Abstract:The most established basis for estimating an Acceptable Biological Catch was by a conventional stock assessment, which typically used -shery time series data to estimate current stock size and productivity. However, majority of -sh stocks lack adequate description of catches, surveys, efforts, or information about life history characteristics to support a conventional stock assessment. Recent requirements to set scienti-cally-based catch limits, along with stock depletion and growing consumer demand for sustainably managed -sheries, have created an emerging number of methods for estimating over-shing thresholds and setting catch limits for stocks with limited data. This research aimed to evaluate methods that determine an ABC as a basis for setting annual catch limits for small yellow croaker, . Using a management strategy evaluation approach, 54 established management procedures (MPs) for setting catch-limits in -sheries with three fishing effort trend scenarios were compared. Performance was evaluated with respect to overfishing, biomass, and yield. According to the trade-offs between the expected relative yield, the probability of over-shing (POF), and the probability of the biomass being below three different reference points in which the relative yield was not less than 50%, POF was less than 50% and the probability of was less than 20%. Our results indicated that there were six MPs that met the established management target under both the generic fleet and increased fleet scenario simulations, while fourteen MPs met management targets under the decreased fishing mortality scenario simulation. FMSYref50 was considered to be the best MP for the yellow croaker fishery within three fishing mortality scenarios. Under the FMSYref50 MP, POF varied with a median of between 5.46% and 6.7%, the probability of was between 15.66% and 22.73%, and the long-term relative yield varied from 52% to 100%. However, the ABC calculated under FMSYref50 was only 10800 tons, which would lead to a sharp decline in production compared with the current state of the fishery. The DynF MP was therefore suggested as the management strategy for the small yellow croaker fishery in consideration of the requirement of reducing numbers of fishing fleets. Under the decreased fishing mortality scenario simulation, the probability of overfishing was 37.84%, the probability of was 38.63%, the long-term relative yield was 84% under the DynF MP, and the ABC was 40300 tons. The sensitivity analysis showed that the ABC allowed by the DynF MP was robust to the uncertainty of production data and abundance index, however, the ABC was sensitive to high imprecision in natural mortality rate, FMSY_M, and current biomass and provided more yield on average given increased observations. This indicated that the accuracy of parameters should be emphatically improved in conducting stock assessments with the DynF MP.

Abstract:The 11 measurable morphological indicators and 18 framework morphological indicators of Leuciscus merzbacheri were studied by methods of principal component analysis, cluster analysis and discriminant analysis, in order to reveal their morphological information and laws which can guide the identification, resource conservation and fine variety breeding of . The results of principal component analysis showed that the contribution rates of three extracted principle components were 57.71%, 9.019%, 6.502% respectively and the cumulative contribution rate of them was 73.23%. The main proportional parameters of principle component 1 gathered in head and caudal peduncle. The parameter of head included six proportional parameters such as HL/BL, ML/BL, SL/BL, /BL6. And the parameter of caudal peduncle included five proportional parameters such as CL/BL、/BL and /BL. Cluster analysis revealed that the genetic relationship of is was closed, and both of them had the father genetic relationship with . A stepwise discriminant method selected eleven parameters which also gathered in head and caudal peduncle, in order to establish the characteristic discriminant function. The data of there kinds of fish were submitted into the characteristic discriminant function to validate. It showed that it is a little bit difficult to discriminate between is easy to distinguish between them. The individual discrimination accuracy (L. baicalensis are more than 80%, and the individual discrimination accuracy ( reached more than 95%. And the comprehensive discrimination rate of no cross-validated method was 91.2% and the one of cross-validated method was 89.4%. The comprehensive discrimination rate of no cross-validated method is high and very closed to the cross-validated method. It meant that the characteristic discriminant function is credible. Three species of in Xinjiang are divided into two branches. The morphological variation of them is mainly reflected on the part of head and caudal peduncle. And three species of in Xinjiang could be discriminated by multiple regression function.

