• Volume 40,Issue 2,2016 Table of Contents
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    • Vertical characteristics of microbial community structures and the relationship with environmental factors in sediments of hybrid snakehead aquaculture enclosures

      2016, 40(2):207-217. DOI: 10.11964/jfc.20150209707

      Abstract (2184) HTML (497) PDF 9.92 M (1642) Comment (0) Favorites

      Abstract:Substrates and electron acceptors essential for microorganisms in aquaculture systems were gradually scavenged in undisturbed sediments according to the efficiency of energy metabolism along the depth, and the depth-related gradient of biogeochemical properties provided niches for metabolically diverse microorganisms. Vertical characteristics of microbial community structures may reflect the redox condition of the sediment which influences the quality of overlying water. In this study, the vertical microbial community composition of bacteria in high density culture of hybrid snakehead ponds sediment (0~50 cm) was investigated by PCR-DGGE, and the correlations between microbial communities with physicochemical characters of interstitial water were also discussed. Five phyla of bacteria including Bacteroidetes, Proteobacteria, Firmicutes, Verrucomicrobia, Planctomycetes were found. Hierarchical clustering (CLUSTER) and non-metic multidimensional scaling (MDS) analysis showed that microbial community of sediment core could be divided into three groups with significant differences, including the upper layer sediment (0~6 cm), middle layer sediment (7~38 cm) and the deep layer sediment (39~50 cm). Marglef's species richness index and Shannon-Wiener diversity index analysis of the vertical microbial communities indicated that middle layer of sediments had higher microbial diversities, which was similar to the studies of nature systems. The survey of vertical physicochemical characters of interstitial water revealed that-N concentrations ranged from 10.98 mg/L to 77.87 mg/L, increased with the sediment depth and stabilized after the depth of 15~18 cm, and PO43--P concentrations ranged from 0.01 mg/L to 0.14 mg/L, declined with the sediment depth and stabilized after the depth of 9~10 cm, and the concentrations of NO3--N,NO2--N,SO42--S, Fe2+ were relatively stable with little vertical variation. BIOENV/BEST analysis found that NH4+-N was the best environment factor which had great impact on the microbial communities, then PO43--P. The two factors are the main environment parameters of quality control in aquaculture water.

    • Effects of the manure collection equipment on growth performance and nitrogen and phosphorus budgets of Cyprinus carpio var. specularis cage culture in reservoir

      2016, 40(2):218-224. DOI: 10.11964/jfc.20150209716

      Abstract (2030) HTML (538) PDF 3.65 M (1677) Comment (0) Favorites

      Abstract:Cyprinus carpio var. specularis with body weight of (167.81±34.66) g was reared in a net cage of 5.0 m×5.0 m×2.0 m without (as a control group) and with the manure collection equipment (as a treatment group)at a stocking rate of 40 individuals/m2 at water temperature of 22~32 ℃, pH value of 6.8~7.5 and dissolved oxygen level upon 5.0 mg/L for 90 days to evaluate the input and recycle of nitrogen and phosphorus in the cage water. The results showed that the growth performance in the cage with the manure collection equipment is superior to that in the control cages, and adding the manure collection equipment had no significant effect on survival ratio (P > 0.05). The recycle rate of nitrogen was found to be 76.83% in the cage with the manure collection equipment and 44.14% in the control cage with very significant difference (P < 0.01). The recycle rate of phosphorus was 63.13% in the cage with the manure collection equipment and 35.18% in the control cage with very significant difference (P < 0.01). There were higher utilization efficiencies of nitrogen (28.36%), and phosphorus (21.30%) in the cage with the manure collection equipment than those (25.57% for nitrogen, and 18.25% for phosphorus), with significant difference (P < 0.05). Emissions of nitrogen and phosphorus were reduced to the reservoir water by adding the manure collection equipment to feeding-cage, and the eutrophication effect of cage culture on the environment was decreased.

