The small yellow croaker Larimichthys polyactis is an economically important marine fish in Northeast Asia.Currently,its natural resources are threatened by overfishing and environmental pollution.Therefore,research o...The small yellow croaker Larimichthys polyactis is an economically important marine fish in Northeast Asia.Currently,its natural resources are threatened by overfishing and environmental pollution.Therefore,research on the reproductive system of the fish is crucial.Here,we studied the testis development and ultrastructural features of spermatogenesis in cultured L.polyactis using anatomical,histological,and ultrastructural techniques.A pair of testes,consisting of a central sperm duct and radial seminiferous lobules,were observed.The reproduction cycle of testes can be divided into stages I–VI.March to May was confirmed as the breeding season for male L.polyactis,while April is the ideal period for artificial breeding.The male L.polyactis can attain sexual maturity within 1 year.The spermatogenesis of L.polyactis comprised spermatogonium,spermatocyte,spermatid,and mature spermatozoon.The morphology of spermatogenic cells changed obviously during spermiogenesis,including nuclear shaping,midpiece and flagellum formation.The mature sperms consist of an ellipsoidal head,a short midpiece,and a long flagellum.The anterior of the head with a kidney-shaped nucleus can be distinguished.The midpiece is located posterior to the head and includes four to six spherical mitochondria.The flagellum has irregular lateral fins.The testis of L.polyactis is an unrestricted lobular type,with cystic spermatogenesis,type II spermiogenesis,and type II spermatozoa.These features are highly similar to those of other Sciaenid species.Our findings provide useful insights into the mechanism underlying testis development and spermatogenesis of L.polyactis,which can facilitate the artificial breeding of this species.展开更多
Length frequency data of small yellow croaker （Larimichthys polyactis） were acquired from the survey vessel in May, July, September and December, 2011 in Haizhou Bay of China. In this study, 921 fish individuals wer...Length frequency data of small yellow croaker （Larimichthys polyactis） were acquired from the survey vessel in May, July, September and December, 2011 in Haizhou Bay of China. In this study, 921 fish individuals were analyzed for the estimation of growth and mortality parameters. Between length and weight, the power coefficient b was 2.7321, 2.9703, 3.0418 and 2.7252 for the 4 surveying months, respectively. The estimated von Bertalanffy growth function parameters were 230mm （L∞） and 0.26yr-1 （K） as were calculated with ELEFAN method equipped in FiSAT computer package. With length-converted catch curve analysis, the total mortality rate （Z） and its 95% confidence interval were 2.16 （1.69-2.64） yr-1, 0.59 （0.15-1.04） yr-1, 1.16 （0.80-1.52） yrl and 0.96 （0.70-1.23） yr1 for the 4 surveying months, respectively, with the pooled data the value was 1.15 （0.81-1.48） yr1. The natural mor- tality rate （M） was 0.516 yr 1 as was calculated with Pauly＇s equation （the annual average sea water temperature was 11 ℃）. Therefore, fish mortality rate was 0.634 yrz. The yield-per-recruit analysis indicated that when tc was 1, Fmax, was 0.7 and F01 was 0.55. Cur- rently, the age at first capture is about 1 year and Fcurrent was 0.634. Therefore, Fcurrent was larger than F0.1 and less than Fmax. This indicates that current fish mortality is at a dangerously high level. With Gulland method, the biological reference point for fishery （Fopt） was estimated as 0.516 yr1, lower than current fish mortality. Accordingly, reducing catch in the region was strongly recom- mended.展开更多
Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased subst...Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k（growth coefficient） and t_0（zero-length age） gradually increased from 0.26 and –0.58 year in 1960 to 0.56 and –0.25 year in 2008, respectively. Although, L∞（body length）sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t_r（inflexion age） decreased from 3.78 year in1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as： fishing vessel power〉feeding grade〉sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.展开更多
