The environmental analysis and site selection of mussel and large yellow croaker aquaculture areas based on high resolution remote sensing

Mussel aquaculture and large yellow croaker aquaculture areas and their environmental characteristics in Zhoushan were analyzed using satellite data and in-situ surveys.A new two-step remote sensing method was proposed and applied to determine the basic environmental characteristics of the best mussel and large yellow croaker aquaculture areas.This methodology includes the first step of extraction of the location distribution and the second step of the extraction of internal environmental factors.The fishery ranching index(FRI1,FRI2)was established to extract the mussel and the large yellow croaker aquaculture area in Zhoushan,using Gaofen-1(GF-1)and Gaofen-6(GF-6)satellite data with a special resolution of 2 m.In the second step,the environmental factors such as sea surface temperature(SST),chlorophyll a(Chl-a)concentration,current and tide,suspended sediment concentration(SSC)in mussel aquaculture area and large yellow croaker aquaculture area were extracted and analyzed in detail.The results show the following three points.(1)For the extraction of the mussel aquaculture area,FRI1 and FRI2 are complementary,and the combination of FRI1 and FRI2 is suitable to extract the mussel aquaculture area.As for the large yellow croaker aquaculture area extraction,FRI2 is suitable.(2)Mussel aquaculture and the large yellow croaker aquaculture area in Zhoushan are mainly located on the side near the islands that are away from the eastern open waters.The water environment factor template suitable for mussel and large yellow croaker aquaculture was determined.(3)This two-step remote sensing method can be used for the preliminary screening of potential site selection for the mussels and large yellow croaker aquaculture area in the future.the fishery ranching index(FRI1,FRI2)in this paper can be applied to extract the mussel and large yellow croaker aquaculture areas in coastal waters around the world.

Spatial-temporal dynamics of bacterioplankton communities in the breeding area of large yellow croaker Larimichthys crocea in Sansha Bay,China

As an important spawning ground for large yellow croaker Larimichthys crocea,Sansha Bay,South China Sea has been a research hotspot.However,studies on the influence of the bacterioplankton community and assessments of its seasonal succession of bacterioplankton in different sea areas in Sansha Bay are still limited.To address the issue,we use 16S rRNA gene amplicon sequencing and functional prediction to investigate the spatial-temporal dynamics of the bacterioplankton community in three distinct areas,i.e.,Breeding Area(BA),Yantian Harbor(YH),and Bay Margin(BM)of Sansha Bay.Results show that the structure of the bacterioplankton community in Sansha Bay had a significant seasonal succession.Moreover,the representative zero-radius Operation Taxon Units in different seasons were significantly different among the three selected sea areas.Specifically,during the breeding season,bacterioplankton communities in BA were characterized by compound-degrading bacteria,such as Rhodococcus and Owenweeksia,while in YH and BM,animal parasites or symbionts such as Vibrio and Arcobacter were dominant.Furthermore,the redundancy analysis and Spearman correlation analysis further explained that water temperature,dissolved oxygen,and ammonia nitrogen were the main environmental factors responsible for the difference.In addition,the bioindicator functions screened by Functional Annotation of Prokaryotic Taxa and random forest machine learning mainly relied on compound degradation,nitrite oxidation,and photoheterotrophy.The compound-degradationcorresponded bacterioplankton genera such as Rhodococcus had relatively higher abundance in BM,while Nitrospina corresponding to nitrite oxidation tended to be abundant in YH and BA.Based on the spatial and temporal variation in the composition and function of bacterioplankton,our findings provide a basis for understanding the theory of bacterioplankton community structure in the inner-bay habitat of the large yellow croaker in Sansha Bay.

