基于耳石微化学的长江安徽和县江段刀鲚生境履历重建

为了解长江刀鲚(Coilia nasus)的“生境履历”, 利用电子探针微区分析技术研究了2015年5月17日在长江安徽和县江段捕获的刀鲚短颌鲚与长颌鲚类型耳石Sr和Ca微化学特征。短颌鲚的耳石Sr/Ca值变化动态为2类, 一类比值稳定在2.00左右(1.65±0.87—2.03±0.96), 反映了其纯淡水的生境履历; 另一类比值波动显著, 不仅具有对应淡水生境的低值(2.39±1.18—2.63±0.85), 还具有对应半咸水生境的高值(3.22±1.17—3.29±1.14), 显现了其江海生活的生境履历。长颌鲚耳石的Sr/Ca值均波动显著, 同时具有对应淡水生境的低值(1.35±1.07—2.37±1.04)和半咸水、海水生境的高值(3.47±1.09—8.35±1.25), 表现了其均为溯河洄游的生境履历。Sr面分析结果也与上述Sr/Ca值的结果相印证。长江安徽和县江段刀鲚资源组成复杂, 群体可由纯淡水型和江海生活型的个体共同组成。

RECONSTRUCTING HABITAT HISTORY OF COILIA NASUS FROM THE HEXIAN SECTION OF THE YANGTZE RIVER IN ANHUI PROVINCE BY OTOLITH MICROCHEMISTRY

Coilia nasus is a valuable fish in the middle and lower reaches of the Yangtze River. In order to reconstruct its habitat history, an electronic probe microanalyzer (EPMA) was applied to analyze the microchemistry patterns of element Sr and Ca in otoliths of 17 individuals of two phenotypes belonging to short-jaw C. nasus (once named as C. brachygnathus) and long-jaw C. nasus. Au sample were collected in Hexian section of the Yangtze River in Anhui Province at May 2015. Microchemical results showed that C. brachygnathus individuals could be divided into two types: (1) Sr/Ca ratio was consistently at low phase (<3.0) throughout the otolith, indicating that the individuals only experienced freshwater habitat during their whole life history; (2) Sr/Ca ratio fluctuated between low (2.39±1.18—2.63±0.85) and high (3.22±1.17—3.29±1.14) phases in the otoliths, suggesting the individuals experi-enced not only freshwater, but also brackish water habitats at different stages in their life history. The otolith Sr/Ca ra-tio of long-jaw C. nasus fluctuated significantly between low (<3, reflecting freshwater habitat) and high (>3, reflec-ting estuarine brackish water or sea water habitat) value phases. The 16- color-Sr concentration profiles are in the line with the srlca ratios. All of the above results revealed that the resource composition of Coilia nasus from Hexian sec-tion of the Yangtze River in Anhui Province was much more complex by consisting of freshwater resident and fresh-brackish water migratory short-jaw C. nasus, as well as anadromous long-jaw C. nasus individuals.