    • Effects of early weaning and co-feeding on growth and digestive capacity in larvae of Myxocyprinus asiaticus

      2016, 40(2):225-235. DOI: 10.11964/jfc.20150409853

      Abstract (1980) HTML (538) PDF 4.59 M (1695) Comment (0) Favorites

      Abstract:According to different mixture ratios of four initial feedings [Artemia(Art), Tubifex(Tub), Microparticulate diet (MD) and Spirulina (Spi)], we divided the 10-day-post-hatching (10 dph) larvae into 8 groups at water temperature (24 ± 0.5) ℃ to investigate the effects of early weaning and co-feeding on the growth and digestive capacity of Myxocyprinus asiaticus larvae. There were two groups(Art, Tub) which kept on feeding previous diet and the rest all turned to the microparticulate diet after 40 dph. We recorded the survival rate of each group and measured length, weight and some enzyme activity at different intervals (30, 40, 45, 55 and 65 dph). Results showed that: ① the survival rate of each group performed equally and was greater than 90% before weaning at 40 dph, but the weaned groups gradually decreased after that period. The survival rates of groups (Art, Tub) fed the same diets were significantly higher than those of the corresponding weaning groups (Art/MD, Tub/MD) and the other weaning groups (P<0.05) at the end of experiment. ② Weaning had little effects on the amylase activity of M. asiaticus larvae and the trypsin activity of Art group, but significantly influenced the trypsin activity of Tub group (P<0.05). After 40 dph,there were differences in lipase activity of the Art and Tub groups,but those weaning groups (Art/MD, Tub/MD) had similar trend; ③ The weight and length of these two co-feeding groups (Art + MD + Spi/MD Tub + MD + Spi/MD) were all less than those groups (Art + Spi, Tub + Spi) correspondingly before weaning; ④ The amylase activity of the co-feeding groups and the corresponding groups were all on the rise after weaning, and the co-feeding groups were a little higher than the corresponding groups (P > 0.05). The trends of those two co-feeding groups' trypsin and alkaline phosphatase activity fluctuation were not significant before weaning, but the lipase activity of the co-feeding groups had a special change of descending first, and then ascending on the 5th day after weaning. To sum up, it was a feasible strategy to co-feed M. asiaticus larvae with 3 diets (Art, Spi and MD) and wean on 40 dph, but the ratio and addition time of MD need further study.

    • Reproductive potentiality of individual male Chinese mitten crab (Eriocheir sinensis) under the laboratory-reared conditions

      2016, 40(2):236-242. DOI: 10.11964/jfc.20150810034

      Abstract (2212) HTML (569) PDF 7.04 M (1476) Comment (0) Favorites

      Abstract:The Chinese mitten crab Eriocheir sinensis is a commercial important species in China. The aim of the study is on the individual male reproductive potentiality under the laboratory-reared conditions by evaluating the rationality of the parental sex ratio (♀:=2-3:1) during the process of breeding. The results showed that male has the capacity to complete three successive mating activities; prior to losing mating ability, male has contributed more than 60% semen material including the sperm number of ≥6×109 contained in vasa deferentia; male multiple mating activities have no obvious effect on females' fecundities; after egg-carrying, female spermathecal weights displayed no distinct deviations either in the laboratory or field-reared conditions, while both spermathecae still contained certain semen material, which means that male would have provided enough sperm to satisfy females' fertilization. Therefore, this parental sex ratio should be proper and practical. Moreover, male big size and reproductive strategy should be two important factors to avoid occurrence of sperm limitation, which make the potential ratio of sperm to egg up to (1.59-10.86)×103:1. Besides, our study reveals that this sex ratio adopted extensively in process of seed breeding, can be further optimized and elevated to 4:1.

