• Volume 42,Issue 6,2018 Table of Contents
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    • Fisheries biological characteristics of Sthenoteuthis oualaniensis in the spring season in the El Nino year of 2016 in the Zhongsha Islands waters of South China Sea

      2018, 42(6):912-921. DOI: 10.11964/jfc.20170710907

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      Abstract:Based on the 572 samples of Sthenoteuthis oualaniensis collected by light falling-net fishery during March to May in the spring season in the El Nino year of 2016 in the Zhongsha Islands waters of the South China Sea, the fisheries biological characteristics and the influence of El Nino were studied. The result indicated that the mantle length (ML) range was from 59.5 mm to 207.5 mm with a high concentration in 90 mm to 150 mm accounting for about 66.24 percent for females and from 56.5 mm to 236.5 mm with a high concentration in 60 mm to 120 mm accounting for about 78.81 percent for males, respectively. The body weight (BW) ranged from 7 g to 318 g with a dominative weight from 20 g to 140 g accounting for about 70.18 percent for females and ranged from 7 g to 381 g with a dominative weight from 0 g to 80 g accounting for about 92.14 percent for males, respectively. The ration of the somatic body weight (SBW) to BW ranged from 46.59 to 86.67 percent with an average of 70.19 percent and from 42.86 to 91.11percent with an average of 73.12 percent for females and males, respectively. There were significant differences between the BW and SBW growth, and the relationships between the ML to BW and ML to SBW were best described by the power function for females and exponential function for males by the Akaike's information criterion (AIC), respectively. The ratio of females to males was 41.43:58.57, and the samples were most composed of immatue individuals accounting for about 61.7 and 87.79 percent for females and males. The feeding stage was mainly in 0, 1 and 2 grade accounting for 89.42 percent and all of the samples and the food was mainly composed of squids, pelagic fishes, mollusc and crustacean. The result indicated that the average sea surface temperature of the sample waters of the El Nino year of 2016 was 0.213 degrees centigrade lower than the common year of 2015, and the fisheries biological feature of S. oualaniensis was affected by El Nino with a decrease in the body size probably.

    • Molecular cloning and expression analysis of the MSTN cDNA in Haliotis diversicolor supertexta

      2018, 42(6):817-827. DOI: 10.11964/jfc.20171010990

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      Abstract:Myostatin is an important member of the transforming growth factor (TGF) family that functions to regulate muscle development and growth in animals, The purpose of this study was to characterize and predict function of the myostatin gene of Haliotis diversicolor supertexta which is an important aquaculture shellfish. In this study, the myostatin (Hs-MSTN) cDNA of H. diversicolor supertexta were cloned and characterized by rapid amplification cDNA ends (RACE) methods. The full length of Hs-MSTN cDNA sequence consists of 3 755 bp containing a 5' untranslated region (UTR) of 324 bp, a 3' UTR of 1 985 bp, and an open reading frame of 1 446 bp encoding a protein with 481 amino acid residues, with a calculated molecular mass of 54.96 ku, and the theoretical isoelectric point of 9.41, The structure of Hd-MSTN included a putative signal peptide (1-17 aa), a TGF-β propeptide domain (157-367 aa) and a conserved TGF-β domain (379-481 aa). Multiple sequence alignment results revealed conservation of the RRPR proteolytic site and nine conserved cysteines of the Hs-MSTN with MSTN from other animals, and two propeptide proteolytic sites RQRR (120-124 aa) and RYRR (235-239 aa) were found. Phylogenetic analysis showed that the Hs-MSTN gene was clustered in the same subgroup with the H. rufescens, Quantitative real-time PCR detection results indicated that the Hs-MSTN genes were expressed widely in adductor muscle, mantle, gonad, liver, gill, foot and the highest expression level was observed in the adductor muscle, mantle, foot, and Hs-MSTN transcript was widely detected in early developmental stages:unfertilized egg, fertilized egg, 4-cell embryos, 8-cell embryos, gastrulae, larvae, juvenile stage, and the higher in fertilized egg, in 4-cell embryos and 8-cell embryos and the expression level increases in gastrulae, larvae and decreases in juvenile stage. Our results indicate that MSTN is involved in muscle growth regulation of H. diversicolor supertexta.