The small yellow croaker Larimichthys polyactis is a benthic marine fish species of high ecological and commercial importance and is widely distributed in the northwestern Pacifi c Ocean,especially in the Chinese coas...The small yellow croaker Larimichthys polyactis is a benthic marine fish species of high ecological and commercial importance and is widely distributed in the northwestern Pacifi c Ocean,especially in the Chinese coastal waters of the Bohai,Yellow,and East China Seas.As a highly migratory species,the whole life migration of L.polyactis has been intensively studied.However,knowledge about its early life migration is scarce,and population divisions are inconsistent,limiting the ability of fishery scientists and administrators to evaluate the design and potential benefits of thorough conservation and resource-management strategies.In the present study,otolith Sr/Ca was analyzed to investigate the early migratory patterns and discriminate the populations of L.polyactis in the Yellow Sea,including two spawning groups and one overwintering group.The variation in Sr/Ca ratios of ontogenetic growth zones,including the nucleus(N),larval(L),metamorphosis(M),juvenile(J),and edge(E)zones,was measured by electron probe microanalysis.The variation in Sr/Ca ratios in early developmental growth zones was generally characterized by an evident downward trend from the N to J zone,which suggests that the early migratory pattern of L.polyactis might be from inshore to nearshore water.Canonical discriminant analysis,based on the otolith Sr/Ca ratios of the N,L,M,and J zones,allowed the successful discrimination of the two populations,namely,the northern and southern Yellow Sea groups,whose diff erences were mainly reflected in the L and J zones.Compared with previous studies,the traditional geographic boundaries(34°N)separating these two populations might be moving northward.The application of otolith Sr/Ca ratios based on ontogenetic stage could improve our understanding of the migration and population discrimination of L.polyactis from the Yellow Sea.展开更多
The homodimeric kinesin-2 protein KIF17 functions in intracellular transport and spermiogenesis in mammals.However,its role in fish spermiogenesis has not been reported.Here,we aimed to clone full-length kif17 cDNA an...The homodimeric kinesin-2 protein KIF17 functions in intracellular transport and spermiogenesis in mammals.However,its role in fish spermiogenesis has not been reported.Here,we aimed to clone full-length kif17 cDNA and determine the molecular characteristics and expression patterns of KIF17 in Larimichthys polyactis spermiogenesis.The full-length cDNA of L.polyactis kif17(Lp-kif17)was sequenced and found to contain a 332-bp 5′untranslated region,480-bp 3′untranslated region,and 2433-bp open reading frame encoding 810 amino acids.Bioinformatics analyses showed that L.polyactis KIF17(Lp-KIF17)shared high sequence similarity with homologs in other animals and possessed an N-terminal motor domain with microtubule-binding sites and adenosine triphosphate(ATP)hydrolysis sites,a stalk domain containing two coiled-coil regions,and a C-terminal tail domain.The Lp-kif17 mRNA was widely expressed in various tissues,with the highest level in the brain,followed by that in the testis.Fluorescence in situ hybridization(FISH)analysis revealed that Lp-kif17 was continuously expressed in spermiogenesis,showing that it had potential functions in this process.Using immunofluorescence(IF)analysis,we found that Lp-KIF17 colocalized with tubulin and was transferred from the perinuclear cytoplasm to the side of spermatid where the tail forms during spermiogenesis.These findings suggested that KIF17 is involved in L.polyactis spermiogenesis.In particular,it may participate in nuclear shaping and tail formation by interacting with perinuclear microtubules during spermatid reshaping.In addition to providing evidence for the role of KIF17 in fish spermatid reshaping,this study provides important data for studies of reproductive biology in L.polyactis.展开更多
