西南大西洋阿根廷滑柔鱼夏季产卵种群繁殖生物学的初步研究

根据我国鱿钓船于2012年12月—2013年3月渔汛期间,在西南大西洋公海海域作业时随机采集的阿根廷滑柔鱼夏季产卵种群样本(雌性148尾,雄性99尾),初步研究了其种群繁殖生物学。结果表明,渔汛期间阿根廷滑柔鱼夏季产卵种群雌性胴长172~252 mm,雄性胴长164~248 mm。随着月份推移,雌性占比逐月递减,从12月份的84.21%递减至次年3月份的27.03%;雄性个体占比则逐月递增,从12月份的15.79%递增至次年3月份的72.97%。雌性样本超过30%的个体性腺发育成熟并且部分处于繁殖期,雄性个体超过60%的个体性腺发育成熟并且部分处于繁殖期。雌雄个体的胴长和体质量均在性腺功能发育成熟时达到最大值,但是雌性胴长大于雄性,体质量却小于雄性。性腺指数、缠卵腺指数和精荚复合体指数随着个体生长逐渐增长。雌性个体性腺指数为0.001 2~0.31,平均值0.074;缠卵腺指数为0.003 1~0.55,平均值0.29;两者随着个体生长逐渐增长,在性腺功能成熟时达到最大值。雄性个体性腺指数为0.007 5~0.084,平均值0.038;精荚复合体指数为0.000 79~0.035,平均值0.012;两指数在繁殖期时达到最大值。

Preliminary study on reproductive biology of summer spawning stock of Illex argentinus in the southwestern Atlantic Ocean

Illex argentinus is a neritic-oceanic squid species,not only supporting the most important world cephalopod fishery in the terms of landing volumes,but also playing an important role in the southwestern Atlantic Ocean ecosystem owing to its high abundance.However,like other annual lifespan Ommastrephid species,it has been found that the recruitment abundance was closely related to the reproductive success the year before.So,in this study,148 females and 99 males of summer spawning stock of I.argentinus were randomly sampled from the catch of Chinese jigger fleet during the fishing season from December 2012 to March 2013,in the high sea of southwestern Atlantic Ocean,and their reproductive biology was studied,in order to fully understand the important reproductive aspects of this species biology.Results showed that the mantle length of this stock during the fishing season was in the range of 172-252 mm for females and 164-248 mm for males.According to the sampled months,the proportion of females decreased monthly,from 84.21% in December to 27.03% in March,but inversely for males,which had the smallest proportion of 15.79% in December,and then increased to the largest proportion of 72.97% in March.Among the females,more than 30% of individuals were mature and some of them were spawning.However,the mature males were in the proportion of more than 60%,nearly twice of that of females,and some of them had mated.With the gonads development,both of females and males grew gradually and attained their largest mantle length and body weight at the functionally maturity stage.The mantle length of females was longer than that of males according to the maturity stages,whereas the body weight of females was lighter than that of males,and the possible reasons were discussed.Moreover,the gonadosomatic index(GSI)for both sexes,nidamental gland index(NGI)for females and spermatophoric complex index(SCI)for males gradually increased with growth,even though the males' SCI was at a same low level during the immature phase.The females' GSI and NGI were in the range of 0.001 2-0.31,with a mean value of 0.074 and 0.003 1-0.55,with a mean value of 0.29,respectively,and both indices attained their greatest value at the functionally maturity stage.The males' GSI ranged from 0.007 5 to 0.084 with a mean value of 0.038,and SCI ranged from 0.000 79 to 0.035 with a mean value of 0.012.These two indices attained their greatest value when the individuals were being mated.