    • Analysis and appraisement of nutrient quality for sea cucumber Apostichopus japonicus in industrial culture

      2016, 40(2):243-254. DOI: 10.11964/jfc.20150709960

      Abstract (2729) HTML (565) PDF 765.05 K (2508) Comment (0) Favorites

      Abstract:Sea cucumber Apostichopus japonicus belongs to Echinodermata, Holothuroidea, Aspidochirotida, anepibenthic, temperate species, which is an important fishery resource in many countries. A. japonicus culture is the major aquaculture industry in China, accounting for, in 2013, approximately 190 thousand tons of the production and 1.2 billion US dollars of the profit, respectively. Pond culture mode of A. japonicus has been developed for many years in Liaoning and Shandong province. However, with the expansion of pond culture, the problems have emerged, such as geographical limitations, environmental disruption, food safety problem and high environmental risk. Industrial culture of A. japonicus is a newly-developed culture mode, which has been the transformation and upgrading of traditional pond culture mode, with characteristics such as high-efficiency, controllable and environmental. With this method, A. japonicus can be cultured indoors, under controllable conditions and with higher yield. However, little is known about the nutrient compositions for A. japonicus in industrial culture. Thus, additional information on and a better understanding of the nutrient quality of A. japonicus in industrial culture are necessary. For a better understanding of that, the nutrient compositions have been investigated, in this study, in different sample resources including samples in industrial culture, samples in pond culture, samples in bottom sowing culture and wild samples. The results showed that, the body wall production of A. japonicus in I1, I2, P, N and M were 62.7%, 65.8%, 55.4%, 57.0% and 57.3%, respectively. The body wall production after cooking in I1, I2, P, N and M were 31.1%, 24.8%, 16.1%, 21.3% and 19.2%, respectively. The body wall production in I1 and I2 were higher than that in P, N and M, with no significant differences. The body wall production after cooking in I1 was significantly higher than those in the other treatments. The body wall production after cooking in I2 was significantly higher that those in P and M. The body wall production after cooking in P was significantly lower than those in the other treatments. There were no significant differences in water, fat, energy and sodium among all treatments. The protein content in N and M were significantly higher than those in I1, I2 and P. The carbohydrate content in I1 and I2 were significantly higher than that in N. The total amino acid content in I1, I2, P, N and M were 2.51, 2.77, 2.70, 4.21 and 3.65 g/100g, respectively. The essential amino acid content in I1, I2, P, N and M were 0.84, 0.87, 0.83, 1.14 and 1.06 g/100g, respectively. The highest level of essential amino acid/non-essential amino acids was found in I1, which is 0.50. The lowest level of that was found in N, which is 0.37. Among delicious amino acids in all treatments, the content of sweet amino acid, bitter amino acid, acerbic amino acid and fresh amino acid were 1.27-2.41, 0.81-1.17, 0.54-0.99 and 0.50-0.94g/100g, respectively. The ASS amino acid score in I1, I2, P, N and M were 87.89, 90.42, 85.61, 75.89 and 82.37, respectively. The ASS amino acid score in I1 and I2 were relatively higher than those in P, N and M. The ratio of saturated fatty acids/unsaturated fatty acids in all treatments were 0.86-1.76:1. The functional unsaturated fatty acids, such as C20:4N6, C20:5N3 and C22:6N3, in N were significantly higher than those in the other treatments. Saponin content in N was 0.110 g/100g, significantly higher than those in the other treatments. Niacin and cholesterol were not detected in the samples of this study. The results indicated that, A. japonicus from different sources are similar in nutrient compositions, with high nutritional value. Whereas, some differences were also found among them. Based on the better performance of body wall production and body wall production after cooking in I1 and I2, A. japonicus in industrial culture is expected to possess better economic value than those from the other sources. A. japonicus in I1 and I2 with higher ASS amino acid score indicates that A. japonicus in industrial culture, in amino acid evaluating, has better nutritional value than those from the other sources. Meanwhile, A. japonicus in bottom sowing culture and wild individuals were found to possess higher level of protein and fat, possibly due to wild food sources and long growth period. Taken together, A. japonicus in industrial culture is considered to have good performance in nutritional quality and value.