    • Macrobenthic community characteristics of different culture areas in Sanggou Bay

      2018, 42(6):922-931. DOI: 10.11964/jfc.20170710905

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      Abstract:Two surveys were conducted in Sanggou Bay in September and November 2016 to study macrofauna in bivalve-seaweed integrated culture areas and fish cage areas. The community characteristics such as species number, composition, distribution and biodiversity and the relationships between macrofauna and the environmental factors were analyzed to investigate the influence of different aquaculture activities on the macrofauna. A total of 67 species were identified, including 36 Polychaetes, 12 Mollusca, 16 Crustacea and Pycnogonida, and 3 Echinodermata. The dominant macrofauna species in Sanggou Bay are Polychaetes. The absolutely dominant species in bivalve-seaweed integrated culture areas are Chaetozone setosa and Lumbrineris longiforlia, while in fish cage areas that are L. heteropoda and Tharyx multifilis. Biomass and abundance were found the higher in fish cage area in September compared to the values in November, and the lowest values were found in the bivalve-seaweed integrated culture area in September. Biodiversity, which showed a reversed trend, was found highest in the integrated culture area in September and followed by the values in the fish cage area in November and September respectively. Correlations were found between macrobenthic community characteristics and sediment parameters (total organic carbon, total phosphorus, sulfide and oxidation-reduction potential). The macrobenthic community was affected by the large-scale aquaculture activities in Sanggou Bay, and the effect of fish cages culture was stronger.

    • β-glucan decreases intensity of hypoxia-induced oxidative stress in large yellow croaker (Larimichthys crocea) and its corresponding mechanisms

      2018, 42(6):828-837. DOI: 10.11964/jfc.20170610877

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      Abstract:The aim of the present study was to evaluate the effects of β-glucan on acute hypoxia-induced oxidative stress by determining lipid peroxidation, activities and mRNA levels of antioxidant enzymes (Cu/Zn-SOD, CAT, GPx and GR), and gene expressions of the Keap1-Nrf 2 signaling molecules in the liver of large yellow croaker Larimichthys crocea. Fish were injected with β-glucan at a dose of 0 or 5 mg/kg body weight on 6, 4 and 2 days before being exposed to 1.5 and 7.0 DO mg/L for 24 h. The results showed that normoxia with β-glucan had no effect on lipid peroxidation compared with the normoxic control, and hypoxic stress with β-glucan remarkably reduced lipid peroxidation during the whole experiment compared with hypoxic stress, indicating that β-glucan could ameliorate hypoxia-induced lipid peroxidation. Obtained results also showed a coordinated transcriptional regulation of antioxidant genes, suggesting that Nrf 2 was required for regulating these genes. Furthermore, a negative relationship between the mRNA levels of Nrf 2 and Keap1 indicated that Keap1 plays an important role in switching off the Nrf 2 response. In conculsion, β-glucan could alleviate acute hypoxia-induced oxidative stress in large yellow croaker, emphasizing a central role of transcription factor Nrf 2 in the process.

    • Comparison of growth dynamics between a selected fast-growing strain and the common cultured strain of turbot (Scophthalmus maximus) based on C-R model

      2018, 42(6):932-940. DOI: 10.11964/jfc.20170710891

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      Abstract:In order to evaluate success in selective breeding of Scophthalmus maximus, the nonlinear growth curves of a selected fast-growing strain and the common cultured strain were fitted using Chapman-Richards (C-R) model, and the differences in growth performance of the two strains have been deeply investigated. The results showed that the goodness of fit (R2), time to inflection, weight at inflection and maximum month gain of fast-growing strain and common cultured strain were respectively 0.999 and 0.997, 15.228 and 16.858 months old, 716.712 and 619.862 g, 111.711 and 78.061 g. The instantaneous growth rate, growth acceleration rate and relative growth rate of fast-growing strain were higher than those of common cultured strain during months of 4.5–25, 3–13.8 and 3–15 months old, respectively. However, the instantaneous growth rate and growth acceleration rate of fast-growing strain were lower than those of common cultured strain in other growth stages, and the relative growth rate is almost the same. Furthermore, the fast-growing strain showed earlier starting point (9.05 months old), inflection point (15.23 months old) and ending point (21.40 months old), shorter fast-growing period time interval (12.35 months old) and longer fast-growing body weight intervals (1 187.680 g) than those of common cultured strain. Obviously, the selected fast-growing strain has obtained greater net body weight increment during fast-growing period in a relatively short time.

