基于耳石微化学的黄河垦利段刀鲚生活史初步研究

为研究黄河刀鲚(Coilia nasus)生境履历特征,利用电子探针微区分析技术(EPMA)对采集自黄河垦利段5尾刀鲚个体(D1、D2、D4、D5和D6)的矢耳石进行微化学特征研究。定量线分析结果显示,黄河口刀鲚生境履历较为复杂,所有个体核心区Sr/Ca值较低,表明其淡水孵化特征,但随着个体生长表现出不同的生活履历。个体D2生活史较复杂,其生长轨迹多次往返于淡水—半咸水生境,不具备洄游型刀鲚应有的规律性特征;个体D1、D4、D5和D6具有明显的洄游特征,不同的是个体D1和D4的Sr/Ca最大值分别为6.1和6.2,D5、D6生境已延伸至Sr/Ca值较高的区域,最大值分别达到8.44、8.63,但是由于调水、调沙对黄河口盐度变化影响较大,尚不能判断D5、D6个体生境已延伸至海水区域。分析的结果显示了同样的特征,个体D1、D4核心区表现为蓝色,外缘区域表现为蓝绿色;个体D2核心区表现为蓝色、绿色、黄色交替出现,个体D5、D6核心区域表现为Sr值较低的蓝色区域,随着生长耳石外围逐渐形成较为明显的黄色圆环。基于以上结果,本研究重新建立了黄河口刀鲚的生境履历,多数个体孵化和早期的生活主要在淡水生境完成,之后进入盐度较高的区域,往返于半咸水—海水生境中进行索饵、育肥,直至被捕获。以个体D2为代表的群体生活史较为复杂,推测可能是由于当年山东东平湖汛期放水而被动进入黄河的定居型刀鲚。

Preliminary Investigations on Coilia nasus from the Kenli Section of the Huanghe River Based on Otolith Microchemistry

Life histories for Coilia nasus in the Kenli section of the Huanghe River were reconstructed using otolith microchemistry. An electron probe microanalyzer (EPMA) was used to analyze the Sr and Ca microchemistry patterns in otoliths of five C. nasus individuals(D1,D2,D4,D5 and D6 collected from Kenli section in May 2016. Results of line transect analysis showed that the life history of C. nasus was complex. All individuals were born in fresh water with a lower Sr/Ca ratio in the core area; however, as they grew, they demonstrated different life histories. After leaving the freshwater habitats, D1 and D4 mainly lived in the estuarine environment rather than seawater, where the salinity is relatively lower; the maximum Sr/Ca ratios of D1 and D4 were 6.1 and 6.2 respectively. D2 moved between the freshwater and brackish water habitats without migrating. The Sr/Ca ratios of D5 and D6 were higher, manifesting the maximum Sr/Ca ratios of 8.44 and 8.63, respectively. However, because of water and sediment discharge regulations, we cannot judge whether the habitat of D5 and D6 had been extended to the sea. All differences were confirmed from the mapping results of the EPMA data. The otolith of D1 and D4 presented a bluish pattern in the core area and greenish pattern in the outer regions. The otolith of D2 showed a multicolored pattern (alternating bluish, greenish, even yellowish). The otolith of D5 and D6 presented a bluish pattern with lower Sr/Ca ratios in the core area; as they grew, a yellowish circle was formed in outer regions adjacent to the bluish central regions. Based on the results, we were able to reconstruct the habitat history of C. nasus in the Kenli section of the Huanghe River. Most of the individuals completed their hatching and early life mainly in freshwater habitat, then entered the estuary or seawater, and leaved to and from the fresh-brackish water habitats for feeding until they were captured. The life history of the freshwater stock represented by D2 is relatively complex, and we speculate that it may enter the Huanghe River because of the water drainage during the flood season in Dongping Lake.