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthys crocea,an economically important mariculture fish in China.Apoptosis is a consequence of hypoxia on fish.However,the effects of hypoxia stress on apoptosis in L.crocea remain largely unknown.We investigated the effect of environmental hypoxia on apoptosis in L.crocea.Results show that hypoxia induced apoptosis in L.crocea both in vivo and in vitro.The mitochondrial membrane potential was significantly reduced in large yellow croaker fry(LYCF)cells.The expression levels of Bcell lymphoma/leukemia-2(Bcl-2)m RNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress,respectively,whereas the expression level of Bcl-2 associated X(Bax)mRNA,Casp3 mRNA,and activity of caspase-3/7/9 were significantly increased,indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L.crocea.The expression level of the apoptosis-inducing factor(AIF)protein was significantly increased in the liver and LYCF cells.The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L.crocea,demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis.In addition,the activity of caspase-8 was significantly increased,indicating that hypoxia stress induced extrinsic apoptosis in L.crocea.Therefore,hypoxia induced apoptosis in L.crocea through both the intrinsic and extrinsic pathways.The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.

Comparative study on the organoleptic quality of wild and farmed large yellow croaker Larimichthys crocea

To fill the blank in systematic study on the organoleptic quality of large yellow croaker Larimichthys crocea,we analyzed the organoleptic quality of the fish meat of wild,trash-fish-fed,and compound-feed-fed large yellow croaker.Six fish(weight:500 g)per group were sampled in the same period,and 89 indices of fish organoleptic quality were measured and analyzed.Results reveal significant differences in the body condition factor,skin/muscle color,flesh texture,odor,and taste aspects between wild and farmed fish.Compared with the wild fish,farmed fish showed fatter body shape,whiter skin or muscle color,tender muscle,higher level of fishy odor or volatile intensity,but lower delicious taste.In addition,compared with trash-fish feeding,compound-feed feeding could improve the body shape,skin color,flesh texture,and fish taste of large yellow croaker,but it also increased the fishy odor.In principle component analysis and cluster analysis,the present study preliminarily established the systematic evaluation with multiple indices to the quality of large yellow croaker.It shall be helpful for the evaluation or improvement of the quality of farmed large yellow croaker.

Molecular characterization of an IL-1β gene from the large yellow croaker（Larimichthys crocea） and its effect on fish defense against Vibrio alginolyticus infection

Interleukin 1β（IL-1β）, the first interleukin to be characterized, plays a key role in regulating the immune response. In this study, we determined the c DNA and genomic DNA sequences of the IL-1β gene from the large yellow croaker, Larimichthys crocea. Phylogenetic analysis indicated that the IL-1β（Lc IL-1β） gene was most closely related to that of European seabass（Dicentrarchus labrax）, sharing 67.8% amino acid identity. In healthy large yellow croaker, Lc IL-1β transcription was detected in all tested tissues, with the highest level found in the head kidney. Upon Vibrio alginolyticus infection, Lc IL-1β transcription in all tested tissues was significantly upregulated. Intraperitoneal injection of recombinant Lc IL-1β（r Lc IL-1β） improved the survival rate and reduced the tissue bacterial load after V. alginolyticus infection. In addition, r Lc IL-1β induced monocytes/macrophages（MO/MΦ） chemotaxis and increased phagocytosis and bactericidal activity in vitro. These results suggest that Lc IL-1β plays an important role in the large yellow croaker immune response against V. alginolyticus.

Migration and population structure characteristics of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea

Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics（especially body length and sex ratio） in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0＋ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios（female to male） were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that ＂the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds＂ but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure.

Replacement of Dietary Fish Oil with Vegetable Oils Improves the Growth and Flesh Quality of Large Yellow Croaker(Larmichthys crocea)