    • cDNA cloning and expression characteristics of MHC II invariant chain in Platichthys stellatus

      2016, 40(2):145-155. DOI: 10.11964/jfc.20150509901

      Abstract (2461) HTML (559) PDF 6.04 M (1804) Comment (0) Favorites

      Abstract:In the present study, full length cDNA sequence of the major histocompatibility complex II invariant chain (MHC II) Ii gene was cloned in Platichthys stellatus by using 3'RACE and 5'RACE technique, and the sequence and structural analysis of the MHC II Ii gene by using bioinformatics method. The results showed that the MHC II Ii cDNA sequence consisted of 1766 bp, including 135 bp at 5' region, 794 base pairs at 3'untranslated region and an open reading frame with 837 bp which could encode 279 amino acids. The theoretical molecular weight was 30.848 kDa, pI was 6.89. Comparison of the amino acid sequences and phylogenetic analysis showed that the P. stellatus MHC II Ii had the close relationship with Dicentrarchus labrax, Lutjanus argentimaculatus and Siniperca chuatsi. The results of different tissues indicated that the expression levels of MHC II Ii mRNA were higher in spleen and head kidney, lower in gill, blood, muscle, heart and gonads by Real-time Quantitative PCR technique. After pathogen infection, the expression levels of immune spleen and head kidney increased most significantly, and liver and intestinal expression levels increased slightly. This study can provide a theoretical basis for the function and regulation mechanism of P. stellatus MHI, and for basic research of marine fish disease resistance breeding.

    • Effect of ultra-high pressure combined with 6-gingerol processing on volatiles in Japanese seaperch (Lateolabrax japonicus)

      2016, 40(2):255-266. DOI: 10.11964/jfc.20150810023

      Abstract (2100) HTML (542) PDF 1.29 M (1917) Comment (0) Favorites

      Abstract:In order to reveal the effects of ultra-high pressure combined with 6-gingerol on volatiles in Japanese seaperch and promptly grasp the quality changes of Japanese seaperch fillets, the effects of ultra-high pressure (200 MPa) combined with 6-gingerol on quality and volatiles in Japanese seaperch were examined by electronic nose and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (GC-MS). Changes of color, structure features and volatiles in Japanese seaperch were assessed for treated groups and control group. The results indicated that the effects of ultra-high pressure combined with 6-gingerol on the quality of Japanese seaperch were significantly better than other groups. Color and structure features were also improved effectively. Electronic nose could distinguish the flavor characteristics of Japanese seaperch fillets at different treatments. Principal component analyses (PCA) showed that the noticeable difference between undeodorized and deodorized samples could be well discriminated by electronic nose. The analyses of GC-MS showed that the volatile components of Japanese seaperch fillets at different treatments changed significantly. There are 43, 40, 49 and 30 kinds of volatile substances in control, 6-gingerol, 200 MPa and 6-gingerol combined with 200 MPa groups respectively, including ethanol, aldehydes, ketones, acids, esters, hydrocarbon compounds, aromatic series and nitrogen containing compounds, etc. All these component differences resulted in their flavor style differences.

    • Molecular characters of Tc1-like transposon isolated from Coilia nasus and implication of the copy number variation

      2016, 40(2):156-163. DOI: 10.11964/jfc.20150409849

      Abstract (2055) HTML (533) PDF 5.35 M (1600) Comment (0) Favorites

      Abstract:Coilia nasus occurs as two different ecotypes in Yangtze River. To investigate the cause of the difference between population structures, we performed molecular clone and transposon displaying technology to obtain a novel Tc1-like transposon, named Cn-Tc1, from C. nasus. Cn-Tc1 with full length of 1 896 bp is the first Tc1-like transposon reported in Engraulidae fishes. Cn-Tc1 itself harbored an insertion of Tc1-like transposon of 1040 bp, suggesting that burst of Cn-Tc1 occurred in genome for several times. The lengths of inverted terminal repeats at the 5'and 3'ends of Cn-Tc1 were 64 and 83 bp, respectively. The sites at the insertions have a "TATA" motif. The predicted transposase showed a conserved DNA-binding structure, indicating that maybe Cn-Tc1 has potential for transposition. GC contents of the flanking sequence are higher than that of AT, showing an uneven distribution. A real-time PCR method was used to calculate the copy numbers of Cn-Tc1 in different populations including Jingjiang (JJ) in Jiangsu province, Xiangshan (XS) in Zhejiang province, Dongting Lake (DT), Poyang Lake (PY), Taihu Lake (TH), and Chongming (CM) in Shanghai. The copy numbers per haploid genome are 3.140×103, 2.992×103, 6.876×103, 5.205×103, 5.531×103, 3.046×103, respectively. With One-Way ANOVA analysis, there is no difference among XS, CM and JJ. When the three populations incorporated into one group of the migration, the difference among the group and other populations is significant. There is no difference among PY, TH and DT, but when incorporated into one group of the residence, the difference between the residence and the migration is significant. Our results indicated that the mutation of genetic structure caused via Cn-Tc1 facilitated the adaptive evolution of C. nasus populations by natural selection of genetic mutation.

