2019 Vol. 15 No. 5
A total of 119 individuals of Sillago japonica were collected from six sampling sites (Laizhou, Jiaonan, Zhoushan, Xiamen, Shantou and Beihai). The length of 450 bp NADH dehydrogenase subunit 2 (ND2) gene fragment was amplified and sequenced. No base insertion or deletion mutations occurred and 77 mutation sites were detected, including 30 parsimony informative sites and 28 singleton polymorphic sites. Sixty-one haplotypes were defined in 119 sequences. The average haplotype diversity (Hd) and nucleotide diversity (π) were 0.945 3±0.015 5 and 0.009 718±0.005 445, respectively. The average genetic distance among the six populations was 0.008 3, and the genetic differentiation index FST value was less than 0.05, indicating no significant genetic differentiation among the populations. Analysis of molecular variance (AMOVA) shows that genetic variation of S. japonica mainly resided among individuals within populations (99.96%). The neutral tests (Tajima's D and Fu's Fs) were both negative and deviated from the neutral significantly. Besides, the nucleotide mismatches distribution showed a unimodal distribution, indicating that S. japonica had experienced population expansion in history. The estimated expansion time was about 0.12−0.29 million years ago in late Pleistocene.
According to the catch statistics data during 1950−2015, we applied a Catch-MSY model to estimate the allowable catches and maximum sustainable yields (MSYs) for 24 commercial fish groups and total allowable catch (TAC) in Pakistani coastal waters. Results show that MSY and TAC in Pakistani coastal waters were 40.53×104 t and 36.47×104 t, respectively. The total catches in 2015 were less than MSY, suggesting that the fisheries are not overfished. The MSY results show that eight fish groups (cobia, Barracudas, Groupers, Butterfishes, common dolphinfish, dorab wolf-herring, crevalle jack and largehead hairtail) have been overfished at present since the catches in 2015 exceeded MSY. At present, the marine fishery resources in Pakistani coastal waters are fully exploited. Most commercial fish groups are overfished or recovering after collapse and their development potential is relatively small. It is recommended to exploit oceanic fishery resources such as Sthenoteuthis oualaniensis in Arabian Sea in future fisheries development.
In order to understand the characteristics of trophic structure of main fishery in typical gulf of southern China with significant habitat difference, we analyzed the ratio of carbon and nitrogen stable isotopes (δ13C and δ15N) of major fishery species collected in Hailing Bay and Lingshui Bay in wet season of 2015, and calculated several quantitative metrics based on the δ13C and δ15N ratios so as to quantitatively characterize the trophic structure in community-wide aspect. The results show that the average δ13C [−15.36±0.62)‰] and δ15N [(15.53±0.94)‰] values of main fishery species in Hailing Bay were significantly higher than those in Lingshui Bay [(−17.44±1.21)‰ and (13.78±1.31)‰, P<0.01]. However, the NR and TA values of Hailing Bay were lower than those of Lingshui Bay, showing longer food chain length and higher diversity in Lingshui Bay. Calculated by 3.4‰ as a nutrient grade of nitrogen stabilized isotope enrichment, the grade distance of Lingshui Bay fishery was only 1.37, lower than 1 of Hailing Bay, indicating that both Lingshui Bay and Hailing Bay have relatively less high trophic organisms and the food webs are often disturbed.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to measure the concentration of trace elements in the otolith of the South China Sea squid (Sthenoteuthis oualaniensis). The composition of trace elements in the otolith and the change of the ratio of trace elements to calcium (Ca) were analyzed. The differences and the relationship between the otolith and habitat were discussed. The results show that the main trace elements are Ca, Sr, Na, Fe, Ba and Mn. Analysis of variance (ANOVA) reveals no significant difference between populations and genders (P>0.05). There was significant difference in the ratio of trace elements to calcium among different regions of statolith (P<0.01) except for Fe/Ca. The Sr/Ca ratio was the highest in the nucleus and then decreased. There was no significant difference in Sr/Ca ratios among different spawning groups and geographical regions (P>0.05). There was a positive relationship between Sr/Ca and temperature, and a negative relationship with salinity at the larval stage. Sr/Ca can be used as a good temperature indicator. Na/Ca first increased and then decreased, highest at the dark zone. Na/Ca is significantly different among different spawning populations at the nuclear and post nuclear zones (P<0.01). Mn/Ca and Ba/Ca, which first decreased and then increased (lowest in the dark region), increased at the edge zone and peripheral zone. There was a positive relationship between Ba/Ca and salinity at adult stage, and Ba/Ca can be used as an indicator of vertical movement. Fe/Ca was significantly different among different spawning populations and geographic areas (P<0.01). It is shown that Na/Ca and Fe/Ca are suitable for distinguish of different groups of squid, and Sr/Ca and Ba/Ca can be used to estimate the habitat environment of squids in the South China Sea.