    • 1H NMR-based metabolomics studies on the effect of Zn in blunt snout bream (Megalobrama amblycephala)

      2018, 42(6):838-845. DOI: 10.11964/jfc.20170410789

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      Abstract:A 1H NMR-based metabolomics approach was used to explore the impact of dietary Zn on the serum metabolic profile of Megalobrama amblycephala. Fish were fed diets containing graded levels of Zn (7.4, 32.1, and 332.4 mg/kg diet; supplied as ZnSO4·7H2O) for 12 weeks. We identified 52 metabolites in serum including 23 amino acids or intermediary metabolites, 16 organic acids, 4 sugars, 4 nucleic acids, 3 vitamins and 2 others. Multivariate data analyses (PLS-DA and VIP) showed dietary Zn affected the metabolic profile impartially and these metabolites (such as proline, lactate, glucose, alanine, lysine, glutamine, creatine, trans-4-hydrox-L-proline, taurine, serine, τ-methylhistidine, arginine, valine, methionine and mannose) were identified as charactisteristic metabolites. These metabolites are mainly increased in the groups (7.4 and 332.4 mg/kg diet) compared with the group (32.1 mg/kg), suggesting that Zn deficiency and excess inhibited amino acid and carbohydrate metabolism. In conclusion, proline, lactate and glucose were found to have potentials for being new biomarkers for Zn nutritional status of M. amblycephala.

    • Correlation and path analysis of quantitative traits of new variety of Sinonovacula constricta at different months of age

      2018, 42(6):941-949. DOI: 10.11964/jfc.20171111056

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      Abstract:In order to detect the correlation between quantitative characters for one new variety "Shenzhe No. 1" of Sinonovacula constricta at different months of age, more than 60 individuals of S. constricta at 4th, 9th and 11th month age were randomly selected to measure the shell length (SL), shell height (SH), shell width (SW) and body weight (W). And the correlation and path analysis method were used to analyze the effect of phenotypic character on qualitative traits. Then results showed that the correlations among the qualitative characters reached extremely significant levels. The shell length showed the greatest correlation coefficients to the live weight of the 4-month age and 11-month age (0.911 and 0.631) respectively. However, the shell height showed the greatest correlation coefficients to the weights of the 9-month age (0.653). The result of the path coefficient analysis showed that the highest path coefficients were the shell length (0.562), shell width (0.433), and shell height (0.394) at 4th, 9th and 11th month age, respectively. The results of the determinant coefficients were consistent with the results of the path analysis. The multiple regression equations were obtained to estimate live weight of S.constricta as 4th, 9th and 11th month age weights (W):W4=-0.756+0.039SL+0.112SW, R2=0.849; W9=-10.622+0.095SL+0.404SH+0.644SW, R2=0.631; W11=-23.772+0.207SL+0.805SH+0.587SW, R2=0.909. The study provides theoretical basis and good measures for the selection of the parents and aquaculture production forecast in the breeding of S. constricta.

    • Effect of Aureococcus anophagefferens on the antioxidant enzyme system in Perna viridis

      2018, 42(6):846-853. DOI: 10.11964/jfc.20170810923

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      Abstract:Effects of Aureococcus anophagefferens on superoxide dismutase (SOD) activity, malondialdehyde (MDA) and glutathione (GSH) contents of mussel Perna viridis were studied by feeding P. viridis with pure culturing A. anophagefferens and co-occurring algae (A. anophagefferens and Tetraselmis subcordiformis). Mussels fed with T. subcordiformis were set as control. The results showed that A. anophagefferens significantly effected the antioxidant enzyme system in mussel P. viridis including SOD, MDA, and GSH. SOD activity and MDA, GSH contents fluctuated after P. viridis exposing to A. anophagefferens. The high and moderate cell densities of A. anophagefferens can affect the SOD activity significantly within a short time (3 h). SOD activity in the mussel exposing to the co-occurring algae, by contrast, increased slowly, suggesting that T. subcordiformis can prolong reaction time of the antioxidant system. Compared with control group, GSH content in each experiment group was significantly reduced in 2 d. GSH contents had no difference in the mussel exposed to co-occurring algae and pure culturing A. anophagefferens, which suggested that T. subcordiformis has no positive effect on restoration of the antioxidant system in mussels.