We investigated the effect of the replacement of dietary fish oil with vegetable oils on the growth and flesh quality of large yellow croaker(Larmichthys crocea). The basal diet(FO) was formulated to contain 66.5% fish meal and 6.4% menhaden fish oil; whereas the other 3 experimental diets were formulated by replacing the fish oil with 50% soybean oil(SO50), 100% soybean oil(SO100) and 100% palm oil(PO100), respectively. The 4 diets were randomly assigned to 4 floating sea cages(3.0 m × 3.0 m × 3.0 m), and each was stocked with 250 fish individuals with an initial average weight of 245.29 g ± 7.45 g. The fish were fed to apparent satiation twice a day at 5:00 and 17:00, respectively, for 12 weeks. Experimental analysis showed that the specific growth rate of fish fed SO50 or PO100 were significantly higher than that of fish fed FO or SO100(P<0.05), and crude lipid contents of ventral muscle and viscera were significantly lower in fish fed FO than in those fed the other 3 diets(P<0.05). No significant differences in condition factor, viscerosomatic index, hepatosomatic index, gutted yield and colorimetric values of fish among the dietary treatments were observed(P>0.05). Compared to FO diet, SO50, SO100 and PO100 diets led to substantial decreases in the liquid loss and water loss from fresh fillets(1 d, 4℃)(P<0.05). Similarly, thiobarbituric acid reactive substance(TBARS) values of fillets under different storage conditions(1 d, 4℃; 7 d, 4℃; 4 weeks,-20℃; 8 weeks,-20℃) decreased significantly after partial or complete replacement of fish oil with vegetable oils. These findings indicated that the growth performance and selected flesh quality properties(liquid holding capacity and TBARS value) of large yellow croaker were substantially improved by replacing dietary fish oil with vegetable oils.

Cloning and mRNA expression of macrophage migration inhibitory factor (MIF) gene of large yellow croaker (P seudosciaena crocea)

Mammalian macrophage migration inhibitory factor （MIF） plays an important role as an indispensable mediator in the pathogenesis of inflammatory disease like septicemia, but little is known about the role of MIF homologue in fish septicemia. The authors have cloned the MIF homologue in large yellow croaker Pseudosciaena crocea （LycMIF） using RACE approach. The full-length cDNA of LycMIF was 634 bases and contained an ORF of 345 bases encoding a protein of 115 amino acid residues. As demonstrated by RT-PCR and QRT-PCR assay, MIF mRNAs were constitutively expressed in 11 selected tissues and were abundant in brain and liver. Moreover, the LycMIF transcripts in the liver and head kidney were responsive to bacteria infection and could be significantly up-regulated. Our results provide the first direct evidence that fish MIF was implicated in pathogenesis of fish vibrosis and play an important role in response to bacteria infection.

Stable isotopic composition of otoliths in identification of stock structure of small yellow croaker(Larimichthys polyactis) in China

Oxygen and carbon isotope ratios（δ^（18）O and δ^（13）C） in otoliths were used to identify the stock structure of small yellow croaker,Larimichthys polyactis.Otoliths were collected from fish at five locations across the Yellow Sea and the Bohai Sea representing most of their distributional range and fisheries areas.The significant differences in the isotopic signatures showed that the five locations could be chemically distinguished and clearly separated,indicating stock subdivision.Correlation of δ^（18）O and δ^（13）C values suggested that population of L.polyactis could be divided into the Bohai Sea group,the southern Yellow Sea group and the central Yellow Sea group.Discriminant analysis of δ^（18）O and δ^（13）C values demonstrated a high significant difference with 85.7% classification accuracy.The spatial separation of L.polyactis indicated a complex stock structure across the Yellow Sea and the Bohai Sea.These results indicate that optimal fisheries management may require a comprehensive consideration on the current spatial arrangements.This study has provided further evidence that measurement of the stable isotopes ratios in otolith can be a valuable tool in the delineation of fishery management units.

