Fishery Biology Of Scomberomorus Niphoniusin The Northern Waters Of The East China Sea

Scomberomorus niphonius,commonly known as mackerel,mackerel,etc.,belongs to Perciformes,Scombridae,Scomberomorus is a warm-temperate pelagic migratory economic fish,widely distributed It is located in the Sea of Japan in the Northwest Pacific,the Pacific coast of Japan,the coast of the Korean Peninsula,and the Yellow Sea and East my country Sea.Scomberomorus niphonius is one of the most productive and important economic fish species in my country,and it is also an important fishing target in many countries and regions such as Japan,South Korea and Taiwan.Under the background of severe decline in fishery resources,Scomberomorus niphonius occupies an important position in offshore fisheries.Scomberomorus niphonius is one of the few species that maintain high yields in my country.Therefore,the research on thefishery biology and fishery oceanographyof Scomberomorus niphonius is of great significance to the rational development and utilization of the resource status and scientific management.In order to understand the status quo of the blue-spotted mackerel population under high fishing pressure and find out the biological characteristics of its fishery,this paper analyzes the basic biological data of Scomberomorus niphonius to study the growth characteristics of its bait and overwintering individuals,and analyze the impact Potential factors for growth;by analyzing the external morphological parameters of otoliths,the growth law of otoliths is analyzed,and possible factors affecting the changes of otoliths are explored;the age of otoliths can be identified through reading of otoliths,and then the law of growth can be grasped And group composition;based on the analysis of the composition of otolith trace elements and the changes in the concentration of main trace elements in different life history stages,the analysis of the group composition and population connectivity of Scomberomorus niphonius is expected to provide a basis for the rational development and utilization and scientific management of this resource.The main results are as follows:（1）Basic biological characteristics of Scomberomorus niphonius.Based on the collected 367 S.niphonius samples,the relationship between fork length and body weight（W=a L^b）is obtained,in which the estimated mean value of condition factor a is 3.022.×10^-5,and the estimated mean value of allometric growth parameter b is2.794.To better understand the seasonal and sexual variations in relationships between the fork length and weight（W=a L^b）of S.niphonius,we used the trawl survey data at the East China Sea fishing grounds from October 2018 to March 2019 and constructed a generalized linear model and nine linear mixed models...Both the BIC value and the root mean square error value indicated that the most complex linear mixed model（i.e.month and gender have random effects on both parameters a and b）had the best performance.According to the results of the difference analysis between the best model and the generalized linear model,the relationship between the fork length and weight of S.niphonius varied significantly between seasons and sexes（P<0.01）.In the best model,b was higher in October and November（feeding period）and lower in December and January（overwintering period）,while a was the opposite.For sexual differences,b was higher in males and lower in females.It can be concluded that the relationship between the fork length and weight of S.niphonius was significantly affected by season and sex.The linear mixed model allows the easier combination of season and sex,which would be of great value in the heterogeneity studies of fish life history traits.The monthly and gender differences in Scomberomorus niphonius may be related to internal gene expression,living habits and habitat environment.（2）The external morphological characteristics of Scomberomorus niphonius otoliths.The results show that the otolith of Scomberomorus niphonius is milky white,approximate rectangular,the back convex,the front concave,the outside has more protruding small teeth,is serrated,the overall bending to show the tile shape.There is no significant difference between the left and right sagittal otolith.The weight of the otolith and 6-item morphological parameters were significantly correlated with the fork length,and all of them were the best fit results of the exponentiation function.With the growth of Scomberomorus niphonius,the morphological characteristics of the otolith varies significantly with the fork length,the total length of the otolith is increasing,and the dorsal and ventral regions continue to shrink to the center of the otolith,the length of the posterior region increases,the wing length is increasing,the overall appearance of vertical shrinkage,horizontal growth trend.Therefore,it is speculated that the first sexual maturity fork length of Scomberomorus niphonius is between 350mm-400mm.（3）Study on the age and growth of Scomberomorus niphonius otoliths and the group composition.The results show that the proportion of the small individual group first decreases and then increases,and the proportion of large individual group first increases and then decreases.The age data of the otoliths of 350 Japanese Spanish mackerel,the age ranged from 110 to 281 d,and the average age was（190.11±48.61）d.According to the otolith age data of the blue-spotted mackerel,the peak incubation period was calculated.The results showed that the incubation period of the Japanese Spanish mackerel in the northern part of the East China Sea was from late April to late June,and the peak incubation period was concentrated in late May to early June.The Gaussian mixture model based on the EM algorithm analyzes the distribution characteristics of the incubation peak period.The results show that the Japanese Spanish mackerel has 4 incubation peak periods,so it is guessed that there may be 4spawning groups in the sample.The four peak hatch periods were matched with the sea surface temperature data of the main spawning grounds of the Japanese Spanish mackerel in the East Yellow Sea.The results show that the 4 spawning groups may be distributed from the Yangtze River Estuary,Lusi,Haizhou Bay and Shidao fishing grounds.（4）Preliminary study on the microchemistry of Scomberomorus niphonius otoliths.The main trace elements in Scomberomorus niphonius otoliths are Mg,Na,Ca,Mn,Cu,Sr and Ba.Except for Ca,the content of Na and Sr is relatively high,and the change trend of each trace element in the time series is obvious.Among them,the relative importance of Na,Mg,and Mn is relatively high,which can better characterize the changes in their early life history.His life history is mainly divided into five stages:0～150μm,150～450μm,450～750μm,750～1200μm and above1200μm.The analysis shows that there are significant differences between different life history stages,and the embryonic stage and hatching stage are significantly higher than the feeding,overwintering and spawning stages.Compared with other elements,Na,Mg and Mn are more suitable as the iconic elements to reconstruct the habitat history of the Janpanese Spanish mackerel.According to the ratios of Na:Ca,Mg:Ca and Mn:Ca,the habitat history of the Janpanese Spanish mackerel was reconstructed in the northern waters of the East China Sea.It was found that they lived in a habitat with high concentrations of Na,Mg and Mn during embryonic development and incubation.The stage spawning ground is closer to the coastal shallow waters where the concentration of free Na,Mg and Mn is higher,and the subsequent growth and development stage will be in a habitat with a slightly lower concentration of Na,Mg and Mn for a long time for overwintering and spawning migration.Therefore,Na:Ca,Mg:Ca and Mn:Ca can be used as potential indicators to construct the habitat history of the Janpanese Spanish mackerel.