    • Establishment of bioenergy models to predict growth, feed requirement and waste output of grass carp (Ctenopharyngodon idella)

      2018, 42(6):950-967. DOI: 10.11964/jfc.20170510828

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      Abstract:In order to predict the growth performance, feed requirement and waste output, and improve the precision of feeding management, the current study reported some bioenergy models developed in grass carp (Ctenopharyngodon idella). In this study, the growth rate of C. idella at different growth stages was calculated by specific growth rate (SGR), daily growth coefficient (DGC), thermal-unit growth coefficient (TGC), average daily growth (ADG) growth models. The optimal growth model was selected by the least squares method. Feed requirement was estimated based on digestible energy requirement (DEreq), calculated from the summation of recovered energy (RE), basal metabolism energy (HeE), heat increment of feeding (HiE), and urinary and branchial energy (UE+ZE), all estimated by compiling and analysing data from published studies. The waste outputs were estimated using a nutrient mass balance approach. Feed requirement model simulations were compared with the results from a growth trial based on C. idella fed with 33%, 28% and 23% crude protein for different growth stages. The result shows that the modified TGC models produced a better fit of the growth trajectory of the fish across production stages compared with other growth models (SGR, ADG, DGC). Values predicted for body weight and feed conversion (FCR, feed:gain) by the models were highly correlated to the observations from the growth trial. The digestible energy requirement is about 1.55×107 kJ for 1 t C. idella with the body weight of 0.5-2 500 g, and total solid wastes (TSW) output of C. idella was estimated at about 440 and 623 kg per tonne of feed fed and per tonne of fish produced, respectively. These results indicate that the model can effectively estimate the growth, feed requirement and waste output in the actual culture operations of C. idella, and could be a valuable tool for the differential marketing, reducing the cost of feed and feed waste, and for pollution assessment.

    • Effects of Cu2+ on growth, immunity and gonad development of Strongylocentrotus intermedius

      2018, 42(6):854-862. DOI: 10.11964/jfc.20170810931

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      Abstract:This study was conducted to investigate the effects of Cu2+ on the weight gain rate (WGR), gonadosamatic index (GI), antioxidant enzyme activities and transcription of major yolk protein gene (MYP) in Strongylocentrotus intermedius. All experimental sea urchins were randomly divided into six tanks (200 L), and each tank was stocked with 20 individuals. Then, the test group was added CuSO4·5H2O to a final concentration of 0.02 mg/L Cu2+ with natural sea water as the control group. The experiment lasted for 60 days. Results showed that WGR and GI were significantly lower in the test group than those in the control group at 60 days. The activities of CAT and GST in the coelomic fluid of sea urchins in the test group were significantly lower at day 60 than those at day 30, and the activity of CAT was lower in the test group than that in the control group. The MYP transcription was significantly lower in the gonads of the test group than that in the control group, but the expression of MYP was significantly higher in the digestive tract of the test group than that in the control group. The total protein content was significantly higher in the coelomocytes of the test group than that in the control group. Results above showed that the WGR, GI and antioxidant enzyme activities of sea urchins could be reduced by Cu2+. This may be caused by inhibiting MYP expression in the gonad and the MYP transportation from the digestive tract to the gonad.

    • Temporal variations in physiological characteristics of the sea cucumber (Apostichopus japonicus) bottom-cultured in a subtropical fish farm

      2018, 42(6):863-869. DOI: 10.11964/jfc.20170710895

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      Abstract:An in situ experiment was carried out to estimate the temporal variations in physiological characteristics of the sea cucumber Apostichopus japonicus bottom-cultured in a subtropical fish farm. Results showed that the oxygen consumption rates of the A. japonicus in the fish farm ranged from 0.012 to 0.016 mg O2/(g·h), and no significant differences were observed between the values at different sampling times (P=0.145). This indicated the energy consumption for the basic metabolic needs of the animals didn't vary obviously during the experiment; however, the oxygen consumption rate of A. japonicus in the reference site during the May sampling was significantly higher than those in February, March and June, which indicated that high energy consumption at the beginning of aestivation. During the February and March samplings, the oxygen consumption rates of A. japonicus in the fish farm were significantly higher than those in the reference site during this period, indicating the higher metabolic rates of the animals in the fish farm. The ammonium excretion rates of A. japonicus in the fish farm decreased with time, and the value at the February sampling[(0.061±0.009) μmol/(g·h)] was significantly higher than those in May[(0.045±0.011) μmol/(g·h)] and June[(0.035±0.007) μmol/(g·h)], because water temperatures in winter and spring were suitable for the growth of A. japonicus, and animals in the fish farm could assimilate more food of better quality from the surrounding environment. A. japonicus in the fish farm underwent aestivation and their guts degenerated after May, and their ammonium excretion rates decreased simultaneously. The ammonium excretion rates of the A. japonicus in the reference site were low and constant during the whole study period, which indicated that animals were always in low nutritional condition. The O/N ratios of both sites ranged between 10 and 30, which indicated the mixed utilization of carbon-based substrates and protein acted as the catabolic substrate for A. japonicus. The O/N ratios of A. japonicus in the fish farm was lower than the reference site from February to May, which demonstrated the protein-dominated catabolism of the animals, and it corresponded to the higher food quality in the fish farm.