Abstract:Hypoxia-inducible factor is a key factor in HIF signaling pathway and plays an significant role in Hypoxia response in animals. To determine the response of hypoxia-inducible factor (HIF-1) gene of Scapharca broughtonii under hypoxia stress and to reveal the unique hypoxia-adapting mechanism of Scapharca broughtonii. The cDNA sequence of HIF-1α (named ) by EST and RACE methods were obtained. The mRNA expression in the gene under hypoxia stress was also studied.Sequence analysis revealed that the cDNA was 2741 bp in length, including an open reading frame (ORF) of 2136 bp encoding a polypeptide of 711 amino acid residues with conserved HLH, PAS-A, PAS-B and PAC motif. The predicted molecular weight is 80.8 kDa and isoelectric point (pI) is 5.57. The analysis of structure and putative functional sites showed Chlamys farreri HIF-1 and the corresponding homologous molecule in mollusks clustered into one branch. The mRNA expression analysis of in tested tissues by quantitative real-time PCR (qRT-PCR) revealed that the mRNA of the the gene could be all detected in foot, gill, mantle, adductor muscle, haemocytes and hepatopancreas. The expression level of in haemocytes were more than that in other tissues. Under the hypoxic stress of 0.5 mg/L, 2.5 mg/L and 4.5 mg/L dissolved oxygen (DO) in seawater, SbHIF-1 in each tissue responded positively, and hemolymph and gill were more responsive than the other four tissues. n haemolymph, the expression of SbHIF-1 was significantly different from that of control group after 4 hours of DO stress ( reached the highest level, which was 519.43 times of that of control group. The response of each tissue to at different DO concentrations showed that the activation of SbHIF-1 was relatively high in 0.5 mg/L of the three treatment concentrations. This study clarified the structural characteristics, temporal and spatial expression characteristics of SbHIF-1 gene and its response to hypoxia stress, which enriched the research data of marine shellfish HIF gene.

Abstract:is a commercially important oyster species in East Asia as it is edible during the summer when the other oyster species are unavailable. Salinity is one of the important limiting factors to the survival and distribution of this stenohaline species. The molecular mechanism behind the response of this species to hypo-salinity stress remains unclear. Quantitative Real-Time PCR (qRT-PCR) has been widely used for the analysis of gene expression. The optimal reference gene is constantly transcribed in different types of cells, tissues, and species and under various experimental conditions. However, reference genes that meet all of these conditions are almost non-existent. The selection of a proper reference gene is a precondition for accurate analysis of the expression level of a target gene in quantitative real-time PCR. A total of five candidate reference genes, elongation factor 1a (EF1A), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), heterogeneous nuclear ribonucleoprotein A2/B1 (RO21), -tubulin (TUB), and α-tubulin (TUA), were analyzed by qRT-PCR in four tissues (gill, mantle, visceral mass, and adductor muscle) under three salinity conditions of 10, 20, and 30 psu for one week. Three algorithms, geNorm, NormFinder, and BestKeeper, were used to evaluate the expression stability of the candidate reference genes. The results showed that EF1A was most stable in the different tissues under normal conditions. Under salinity stress, GAPDH was the most stable gene according to overall ranking. In contrast, TUB and TUA were the least stable genes and were not suitable as reference genes. This study showed that different algorithms may generate inconsistent results. Therefore, a combination of several reference genes should be selected to accurately calibrate system errors, especially for studies of different tissues in which candidate reference genes have more unstable expression. The present study was the first to select reference genes by qRT-PCR and to provide a useful basis for selecting appropriate reference genes. The present study also has important implications for gene expression and functional genomics research related to salinity stress in this species or other bivalve species.

Abstract:The appearance of one-year precocious crabs is a severe problem in the development of the Chinese mitten crab () industry. To understand the impact of one-year precocious traits of on its offspring, one-year precocious inbred families (PI) and hybrid families (PHN) comprising one-year precocious crabs and two-year normally mature crabs were constructed to comprehensively evaluate the culture performance and total edible yield of the offspring. The results illustrated that during the juvenile in PI was always higher than in PHN. The weight gain rate (WGR), specific growth rate (SGR), and precocious rate of F₁ females from PI were higher than F₁ females from PHN ( females from PI was significantly lower than F₁ females from PHN ( male survival rate was also slightly lower than in PHN. Although the total yield of F₁ from PHN was higher, there was no statistically significant difference (>0.05). The final body weight of juveniles was normally distributed, and highest proportion of final body weights were between 3.00 g and 8.99 g. The results also showed that during the adult culture stage, the mean body weight of PI individuals was lower than those from PHN in the pre-growth period (March-May), and that the mean body weight of PHN individuals was higher than PI individuals in the late growth stage (July-September). The WGR and SGR values of PHN individuals were higher than those of PI individuals in the March-May and July-September periods. Puberty molting and gonad development was slightly earlier in PI crabs than in PHN individuals, but no statistically significant difference was observed (>0.05). Overall, the survival rate and yield were higher for PI than PHN, but feed conversion ratio was significantly lower in PI individuals (<0.05). A greater number of PHN crabs had final body weights of <125.00 g and ≥ 250.00 g. There was significant difference between the number of individuals in the two groups with body weights <125.00 g (<0.05). In terms of total edible rate (TEY), TEY of PI was higher regardless of gender. The female TEY for PI was higher than for PI males, but there was no statistically significant difference ( produce individuals with larger mean body weights, slightly higher precocious rates during the juvenile culture stage, and early puberty molting, and also produce higher survival rates, and higher yields during the adult culture stage. However, PHN of produce higher survival rates and yields during the juvenile culture stage, and produce individuals with late puberty molting and lower feed conversion ratios.

