有明银鱼耳石显微结构和微化学研究

MICROSTRUCTURE AND MICROCHEMISTRY IN OTOLITH OF ARIAKE ICEFISH (SALANX ARIAKENSIS)

1998年从鸭绿江捕取有明银鱼成鱼 ,生物学测量后剖出耳石。每尾鱼 1对矢耳石中的 1个用于制片 ,显微镜下观察其显微结构 ,另 1个制片镀碳膜后 ,用扫描电子微探针测定Sr和Ca的浓度比率。Sr和Ca分析的标准样用SrSO4 和CaSO4 。 31尾鱼 (体长 116～ 15 7mm)耳石长半径 (Y)与鱼体长 (X)成线性关系 ,其方程式为Y =2 72 16X +9 2 2 92 ,r =0 9178,P <0 0 1。耳石中心和耳石原基的平均直径分别为 2 2 5 5± 2 88μm和6 95± 1 30 μm。 13尾鱼耳石上的日轮数为 30 5～ 35 4,大约在 45～ 70日轮处出现过渡轮。日轮间距 0 94～ 1 14μm ,最大间距在 190～ 2 2 0日轮处 ,最小间距出现在 2 80日轮之后。耳石中Sr、Ca浓度比例在第 5至第 7测点出现第 1个高峰 ,这与稚鱼为了越冬洄游到海中时间相吻合。第 2个高峰出现在 2 8～ 32测点 ,这与鱼产卵上溯洄游时间相符。个体发育过程中生理和生态条件的变化 ,可引起耳石中Sr、Ca比率的改变 ,但栖息水域盐度的突然改变是导致Sr、Ca比率显著增高的主导因素。

Adult Ariake icefish (Salanx ariakensis) in Yalujiang river estuary were collected in September 1998. After biological measurements of the samples, the sagittae were removed from the fish. One of the sagittae from each individual was sectioned to examine its microstructure under microscope, the other one was polished and coated with carbon for measurement of the concentration ratio of strontium and calcium in otoliths by using a wavelength dispersive X ray electron microprobe (EMP 820Q). In the analysis of Sr and Ca, CaSO 4 and SrSO 4 were used as standards.\;The long radius Y (μm) of the otolith was linearly related to the fish length X (SL, mm), and the equation total from 31 individuals (SL 116～157 mm) was Y=2 7216X+9 2292, r=0 9178, P <0 01. The mean diameters of core and primordum in otolith were 22 55± 2 88 μm and 6 95±1 30 μm, respectively. The number of daily growth increments in otolith of 13 adults ranged from 305 to 354. The transition zone (mark ring)occured appromately at 45～70 days increments. The width of daily growth increments was from 0 94 μm～1 14 μm, the largest width at 190～220 days increments and the smallest width appeared after 280 increments. The first peak of Sr/ Ca concentration ratio appeared at the 5 th ～7 th measurement point that coincided with the time of migration of the juvenile fish to the sea for overwintering. While the second peak appeared from the measurement points 28 to 32 which coincided well with the time of the fish anadromous migration for spawning. The changes of physiological and ecological condition during ontogenic development of the fish lead to the Sr/ Ca ratio alteration in the otolith, but the drastic change of salinity in habitability water that was the dominant factor causing the Sr/Ca ratio significantly increase.