    • HPLC fingerprint of large yellow croaker (Larimichthys crocea) and its application to geographical origin traceability and species identification

      2016, 40(2):164-177. DOI: 10.11964/jfc.20150509863

      Abstract (2260) HTML (534) PDF 4.53 M (1628) Comment (0) Favorites

      Abstract:Large yellow croaker (Larimichthys crocea) is one of the important economic fishes in China. Since 1970s, wild resources of large yellow croaker have been almost extinct due to overfishing. To solve the production problem, artificial breeding and cultured technology for large yellow croaker obtained successful breakthrough and the output of large yellow croaker was improved significantly. However, the quality of the cultured and wild large yellow croaker has great difference. In addition, the quality of cultured large yellow croaker from different environment is uneven. Therefore, the quality control methods for large yellow croaker are important for the development of large yellow croaker breeding industry. At present, fingerprint analysis has been widely applied to quality control systems of traditional Chinese medicines because of its advantages and popularity, and more chromatography and spectral methods including high-performance liquid chromatography (HPLC), gas chromatography, infrared spectrometry and mass spectrometry have been used for the fingerprint analysis, but HPLC fingerprint technology is rarely used in the quality control of aquatic products at present. In this paper, conditions for sample pre-processing, component extraction and HPLC analysis method were optimized, and a validated HPLC method coupled with cluster analysis, principal component analysis and discriminant analysis has been developed for the study of the HPLC fingerprint of large yellow croaker. Under the optimum conditions, muscles from cultured large yellow croaker (L. crocea) from Zhoushan and Fujian, L. polyactis, Nibea albiflora and Collichthys niveatus were freeze-dried and their chemical components were extracted using ethyl acetate. The chemical components from different samples were detected by Agilent 1260 DAD-HPLC on Thermo ODS-C18 (250 mm × 4.6 mm, 5μm) eluted by acetonitrile-water (0.1% H3PO4) under the optimum conditions: Flow rate 0.5 mL/min, inject volume 20μL, and wavelength 210 nm. The HPLC fingerprints and mutual mode of large yellow croaker from Zhoushan and Fujian, L. polyactis, N. albiflora and C. niveatus were established using similarity evaluation system for chromatographic fingerprint of TCM (Version 2004). Similarity analysis results indicated that the similarity order of other samples to large yellow croaker from Zhoushan was large yellow croaker from Fujian > L.polyactis > N. albiflora > C. niveatus. The same species had the similar characteristic peaks of HPLC and could be clustered together, but cluster analysis could not distinguish large yellow croaker from Zhoushan and Fujian. In the principal component analysis, three principal components (PC1, PC2 and PC3) were selected and accounted for 80.36% of the original data. According to the results of principal component scores, the scatter diagram of 62 samples was drawn, and each sample was able to form distinct cluster in the principal component space, then the identification of large yellow croaker from Zhoushan and Fujian, L.polyactis, N. albiflora and C. niveatus was basically achieved. Based on the results of principal component analysis, PC1 was used to develop the discrimination function for distinguishing different type samples. The accuracy of the discrimination function was 98.4%. Therefore, the established method had good stability, precision and reproducibility, and it was also a very reliable and useful method for distinguishing large yellow croaker from different species and/or environment. On the whole, HPLC fingerprint combined with reasonable methods of mathematical statistics provides an effective method for large yellow croaker geographical origin traceability and species identification.