Abstract:We compared the effects of different salinities, different temperatures, and caffeine on triploid induction of in terms of cleavage rate, D larval rate and triploid rate. The effects of intensity or concentration, duration of treatment, egg density, and induction time were also studied. After the zygotes were fertilized at 31℃ and salinity of 15, optimum results were obtained 15 min post fertilization after hyperosmotic shock in the salinity of 40 for 10 min treatment, with a zygote density of 1.0×10⁷ ind/L. Under these conditions, the cleavage rate was (39.60±2.14)%, D larval rate was (31.46±1.06)%, and triploid rate was (59.53±5.90)%. The induction time and duration of treatment obtained the same results as that of the high salinity treatment; however, the zygote density was 2.0×10⁷ ind/L and zygotes were induced by 10℃ seawater, with these conditions optimum at low temperature. Here, the cleavage rate was (21.00±4.90)%, D larval rate was (12.68±1.21)%, and triploid rate was (51.09±2.67)%. Additionally, spawn was fertilized at 31℃ and a salinity of 15 and, 15 min after fertilization, 2.0 g/L caffeine was added for a duration of 20 min at a zygote density of 1.0×10⁸ ind/L, which were the optimum conditions of triploid induction by caffeine. Under these conditions, the cleavage rate was (85.46±4.78)%, D larval rate was (71.79±3.92)%, and triploid rate was (56.36±2.07)%. At the optimum conditions, the efficiency of triploid induction in caffeine (0.405) was higher than that of the high salinity (0.187) and low temperature (0.065) treatments. In addition, the triploid rate of larvae induced by the high salinity or low temperature was greatly decreased and the survival rates were lower than those noted for caffeine treatment. Therefore, caffeine was more applicable for triploid induction of than the other two methods, i.e., high salinity and low temperature. This study provides basic knowledge and practical evidence for triploid induction of .

Abstract:In order to establish an SNP (single nucleotide polymorphism) acquisition system for the (insulin-like growth factor 2) gene, a total of 33 DNA samples extracted from 10 different carp species were sequenced and the data were analyzed to verify the function and efficacy of the breeding process for the new Huanghe carp strain. By determining the position and distribution of SNPs on the genome and obtaining the gene by segmentation at the genomic DNA level in this way, the applicability of primers from different carp species for use in Huanghe carp new strains was verified. As a result of the segmentation at the genomic DNA level, eight pairs of polymerase chain reaction (PCR) primers were obtained, and the corresponding SNPs were determined by direct sequencing and restriction fragment length polymorphisms. Furthermore, direct sequencing showed a single band from the PCR of Huanghe carp and Jian carp as well as the progenies resulting from their reciprocal crosses, which allowed us to confirm the validity of the target fragment. Finally, analysis of the Huanghe carp body weight data combined with the latest results allowed the detection of an SNP significantly associated with the body weight using primers. Likewise, another SNP was detected in association with the expression level of this gene. The methods used in this study were able to detect the SNPs of genes in the molecular breeding of carp within the range of the whole genome, to verify that the mutation at the No. 227 site on the primer of Huanghe carp led to reduced body weight, and to identify another SNP related to the expression level of IGF2b. This will provide the background for the study of polymorphic molecular markers and other functional genes in other species.

