi = Log~FL in cm 
xi = Log FDL for FDL 5 17.5 cm ' 
Figure 2 shows these results. , .  t 
(2)'yz = 1.1647 x2 + 0.2942 (n = 1714) 
x2 = Log FDL €or FDL 2 17.5 cm 
These results are illustrated in figure 3 
f y2 = Log FL in cm 
FDL of 17.5 cm is the crossing point of the two regression lines. 'p 
N 
Fonds Documentaire ORSTOM 
Cote: PA 8398 EX : 4 
3.3. Relationship FL-WT 
A general relationship taking into account all available data (n 
= 2242) is shown.in figure 4 and the equation given below : 
y = 2.9773 x - 4.6607 
y = Log FIT in kg. . i  
x = Log FL in cm. 
FDL 2 1.9.0 cm 
FDL 5 64.0 cm 
These data have been divided into two groups on both sides of 64 
cm FL, the crossing point of the two regression lines: 
(1) yi = 2.7537 xi - 4.2747 (n =716) 
yi = Log FIT in kg. 
XI = Log FL for FL 5 64 CITI 
Figure 5 
(2) y2 = 3.0450 ~2 - 4.8001 ' 
y2 = Log WT in kg. 
x2 = Log FL for FL Z 64 cm 
Figure 6 
1 
3.4. Relationship FDL-FIT 
A general relationship with al1 data available (n = 2226) is 
shown in figure 7 and the equation is as follows : 
y = 3.4157 x - 3.7086 
y = Log WT in kg. 
x = Log FDL in cm. 
A s  for other relationships, two data groups have been idehtified 
on both sides of 19.0cm FDL : 
( 1 )  yi = 2.7641 xi - 2.9131 (n = 692) 
y1 = Log WT in kg. 
x i  = Log FDL for FDL 5 19.0 cm 
Figure 8. 
( 2 )  y z  = 3.5637 x z  -'3.9612 (n ='1536) 
, *  
Log WT = 3.5837 Log FDL - 3.9612 
Log WT = 2.7537 Log FL - 4.2747 
y'2 = Log WT in kg. 
xz = Log FDL for FDL 2 19.0 cm 
FDL 2 64.0 cm 
Figure 9 .  
Log WT = 3.0450 Log FL - 4.8001 
4. CONCLUSIONS 
All relationships used f o r  Western Indian Ocean purse seine 
fisheries are listed in tables 1. 
Tables 2, 3 and 4 are giving the yellowfin relationships 
respectively for FDL-FL. FDL-WT .and FL-WT. 
I /  
FDL 5 17.5 cm- 
FDL 2 17.5 cm 
FDL I 19.0 cm 
FDL 1 19.0 cm 
FDL I 64.0 cm 
FDL 164.0 cm 
REFERENCES 
MONTAUDOUIN (de) X. ,  J .P .  HALLIER and S. HASSANI, 1991. Length- 
weight relationships for yellowfin (Thunnus albacares.) and 
skipjack (Katsuuonu, 9 p.darda) from Western Indian Ocean. IPTP 
Collective Volume of Working Documents, Vol 4, TWS/90/48 : pp 47- 
65. , $ 7  : 
FL = 3.2456 FDL0.98SS 
FL = 1.9688FDL1.1647. 
WT = 1.2215~10-3 FDL2.7641 
WT = 1.0935~10-4 FDL3.5837 
WT = 5.3125~10-5 FL2.7537 
WT = 1.5845~10-5 FL3.0460 
. Y  
Table 1 :, YELLOWFIN LENGTH-WEIGHT RELATIONSHIPS 
l * 
I FDL 5 17.5 cm I Log FL = 0.9899 Log FDL + 0.5113 I 
I-FDL 2 17.5:~" I Log FL 1.1647 Log FDL + 0.2942 I 
I FDL 5 19.0 cm I t  Log WT = 2.7641 Log FDL - 2.9131 I 
I 
T a b l e  2 : YELLOWFIN F I R S T  DORSAL LENGTH - FORK LENGTH 
RELATIONSHIP 
FDL cm 
. 
