260 
Fishery Bulletin 111(3) 
Table 4 
Coefficients of determination 
(r 2 ) and correlation (r) 
and P -values (P) for the relationship between batch fe- 
cundity (BF) and relative batch fecundity (BFrel) with 
different biological parameters 
fork length, weight, go- 
nadosomatic index (GSI), hepatosomatic ind 
ex (HSI), 
and condition factor 
( K) in our 
study of Yellowfin Tuna 
(Thunnus albacares) 
reproduction in the western Indian 
Ocean. 
r 2 
r 
P 
BF 
Length (cm) 
0.2114 
0.4598 
<0.005 
Weight (g) 
0.2022 
0.4497 
<0.005 
GSI 
0.7579 
0.8706 
<0.001 
HSI 
0.0237 
0.1541 
0.6706 
K 
0.0611 
-0.2472 
0.1145 
BFrel 
Length (cm) 
0.0377 
0.1943 
0.2174 
Weight (g) 
0.0263 
0.1622 
0.3046 
GSI 
0.8099 
0.8999 
<0.001 
HSI 
0.0696 
0.2639 
0.4612 
K 
0.0184 
-0.1357 
0.3914 
determine whether the appearance of regenerating 
phase ovaries among young individuals indicates that 
females have skipped the spawning season. 
Condition indices related to reproduction 
ability than in the first spawning period (from Novem- 
ber to February), and no distinct pattern was evident. 
For the period of higher spawning activity (November- 
February), condition indices showed a clear pattern of 
energy mobilization from the muscle to the liver or 
gonad for reproduction. In contrast, during the second 
spawning period (June), energy was mobilized at a low- 
er level because of lower spawning activity. 
The protracted spawning season and population 
asynchrony in spawning activity of Yellowfin Tuna 
could mask temporal variations in energy allocation 
and the mobilization of the factors that were analyzed 
(Dominguez-Petit et al., 2010). Therefore, the assess- 
ment of variation in energy reserves by maturation 
phases was performed to study the energy cycle in fe- 
males undergoing ovarian development (Alonso-Fernan- 
dez and Saborido-Rey, 2012). The results showed a high 
energy investment in reproduction. The GSI showed an 
increase in the ovary mass from the immature phase 
to hydration stage, and the HSI described an increase 
of liver mass mainly between the vitellogenic process 
and maturation. This HSI pattern is evidence of the 
importance of the liver in the energy accumulation 
and synthesis of those energetic compounds (e.g., lip- 
ids and vitellogenin) essential for ovarian development 
(Dominguez-Petit et al., 2010). The decrease of K dur- 
ing the vitellogenic process and the low values of K 
at the GVM and hydration stages could indicate the 
role of the muscle in the mobilization of energy to the 
gonad or liver to fulfill the energetic requirements of 
maturation, principally during vitellogenesis (Zabou- 
kas et al., 2006; Dominguez-Petit et al., 2010). 
Condition indices are im- 
portant parameters for tun- 
ing the estimation of repro- 
ductive potential (Marshall 
et al., 1999). Analysis with 
such indices throughout the 
spawning season allows the 
determination of energy al- 
location during reproduction 
(Murua and Motos, 2006). In 
our study, during the peak 
spawning period (November- 
February), GSI, HSI, and K 
reflected a seasonal pattern 
in the accumulation and de- 
pletion cycles of energy re- 
serves. The increase in the 
GSI and HSI at the expense 
of K was observed both in 
smaller (<100 cm FL) and 
larger (>100 cm FL) females, 
and the exchange of energy 
was more pronounced in the 
larger size group. These 3 
condition indices from March 
to July showed higher vari- 
Table 5 
Estimates of the length at 50% maturity (L50) and the fork length at which all 
specimens achieve maturity (L100) for female Yellowfin Tuna (Thunnus albacares) 
reported for previous studies in different areas of the Indian Ocean. The methods ap- 
plied for the classification of ovaries were macroscopic (Macro.) and microscopic (i.e., 
histological. Micro.). The criterion for the maturity threshold in all of these studies 
was the presence of vitellogenic stage oocytes. 
Studies 
Estimation 
type 
Method 
Length (cm) 
Stequert and Marsac, 1989 
L 50 
Macro. 
120-140 
Hassani and Stequert (see A - 5 m the text) 
L50 
Macro. 
110-115 
Nootmorn et al. (see A- 4 in the text > 
L50 
Macro. 
110 
Karpinski and Hallier 7 
L50 
Macro. 
104-112 
Zhu et al. 2008 
L50 
Macro. 
114 
Timochina and Romanov (see A- 3 ln the text > 
L100 
Micro. 
120 
Maldeniya and Joseph 5 
L50 
Macro. 
100 
'Karpinski, B., and J. P. Hallier. 1988. Preliminary results on yellowfin spawning 
in the western Indian Ocean. Indo-Pacific Tuna Development and Management Pro- 
gram (IPTP) Coll. Vol. Work. Doc.TWS/88/31, 50-59 p. 
8 Maldeniya, R., and L. Joseph. 1986. On the distribution and biology of yellowfin 
tuna (T. albacares ) from the western and southern coastal waters of Sri Lanka. FAO/ 
IPTP Coll. Vol. Work. Doc. 2: TWS/86/18, 21-32 p. 
