马绍尔群岛海域大眼金枪鱼耳石形态

耳石是鱼类生态的重要信息载体。根据2009年11月-2010年1月马绍尔群岛海域采集的大眼金枪鱼(Thunnus obesus)样本中获得的222对矢耳石,对其形态特征进行观察和测量。观察发现,矢耳石上有3条凹沟,可将矢耳石分为背区、翼区、吻区和侧区4个区。t检验表明,左右矢耳石形态参数无显著性差异(P=0.999)。对矢耳石12个形态参数作主成分分析,结果显示,背区长(DL)、翼区前长(WFL)、翼区长(WL)和最大厚度(MST)可以代表矢耳石尺度特征,背区夹角(DA)和翼区夹角(WA)代表矢耳石角度特征。DL与MST的关系可用指数表达,叉长(FL)与DL间可用多项式表达、叉长与WFL和矢耳石重量(OW)间可用逻辑斯蒂克模型表达。随叉长增加,矢耳石核心向背区、侧区和吻区方向移动。对不同DL组的DA进行多重比较分析,发现DA在DL为500～700μm间出现生长波动,结合FL与DL之间关系,认为大眼金枪鱼初次性成熟时DL为600μm左右,叉长在80～130 cm之间。

Morphology of bigeye tuna otolith in waters near Marshall Islands

The otolith of fish is an important source of ecological information.It is a popular and successful tool in discriminating between and within fish stocks to study the morphologic characteristics of the otolith.A total of 222 pairs of sagittal otolith were collected randomly from Nov.2009 through Jan.2010 in waters near Marshall Islands.The morphologic characteristics of them were observed and measured.There were three channels on them which divide the sagittal otolith four areas(dorsum,wing,rostrum,and lateral).There was no significant difference between the morphological parameters of the left sagitta and the right sagitta(P=0.999).The result of principal component analysis on 12 morphologic parameters showed the dorsal length(DL),wing front length(WFL),wing length(WL) and maximum statolith thickness(MST) can be used to represent the size features of the sagittal otolith;the dorsal angle(DA),and wing angle(WA) might reflect its angle features;these six parameters can be used to indicate the morphologic characteristics of the otolith.The optimum relationship between DL and MST was described by exponential function,the optimum relationship between fork length(FL) and DL was described by quadratic multinomial,while the optimum relationship between FL and weight of sagittal otolith(OW) was the logistic function.The sagittal otolith was growing and the core of sagittal otolith was shifting to the dorsum,rostrum,and lateral areas while the fork length was increasing.There was fluctuation for DA when the length of DL was between 500 μm and 700 μm by One-way random block design.The DL was about 600 μm and the forklength was about 80-130 cm while bigeye tuna was mature.