    • Effect of ferrous chelate Trichiurus lepturus protein on the immune characteristics of Misgurnus anguillicaudatus

      2018, 42(6):968-974. DOI: 10.11964/jfc.20170710903

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      Abstract:The test of the digestive enzyme activity, observation of intestinal tissue and the living imaging technology were applied to investigate the effect of the ferrous chelating peptide on the digestive tract. The test of indexes of biochemical indexes of serum and liver, and observation of the liver were used to investigate the effect of the ferrous chelating peptide on immunological characteristics of Misgurnus anguillicaudatus. The result showed lipase activity was significantly higher than that of the control group when the ferrous chelating peptide was 2 g/kg; amylase activity of pepsin was significantly higher than the normal control group when the ferrous chelating peptide was 1 g/kg; trypsin activity in each experimental group compared with the control group had no significant difference. SOD and lysozyme in serum were significantly higher than those of normal control group when the ferrous chelating peptide was 2 g/kg; compared with the normal control group, CAT at ferrous chelating peptide concentration of 1 g/kg showed significant difference. Compared with control group, the morphological structure of each experimental group had no change. With the application of living imaging technology, complexes of ferrous chelating peptide with FITC marked stayed in M. anguillicaudatus for a long time and fluorescence intensity was mainly enriched in the upper body of M. anguillicaudatus, hence, after absorption, the ferrous chelating peptide was speculated to be distributed in the liver, gallbladder and other organs. The results showed that the hydrolysis of ferrous chelate peptide could improve the digestive enzyme activities of loach and enhance non-specific immunity of loach.

    • Distribution of the age 0 group Pacific cod (Gadus macrocephalus) in the Yellow Sea and its relationship with environmental factors

      2018, 42(6):870-880. DOI: 10.11964/jfc.20170710899

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      Abstract:Pacific cod Gadus macrocephalus is distributed around the rim of the North Pacific Ocean, and it's considered as an ecologically important species. Studies on the biological characteristics and distribution patterns of juvenile Pacific cod would be helpful to understand cod population dynamics. Based on the data collected during the fishery resources surveys carried out in June, August, October and December 2016, the growth of the age 0 group Pacific cod in the Yellow Sea was studied, and the generalized additive model (GAM) was used to analyze the distribution characteristics and their relationship with environmental factors of the age 0 group Pacific cod. The results showed that the age 0 Pacific cod was allometric. Growth rate of the body weight was not equal to the body length, and the weight gain was faster. Allometric factor b was 3.3161. The age 0 group Pacific cods in the Yellow Sea were distributed in the waters in bottom salinity range of 31.7 to 33.3, in bottom water temperature range from 6.6 to 12.1℃ and in depth range of 35.8 to 87.2 m. The favorite sediment in the nursery habitats was fine silty sand and soft clay mud. The seasonal variation in the distribution pattern of the age 0 group Pacific cod was synchronized with the seasonal variation of the Yellow Sea cold water mass. The environmental factors which had significant effects on the ecological density of the cod juvenile were in the order of bottom water temperature, sediment and bottom salinity,while the depth had no significant influence on the juvenile density.

    • Degradation regularity of ATP-related compounds in Aristichys nobilis and Epinephelus fuscoguttatus during storage

      2018, 42(6):975-983. DOI: 10.11964/jfc.20171111049

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      Abstract:The changes of ATP-related compounds in Aristichys nobilis and Epinephelus fuscoguttatus were studied during the storage at (4±1)℃ and (0±1)℃. Hyperchloric acid was used to precipitate proteins, 6 ATP-related compounds were analysed by high performance liquid chromatography (HPLC). Results showed that ATP in both fishes was rapidly degraded at (4±1)℃; ADP, AMP contents were always low; IMP content increased rapidly, then slowly decreased;the content of HxR in A. nobilis was relatively high, however, the content of HxR in E. fuscoguttatus was less; Hx began to largely generate after 4 days; at (0±1)℃, ATP in both fishes was also degraded quickly and ADP and AMP contents were low; IMP degradation rate became slow; the rate of formation and decomposition of HxR in both fishes was slowed down; Hx generation rate was stable. IMP and HxR were rate-limiting steps in A. nobilis, while IMP was rate-limiting step in E. fuscoguttatus. Different storage temperatures had little effect on ATP degradation, but would affect change rate of its associated compounds, and the degradation of ATP-related compounds in different species was also different.