FDL cm WT he 
0.7 
0.8 
0.9 
1.0 
1.3 
1.5 
1.6 
1.8 
2.0 
2.2 
2.4 
2.6 
2.8 
3.1 
3.3 
3.6 
3.9 
4.2 
4.6 
5. O 
5.5 
6.0 
6.5 
7.1 
7.7 
8.3 
8.9 
9.6 
10.4 
11.2 
12. o 
12.9 
13.8;: 
14.7 
15.7 
16.8 
17.9 
19.0 
20.2 
21.5 . 
22.8 
1,. 2 
10.0 
10.5 
11.0 
11.5 
12'. o 
12.5, 
13.0 
13.5 
14.0 
14.5 
15.0 
15.5 
16.0 
16.5 
17.0 
17.5 , 
18.0 
18.5 
19.0 
19.5 
20.0 
20.5 
21.0 
21.5 
22.0 
22.5 
23.0 
23.5 
24.0 
24.5 
25.0 
25.5 
26.0 
26.5 
27.0 
27.5 
28.0 
28.5 
29.0 
29.5 
30.0 
30.5 
F L ,  cm 
32 
33 
'35 
36 
38 
40 
41 
43 
44 
46 
47 
49 
50 
52 
54 
55 
57 
59 
61 
63 
64 
66 
68 
70 
72 
74 
76 
78 
80 
82 
84 
86 
88 
90 
91 
93 
95 
97 
99 
101 
103 
105 
FDL CIT 
31.0 
31.5 
32.0 
32.5 
33.0 
33.5 
34.0 
34.5 
35.0 
35.5 
36.0 
36.5 
37.0 
37.5 
38.0 
38.5 
39.0 
39.5 
40.0 
40.5 
41.0 
41.5 
42.0 
42.5 
43.0 
43.5 
44.0 
44.5 
45.0 
45.5 
46.0 
46.5 
47.0 
47.5 
48.0 
48.5 
49.0 
49.5 
50.0 
FL cm 
107 
109 
111 
114 
116 
118 
120 
122 
124 
126 
.12 8 
130 
132 
134 
136 
138 
140 
142 
145 
147 
149 
151 
153 
155 
157 
159 
162 
164 
166 
168 
170 
172 
174 
177 
179 
181 
183 , 
185. 
187 
T a b l e  3 : YELLOWFIN F I R S T  DORSAL LENGTH-WEIGHT ' 
RELATIONSHIP 
10.0 
10.5 
11.0 
11.5 
12.0 
12.5 
13.0 
13.5 
14.0 
14.5 
15.0 
15.5 
16.0 
16.5 
17.0 
18.0 
18.5 
19.0 
19.5 
20.0 
20.5 
21.0 
21.5 
22.0 
22.5 
23.0 
23.5 
24.0 
24.5 
25.0 
25.5 
26.0 
26.5 
27.0 
27.5 
28.0 
28.5 
29.0 
29.5 
30.0 
30.5 
.17.5 
FDL cm 
31.0 
31.5 
32.0 
32.5 
33.0 
33.5 
34.0 
34.5 
35.0 
35.5 
36.0 
36.5 
37.0 
37.5 
38.0 
38.5 
39.0 
39.5 
40.0 
40.5 
41.0 
41.5 
42.0 
43.0 
43.5 
44.0 
44.5 
45.0 
45.5 
46.0 
46.5 
47.0 
47.5 
48.0 
48.5 
49.0 
49.5 
50.0 
.42. 5 
WT ke: 
24.1 
25.6 
27.1 
28.6 
30.2 
31.9 
33.6 
35.4 
37.3 
39.2 
41.3 
43.3 
45.5 
47.8 
50.1 
52.5 
55.0 
57.5 
60.2 
62.9 
65.8 
68.7 
71.7 
74.8 
78.0 
81.3 
84.7 
88.2 
91.8 
95.5 
99.3 
.03.2 
.07.3 
.11.4 
~15.7 
120. o 
124.5 
-29.2 
.33.9 
v 
W 
p3 
r 44 I 45 
I 46 
!- 
1 .8  96 17 .2  
1.9 97 17.8 
2 .0  98 18.3 
Table 4 : YELLOWFIN FORK LENGTH-WEIGHT RELATIONSHIP 
43 1.7 95 
47 . 2.1 99 
100 
1[11 ' 
102 
2 .7  
2.8 
5 4  
3.3 107 
I 56 3.5 1 108 . 
