东太平洋赤道海域茎柔鱼(Dosidicus gigas)的体型月间变化及环境效应

MONTHLY VARIATION IN BODY SIZE OF DOSIDICUS GIGAS AND ENVIRONMENTAL RESPONSES IN THE EQUATORIAL WATERS OF EASTERN PACIFIC OCEAN

为了掌握茎柔鱼体型生长变化及其与栖息环境因子的效应关系, 2017年2—4月和6—8月,在东太平洋赤道海域逐月随机采集了3 628尾茎柔鱼样本,进行体质量、胴长的月间变化分析和胴长与海表温、叶绿素a浓度的效应关系研究。结果显示,雌性个体胴长分布范围为163—468mm,体质量分布范围为123—3034g;雄性个体胴长分布范围为171—475mm,体质量分布范围为145—2 681 g。不同月份之间,雌性、雄性个体的胴长和体质量均存在显著性差异,雌雄性个体胴长、体质量均以2月份的最大, 6—8月份的较小。然而,每个月份雌性、雄性个体的胴长分布均为单峰值区间分布。体质量-胴长幂函数关系显示,2—4月份雌雄性个体多倾向于匀速生长、体征较差,6—8月份个体则以负异速生长为主、体征较为良好。雌性、雄性个体胴长与采样海域海表温、采样纬度呈显著的正效应关系,采样海域叶绿素a浓度对雌性胴长产生正效应影响。研究表明,东太平洋赤道海域茎柔鱼体型的月间差异性显著,体型变化与采样海域海表温、采样纬度关系密切,并且雌性体型与海域叶绿素a浓度呈正效应关系。

The jumbo squid Dosidicus gigas is endemic to the eastern Pacific Ocean and plays a critical role being prey or predator,and it is an important species in the world invertebrate fishery.To understand the body size changes of D.gigas and the environmental responses,we randomly collected 3628 specimens from the equatorial waters of eastern Pacific Ocean during February-April and June-August 2017.The specimens were analyzed for the monthly changes of body weight(BW)and dorsal mantle length(ML),and the generalized linear mixed-effects relationships between ML and sea surface temperature and chlorophyll a concentration.The results show that female squids ranged between 163 mm and 468 mm ML and between 123 g and 3034 g BW,and males ranged between 171 mm and 475 mm ML and between 145 g and 2681 g BW.Both female and male squids varied significantly in dorsal mantle length and body weight among the sampling months,in which females and males both were found in the largest size in February and relatively smaller size in June to August.Specimens from each sampling month exhibited a unimodal distribution of dorsal mantle length consistently.As the power regression of BW-ML revealed,both female and male squids sampled during February to April showed likelihood of isometric growth but in a poorer body condition,while those sampled from June to August were mostly found allometric growth with a better body condition.In addition,to understand the relationships of dorsal mantle length to environmental variables and sampling latitudes,the generalized linear mixed-effect models using sampling month as random effect were performed,and a positive and significant effect of sea surface temperature on the attainment of dorsal mantle length was found in both sexes.Meanwhile,the effect of sampling latitudes on the dorsal mantle length of both sexes was also significant,showing an increase trend of ML towards the equator.The effect of chlorophyll a concentration on the dorsal mantle length was found significant in female squids only.Therefore,the monthly change of body size of D.gigas was significant in the equatorial waters of eastern Pacific Ocean,and was correlated with the sea surface temperature and chlorophyll a concentration.