Abstract:Oujiang color common carp, , is a good culturing fish with edible and ornamental traits. It has more than 1200 years of cultural history in the Oujiang drainage of Zhejiang province. In the last 20 years, some researchers have studied its growth performance, genetic diversity, and disease resistance traits. However, the cause and mechanism behind the growth differences among the different color patterns of Oujiang color common carp remain unknown. This study aimed to unveil the metabolic and physiological differences in growth, feeding rate, digestive enzyme activity, and respiration metabolic rate, and the correlations between these factors among four color patterns of Oujiang color common carp ("whole red", WR; "whole red with big black spots", RB; "whole white", WW; and "whole white with big black spots", WB). Our results indicated absolute weight gain rate (AGR), specific growth rate (SGR), daily food intake, daily feeding rate, and trypsin activity were highest in RB, followed by WB, WR, and WW. All of the above measured indexes were significantly higher in RB and WB compared to WR and WW (<0.05). Regarding Oujiang color common carp with red skin (RB and WR), significantly higher feeding rates were identified during the day compared to during the night (<0.05), however, no such significant changes were identified for Oujiang color common carp with white skin (WB and WW) (>0.05). A significant correlations were identified between specific growth rate and daily food intake, between specific growth rate and trypsin activity, and between daily food intake and trypsin and lipase activities (<0.05) indicating that the higher growth rates of RB and WB maybe associated with higher feeding rate and increased digestive enzyme activities. Meanwhile, significant differences in respiration oxygen consumption rate were identified among the four color patterns of Oujiang color common carp, with RB having the highest respiration oxygen consumption rate, followed by WR, WB, and WW. This indicated that Oujiang color common carp with red skin had higher respiration oxygen consumption rates than fish with white skin. Our results provide valuable metabolic and physiological characteristics of the four color patterns of Oujiang color common carp, which will directly guide the aquaculture and breeding of the species in the future.

Abstract:Dali Nor lake is one of the four lakes in Inner Mongolia. It is a typical saline-alkaline lake with high concentrations of carbonate salts (alkalinity up to 60 mmol/L, pH 9.6, and salinity 6‰). Amur ide () is one of the two existing fish in the Dali Nor lake with economic value. Amur ide inhabiting Dali Nor lake undertake spawning migration. To investigate the metabolic regulation mechanism of during spawning migration form Dali Nor lake to Gongger river, we measured serum biochemical parameters, glycogen storage in the hepatopancreas and muscle, and key metabolic and digestive enzyme activities in the hepatopancreas and intestinal tract in collected from Dali Nor lake and Gongger river. In addition, we studied serum biochemical parameters in during a 24 h transfer from Dali Nor Lake to Gongger River water. Compared to lake fish, river fish had significantly lower serum glucose concentrations and significantly elevated cholesterol concentrations. Serum protein and triglyceride concentration did not differ significantly between river and lake fish. Liver glycogen content of the river fish was found to be remarkably higher than that of the lake fish, while muscle glycogen content remained at the same level as the lake fish. Measured metabolic enzyme activities showed that glutamate transaminase (GOT) activity in the hepatopancreas significantly decreased in river fish, while there was no change in alanine aminotransferase (GPT) and hexokinase (HK) activities. It was noted that the activities of all measured digestive enzymes (pepsin, trypsin, amylase and cellulose) increased significantly in both in the liver and the intestinal tract in river fish compared to lake fish. During the 24 h lake-to-river water transfer, serum glucose and protein levels decreased significantly, while triglyceride and cholesterol concentrations did not change. It was concluded that during spawning migration from Dali Nor Lake to Gongger River, can maintain higher metabolic rates and store glycogen in liver in order to provide energy for their subsequent reproduction. The elevated digestive enzyme activities of river fish represent an improved digestibility coefficient, which provides more energy for their reproductive activity.

Abstract:An investigation into the developmental and morphological differences among the hatching larvae of three Chinese Oryzias curvinotus, was conducted. All embryos and larvae were cultured in a water bath with a temperature of (27.0±1.0)℃. The results showed that there are significant differences in morphology among the hatching larvae; specifically, the body length of O. sinensis[(4.04±0.19) mm], and [(3.88±0.17) mm]. One-way analysis of variance (ANOVA) revealed that 90.9% of measurements were significantly different among the three species' hatching larvae (20 of the 22 measurements). Further, Principal Component Analysis (PCA) showed that total body length (TL), head length (HL), HL vs. body depth (BD), TL/BD, anal length (AL), mouth width (MW), and yolk length (YL) were the main variables contributing to the morphological differences among the hatching larvae. Additionally, discriminant analysis confirmed the differences among the larvae, and the larvae were separated from one another in the combined plot for the discriminant analysis. The above results were also confirmed by analysis of similarity (ANOSIM). ANOSIM showed that the differences among the larvae had statistical significance (O. pectoralis and O. sinensis larvae, and larvae were isolated in the dendrogram constructed from the cluster analysis. This result correlates to their geographical distributions, because populations are found closer to one another than to populations in the wild. Finally, the chromatophore pigment pattern on the body could be used to discriminate the O. sinensis larvae than on the larvae of the other species, and the chromatophore pigment on the petrol fins of larvae pectoral fins. Also, many morphological measurements could be used to discriminate between larvae.