The small yellow croaker(Larimichthys polyactis)belongs to the family Sciaenidae,which is an offshore warm fish species and widely distributed in the western Pacific.In this study,the variation of genetic diversity an...The small yellow croaker(Larimichthys polyactis)belongs to the family Sciaenidae,which is an offshore warm fish species and widely distributed in the western Pacific.In this study,the variation of genetic diversity and genetic differentiation among L.polyactis populations was analyzed by mitochondrial DNA control region.A total of 110 polymorphic sites were checked,which defined 134 haplotypes.High level of haplotype diversity(h=0.993±0.002)was detected in the examined range.Population genetic structure analyse(analysis of molecular variance,Fst)showed there were high gene flow among L.polyactis populations.The result showed that there were relatively high genetic diversity and low genetic differentiation among the Yellow Sea and the East China Sea populations,which can be attributed to diverse habitats,wide distribution range and high mutation rate of control region.Using phylogenetic methods,coalescent analyses(neutrality tests,mismatch distribution analysis,Bayesian skyline analyses)and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidence,we inferred that the genetic make-up of extant populations of L.polyactis was shaped by Pleistocene environmental impacts on the historical demography of this species.Besides,relatively constant genetic diversity and larger effective population size were detected in recent L.polyactis population.The result showed that the fishing policy certainly,such as the summer closed fishing,played a role in protecting resources of L.polyactis.This study can offer a wealth of biological novelties which indicates genetic structure of L.polyactis population and provides the foundation for resources protection and policy setting.展开更多
We used data from bottom trawl surveys to study the factors influencing the abundance of small yellow croaker, Larimichthys polyactis, in the southern Yellow Sea （SYS） and the East China Sea （ECS）. The resource de...We used data from bottom trawl surveys to study the factors influencing the abundance of small yellow croaker, Larimichthys polyactis, in the southern Yellow Sea （SYS） and the East China Sea （ECS）. The resource density index （RD1） was generally higher in summer and autumn than in spring and winter. RDIs were also significantly greater in the SYS than in the ECS in summer and autumn. The bottom water salinity and depth of spatial distribution of small yellow croaker was similar between the two areas in summer, but different in other seasons. Regression analysis suggested that environmental factors such as bottom water temperature, salinity, and depth influenced the RDIs in summer in these areas. Growth condition factor （GCF） in the two areas varied monthly and the croaker in the SYS grew more slowly than those in the ECS. This was likely due to the low bottom temperature of the Yellow Sea Cold Water Mass in summer and autumn or to higher human fishing pressure in the ECS. To ensure sustainable utilization of the croaker stocks in these regions, we recommend reducing the fishing intensity, increasing the cod-end mesh size, and improving the protection of juveniles.展开更多
T his study compared and evaluated the efficiency of two otolith shape descriptors(i.e., the elliptic Fourier transform(EFT) and discrete wavelet transform(DWT)) and morphometrics for stock discrimination. To accompli...T his study compared and evaluated the efficiency of two otolith shape descriptors(i.e., the elliptic Fourier transform(EFT) and discrete wavelet transform(DWT)) and morphometrics for stock discrimination. To accomplish this, sample fish from three stocks of yellow croaker L arimichthys polyactis along the Chinese coast(LDB stock from the Liaodong Bay of the Bohai Sea, JZB stock from the Jiaozhou Bay of the Yellow Sea and CJE stock from the Changjiang River estuary of the East China Sea) were used for otolith morphology analyses. The results showed that morphometrics produced an overall classification success rate of 70.8% in contrast with success rates of 80.0% or 82.0% obtained using EFT or DWT, respectively. This suggests that the two shape descriptors comparably discriminated among the stocks and performed more efficiently than morphometrics. During data adjustment and acquisition, some size variables were excluded from the subsequent discriminant analysis for stock discrimination because they were statistically "inef fective," which could reduce the efficiency of morphometrics and lead to relatively low overall classification success. Both EFT and DWT retain the contour coefficients and thus provide a detailed description of otolith shape, which could improve discriminatory efficiency compared with morphometrics.展开更多