In order to select asuitable method for water quality evaluation in the Pearl River Delta (PRD), we accessed and analyzed the water environment factors and phytoplankton data in PRD in 2015. Four phytoplankton indices, including Shannon index, evenness index, richness index and biomass index, were selected from six common phytoplankton indices based on similarities by using self-organizing map (SOM). Then, we compared the water quality evaluation results of the above indices and environmental factors. The results based on dissolved oxygen and ammonia nitrogen could reflect the spatial differences between city centers and other regions, but total nitrogen and total phosphorus were not suitable for water quality evaluation. However, the results based on Shannon and biomass indices could reflect the differences between city centers and other regions, but evenness and richness indices were not suitable for water quality evaluation. Except for total nitrogen and total phosphorus, the evaluation results of other environmental factors and four phytoplankton indices show that the water quality of the survey area was generally good, but the water quality of stations around the city was slightly poor. Thus, issolved oxygen, ammonia nitrogen, Shannon index and biomass index are suitable environmental factors and phytoplankton index for water quality evaluation.
Sargassum hemiphyllum, a common species in coastal waters of Guangdong Province, was selected to study its physiological response to different concentrations of heavy metal (Cd2+) stress and its tolerance to Cd2+ stress in laboratory semi-static experiments, so as to provide a basis for remediation of heavy metal pollution in that area. The results show that chlorophyll a (Chl a), carotenoid (Car), soluble protein (SP), soluble sugar (SS) and antioxidant enzyme activity (SOD and CAT) of S. hemiphyllum at Cd2+ concentration of 0.1 mg∙L−1
had no significant difference with the control (P>0.05). The contents of Chl a, Car, SP, SS, SOD and CAT at ρ(Cd2+) of 0.5−12.5 mg∙L−1, were significantly higher than those of the control (P<0.05); there was no significant change in MDA contents under Cd2+ concentration of 0.1−0.5 mg∙L−1 (P>0.05), and significant increase at Cd2+ concentration of 2.5−12.5 mg∙L−1 (P<0.05). Therefore, S. hemiphyllum had stronger stress resistance at Cd2+ concentration of ≤0.5 mg∙L−1, while excessive Cd2+ stress of >0.5 mg∙L−1 will be harmful for its photosynthesis and antioxidant function.
We collected 721 individuals of Acanthopagrus schlegeli in Daya Bay in January, March, April, August−December, 2018, and then investigated the annual variation of reproductive characteristics of A. schlegeli in Daya Bay so as to provide a theoretical basis for its artificial breeding and conservation. The results show that: 1) the spawning period falls between November and March. The total length ranged 175−487 mm for females [averge (297.92±56.61) mm]. The body mass ranged 90.96−1 907.12 g for females [average (511.36±307.53) g]. The total length ranged 110−440 mm for males [average (237.61±61.05) mm]. The body mass ranged 21.92−1 370.00 g for males [average (277.76±210.33) g]. The full lengths of females were significantly longer than those of males (P<0.001). 2) The gonad maturity coefficient and gonad development indicate that the reproductive period of A. schlegeli in Daya Bay was from November to March. 3) The existence of androgynous individuals indicates that the species will undergo sexual reversal, and the males will mature first and then change to females. 4) The total lengths (TL) at 50% sex maturity for females and males were 248.52 mm and 148.03 mm, respectively. 5) A. schlegeli is a multiple spawner with indeterminate fecundity by oocyte size-frequency distributions. The number of the individual fertility ranged from 84 100 to 2 655 168 granules (average 728 732±499 547). The relative fertility of total length was 380.54−8 271.55 eggs·mm−1 [(2 731.44±1 630.93) egg·mm−1]. The relative fertility of body mass was 277.58−3 592.83 eggs·g−1 [average (1 443.87±766.82) eggs·g−1]. There was a linear correlation among absolute fecundity and total length, body mass and gonadal mass.