Diagnosis of iridovirus in large yellow croaker by PCR

A rapid and sensitive PCR-based method for the detection of the large yellow croaker iridovirus (LYCIV) is described, which involves the amplification of a 295 bp fragment of the LYCIV ATPase gene from DNA isolated from naturally infected fish spleen. Sequencing of LYCIV ATPase gene fragment showed it shared 100% nucleotide sequence homology with the corresponding region of the ATPase gene of red sea bream iridovirus (RSIV) and sea bass iridovirus (SBIV), suggesting that LYCIV was homologous with RSIV and SBIV at least in part of the gemone. The specificity and sensitivity of the PCR procedure were tested on the iridovirus-infected fishes, the expected fragment was detected from spleen DNA samples of infected fishes, whereas no fragments were amplified from healthy fish spleen DNA, white spot syndrome baculoviruses (WSBV) DNA and pseudorabies virus (PRV) DNA. Detection limit of this method was 10(-7) ng positive plasmid DNA containing target sequence, equal to about 100 virions. In the infected experiment, first positive detection (1/4) appeared at Day 3 post-infection, all fish (4/4) tested positive at Day 7, however obvious symptoms were observed at Day 8, so LYCIV infection could be detected prior to the appearance of obvious symptoms. These results indicate that this PCR method could be used for early, rapid and specific detection of LYCIV infection.

Analyses of egg size,otolith shape,and growth revealed two components of small yellow croaker in Haizhou Bay spawning stock

The geographical variations in life history characteristics of small yellow croaker Larimichthys polyactis, caused by experienced different environmental conditions, have been observed in China seas. Previous studies based on spatial distribution, migration route, and body morphometrics suggested a complex stock structure. In this study, to clarify the source of a spawning stock, we investigated the reproduction strategy and inter-structure of the Haizhou Bay (HZB) spawning stock in the middle Yellow Sea from both egg survey and adult otolith increment analysis. Egg and adult samples were collected from three surveys during spawning season in 2013. Distinct spatial and temporal variations were detected in egg distribution and size, and otolith shape analysis of adult fishes revealed two morphotypes with different increment growth using random forest cluster. The results indicate the existence of two components within the same spawning stock in HZB from different wintering grounds, and accordingly special protection should be required for this stock given the significance to maintain connectivity between adjacent subpopulations.

Trophic ecology of small yellow croaker (Larimichthys polyactis Bleeker): stable carbon and nitrogen isotope evidence

The trophic ecology of the small yellow croaker （Larimichthys polyactis） was studied using stable isotope analyses. Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes. Stable carbon isotope ratios （~3C） ranged from -20.67 to -15.43, while stable nitrogen isotope ratios （~SN） ranged 9.18-12.23. The relationship between fi^3C and ~SN suggested high resource partitioning in the sampling area. Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes （such as ocean current, wind and tide） and different carbon sources. Furthermore, the stable isotope ratios may also explain the ontogenetic variability in diet and feeding, because δ13C and δ15N varied significantly with increasing body size. The findings are consistent with other studies on diet analyses in small yellow croaker. It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.

Establishment of a Spleen Cell Line from Large Yellow Croaker Pseudosciaena crocea and its Primitive Application in Foreign Gene Transfection

A large yellow croaker,Pseudosciaena crocea,spleen(LYCS)cell line was established and the feasibility of using it for foreign gene transfection was evaluaed in this study.Primary culture of LYCS cells was initiated from spleen tissue pieces,which were cultured at 25℃ in Dulbecco's modiced Eagle medium/F12 medium(DMEM/F12,1:1)(pH7.2),supplemented with 20% fetal bovine serum,carboxymethyl chitosan,chondroitin sulfate,basic fibroblast growth factor(bFGF)and insulin-like growth factor-I(IGF-I).The cultured LYCS cells,in fibroblast shape,proliferated to 100% confluency 20 days later.Chromosome analyses indicated that the LYCS cells exhibited chromosomal aneuploidy with a modal chromosome number of 48 which displayed the normal diploid karyotype of P.crocea(6m+6sm+36t,NF=60).A LYCS cell line,with a population doubling time of 48.7 h at passage 60,has been established and subcultured to passage 70.Transgenic feasibility test demonstrated that positive green fluorescence protein(GFP)expression was observed in LYCS cells after pcDNA3.1-GFP plasmid transfection.In conclusion,a continuous foreign gene trans-fection feasible LYCS cell line has been established successfully.The cell line might serve as a valuable tool for studies of transgenic breeding and has potential applications for different kinds of cytotechnological studies.