Abstract:To verify the feasibility of the high-salinity seawater pretreatment method and to ascertain the optimum conditions for production, the effect of high-salinity stress on the photosynthesis of was studied using methods from experimental ecology. In this study, branches of were incubated at five high salinity levels (40, 45, 50, 55, and 60 psu) for 30 min, with natural seawater (33 psu) as a control. Afterwards, these incubated branches of algae were transferred to natural seawater to recover for 12 h and 24 h, respectively. pH compensation point, chlorophyll fluorescence parameters, oxygenic photosynthesis, and the contents of photosynthetic pigments were measured at different salinity levels and recovery times. After algae were incubated at 40 psu for 30 min, the pH compensation point increased slightly, while RO and decreased significantly. When salinity was higher than 40 psu, the pH compensation point and (Ⅱ) decreased, while RO decreased with increasing salinity level above 40 psu. The Chl a/Car value was significantly different among the different salinity treatment levels (<0.01), while no significant difference was found between different incubation times within the same level of salinity. Significant changes in PE content (<0.01) were observed, especially at 45 and 55 psu. After 12 h recovery, the overall value of stressed algae was still significantly lower than of control algae ((Ⅱ) began to increase. After 24 h recovery, the photosynthetic indices of stressed algae including (Ⅱ), Chl a, Car, PE, PC, and Chl a/Car were close to fully recovered. This study indicated that the algae can adjust its photosynthetic characteristics under high-salinity stress, and as a result its photosynthetic parameters are able to return to a normal level after 24 h recovery. In conclusion, the pretreatment method is feasible, and exposure to salinity of 50-55 psu for 30 minutes is a suitable treatment condition.

Abstract:The major histocompatibility complex (MHC) is a large group of genes that encode cell surface glycoproteins and play a crucial role in the acquired immune systems of all teleosts. The study of the MHC is a major focus in the field of fish molecular immunology, and for the auxiliary breeding of disease resistant fish. The great blue-spotted mudskipper () is special for its unique behavioral, physiological, and biochemical characteristics suitable for amphibian life. This study firstly analyzed the sequence characteristics of the gene, then reconstructed the phylogenetic tree and explored the possible molecular evolution. Finally, the mRNA spatial expression pattern of the gene was assessed in healthy tissues, and hepatic and splenic expression patterns were examined after viral mimetic poly(I:C) injection. The results showed that the open reading frame (ORF) was 1,101 bases in length, encoding 366 amino acid residues, with a molecular mass of 41.1 kD and theoretical isoelectric point (pI) of 4.83. The gene included five domains:the leader peptide, α1 domain, α2 domain, α3 domain, and the transmembrane domain. The following secondary protein structure was predicted:-turn for 7.65%, extended strand for 21.31%, and random coils for 33.88%. There were three protein kinase C phosphorylation sites, one casein kinase Ⅱ phosphorylation site, and one N-glycosylation site. Phylogenetic analysis showed that the was most closely related to the . The spatial expression analysis showed that was expressed in all tissues examined, particularly in the kidneys and spleen, followed by the gills and intestines. At 0 h, 6 h, 12 h, 24 h, 36 h, 48 h, and 72 h after stimulation there were no significant changes (>0.05) in expression levels in the control group. During poly(I:C) challenges which were intraperitoneally injected into the liver, mRNA expression level was increased at 6 h (1.63-fold) and the expression increased significantly and was at its maximum at 12 h (<0.01, 5.30-fold). Then, the expression level decreased at 24 h, but was still significantly higher than the control group (<0.05, 2.98-fold). At 36 h, expression level increased again, and was still significantly higher than the control group (<0.01, 4.68-fold). Expression gradually decreased to 2.22-fold and 1.46-fold the control values at 48 h and 72 h, respectively. In spleen tissues, the expression level of mRNA in the experimental group was significantly increased at 6 h (<0.01, 6.25-fold), and the expression level of the experimental group increased significantly to its maximum (<0.01, 9.71-fold) at 12 h. The maximum value expression level was reached earlier than in liver tissue. At 24 h, the expression level also decreased, but was still higher than the control group (<0.05, 3.25-fold). At 36 h, the expression level increased again and was significantly higher than that in the control group (<0.01, 5.81-fold), expression levels gradually returned to normal levels at 48 h and 72 h (1.21-fold and 1.38-fold, respectively). The results suggested that Boleophthalmus pectinirostris against poly(I:C) challenges.

