The Study On Growth And Development Of Coilia Mystus In The Yangtze Estuary Based On Otolith Microstructure

Coilia mystus commonly known as roasted seeds fish,which belonging to Clupeiformes,Engraulidae,Coilia.It mainly in estuaries and adjacent waters and distributed in the Yellow sea,the bohai sea,the east China sea and the south China sea.It is an important economic fish in the Yangtze estuary.Due to the construction of water conservancy projects and environmental pollution,resource of Coilia mystus has been in recession in the Yangtze River Estuary.For better protection and utilization the resources,the age structure,growth characteristics,life history and the growth and development of larvae and juveniles were research and discussed.In order to provide scientific protection measures.The main results are as follows: 1.Age structure and growth characteristics of reproductive population of Colia mystus in the Yangtze EstuaryCoilia mystus is the river migratory fish,which are distributed in the Yellow sea,the Bohai sea,the east China sea and south China sea in our country.Most are distributed in Yangtze estuary as one of the important fish of Yangtze estuary.Coilia mystus is the only fish,which still have certain production type in traditional five catching season in Yangtze estuary currently.To assess the age structure and the change trend of growth characteristics,124 specimens of female Coilia mystus from the Yangtze estuary taken from April to November of 2014 were analyzed.Results showed that the age group of Coilia mystus included of 1 to 3years old groups.One age accounted for 28.22% of the total sample,2age accounted for 58.84%,3 age accounted for 16.94%.This proves that 1 and 2 age are the dominant groups.The body length range from 108.00 to 189.00 mm,with an average of(151.66±21.13)mm,and the body weight varied from 5.00 to 35.00 g,with an average of(16.97±6.34)g.Body length and body weight were fitted into the function(R2=0.9353),with the t test,the parameter of b is equal to 2.819,which is not different significant with the constant of 3(P> 0.05).That indicated Coilia mystus belongs to grow at a constant speed type.Based on the von Bertalanffy growth equation:,,it showed that the age at inflection point body weight growth curve was 1.11 years old and it is consistent with the least mature age.Body length and body weight were 131.02 mm and 11.05 g,respectively,at the age of the inflection point.The breeding group of Coilia mystus showed a trend of younger age and miniaturization.To better use and protection of Coilia mystus resources,fishing should be carried out after the inflection point.And some measures should be taken to protect Coilia mystus resources,such as reducing the fishing intensity and protecting the spawning grounds.2.The sagittal otolith growth and development at different development stages in larval and juvenile Coilia mystus in the Yangtze estuaryCoilia mystus is a very important commercial fish distributes widely in in the Yangtze estuary.It is a migratory species,which grows and matures in the coastal waters and then maturally migrates into the Yangtze estuary for spawning.Otolith growth and development at different stages in larval and juvenile Coilia mystus can help to understand the characteristics under natural conditions.An understanding of early growth and development of otolith is essential not noly for wild population conservation,but also for artificial seeding production.In this study,a total number of 103 larvel and juvenile Coilia mystus were colleted in the Yangtze estuary,from April to August,2014.Otolith analysis revealed that age of specimens ranged from 5 to 48 days old in age.To study the early growth and development in different stage,the body length of 103 ind Coilia mystus were measured.Statistics showed that the cubic function described best the increase of body length with age.The increase of body length can be divided into three stages,5~11d,12~30d,31~48d.The growth rate was significantly different among these stages(P<0.05).To study the morphological development,the otolith length and otolith width were measured,and the analysis showed that the growth of otolith length and otolith width as the growth of body length.After 17,19 days the growth rate increased by about 2-fold.Piecewise regression analysis between otolith length,width and otolith age was carried out in order to determine the allometric growth pattern,and the inflection point of otolith length and otolith width both occurred at 19,20 days.The growth rate before the knot was slow grow,while after the knot was rapid grow.The otolith morphology of Coilia mystus change significantly at different stages of early life history.The otolith is circular of yolk-sac stage and preflexion stage;The otolith length growth is greater than the otolith width of flexion stage,and the otolith is becoming oval;After become stable form,the ratio of otolith length and otolith width remained stable.3.Study on the otolith microchenmistry and life history of Coilia mystus in Yangtze river estuaryCoilia mystus is an important economic fish in Yangtze river estuary.And it is the river migratory fish.During the spawning season,it was assembled to swim to the brackish water to lay eggs.In order to explore the life history characteristics of Coilia mystus in Yangtze river estuary,laser ablation-ICP-mass spectrometry(LA-ICP-MS)was applied to analyze the microchemistry pattems of element Sr and Ca in ototliths.Analysis results on the line transect clearly indicated that there are two different life history.One kind of migratory habits is significant,and another is not obvious.The two life history has characteristic and common characteristics.The common characteristics is that its early life is in the brackish water.And the different characteristics as follows.one kind of the life history has more complicated life history.It is showed that laying eggs and hatching in brackish water and growing in sea water for the otolith Sr / Ca ratios.The Sr / Ca ratios of the other is relatively stable at about 7.00.This phenomenon reflects it has the habit of brackish water.And this may be the survival strategy in life history of Coilia mystus.It also shows that there may be a settled life history type of Coilia mystus.The aim of this paper is to invertigate the life history and migration pattems of the otolith microchemistry for Coilia mystus in Yangtze river estuary.And to provide the basic date for resources protection and artificial breeding in the future.