1 57 3 . 6  109 
58 I 3.6 110  
4 .0  111 
60 4.2 112 
4.4 113 E l  
62 4 .6  114 
! 
63 4.8 
16.'; 
18.9  
19.5  
2 0 . 1  
20.7 
21.3 
22.0 
22.6 
23.3 
24.ti 
24.6 
25.3  
2 6 . 1  
26.8  
27.5 
28 .3  
23.1 
82  10.7 
11.1 
' 158 I 
169 I 
160 
1 6 1  
162 
163 
164 
115 
118 
119 
120 
121 
122 
123 
124 
126 
128 
129 
130 
131 
132 
133 
I 127 
155 
156 ! 15'7 ¡ 
29.8 
30.6 
31.4 
32.3 
33.1 
34.0  
34.8 
35.7 
36.6 
37.5 
39.4 
41.3 
42.3 
43.3. 
44.4 
45.4 
46.5 
38.5 
40 ..4 
168 
169 
170 
1 7 1  
1'72 
66 
68 
69  
70 
7 1  
67 
5.5 
6. 0 
6.3 
6.6 
6.9 
5 .8  
wer i~ 
177 6 I 
178 
179 I 
l eo  , 
.I '7 . 5 
46.6 
49.7 
5 il . 8 
"1. il 
53.1 
54 .3  
55.5 
56.7 
!i'7 . Y 
59.2 
60.4 
61.7 
63.0 
64.3 
65.6 
67.0 
68.4 
66.8 
IC *> 
7 1 . 2  
72.6 
74.  0 
'f E, , 5 
7'7 . il 
7 8 . 5  
80.C 
81 .5  
83.1 
8 (i . 'i' 
86.3 
87 .3  
89.6  
92.9 
94.6 
96.3 
98.1 
99.8 
101.6  
103.4 
105.3 . lOÏ.1 
109. o 
110.9 
112.8 
114.8 
116.7 
91 : 9  
118.7 
120.7 
1.22. P 
124.8 
126.9 
d 
1. U8 
Log FL 
1.53. 
Figuro 1 
Figure 2 
(FDL 4 17.5 cm) 
r( 
Log FDL , 
r( 
1 
' P  
d .  21 
Log FI 
1.85 
1.91 
Log IIT 
Figure 3 
(FDL I 17.5 cmj 
Log FDL t; 
‘p 
rl 
Figure 4 
LI. 91, 
’ Log WT 
-0.15: 
L. 91‘ 
.og UT 
rl 
Log FL 
-O, 155i d 
. m  
? 
d 
0.39: 
X 
X 
X 
Figure 5 
(FL E 64 cm) 
1 
a I 
/,y x x x  
Y X X  
. Log FL 
Figure 6 
(FL & 6 4  cm) 
t 
I 
-.I 
Y a  Log FL 
m .  
w 
W 
-0. 
d 
0.94. 
Log wr 
-0.1s 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Figure 8 
(FDL 6.19.0 cm) 
Log FDL 
d 
x x  
Jf X 
x x  
X 
X 
X 
A x  
x x  
d Log PDL 
F! 
d 
I .97 
Log UT 
0.39 
x/ 
x x  
x yx ’ x  x 
X 
Log FDL t: 
d 
‘o. 
. .- 



Workshop on stock assessment of yellowfin tuna in the Indian Ocean

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