基金the NSFC-Zhejiang Joint Fund for the Integration of Industrialization and Informatization(No.U1809212)the Scientific and Technical Project of Zhejiang Province(Nos.2021C02055,2017C02013)+2 种基金the National Natural Science Foundation of China(No.31272642)Healthy Aquaculture,the K.C.Wong Magna Fund in Ningbo Universitythe Collaborative Innovation Center for Zhejiang Marine High-Efficiency。
文摘The small yellow croaker Larimichthys polyactis is an economically important marine fish in Northeast Asia.Currently,its natural resources are threatened by overfishing and environmental pollution.Therefore,research on the reproductive system of the fish is crucial.Here,we studied the testis development and ultrastructural features of spermatogenesis in cultured L.polyactis using anatomical,histological,and ultrastructural techniques.A pair of testes,consisting of a central sperm duct and radial seminiferous lobules,were observed.The reproduction cycle of testes can be divided into stages I–VI.March to May was confirmed as the breeding season for male L.polyactis,while April is the ideal period for artificial breeding.The male L.polyactis can attain sexual maturity within 1 year.The spermatogenesis of L.polyactis comprised spermatogonium,spermatocyte,spermatid,and mature spermatozoon.The morphology of spermatogenic cells changed obviously during spermiogenesis,including nuclear shaping,midpiece and flagellum formation.The mature sperms consist of an ellipsoidal head,a short midpiece,and a long flagellum.The anterior of the head with a kidney-shaped nucleus can be distinguished.The midpiece is located posterior to the head and includes four to six spherical mitochondria.The flagellum has irregular lateral fins.The testis of L.polyactis is an unrestricted lobular type,with cystic spermatogenesis,type II spermiogenesis,and type II spermatozoa.These features are highly similar to those of other Sciaenid species.Our findings provide useful insights into the mechanism underlying testis development and spermatogenesis of L.polyactis,which can facilitate the artificial breeding of this species.
基金supported by the Fundamental Research Funds for Central Universities (Grant No. 201022001)
文摘Length frequency data of small yellow croaker （Larimichthys polyactis） were acquired from the survey vessel in May, July, September and December, 2011 in Haizhou Bay of China. In this study, 921 fish individuals were analyzed for the estimation of growth and mortality parameters. Between length and weight, the power coefficient b was 2.7321, 2.9703, 3.0418 and 2.7252 for the 4 surveying months, respectively. The estimated von Bertalanffy growth function parameters were 230mm （L∞） and 0.26yr-1 （K） as were calculated with ELEFAN method equipped in FiSAT computer package. With length-converted catch curve analysis, the total mortality rate （Z） and its 95% confidence interval were 2.16 （1.69-2.64） yr-1, 0.59 （0.15-1.04） yr-1, 1.16 （0.80-1.52） yrl and 0.96 （0.70-1.23） yr1 for the 4 surveying months, respectively, with the pooled data the value was 1.15 （0.81-1.48） yr1. The natural mor- tality rate （M） was 0.516 yr 1 as was calculated with Pauly＇s equation （the annual average sea water temperature was 11 ℃）. Therefore, fish mortality rate was 0.634 yrz. The yield-per-recruit analysis indicated that when tc was 1, Fmax, was 0.7 and F01 was 0.55. Cur- rently, the age at first capture is about 1 year and Fcurrent was 0.634. Therefore, Fcurrent was larger than F0.1 and less than Fmax. This indicates that current fish mortality is at a dangerously high level. With Gulland method, the biological reference point for fishery （Fopt） was estimated as 0.516 yr1, lower than current fish mortality. Accordingly, reducing catch in the region was strongly recom- mended.
基金The National Basic Research Program(973 Program)of China under contract No.2015CB453303the Aoshan Scientific and Technical Innovation Program under contract No.2015ASKJ02-05the Taishan Scholar Project Special Fund
文摘Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k（growth coefficient） and t_0（zero-length age） gradually increased from 0.26 and –0.58 year in 1960 to 0.56 and –0.25 year in 2008, respectively. Although, L∞（body length）sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t_r（inflexion age） decreased from 3.78 year in1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as： fishing vessel power〉feeding grade〉sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.