    • Isolation and characterization of pepsin-soluble collagen from abalone (Haliotis discus hannai) and preparation of a polyclonal antibody

      2016, 40(2):267-277. DOI: 10.11964/jfc.20150810041

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      Abstract:Abalone mantle is the main by-product from abalone industry which is at a low utilization rate. The characterization of collagen from the abalone adductor and mantle was studied, for providing a theoretical foundation for processing of abalone. Purification and characterization of pepsin-soluble collagen from adductor (PSC1) and mantle (PSC2) of abalone (Haliotis discus hannai) were conducted. A polyclonal antibody was prepared against pepsin-soluble collagen from abalone adductor (PSC1). The results of SDS-PAGE suggested that the structures of PSC1 and PSC2 were (α1)3 and the molecular weight of α1 chain was approximately 140 ku, which was the characteristic of typeⅠcollagen from aquatic invertebrates. Peptide mass fingerprinting (PMF) of PSC1 analysis obtained 6 peptide fragments including 75 amino acid residues which were identical with collagens from H. discus with 100% identity and H. tuberculata with 88% identity, suggesting PSC1 is collagen. Amino acid composition analysis showed that PSC1 and PSC2 had similar composition, while the amino acid content of them were lower than calf skin collagen by acid extraction. Circular dichroism (CD) spectrum analysis demonstrated a rotatory maximum at 220 nm and a negative peak at 197 nm of PSC1 and PSC2 solution, which were typical characteristics of the collagen triple helix structure. FTIR spectra further confirmed that both PSC1 and PSC2 have similar triple helical structure. According to Western blot analysis of collagens from 4 kinds of aquatic animals, the polyclonal antibody only positively reacted with α, β and γ chains of PSC1 and PSC2 from abalone, whereas no reactivity against collagens from Oreochromis niloticus, Cyprinus carpio and Stichopus japonicas was identified, indicating high specificity of the polyclonal antibody.

    • Phylogenetic relationship and genetic differentiation of two geographical populations of Carassius auratus in Guizhou Province

      2016, 40(2):178-188. DOI: 10.11964/jfc.20150709970

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      Abstract:Carassius auratus in Pu'an and Caohai Lake are the special isolated groups of C. auratus in the Karst Mountain Areas. In order to fully understand the genetic structure systematically and discuss the phylogenetic relationship and genetic differentiation of the two populations, the mitochondrial DNA control regions of two geographical populations were analyzed by sequencing technology in this study. The results showed that C. auratus in Pu'an had eight types of sequence length of 919 and 921-927 bp, belonging to 27 kinds of genotypes and 14 kinds of haplotypes; C. auratus in Caohai Lake had three sequence types of sequence length of 923-925 bp, belonging to 11 kinds of genotypes and 6 kinds of haplotypes; The sequences variation due to base substitution and the deletion/insertion. Clustering analysis confirmed that C. auratus in Pu'an were the mixed groups of C. auratus gibelio and C. auratus including their 3 sublineages. C. auratus in Caohai Lake was the mixed groups of 2 sublineages of C. auratus. The populations of C. auratus and C. auratus in Pu'an had medium genetic diversity and the populations of C. auratus and C. auratus in Caohai Lake had low genetic diversity, while the population of C. auratus gibelio in Pu'an had extremely low genetic diversity. The study indicated that the two geographical groups of C. auratus had a characteristic of complicated group composition and matrilineal diversity. As the longterm geographical isolation, reproductive isolation and lack of gene flow resulted in the difference of genetic drift and evolutionary rate, which made the genotype and haplotype of D-loop also had obvious geographical distribution pattern, the genetic differentiation was remarkable among various groups. C. auratus gibelio in Pu'an and in northeast of China belong to the same origin of matrilineal line, the degree of population genetic variation was so low that improving the quality of the parents was urgent. The founder effect, the bottleneck effect and genetic drift led to the low genetic diversity current situation of C. auratus in Caohai Lake. This experiment might enrich the fish population genetics research materials in the Karst Mountain and provide basic data for identification and evaluation of the germplasm resources of the local C. auratus.