A Comparison Study on Flesh Quality of Large Yellow Croaker (Larimichthys croceus) Cultured with Three Different Modes

To compare the flesh quality of large yellow croaker cultured with three different modes, enclosure culture(EC), cage culture with feeding trash fish(CCF) and cage culture with feeding formula diet(CCD), thirty six fish individuals of EC(484.6 ± 79.8 g), CCF(432.7 ± 87.9 g) and CCD(416.9 ± 49.5 g) were sampled to measure body color, flesh water holding capacity, flesh proximate composition, amino acids and fatty acids composition, and collagen and inosinic acid contents. The analysis showed that there was no significant difference in the yellowness of skin and the contents of crude protein and inosinic acid between CCD and EC(P > 0.05), and the two modes showed higher values than CCF(P < 0.05). Most of the amino acids(AA) in flesh were higher in EC than in CCF(P < 0.05), but CCD showed no difference in AA composition from the other two modes(P > 0.05). EC and CCD had higher contents of collagen, free AA and lower drip loss than CC(P < 0.05). In polyunsaturated fatty acids, EC showed significantly higher levels of C20:5 n-3 and C22:6 n-3 than CCF and CCD(P < 0.05), but CCD had significantly higher C18:2 n-6 than CCF and EC(P < 0.05). In conclusion, the flesh quality of CCD fish is similar to EC fish, and these two modes have better flesh quality than CCF.

Effect of Dietary Olaquindox on the Growth of Large Yellow Croaker(Pseudosciaena crocea R.) and the Distribution of Its Residues in Fish Tissues

Olaquindox(OLA), one of quinoxaline-N, N-dioxides, has been put under ban. However it was used as a medicinal feed additive early; it promotes the growth of livestock and prevents them from dysentery and bacterial enteritis. In this study, we evaluated the effect of dietary OLA on the growth of large yellow croaker(Pseudosciaena crocea R.) and the histological distribution of OLA and its metabolite 3-methyl-quinoxaline-2-carboxylic acid(MQCA) in fish tissues. Four diets containing 0(control), 42.5, 89.5 and 277.2 mg kg-1 OLA, respectively, were formulated and tested, 3 cages(1.0 m × 1.0 m × 1.5 m) each diet and 100 juveniles(9.75 ± 0.35 g) each cage. The fish were fed to satiation twice a day at 05:00 am and 17:00 pm for 8 weeks. The survival rate of fish fed the diet containing 42.5 and 89.5 mg kg-1 OLA was significantly higher than that of fish fed the diet containing 0 and 277.2 mg kg-1 OLA(P < 0.05), while the weight gain rate of fish fed the diet containing 42.5 and 89.5 mg kg-1 OLA was significantly higher than that of fish fed the diet without OLA(control)(P<0.05), but similar to that of fish fed the diet with 277.2 mg kg-1 OLA. Fish fed the diet with 277.2 mg kg-1 OLA had the highest content of OLA and MQCA in liver(3.44 and 0.39 mg kg-1, respectively), skin(0.46 and 0.09 mg kg-1, respectively) and muscle(0.24 and 0.06 mg kg-1, respectively). In average, fish fed the diet containing OLA had the highest content of OLA and MQCA in liver which was followed by skin and muscle(P < 0.05), whereas OLA and MQCA were not detectable in control. Our findings demonstrated that OLA and MQCA accumulated in large yellow croaker when it was fed with the diet containing OLA, thus imposing a potential safety risk to human health.

