Farley Jessica H, Eveson J Paige, Davis Tim L O, Andamari Retno, Proctor Craig H, Nugraha Budi, Davies Campbell R
Wealth from Oceans Flagship, CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia.
Institute for Mariculture Research and Development, Gondol, Bali, Indonesia.
PLoS One. 2014 May 5;9(5):e96392. doi: 10.1371/journal.pone.0096392. eCollection 2014.
The demographics of the southern bluefin tuna (SBT) Thunnus maccoyii spawning stock were examined through a large-scale monitoring program of the Indonesian longline catch on the spawning ground between 1995 and 2012. The size and age structure of the spawning population has undergone significant changes since monitoring began. There has been a reduction in the relative abundance of larger/older SBT in the catch since the early 2000s, and a corresponding decrease in mean length and age, but there was no evidence of a significant truncation of the age distribution. Pulses of young SBT appear in the catches in the early- and mid-2000s and may be the first evidence of increased recruitment into the spawning stock since 1995. Fish in these two recruitment pulses were spawned around 1991 and 1997. Size-related variations in sex ratio were also observed with female bias for fish less than 170 cm FL and male bias for fish greater than 170 cm FL. This trend of increasing proportion of males with size above 170 cm FL is likely to be related to sexual dimorphism in growth rates as male length-at-age is greater than that for females after age 10 years. Mean length-at-age of fish aged 8-10 years was greater for both males and females on the spawning ground than off the spawning ground, suggesting that size may be the dominant factor determining timing of maturation in SBT. In addition to these direct results, the data and samples from this program have been central to the assessment and management of this internationally harvested stock.
通过1995年至2012年间对印度尼西亚延绳钓在产卵场渔获量的大规模监测计划，对南方蓝鳍金枪鱼（SBT）麦氏金枪鱼产卵群体的种群统计学特征进行了研究。自监测开始以来，产卵群体的大小和年龄结构发生了显著变化。自21世纪初以来，渔获物中较大/较老的南方蓝鳍金枪鱼相对丰度有所下降，平均体长和年龄也相应降低，但没有证据表明年龄分布出现显著截断。21世纪初和中期，年轻南方蓝鳍金枪鱼脉冲出现在渔获物中，这可能是自1995年以来该产卵群体补充量增加的首个证据。这两个补充脉冲中的鱼大约在1991年和1997年产卵。还观察到性别比例与大小相关的变化，叉长小于170厘米的鱼以雌性为主，叉长大于170厘米的鱼以雄性为主。叉长超过170厘米的雄性比例随大小增加的这种趋势可能与生长率的两性异形有关，因为10岁以后雄性的年龄体长大于雌性。产卵场8至10岁鱼的平均年龄体长在雌雄两性中均高于非产卵场，这表明大小可能是决定南方蓝鳍金枪鱼成熟时间的主导因素。除了这些直接结果外，该计划的数据和样本对于这种国际捕捞种群的评估和管理也至关重要。
