262 
Fishery Bulletin 111(3) 
Gonad-free weight (g) 
0 10P00 20P00 30P00 40000 50P00 60P00 
Figure 6 
Linear regression between batch fecundity (BF) and fish gonad-free weight (W g ), 
and power function between BF and fork length (FL) for Yellowfin Tuna (Thun- 
nus albacares) sampled in the western Indian Ocean in 2009 and 2010 
2007). Lauth and Olson (1996) suggested that tuna may 
boost batch fecundity in response to greater amounts 
of forage, in accordance with the results reported by 
Itano 2 for the Pacific Yellowfin Tuna. Batch fecundity 
enhancement by feeding might explain the observed 
high interindividual variation in the BF. Apart from 
prey availability, other biotic and abiotic parameters, 
such as fish condition, genetic variation, geographic dif- 
ferences in sampling locations, and temperature, have 
been reported to be associated 
with variability in the produc- 
tivity of fish species (Schaeffer, 
1998; Murua and Motos, 2006). 
Conclusions 
Advances in the management of 
fish stocks rely to a great extent 
on updated knowledge of repro- 
ductive dynamics and its imple- 
mentation in stock assessments. 
The results described here will 
contribute to the improvement 
of the understanding of the re- 
productive dynamics of Indian 
Ocean Yellowfin Tuna. The L 50 
was estimated at 75 cm FL with 
the maturity threshold set at 
the CA stage of ovarian develop- 
ment. Two reproductive periods 
were detected in which reproduc- 
tive activity was higher in large 
females than in small ones. Sim- 
ilarly, large females had higher 
contribution of fecundity than 
did small females; however, more 
research on fecundity is required 
to investigate the principal fac- 
tors that affect its variability at 
individual and population levels. 
We suggest that Yellowfin Tuna follow a capital-income 
breeder strategy during ovarian development, by mo- 
bilizing accumulated energy and incorporating energy 
from feeding. However, further research on the proxi- 
mate composition (e.g., lipids and proteins) of this spe- 
cies through analyses of different tissues is required to 
obtain more precise descriptions of energy allocation 
and mobilization during the reproductive cycle of Yel- 
lowfin Tuna. 
Table 6 
Estimates of the batch fecundity (BF) and the relative batch fecundity (BFrel) of Yellowfin 
Tuna ( Thunnus albacares ) reported for previous studies in different areas of Pacific and In- 
dian Oceans. Values are expressed in millions for BF and in oocytes per gram of gonad-free 
weight for BFrel. 
Studies 
Area 
BF 
BFrel 
Hassani and Stequert {see f n ■ 5 m tke text) 
Western Indian Ocean 
0.50-8.00 
- 
Timochina and Romanov (see f n - 3 ln the text) 
Western Indian Ocean 
3.27 
- 
Schaefer 1996 
Eastern Pacific Ocean 
1.57 
68.0 
Schaefer 1998 
Eastern Pacific Ocean 
2.50 
67.3 
Itano (see f n ' ^ the text) 
Hawaii area 
3.45 
63.5 
Itano 2 
Equatorial western Pacific 
2.16 
54.7 
Sun 6t al (see f n ‘ 6 * n the text) 
Western Pacific Ocean 
2.71 
62.1 
