Releasing Enhancement Of Large Yellow Croaker(Larimichthys Crocea)in Dongtou Sea Water And Its Effect Evaluation

Large Yellow Croaker is one of the most important economic fish species in China.In order to verify the migration distribution, tagging releasing activities the first time began from the 1960 s. Fishing resources in wintering ground was destroyed totally at the end of the 1970 s. Fujian Province firstly broke through the larval rearing techniques which made a basement for releasing enhancement in the 80 s of last century. Afterwards Zhejiang province began to explore the enhancement work of Large Yellow Croaker of daiqu clan in the end of the 90 s of last century(1998) and accumulated a mass of materials. Meanwhile it made a series of achievements in larval rearing 、 releasing techniques 、 standard the choice of sea area and relative criterion. Studies on releasing effect was rare and difficult from the duplicated document literature, most of which were about research on releasing situation and migrating route. It is necessary to make an assessment about releasing effects abut Large Yellow Croaker with further implement.The materials about the Large Yellow Croaker’s releasing enhancement in Dongtou water in this article from project of ecology compensation of CNOOC from 2013 to 2015.The following is about main contents of this thesis.Chapter one is a preface which introduced the research background, research current situation, research purpose and significance.Chapter two was divided into three portions regard as the section of materials and methods. The first part mainly introduced the concerning requirements about the krill and releasing methods. Several investigation methods were stated in the second portion: First,Fixed point survey in releasing sea area; second, survey on the sea of the Peripheral releasing water; third, fishery dynamic monitoring referring to all kinds of fishing methods;forth, social investigation and collection of tagging fish after releasing. The third section of chapter two is about evaluation methods of releasing effect. It included contrastive analysis about resource density and growth situation of Large Yellow Croaker in three years;various methods to estimate quantity of resource and yield by dealing with survey data;calculation of the ratio of output and input; recapture rate of tagging fish after collection.Chapter three stated the enhancement and releasing of Large Yellow Croaker in Dongtou sea area from year 2013 to 2015 in detail.Chapter four is a conclusion about the investigation of releasing situation. Fixed point survey in releasing sea area shows that: comparing 2013, biological density and tail density in 2015 increased 130% and 30.9% respectively in September; comparing 2014, biological density and tail density in 2015 increased and expanded in spatial distribution both in April and May by the method of survey on the sea in the Peripheral releasing water. The quantity of vessels and yield of fishing large yellow croaker were obtained by fishery dynamic monitoring. The information of market price of Large Yellow Croaker in different time and size as well as the number of tagging fish was collected.Chapter five is to make an effect assessment adapting different methods by disposing the collected data.(1) the body length and weight of releasing fish increased different range from 2013 to 2015 through Comparison; the range of value of vasnctson is from 2.03 to 4.26;(2) the age structure age of releasing fish tend to more complicated; all the above truths show that releasing fish grow well in natural environment.(3) the instantaneous quantity of resources of large yellow croaker in September of 2013 and 2015 are 4.13 t and 9.5t by the method of Sweeping the sea area.(4)The results of fishery production investigation showed that the total capture of Large Yellow Croaker from year 2013 to2015 were 114.43t、132.66 t and 134.42 t. The yield increase in different range in every year.And the number is 90.3t、152.43t、156.26 t respectively with assessment model.(5) the ratio of output and input in three years close to 11:1 by estimate the catch in theory; The results showed that recapture rate of tagging fish in 2014 was 1.69%.(6) finally, an overall assessment is given from aspects of economy, society, ecology.Chapter six the problems in this paper were discussed.(1) The relationship between the ratio of quantity of releasing and yield, instantaneous resources showed an obvious positive correlation.(2) discussions of the option of methods of assessment(3) the analysis of factors concerning the evaluation methods.Chapter seven is a brief conclusion of this article.