Abstract:High seawater temperatures in summer have a significant effect on the biochemical responses of the Pacific oyster, , and influence the survival rate of cultured oysters. In this study, we investigated the high temperature tolerance of ‘Haida No. 3’ through exposure to acute and gradually increasing temperature stresses over 72 h, and measured changes in five immune indicators:catalase (CAT), superoxide dismutase (SOD), lysozyme (LSZ), total antioxidant capacity (T-AOC), and malondialdehyde (MDA). In the gradual temperature increase test, we increased the seawater temperature progressively (2℃/d). In the acute seawater temperature increase test, we transferred oysters from rearing temperature (16℃) to 18℃, 22℃, 26℃, 30℃, and 34℃ directly. The results showed that when the water temperature was increased gradually, the survival temperature maximum (STMax) of ‘Haida No. 3’ was 33.63℃, that the critical temperature maximum (CTMax) was 40.13℃, and that the 50% critical temperature maximum (50%CTMax) was 36.67℃. In the acute water temperature increase test, the median lethal temperature after 72 h (72-h LT₅₀) was 30.13℃. In each treatment, the five immune indicators in the visceral mass changed significantly as exposure time increased. Within the first 12 h, significant increases were observed in the activities of CAT, SOD, LSZ, and T-AOC, after which their activities returned to their initial levels. The content of MDA was at its highest level between 6 h and 9 h, after which it decreased gradually. All of these results indicate that high-temperature stress induces significant changes in both the antioxidant immune response and in the activity of lysozyme in ‘Haida No. 3’ and greatly influences its survival. The high temperature tolerance noted in this study will provide a reference for the application and promotion of Pacific oyster strain ‘Haida No. 3’.

Abstract:The aim of this study was to obtain the most recent data and investigate the biological characteristics under a changing environment for jumbo flying squid, collected by a Chinese squid jigging vessel from February to April 2018 in the eastern equatorial Pacific Ocean (110°W-114°W, 2°40'S-2°N). The distribution of mantle length (ML), body weight (BW), maturity stages, and stomach stages from February to April was studied using the frequency distribution method. The relationship between ML to BW and the first mature ML was obtained by best power exponent fit. The differences in the growth of female and male squids among different months were discussed based on the remote sensing temperature that was dependent on sampling location. Ranges of ML and BW of female squid were 20-46.7 cm and 240-3420 g, respectively, and averages were (30.6±4.47) cm and (939.07±460.02) g, respectively, whereas for males, ranges of ML and BW were 22.2-42.5 cm and 310-2270 g, and the averages were (31.3±3.93) cm and (925.57±358.6) g, respectively. The dominate ML of males in February, March, and April was 26-28 cm, 30-32 cm, and 28-30 cm, whereas females were 24-26 cm, 28-30 cm, and 26-28 cm, respectively. The dominate BW of males and females in February, March, and April was 400-600 g, 600-800 g, and 600-800 g, respectively. The equation of the relationship between ML and BW was fitted with the power exponent. The effect of sex on the exponent "" of the BW-ML relationship was significant in March, thus there was a significant difference in body growth between female and male individuals as revealed the analysis of covariance (<0.01). There were also significant differences in body growth among the three months for the same sex (<0.05). From February to April, the stomach stages of males and females were mainly 1 to 2 with the ratio of higher stomach stages decreasing with each month. The sexual ratio of females to males was 2.04:1. The maturity stages of males were mainly Ⅱ with the ratio of maturity stage increasing with each month. The ML at first maturity of males was 32.72 cm. The maturity stages of females were mainly I with the ratio of the immature stage accounting for greater than 97%. A linear relation was found for ML and BW and maturity stages for both male and female squid. From February to March was a period of rapid growth and development, especially for males. However, in April, the dominant group no longer grew. Thus, the maturity stages of males develop earlier than the maturity stages of females, and the mature males leave the equatorial waters and begin to migrate.

Abstract:There are generally two sources of data for fisheries stock assessment:fishery-dependent and -independent data. The former involves data collected on commercial fishing vessels by fisheryman, while the latter requires routine surveys by researchers that are time-consuming and expensive. Fishery-dependent data is easier to obtain, but there may be problems with regard to its representativeness. This study used (a species of mantis shrimp found in the Western Pacific) as an example to compare the performance of fishery-dependent and -independent data in the parameter estimation of the von Bertalanffy growth equation. With the decline of fishery resources in recent years, has become an important fishery species in China's coastal areas. At present, the research on the biology of is not systematic and this restricts the scientific evaluation and management of fishery resources. Bootstrap re-sampling was used to establish the same sample size. Both types of data were collected from the coast of Shandong province using a 220 kW single-trawling vessel with a bottom trawl of 1380 mesh×4.67 cm (height 7.53 m and width 15 m when deployed). The growth parameters were estimated using a length-frequency method, Electronic Length Frequency Analysis (ELEFAN). Our results showed that the asymptotic body length () estimated using fishery-independent data were 193.27 mm and 0.62, respectively, whereas the estimated by fish-ery-dependent data were 171.63 mm and 0.66, respectively. Nonparametric tests indicated that the three parame ters, s) of were significantly different between the estimates obtained from the two sampling methods. The results suggest that fishery-dependent data may reflect the growth pattern to a certain extent, i.e., the estimates of are close to the results obtained using fishery-independent data, but there is a large error in estimating . Therefore, the estimation of growth characteristics should rely on fishery-independent data for , whereas fishery-dependent data can be used as auxiliary information.