Genetic Variation Among White Croaker Populations

To investigate the genetic structures and differentiation of different wild populations of white croaker （Pennahia argentara）, horizontal starch gel electrophoresis was performed on 133 individuals collected from five different locations in China and Japan. The eleven enzyme systems revealed 15 loci, of which eleven were polymorphic. The percentage ofpolymorphic loci of white croaker populations varied from 6.67% to 53.3.3%; the mean observed and expected heterozygosity ranged from 0.0033 to 0.0133 and 0.0032 to 0.0191, respectively. The expected heterozygosity revealed a low genetic variability for white croaker in comparison with other marine fishes. The genetic distances between populations ranged from 0.00005 to 0.00026. A weak differentiation was observed within each clade and between clades; and no significant differences in gene frequencies among populations were observed in white croaker. Among the five populations, three Chinese populations showed more genetic diversity than that in Japanese populations.

Intragenic and intergenic sequences regulating the expression of the 5'-to-5' linked adult α-and β-globin genes from large yellow croaker Pseudosciaena crocea

One adult α-globin gene and one β-globin gene have been cloned from the large yellow croaker Pseudosciaena crocea. Linkage analysis indicated that the α- and β-globin genes were oriented head-to-head relative to each other. To identify the regulatory elements present in the intergenic and intragenic regions of the globin complex, the intergenic region alone or together with the β-globin gene first intron was cloned into the luciferase-reporter vector pGL3-Basic respectively, and the chimeric constructs were tran- siently transfected into Vero cells and primary fish erythrocytes. The intergenic region cannot support the high-level expression of luciferase. However, the promoter activity of the intergenic region was strongly stimulated by the positive regulatory elements （PRE） located in the β-globin gene intron 1. Thus, it is proposed that the intergenic promoters and intragenic PRE were necessary for the effective expression of the linked α- and β-globin genes.

Thermal tolerance evaluation and related microsatellite marker screening and identification in the large yellow croaker Larimichthys crocea

Thermal tolerance to high temperature was evaluated in the large yellow croaker Larimichthys crocea. The survival thermal maximum for L. crocea was 33.0℃, the 50% critical thermal maximum （50% CTMax） was 35.5℃, and the critical thermal maximum （CTMax） was 36.0℃. Three microsatellite markers （LYC0148, LYC0200 and LYC0435）, associated with thermal tolerance were screened and identified using a Bulked Segregation Analysis （BSA） method. These markers have six amplified fragments in which four are related to thermal tolerance. These fragments were cloned and sequenced, and the results showed the core motif were all ＂AC＂ repeats. For LYC0148 and LYC0200, the lengths of fragments are 18l bp and 197 bp, respectively. For LYC0435, which has two fragments, the fragment lengths are 112 bp and 100 bp. The results provide useful molecular markers for thermal-tolerance breeding of large yellow croaker in the near future.

Population dynamics modelling with spatial heterogeneity for yellow croaker(Larimichthys polyactis)along the coast of China

As one of the top four commercially important species in China,yellow croaker(Larimichthys polyactis)with two geographic subpopulations,has undergone profound changes during the last several decades.It is widely comprehended that understanding its population dynamics is critically important for sustainable management of this valuable fishery in China.The only two existing population dynamics models assessed the population of yellow croaker using short time-series data,without considering geographical variations.In this study,Bayesian models with and without hierarchical subpopulation structure were developed to explore the spatial heterogeneity of the population dynamics of yellow croaker from 1968 to 2015.Alternative hypotheses were constructed to test potential temporal patterns in yellow croaker’s population dynamics.Substantial variations in population dynamics characteristics among space and time were found through this study.The population growth rate was revealed to increase since the late 1980s,and the catchability increased more than twice from 1981 to 2015.The East China Sea’s subpopulation witnesses faster growth,but suffers from higher fishing pressure than that in the Bohai Sea and Yellow Sea.The global population and two subpopulations all have high risks of overfishing and being overfished according to the MSY-based reference points in recent years.More conservative management strategies with subpopulation considerations are imperative for the fishery management of yellow croaker in China.The methodology developed in this study could also be applied to the stock assessment and fishery management of other species,especially for those species with large spatial heterogeneity data.

Biological responses of small yellow croaker(Larimichthys polyactis) to multiple stressors: a case study in the Yellow Sea, China

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.