Zudaire et al.: Reproductive potential of / hunnus albacares in the western Indian Ocean 
257 
Table 3 
Summary of oocyte developmental stages and corresponding reproductive phases by 5-cm size class (fork lengths) in our 
study of Yellowfin Tuna (Thunnus albacares) reproduction in the western Indian Ocean. The numbers of individuals in our 
study that were at each developmental stage are shown in the columns organized by histological classification of the ova- 
ries (Brown-Peterson et al. 2011; Zudaire et al., 2013); immature phase, including the primary growth stage (PG); develop- 
ing phase, including the cortical alveolar (CA), primary vitellogenesis (Vtgl), and secondary vitellogenesis (Vtg2) stages; 
spawning-capable phase, including the tertiary vitellogenesis (Vtg3), germinal vesicle migration (GVM), and hydration stages 
(Hydr.); and regenerating phase. 
Length (cm) 
Immature phas 
PG 
Mature phases and developmental stages 
Total 
P 
Developing to spawning-capable 
Regenerating 
CA 
Vtgl 
Vtg 2 
Vtg 3 
GVM 
Hydr. 
48-53 
15 
2 
17 
53-58 
45 
6 
51 
58-63 
51 
3 
54 
63-68 
12 
5 
17 
68-73 
15 
8 
1 
1 
25 
73-78 
19 
10 
5 
1 
2 
1 
38 
78-83 
26 
51 
8 
7 
4 
1 
8 
105 
83-88 
25 
42 
17 
5 
6 
2 
10 
107 
88-93 
6 
32 
16 
3 
1 
58 
93-98 
4 
28 
16 
12 
4 
2 
4 
70 
98-103 
7 
14 
7 
3 
5 
1 
1 
38 
103-108 
17 
12 
6 
4 
2 
10 
51 
108-113 
4 
14 
1 
1 
6 
26 
113-118 
1 
3 
1 
1 
6 
12 
118-123 
3 
13 
2 
1 
19 
123-128 
1 
12 
5 
1 
19 
128-133 
1 
3 
20 
11 
1 
36 
133-138 
1 
2 
21 
16 
1 
41 
138-143 
4 
1 
3 
11 
5 
1 
25 
143-148 
1 
1 
2 
3 
1 
8 
148-153 
1 
1 
2 
Total 
238 
82 
44 
112 
48 
6 
42 
819 
247 
572 
was positively related to GSI, length, and weight; BFrel 
was related only to GSI; HSI and K showed no signifi- 
cant relationship with BF or BFrel (Table 4). The GSI 
showed the best correlation with BF and BFrel (coef- 
ficient of correlation [r] =0.87 and r=0.89, respectively). 
In contrast, low values for r 2 were found for length and 
weight (0.25). The intercept of the regression line be- 
tween the BF and fish weight relationship was signifi- 
cantly different from 0.00 (P<0.05), a result that could 
indicate that the number of oocytes produced per gram 
of female is not linearly related to weight, and, there- 
fore, larger females produce more oocytes per gram of 
gonad-free weight than do smaller females (Fig. 6). A 
decrease in mean BF values from November (3.79 mil- 
lion) to June (2.26 million) was observed. Neverthe- 
less, the ANOVA of the BF estimates by month did not 
reveal statistically significant relationships between 
months at a 95% confidence level (ANOVA; P(5,42)=l-52, 
P=0.2081). The BF appeared to be highly variable by 
month, making it difficult to identify a clear pattern 
for female fecundity. 
Discussion 
Length at 50% maturity 
Analyses of L50 for female Yellowfin Tuna in the Indian 
Ocean in other studies resulted in different estimates 
(Table 5). To our knowledge, our study is only the sec- 
ond one where the L50 of Yellowfin Tuna in the Indian 
Ocean has been examined by histological method. Ti- 
mochina and Romanov 3 previously used a histological 
3 Timochina O. I., and E. V. Romanov. 1991. Notes on re- 
productive biology of Yellowfin tuna in the western Indian 
Ocean. IPTP (Indo-Pacific Tuna Development and Manage- 
ment Program), Coll. Vol. Work. Doc. TWS/91/32, 60 p. P.O. 
Box 2004, Colombo, Sri Lanka. 