Abstract:The dietary composition and its ontogenetic shift of the Japanese grenadier anchovy () in the Qingcaosha Reservoir of Shanghai, China were examined using stable carbon and nitrogen isotopes to complement stomach content analysis. The cluster analysis showed that the gravimetric percentage (%) differed significantly between small-sized (body length < 99 mm, SS), medium-sized (between 99 mm and 150 mm, MS), and large-sized (>150 mm, LS) anchovy individuals. Occurrence rate (%) and percent index of relative importance (IRI%) did not differ between SS and MS individuals, which of them were significantly different from those of LS individuals. There was no significant difference in numerical percentage (%) between the three body length classes. Combining the results of all the four indices, zooplankton was the main dietary source for SS anchovy, and shrimp and fish were the main dietary sources for LS anchovies. For MS anchovy, zooplankton made up the largest proportion of the diet by %. A dual stable isotope mixing model showed that shrimp and fish made the largest contribution to the diet of the LS anchovy. The N value increased linearly with increasing body length, and C varied as a quadratic polynomial function of body length. The N[(15.18±0.79)‰] and trophic level (TL:3.63±0.23) of LS anchovy were significantly larger than those of the MS anchovy[δ¹³C did not differ significantly between the LS and MS classes (>0.05). Combining the stomach content and stable isotope analysis, an ontogenetic dietary shift was noted from the pelagic zooplankton to benthic organisms as primary carbon sources before and after the diet shift. This indicates the dominant species of anchovy could play an important role in the coupling of the pelagic and benthic food webs of the reservoir.

Abstract:To investigate genetic diversity and structure of wild populations in the Yangtze River, a total of seventy-nine individuals from four wild populations (i.e., CS-Chishui River, NJ-Nanjing, YC-Yichang, and YY-Yueyang) were analyzed using the complete sequences of the mitochondrial markers Cyt b sequences were 1141 bp in length, and 26 haplotypes were detected. The Cyt haplotype diversity ranged from 0.685 (CS) to 0.924 (YC) and nucleotide diversity ranged from 0.176% (CS) to 0.285% (YY). Genetic distances within or between populations were both between 0.002 and 0.003. The whole D-loop sequences were 834-840 bp in length and 46 haplotypes were detected. D-loop haplotype diversity ranged from 0.754 (CS) to 0.990 (NJ) and nucleotide diversity ranged from 0.548% (CS) to 1.412% (YC). Genetic distances within populations were between 0.005 (CS) and 0.014 (YC), and from 0.008 to 0.012 among populations. The differences between these four populations of have not risen to the subspecies level based on the genetic distances. Analysis of molecular variance (AMOVA) with Cyt and D-loop sequences showed that most variance occurred within populations, suggesting that this is the main source of total variance.

Abstract:Fishery resources density, spatial distribution, and size composition were studied in February, April, September, and November 2017, primarily based on an acoustic method to explore the fish gathering effect of artificial reefs in Fangchenggang Gulf. A total of 201 nekton and benthic invertebrate species (including 126 fish species, 32 crab species, 20 decapod species, 11 squilloidea species, and 12 cephalopoda species) were collected in artificial reefs (and areas adjacent to the reefs) in the Fangchenggang Gulf. The results of a two-way ANOVA showed that the spatial and temporal differences in fishery resource density in the investigated area are significant (<0.001). The interaction between seasons and regions is also significant (<0.001). The fishery resource density of the artificial reefs area (547745 ind/n mile²) was nearly 2.7-times greater than that of the surrounding area (203990 ind/n mile²), showing an obvious fish gathering effect of artificial reefs in February. The types of fish were mainly benthic and rockfishes such as . Small size individuals accounted for a large percentage in the artificial reef area and their average target strengths (TS) were -55.6 dB (in February), -54.5 dB (in April), -53.6 dB (in September), and -52.2 dB (in December), respectively, which displayed a gradually increasing trend of TS values with the individual growth. In the vertical direction, more than 90% of single echo detections were distributed in the middle and deeper layers (9~16 m) of the artificial reef area in the February and April investigations. In conclusion, the construction of artificial reefs in Fangchenggang Gulf revealed an obvious downward gathering effect on the small size rockfishes, which supports the need for systematic evaluation of the ecological effect of marine ranching.