In order to promote the development and utilization of Grateloupia and provide reference for its food and processing, we investigated the species composition, biomass, growth environment and mouthfeel of Grateloupia on floating rafts in Nan'ao, Shantou, Guangdong Province and Dongshan, Fujian Province once a month from January to April 2018. The results show that the water velocity and temperature were 0.039−0.985 m·s–1 and 19−23 ℃, respectively, and the water velocity in Dongshan was greater than that in Nan'ao. By morphology, cross-section and rbcL sequence analyses of the samples collected from the floating raft, we found eight Grateloupia species (G.lanceolata, G. turuturu, G.taiwanensis, G.carnosa, G.livida, G. haimensis, G. prolongata and G. sparsa). The dominant species were G. lanceolata and G. turuturu whose highest biomass were 901.26 g·m–1 and 352.9 g·m–1, respectively. G. lanceolata that grew with higher water velocity had longer body length that could reach 142 cm. The mouthfeel of G. turuturu and G. prolongata was the worst but that of G. lanceolata and G. livida was the best. G. lanceolata and G. livida had better mouthfeel in January to March than in April. It is worth developing G. lanceolata as marine vegetable for its bigger biomass, size and its better mouthfeel.
We compared the density, pH, dissolved oxygen and colony structure of Nitzschia closterium f. minutissima bred in negative pressure photobioreactor and open bucket, respectively. It is shown that the algae grew fast in negative pressure photobioreactor with the highest density of 1.33×107 cells·mL–1, significantly higher than that in open bucket (8.36×106 cells·mL–1). The pH in algal solution increased with increase of algal density, and there was a significant positive correlation between them (P<0.01). The highest pH values in negative pressure photobioreactor and open bucket were 10.3 and 9.3, respectively. Oppositely, in negative pressure photobioreactor, the dissolve oxygen of algea decreased with increase of algal density, which finally stabilized at about 6.5 mg·L–1. The decline of dissolved oxygen might be related to the fact that Roseobacter had become the dominant bacteria. Results of 16S rDNA gene high-throughput sequencing show that the bacterial diversity decreased significantly (P<0.05). Proteobacteria and Bacteroidetes were dominant bacteria at early stage of breeding. However, the dominant bacteria were Cyanobacteria and Roseobacter at late stage in negative pressure photobioreactor, which was obviously different from that in open bucket.
Taking lethal time of high ammonia nitrogen and freshwater tolerance as indices, we estimated the heritability of ammonia nitrogen tolerance and freshwater tolerance of Penaeus monodon. We established 27 full-sib families including five half-sib families of P. monodon based on two breeding populations of P. monodon from Nanhai No.1 and African strain. Besides, we estimated the variance components and genetic parameters for ammonia nitrogen tolerance and freshwater tolerance by using one trait animal model and ASReml software. Then we calculated the estimated breeding values of all animals and families with best linear unbiased prediction. The heritability for ammonia nitrogen tolerance and freshwater tolerance were 0.11±0.04 and 0.29±0.08, respectively (P<0.05). The family phenotypic value correlation coefficients between ammonia nitrogen tolerance and freshwater tolerance was 0.15, showing low linear positive correlation and statistically insignificant difference. The family breeding value correlation coefficients between ammonia nitrogen tolerance and freshwater tolerance was 0.57, showing moderate linear positive correlation and statistically significant difference (P<0.01). Thus, the resistance to freshwater stress can also be improved to some extent with selection of characteristics of ammonia tolerance of P. monodon.
