Nakamura (1975) indicated that female black marlin(161–320 cm) caught in the northwestern Coral Sea with well-developed gonads (gonad weights >2 kg) were spawners. However,determining the maturity of fish on the basis of gonad weight or GSI values could lead to erroneous estimates (e.g. low GSI values for large mature fish). Histological methods are the most preciseway to determine the maturity of fish. Based on these methods,Domeier and Speare (2012) reported that female black marlin>100 kg were mature and Merrett (1971) suggested that the smallest size-at-maturity was ∼170–180 cm EFL in the westernIndian Ocean. In this study, the size-at-50% maturity for female black marlin was estimated at ∼195 cm (∼5.5 years of age, based on the grow curve estimated by Sun et al., 2014), while the smallestmature female captured was ∼194 cm EFL. The mean diameter of the MAGO showed a clear gap between mature and immature females in Area I and a mean oocyte diameter of ∼277 m (small-est mature female) may provide a numerical threshold area todetermine maturity.
Nakamura (1975) indicated that female black marlin(161–320 cm) caught in the northwestern Coral Sea with well-developed gonads (gonad weights >2 kg) were spawners. However,determining the maturity of fish on the basis of gonad weight or GSI values could lead to erroneous estimates (e.g. low GSI values for large mature fish). Histological methods are the most preciseway to determine the maturity of fish. Based on these methods,Domeier and Speare (2012) reported that female black marlin>100 kg were mature and Merrett (1971) suggested that the smallest size-at-maturity was ∼170–180 cm EFL in the westernIndian Ocean. In this study, the size-at-50% maturity for female black marlin was estimated at ∼195 cm (∼5.5 years of age, based on the grow curve estimated by Sun et al., 2014), while the smallestmature female captured was ∼194 cm EFL. The mean diameter of the MAGO showed a clear gap between mature and immature females in Area I and a mean oocyte diameter of ∼277 m (small-est mature female) may provide a numerical threshold area todetermine maturity.
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