Two microchemistry patterns in otoliths of Coilia nasus from Poyang Lake, China.

Abstract

To confirm whether there is anadromous estuarine tapertail anchovy Coilia nasus now in Poyang Lake,an electron probe microanalyzer(EPMA)was applied to analyze the element Sr and Ca microchemistry patterns in otoliths of two individuals collected from Xingzi area of the lake.Results of line transect analysis showed that the ratios of Sr∶ Ca×1 000 in the otolith of the individual with a shorter supramaxilla(PYCB02)were consistently low(1.66±0.54),indicating that it experienced in freshwater habitat during its whole life history.Another individual with a longer supramaxilla(PYCE05)had a complex Sr/Ca ratio pattern which can be divided into three phases(1.82±0.50,5.79±0.91,and 4.14±0.88),suggesting it experienced not only the freshwater,but also the seawater and brackish water during different stages in its life history.All these differences could be well confirmed by the results of X-ray mapping analysis of EPMA.The whole otolith of PYCB02 presented a uniform bluish pattern(low Sr level)from the core to the outermost regions.In contrast,the otolith of PYCE05 showed a multi-color pattern.There were greenish(moderate Sr level),yellowish(moderate Sr level),or even reddish(high Sr level)in outer regions adjacent to the bluish central regions.Results of the two different microchemistry patterns obtained by both the line transect and mapping analyses confirmed objectively,for the first time,the coexistence of resident and anadromous forms of Coilia nasus in Poyang Lake and suggested that Coilia nasus is still possible to migrate anadromously for spawning into Poyang Lake,which is about 800 km away from the river mouth of Yangtze River.These aforementioned microchemistry patterns will provide important information not only to more effectively evaluate and protect the resources of Coilia nasus,but also to rationally plan and guide future ecological economic development in Poyang Lake.