    • The growth, mortality and yield per recruitment of white-spotted conger (Conger myriaster) in the Yellow Sea and the East China Sea

      2018, 42(6):881-888. DOI: 10.11964/jfc.20171111040

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      Abstract:The objective of this study was to provide biological reference points for the fisheries management of Conger myriaster in Yellow Sea and East China Sea. Specifically, we projected the yield per recruitment (YPR) model for C. myriaster, and obtained the biological reference points, such as Fmax and F0.1, and the suggested length of first capture (L50). Through the scientific survey and the commercial fishery survey in the Yellow Sea and East China Sea in 2016 and 2017, 657 individuals of C. myriaster were collected and measured for the total length (cm) and weight (g), in which 256 samples were analyzed for their age according to the otoliths. Based on these 657 samples, the weight-length relationships were studied by a power law model. The condition factor a estimate was 4.5×10-4, indicating the slender eel-like body shape of C. myriaster, while the estimate of parameter b was 3.3, meaning that C. myriaster tends to become relatively fatter or have greater girth as it grows longer. The von Bertalanffy growth model was used to analyze the length-age relationships based on those 256 samples with age data. The asymptotic length L was estimated to be 102 cm, and the estimate for t0, the age at which weight and length were zero, was -0.19. The exponential rate K of approach to the asymptotic length was 0.21 per year, indicating the slow growth rate of this larger demersal carnivorous species. Five scientific bottom trawl surveys were conducted in Haizhou Bay in March, May, July, September and December, 2011, in which 715 samples were collected and measured. In order to estimate the instantaneous total mortality rate Z, these samples were used to project the (length-converted) linearized catch curve to length-frequency data. This catch curve indicated that the estimate of Z was 3.36 and the length of first capture (L50) was 30 cm, meaning that the age of first capture is 1.47 years. The Pauly empirical formula evaluated the natural mortality M to be 0.33, according to the above growth parameters and the water temperature. Therefore, the fishing mortality F was 3.03, and the exploitation ratio was 90%. Based on all above estimates for the growth and mortality parameters, the yield per recruitment models were projected for C. myriaster. YPR increased to maximum, then decreased, when F kept increasing. Different M (0.23, 0.28, 0.33, 0.38 and 0.43) and different lengths of first capture (30 cm, 40 cm, 48 cm, 56 cm and 67 cm) were considered in the YPR model. When M increased, the estimates for Fmax and F0.1 would increase with smaller YPR, while the increase of L50 would result in greater Fmax, YPRmax, F0.1, and YPR0.1. The current YPR of C. myriaster was 27.14. When M=0.33, Fmax was 0.38, one eighth of the current F, while YPRmax was 52.89, nearly double of the current YPR. And when M=0.33, F0.1 was 0.255, 30% smaller than Fmax, while YPR0.1 was smaller than YPRmax by 5%. In conclusion, this fishery is undergoing heavy fishing pressure, with less length of first capture and extremely high fishing effort. Therefore, in order to keep this population health and the sustainable development of this fishery, we suggest to decrease the fishing effort largely and increase the length of first capture. For example, if F decreases from 3.03 to 2 and L50 increases from 30 to 40 cm, YPR would increase by 89%.

    • Analysis of volatile flavor components and fatty acids in fish sauces during fermentation by GC-MS

      2018, 42(6):984-995. DOI: 10.11964/jfc.20170710908

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      Abstract:In order to explore the differences of volatile components at different time points of fish sauce fermentation and the influence of fatty acids on the formation of flavor components, GC-MS techniques were applied to identify volatile flavor components and fatty acids in fish sauces during fermentation process. As a result of GC-MS analysis, 56 volatiles components that can be divided into 7 types were identified in fish sauce samples during different fermented time and further quantified based on internal standard analysis. And 12 kinds of key flavor compounds were selected as main aroma compounds, such as 3-Methylthiopropional. Therefore, the main characteristics flavors of fish sauces can be described as mushroom, potatoes, malt, vanilla, fruity and fishy flavors. The main distribution of fatty acids in fish sauce ranged for C15-C26, and the content of unsaturated fatty acid was high up to 67.23%. Moreover, the contents of linoleic acid and linolenic acid related to flavor changed significantly which were correlated with the changes of volatile compounds during fermentation. Accordingly, fatty acids were important precursor substances for characteristic flavor during fish sauces fermentation.