基金Supported by the National Natural Science Foundation of China(No.31802297)。
文摘The small yellow croaker Larimichthys polyactis is a benthic marine fish species of high ecological and commercial importance and is widely distributed in the northwestern Pacifi c Ocean,especially in the Chinese coastal waters of the Bohai,Yellow,and East China Seas.As a highly migratory species,the whole life migration of L.polyactis has been intensively studied.However,knowledge about its early life migration is scarce,and population divisions are inconsistent,limiting the ability of fishery scientists and administrators to evaluate the design and potential benefits of thorough conservation and resource-management strategies.In the present study,otolith Sr/Ca was analyzed to investigate the early migratory patterns and discriminate the populations of L.polyactis in the Yellow Sea,including two spawning groups and one overwintering group.The variation in Sr/Ca ratios of ontogenetic growth zones,including the nucleus(N),larval(L),metamorphosis(M),juvenile(J),and edge(E)zones,was measured by electron probe microanalysis.The variation in Sr/Ca ratios in early developmental growth zones was generally characterized by an evident downward trend from the N to J zone,which suggests that the early migratory pattern of L.polyactis might be from inshore to nearshore water.Canonical discriminant analysis,based on the otolith Sr/Ca ratios of the N,L,M,and J zones,allowed the successful discrimination of the two populations,namely,the northern and southern Yellow Sea groups,whose diff erences were mainly reflected in the L and J zones.Compared with previous studies,the traditional geographic boundaries(34°N)separating these two populations might be moving northward.The application of otolith Sr/Ca ratios based on ontogenetic stage could improve our understanding of the migration and population discrimination of L.polyactis from the Yellow Sea.
基金Supported by the NSFC-Zhejiang Joint Fund for the Integration of Industrialization and Informatization(No.U1809212)the Scientific and Technical Project of Zhejiang Province(Nos.2021C02055,2017C02013)+1 种基金the National Natural Science Foundation of China(No.31272642)the Healthy Aquaculture,the K.C.Wong Magna Fund in Ningbo University,and the Collaborative Innovation Center for Zhejiang Marine High-efficiency。
文摘The homodimeric kinesin-2 protein KIF17 functions in intracellular transport and spermiogenesis in mammals.However,its role in fish spermiogenesis has not been reported.Here,we aimed to clone full-length kif17 cDNA and determine the molecular characteristics and expression patterns of KIF17 in Larimichthys polyactis spermiogenesis.The full-length cDNA of L.polyactis kif17(Lp-kif17)was sequenced and found to contain a 332-bp 5′untranslated region,480-bp 3′untranslated region,and 2433-bp open reading frame encoding 810 amino acids.Bioinformatics analyses showed that L.polyactis KIF17(Lp-KIF17)shared high sequence similarity with homologs in other animals and possessed an N-terminal motor domain with microtubule-binding sites and adenosine triphosphate(ATP)hydrolysis sites,a stalk domain containing two coiled-coil regions,and a C-terminal tail domain.The Lp-kif17 mRNA was widely expressed in various tissues,with the highest level in the brain,followed by that in the testis.Fluorescence in situ hybridization(FISH)analysis revealed that Lp-kif17 was continuously expressed in spermiogenesis,showing that it had potential functions in this process.Using immunofluorescence(IF)analysis,we found that Lp-KIF17 colocalized with tubulin and was transferred from the perinuclear cytoplasm to the side of spermatid where the tail forms during spermiogenesis.These findings suggested that KIF17 is involved in L.polyactis spermiogenesis.In particular,it may participate in nuclear shaping and tail formation by interacting with perinuclear microtubules during spermatid reshaping.In addition to providing evidence for the role of KIF17 in fish spermatid reshaping,this study provides important data for studies of reproductive biology in L.polyactis.
