Amphidromy related to genetic structure of a hybrid temperate bass population in Ariake Sea

证明有明海存在着一个非常独特的日本温鲈Lateolabrax sp.与中国温鲈Lateolabrax sp.的杂交种群。有明温性鲈鱼在早期幼鱼期即已迁入淡水区。本研究证实了有明温带柔鱼的无游性洄游和种群内遗传结构的存在。1）耳石显微结构分析表明，产卵期为11月下旬至中旬。2月，12月下旬达到高峰。在16 mm左右的海平面和80日龄时出现在筑后河口附近，然后在18 mm左右和100日龄时转移到淡水区。上游采集的鱼体尺寸大于下游。在大牟田潮滩采集的溯河幼鱼和非溯河幼鱼的孵化期和体长分布没有差异。 ...更多信息 0组鱼类的Sr/Ca迁移轨迹大致可分为早期淡水进入组和非淡水进入组。淡水入侵组的比例每年在50%~ 20%之间波动。产卵期成鱼耳石微化学分析表明，有2个不同的类群，岛原类群包括早期有淡水生活史的鱼类，而三隅类群没有淡水生活史。3）线粒体DNA分析表明，不同产卵场的成鱼具有不同的遗传特征;从岛原采集的成鱼具有非常高的中国单倍型百分比（85%），而从三隅采集的成鱼具有非常低的百分比（26%）。这些结果表明，有明海温性鲈鱼至少存在两个亚群，受中国温性鲈鱼基因影响较大的亚群具有非洄游性淡水入侵的潜力，受中国温性鲈鱼基因影响较小的亚群不具有非洄游性淡水入侵的潜力。有明海特有的陆生孑遗鱼类在仔稚鱼晚期和幼鱼早期主要依赖于一种半咸水桡足类中华哲水蚤（Sinocalanus sinensis），而在幼鱼晚期和幼鱼早期则依赖于一种半咸水桡足类中华哲水蚤（Sinocalanus sinensis）。这种地方性和大陆残遗桡足类被推测在很大程度上有助于有明温带鲈鱼作为一个重要的食物资源之前，栖息地转移到淡水的淡水入口。有明海的分布仅限于湾底和海水高度浑浊的河口。少

It has been demonstrated that there is a very unique hybrid population between Japanese temperature bass Lateolabrax japonicus and Chinese temperate bass Lateolabrax sp. exists in Ariake Sea. The Ariake temperate bass has been known to immigrate into freshwater area during the early juvenile period. The present research was conducted to confirm existence of amphidromous migration and genetic intra-population structure of the Ariake temperate bass.1) Otolith microstructure analyses revealed the spawning occurred between late November and mid. February with a peak of late December. The larvae appeared around the Chikugo river estuary at about 16mm SL and 80 days of age, then shifted their habitat to freshwater area at about 18mm and 100 days. Fish size collected at the upper reach of the river was larger than that at the lower reach. Hatch-date and length distributions were not different between river-ascended juveniles and non-ascended juveniles collected at Omuta tidal flat area.2) Oto … More lith Sr/Ca trajectories of 0-group fish were roughly divided into early freshwater ingress and non-freshwater ingress groups. Proportion of freshwater ingress group fluctuated annually between 50% and 20%. Otolith microchemistry for spawing adult fish suggested 2 different groups, Shimabara group included fish with freshwater experience during the early life stage and Misumi group didn't show freshwater experience.3) Mitochondria-DNA analyses showed quite different genetic features between the different spawning grounds ; the adult fish collected from Shimabara had a very high percentage of Chinese haplotype (85%), whereas a very low percentage (26%) in the adult fishes from Misumi. These findings suggest that there are at least two subpopulations of temperate bass in Ariake Sea ; the one more highly influenced by Chinese temperate bass gene has a potential of amrphidromous freshwater ingress and the other one with less influenced by Chinese gene doesn't have amphidromous potential. Migration to freshwater during the early life stage was speculated to be determined by 2 main factors, that is genetic background of subpopulation and biotic/abiotic environmental conditions after spawning.4) All of the continental relict fishes endemic to Ariake Sea were found primarily dependent on a brakish water copepod Sinocalanus sinensis during the late larvae and early juvenile periods. This endemic and continental relict copepod was speculated to largely contribute to freshwater ingress of the Ariake temperate bass as an essential food resource prior to the habitat shift into freshwater. Distribution of this species in Ariake Sea was restricted to the bottom of the bay and to estuaries with highly turbid water. Less