    • Relationship between catch distribution of Portunid crab (Charybdis bimaculata) and environmental factors based on three species distribution models in Haizhou Bay

      2018, 42(6):889-901. DOI: 10.11964/jfc.20170610878

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      Abstract:There are internal relationships between the spatial and temporal distribution of species and environmental factors; however, the randomness and uncertainty of marine ecosystems prevent demonstrating the relationships in an easy way. Based on the seasonal bottom trawl survey data collected from 2011 to 2016 in Haizhou Bay and its adjacent waters, we used three species distribution models, including GLM, GAM and Random Forest to study the spatial distribution of Portunid crab (Charybdis bimaculata) and analyze the relation with environmental factors. We selected influential environmental variables and built models according to criteria such as AIC, deviance explanation and cross validation. The effects of environmental variables on the distribution of C. bimaculata were evaluated on the basis of the SDMs. The results showed similar results among the three models in the interpretation of the relationship between environmental variables and crab distribution. The GAM provided better fit to data, whereas random forest have superior predictive performances than the other models. The models illustrated significant variations of crab abundance among years and seasons, which contributed to over 18 percent and 3.8 percent of total deviance, respectively. Depth and sea surface salinity were influential environmental factors for relative abundance, both positive correlated with relative catches. The spatial distribution of Portunid crab was featured by high catches in northeast area and low in southwest, in accordance with the water depth in Haizhou Bay. We predicted the spatial distribution of C. bimaculata across seasons using FVCOM simulation data and the random forest model to facilitate the exploitation and conservation of the fishery resources.

    • Three-dimensional distribution of fish using an imaging sonar

      2018, 42(6):996-1005. DOI: 10.11964/jfc.20170510831

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      Abstract:In order to obtain the three-dimensional (3D) distribution of fish in a marine ranching, a method using imaging sonar to calculate the 3D coordinates of fish is proposed in this paper. The imaging sonar used in this research is a Dual-frequency Identification sonar (DIDSON). It is a multi-beam sonar that uses acoustic lens to form individual beams. It constructs a high-definition two-dimensional image for target detection by transmitting ultrasonic beams underwater and receiving the echo signals. It sets a new standard for excellence in underwater vision in black and turbid waters due to obtaining near-video quality dynamic images for the identification of objects underwater. In addition, split-beam echo-sounders have also been used on some occasions to monitor the movements of fishes. Despite the improvements achieved in fish monitoring techniques, the interpretation and classification of the data collected by the traditional acoustic techniques are often challenging and require extensive experience and effort. The DIDSON bridges the gap between existing fisheries-assessment sonar and optical systems. In a DIDSON, 96 transducer elements constitute a linear array and each element both transmits and receives acoustic beams such that echo amplitude is determined by the intensity of the reflected signal. It can obtain the distance and azimuth of the target from sonar images, but it is unable to acquire the elevation of the target from the images. To overcome this difficulty and obtain the fish distribution, a new method is proposed. Firstly, the sonar is fixed on the outside of the ship's rail and submerged in the water to collect fish's information through the investigation on navigation. At the same time, the beam emission direction is on the same plane with the sonar's moving direction. After data collection, image processing is conducted, including image construction, background elimination and target extraction from horizontal field-of-view. Target association based on Interacting Multiple Model Joint Probabilistic Data Association Filtering (IMMJPDAF) is carried out to deal with the extracted targets, thus the relations of one target in different frame images can be obtained. The 3D target coordinates are acquired according to the spatial geometric relationship between the positions in two consecutive frame images. Finally, multiple target trajectories in 3D space and the depth distribution of targets are obtained through the correlation algorithm. The experiment was carried out in Dishui Lake which is located in Shanghai. Experimental results showed that the proposed method can effectively acquire the fish movement tracks in 3D space underwater and the distributions in depth. It also showed that most fish swam in the depth 3–5 meters. It will help to analyze the fish behavior and provide technical support for fishery resource assessment in a marine ranching.

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