基金The National Key Research and Development Program of China under contract No.2018YFD0900905。
文摘The small yellow croaker(Larimichthys polyactis)belongs to the family Sciaenidae,which is an offshore warm fish species and widely distributed in the western Pacific.In this study,the variation of genetic diversity and genetic differentiation among L.polyactis populations was analyzed by mitochondrial DNA control region.A total of 110 polymorphic sites were checked,which defined 134 haplotypes.High level of haplotype diversity(h=0.993±0.002)was detected in the examined range.Population genetic structure analyse(analysis of molecular variance,Fst)showed there were high gene flow among L.polyactis populations.The result showed that there were relatively high genetic diversity and low genetic differentiation among the Yellow Sea and the East China Sea populations,which can be attributed to diverse habitats,wide distribution range and high mutation rate of control region.Using phylogenetic methods,coalescent analyses(neutrality tests,mismatch distribution analysis,Bayesian skyline analyses)and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidence,we inferred that the genetic make-up of extant populations of L.polyactis was shaped by Pleistocene environmental impacts on the historical demography of this species.Besides,relatively constant genetic diversity and larger effective population size were detected in recent L.polyactis population.The result showed that the fishing policy certainly,such as the summer closed fishing,played a role in protecting resources of L.polyactis.This study can offer a wealth of biological novelties which indicates genetic structure of L.polyactis population and provides the foundation for resources protection and policy setting.
基金Supported by the National Natural Science Foundation of China for Creative Research Groups (No. 40821004)the National Key Technology Research and Development Program (No. 2007BAD43B01)the Open Fund of Key Laboratory of Marine Ecology and Environmental Science, Institute of Oceanology, Chinese Academy of Sciences (No. KLMEES201001)
文摘We used data from bottom trawl surveys to study the factors influencing the abundance of small yellow croaker, Larimichthys polyactis, in the southern Yellow Sea （SYS） and the East China Sea （ECS）. The resource density index （RD1） was generally higher in summer and autumn than in spring and winter. RDIs were also significantly greater in the SYS than in the ECS in summer and autumn. The bottom water salinity and depth of spatial distribution of small yellow croaker was similar between the two areas in summer, but different in other seasons. Regression analysis suggested that environmental factors such as bottom water temperature, salinity, and depth influenced the RDIs in summer in these areas. Growth condition factor （GCF） in the two areas varied monthly and the croaker in the SYS grew more slowly than those in the ECS. This was likely due to the low bottom temperature of the Yellow Sea Cold Water Mass in summer and autumn or to higher human fishing pressure in the ECS. To ensure sustainable utilization of the croaker stocks in these regions, we recommend reducing the fishing intensity, increasing the cod-end mesh size, and improving the protection of juveniles.
基金Supported by the National Key Basic Research Program of China(973 Program)(No.2015CB453302)the NSFC-Shandong Joint Fund for Marine Science Research Centre(No.U1606404)the Aoshan Science and Technology Innovation Project(No.2015ASKJ02-04)
文摘T his study compared and evaluated the efficiency of two otolith shape descriptors(i.e., the elliptic Fourier transform(EFT) and discrete wavelet transform(DWT)) and morphometrics for stock discrimination. To accomplish this, sample fish from three stocks of yellow croaker L arimichthys polyactis along the Chinese coast(LDB stock from the Liaodong Bay of the Bohai Sea, JZB stock from the Jiaozhou Bay of the Yellow Sea and CJE stock from the Changjiang River estuary of the East China Sea) were used for otolith morphology analyses. The results showed that morphometrics produced an overall classification success rate of 70.8% in contrast with success rates of 80.0% or 82.0% obtained using EFT or DWT, respectively. This suggests that the two shape descriptors comparably discriminated among the stocks and performed more efficiently than morphometrics. During data adjustment and acquisition, some size variables were excluded from the subsequent discriminant analysis for stock discrimination because they were statistically "inef fective," which could reduce the efficiency of morphometrics and lead to relatively low overall classification success. Both EFT and DWT retain the contour coefficients and thus provide a detailed description of otolith shape, which could improve discriminatory efficiency compared with morphometrics.