    • >ROUNDUPS
    • Progress of research on gonadotropin-inhibitory hormone and its receptors in fish

      2016, 40(2):278-287. DOI: 10.11964/jfc.20150709998

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      Abstract:Gonadotropin-inhibitory hormone (GnIH) is a novel hypothalamic neuropeptide which was originally isolated from the quail brain and known for inhibiting the secretion of gonadotropin (GTH) from cultured quail anterior pituitaries. GnIH participates in growth, reproduction, and food intake via the specific seven transmembrane G protein-coupled receptors (GPCRs). To date, GnIH was identified in several teleosts, including goldfish, zebrafish, grass puffer, tilapia and orange-spotted grouper. However, information on the studies of GnIH physiology are limited and contradictory in fish. The regulation of GnIH and its receptors as well as other roles of GnIH awaits further studies in teleosts. This review brifely summarized the progress of research on GnIH and its receptors, with special emphasis on the physiological functions of GnIH in fish and we hope this review will contribute to the futher studies.

    • >PAPERS
    • Morphological characteristics and functional investigation of the abocular side skins on head of six pleuronectiformes fishes

      2016, 40(2):189-197. DOI: 10.11964/jfc.20150309777

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      Abstract:In this study, the morphologies of the abocular side skins on head of six pleuronectiformes fishes were investigated by scanning electron microscopy (SEM). The results showed that a large number of free neuromasts were found on the abocular side skins of Cynoglossus semilaevis and Solea senegalensis with more occurring around the anterior nares and the tips. The free neuromasts in C. semilaevis looked like papillae, covered by many skin wrinkles that consisted of epidermis cells and generally appeared in groups with random arrangement. However, the free neuromasts of S. senegalensis skins, exposed on the surface with a linear arrangement, lie under the bud-like epidermis. A small amount of neuromasts scatter on head skins of Platichthys stellatus, whose morphologies were similar to those of C. semilaevis. Except orifices of mucus secretion, there were no special structures found on the skins of abocular sides of Scophthalmus maximus, Limanda yokohamae and Verasper moseri. According to the differences in organization and distribution of free neuromasts, it is inferred that morphological characteristics of the abocular side skins in pleuronectiformes many be closely related to their feeding behaviors. The distribution characters of free neuromasts on the abocular side skins can provide a certain basis for species classification of pleuronectiformes.

    • Comparative analysis of ichthyoplankton samping gear for early life stages of fish in the Yangtze River estuary and adjacent areas

      2016, 40(2):198-206. DOI: 10.11964/jfc.20150810026

      Abstract (2061) HTML (513) PDF 885.64 K (1927) Comment (0) Favorites

      Abstract:Although it is common sense that the accurate sampling and unbiased data acquired are essential bases for further evaluation, during the field work of ichthyoplankton study, samples from conventional single gear are highly possible to deviate from the population greatly. To choose the more efficient sampling gear, comparative gear tows were conducted from April to July of 2014 in the Yangtze River estuary and adjacent areas with focus on species composition, density estimates (ind./100 m3), developmental stage composition of larval fish assemblages. Larval fish were collected by the plankton net (0.5 mm mesh) and frame net (1.0 mm mesh), respectively. Results indicated that the species richness was higher in the catches of frame net (51 species) than that in plankton net (37 species), along with 34 mutual species between them, while the composition of dominant species showed no significant difference. There was an unpredicted bias in average density of catches between two gears. In April, the average density was higher in catches of plankton net, due to the abundant occurrence of pre-flexion larvae which were too tiny to be efficiently caught by large mesh. In contrast, the average density was higher in frame net than those in plankton net from May to July. The plankton net samples were dominated by pre-flexion larvae, and the average density of pre-flexion larvae of anchovy (Engraulis japonicus) and gobies (Gobiidae spp.) was higher in catches of plankton net. While post-flexion larvae were dominated in frame net, and the average density of postflexion larvae of the dominant species, which were small yellow croaker (Larimichthys polyactis), anchovy and gobies, was higher in frame net samples. These differences suggested that there was significant catch efficiency between the two nets. In conclusion, frame net is more efficient. However, when it comes to specifically collect fishes of elongated type (e.g. anchovy), combination of multiple types of sampling gears should be in consideration. Conversely, an unique frame net is highly adequate for broad type fishes (e.g. croakers).

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