南海中西部海域春季三种金枪鱼类的营养生态位比较

Trophic niche comparison among three tuna species caught from central and western South China Sea in spring

以2018年春季于南海中西部渔场作业的灯光罩网渔业生产船采集的33尾鲔(Euthynnus affinis)、34尾鲣(Katsuwonus pelamis)和40尾黄鳍金枪鱼(Thunnus albacares)为对象,采用碳氮稳定同位素技术以及多元统计分析,研究了3种金枪鱼类碳氮稳定同位素的基本特征和个体发育的食性转换规律,并比较了3种金枪鱼类的营养生态位宽度和重叠度。结果表明:鲔、鲣和黄鳍金枪鱼的δ13C均值分别为(-17.83±0.15)‰、(-17.68±0.18)‰和(-18.05±0.24)‰;δ15N均值分别为(10.78±0.47)‰、(10.26±0.82)‰和(8.72±0.88)‰。Mann-Whitney U非参数检验表明,鲔与鲣之间的δ13C(P<0.01)和δ15N(P<0.05)差异显著,黄鳍金枪鱼与鲔或鲣之间的δ13C(P<0.01)和δ15N(P<0.01)间均存在极显著性差异。Pearson相关分析表明,鲔、鲣和黄鳍金枪鱼的叉长与δ15N值均存在极显著的正相关关系(P<0.01),表明随着3种金枪鱼的个体发育,食性发生转化,其摄食的饵料趋向于高营养级生物。营养生态位多度量指标均表明,黄鳍金枪鱼的营养生态位宽度最大,其次为鲣和鲔,表明黄鳍金枪鱼比鲔和鲣的营养多样性更高。鲔和鲣与黄鳍金枪鱼无营养生态位重叠,而鲣和鲔之间的营养生态位重叠度为0.19,表明两者存在一定的食性竞争。

A total of 33 individuals of Kawakawa(Euthynnus affinis),34 individuals of Skipjack tuna(Katsuwonus pelamis),and 40 individuals of Yellowfin tuna(Thunnus albacares)were collected by light traps and falling nets operated in the central and western South China Sea in spring2018.Carbon and nitrogen stable isotope techniques and multivariate statistical models were used to investigate isotopic characteristics,shifts of ontogenic diet,and trophic niche breadths and overlaps of the three tuna species.The results showed that the mean values ofδ13C were(-17.83±0.15)‰for E.affinis,(-17.68±0.18)‰for K.pelamis,and(-18.05±0.24)‰for T.albacares,and their meanδ15N values were(10.78±0.47)‰,(10.26±0.82)‰,and(8.72±0.88)‰,respectively.Results of Mann-Whitney U test showed significant difference inδ13C(P<0.01)andδ15N(P<0.05)between E.affinis and K.pelamis,and forδ13C(P<0.01)andδ15N(P<0.01)between T.albacares and either E.affinis or K.pelamis.A significant positive correlation was found between fork length andδ15N values of each species,indicating that their diets shifted with growth to higher trophic level.T.albacares exhibited the largest trophic niche breadth,followed by K.pelamis and E.affinis,indicating that T.albacares had a higher trophic diversity than E.affinis and K.pelamis.No overlaps in trophic niche were detected between T.albacares and either E.affinis or K.pelamis.There was,however,a low trophic overlap rate(0.19)between E.affinis and K.pelamis,indicating a certain extent of dietary competition between them.