Abstract:Fisheries resource management is shifting from the management of single species towards the management of the whole ecosystem. Ecosystem-based fisheries management (EBFM) is a relatively new concept and defining and identifying a suitable ecosystem is an important prerequisite for implementing EBFM. Based on survey data of four seasons from 2014 to 2015 in the East China Sea and south of the Yellow Sea, this study classified fishery organisms into different living habit preference groups by clustering according to the biodistribution seasonal characteristics of water temperature, salinity, water depth, latitude, longitude, etc. The preference for hydrological environment, characteristics of spatial distribution, and group composition structure among all groups were analyzed and compared, in order to probe an ecosystem division method for the realization of EBFM. The fishery organisms in the surveyed seas can be divided into five groups:group 1 has a preference for high-temperature and high-salt conditions in the deep southern offshore waters, group 2 has a preference for high-temperature and high-salt conditions in the deep waters of the southern open sea, group 3 has a preference for low-temperature and low-salt-water conditions in the shallow waters near the northern coast, group 4 has a preference for medium-temperature and medium-salt conditions in the intermediate waters near the central area, and group 5 has a preference for low temperature and low salt water conditions in the shallow northern offshore waters. From the perspective of water temperature preference of group species, group 1 obviously prefers warm water, while group 5 prefers cold water. The preference of group 4 was intermediate. From the perspective of spatial distribution characteristics, the group space is distributed in blocks, and there are combinations of combinations, inclusions, and interspersions among various groups. The different groups were concentrated in different areas in different seasons. The starting point of the migration of groups 3, 4, and 5 is close to the end point of the migration. For groups 1 and 2, the starting point and the ending point of the migration are far apart, and a complete migration could not be identified. In terms of group structure and composition, the dominant species in spring and summer of group 1 were flying squid (), respectively. In group 2, the dominant species of spring and winter were horse mackerel (), respectively, and butterfish () was dominant both in summer and autumn. The situation of group 3 is relatively complicated, and the Indian Bombay duck () is dominant in all seasons except summer, the swimming crab () is dominant in spring and summer, and the scaly hairfin anchovy () is dominant in autumn and winter. For groups 4 and 5, there is only one dominant species each, the hairtail (Larimichthys polyactis), respectively.

Abstract:The Pacific saury is an important pelagic fish species in China and is one of the priority species managed by the North Pacific Fisheries Commission. The Pacific saury has a short lifespan and is widely distributed in the North Pacific Ocean. The Pacific saury has a long migration route that passes through the Kuroshio-Oyashio transition zone from subtropical to the north, and returns southward to the coastal waters of Japan and Russia. The fishing grounds of the Pacific saury are mainly distributed in the Sea of Japan, the Pacific Ocean, and the Sea of Okhotsk. This study reviewed and summarized the research progress of the Pacific saury including its life history, population dynamics, fishing grounds, and habitat suitability. This was followed by analyses and prospects of the present research status and the developmental trends of growth biology, reproductive biology, migration, resource fluctuation, and habitat suitability. The main findings are as follows:the life cycle and effects of environmental variables on the growth, sexual maturity, and spawning of the Pacific saury during each life stage were revealed based on the study of day-age of the microstructure of otoliths; the relationship between resource abundance and influencing factors revealed that the ocean-climate change was the main reason for the long-term fluctuation of Pacific saury resources; the main mechanism of the formation of the fishing ground was revealed from research of the habitat adaptation; and a relevant fishery forecasting model was established. The main suggestions include exploring the potential migratory paths and patterns of the Pacific saury based on the otolith microchemical information and the spatiotemporal variations of optimum environmental factors; establishing a reproductive habitat suitability index model to analyze the influence of ocean-climate change on potential habitats of recruitment populations of the Pacific saury; and establishing a schooling habitat suitability index model to develop a rapid forecast reporting system of the fishing grounds for the Pacific saury. This study provides a comprehensive overview and analysis of the progress and achievements of research on the life history, population dynamics, and fishing grounds of Pacific saury, which can provide references for more rational and effective research on stock assessment, formulation of management measures, and development of fishery forecasting of Pacific saury in China.