In order to study the effects of desiccation stress on crayfish (Procambarus clarkii) during crayfish seedling transportation, we investigated the antioxidant stress ability and survival rate of crayfish to desiccation stress (6 h, 12 h, 18 h, 24 h) and resubmersion in water (1 h, 6 h, 12 h) at (20±1) ℃ and with (50±5)% relative humidity (RH). The results show that the desiccation time should not exceed 18 h; the mortality rate at 24th hour was 53.3%, but no juveniles died during the resubmersion. During desiccation, no significant difference was observed in total antioxidant capacity (T-AOC, P>0.05); the superoxide dismutase (SOD) significantly reduced; the catalase (CAT) activity increased with time; the malondialdehyde (MDA) content reached the maximum value after 24 h (P<0.05), and the blood sugar and muscle lactic acid increased significantly with time (P<0.05). During the resubmersion period, the SOD and CAT activities fluctuated without an obvious rule; the MDA content restored to normal level after 12 h but the T-AOC maintained a high level. The lactate contents of 6 h and 12 h groups restored to the control level after resubmersion for 1 h. The blood sugar contents of all treatment groups were always higher than that of the control group (P<0.05). It is shown that the MDA content and SOD activity which can be regarded as immune indices are more sensitive to desiccation stress. The MDA, blood sugar and lactate contents can reflect the physiology of crayfish during resubmersion period.
In order to determine a scientific feeding strategy for Trachinotus ovatus, we investigated the day and night diet feeding, oxygen consumption rhythm and gastrointestinal evacuation time of the fish in laboratory. The diet feeding rhythm was invstigated by a continuous feeding with fixed interval (feeding once every two hours day and night for three continuous days). The oxygen consumption rhythm was measured by flow-water breathing method (measuring once every two hours day and night for 24 h). The gastrointestinal evacuation time was measured by a full feeding method (sampling once every two hours day and night for a day). Results show that T. ovatus had a daytime feeding pattern with two extremely obvious feeding peaks (10:00 and 14:00−16:00, P<0.05), and the peak periods of oxygen consumption appeared at 08:00 and 16:00, respectively (P<0.05). The stomach digesta ratio of T. ovatus decreased sharply after feeding (P<0.05), nearly 50% at 7th hour, and reached to zero after 19 h. However, the bowel digesta ratio of T. ovatus increased sharply after 1−3 hours of feeding, and reached the maximum at 11th hour and the minimum at 21st hour. Thus, it is suggested that the optimal feeding periods of T. ovatus are 09:00−10:00 and 14:00−16:00 with strong light, oxygen consumption and peak feeding. The feeding frequency is 2−3 times per day and the feeding interval is 7−9 h.
In order to promote the high value utilization of pearl oyster (Pinctada martensii), we were determined explore the antibacterial activity and procoagulant activity of enzymatic hydrolysis from its mantle (EHM), and the effects of EHM on open wound healing of skin of mice. Results showed that EHM possessed of procoagulant activity in mice but had no antibacterial activity against 13 tested strains. Compared with the negative control group, the healing rate of wound of mice increased significantly after skin application with EHM for 6 d (P<0.05), but there was no significant difference with comparison with the positive control group (P>0.05). The healing rate was 100% on 14th day for the drug group, and the scar contraction rate was significantly higher than that of the negative control group (P<0.05). Biochemical indicators test indicated that EHM had significant inhibitation effect on inflammatory factor IL-6 (P<0.05); compared with the negative control group, it could promote IL-10 secretion in wound tissues significantly (P<0.05), but there was no significant difference in FGF-2 content in skin tissue of the drug groups (P>0.05), and EGF content in the positive control group was significantly higher than that in the other groups (P<0.05). Howerer, there was no significant difference in the contents of FGF-2 and EGF between the drug groups (P<0.05). In summary, EHM has procoagulant, anti-inflammatory and promotional effects, which can accelerate the open wound healing of soft tissue in mice and has a certain inhibitory effect on superficial scar hyperplasia.
In order to develop a safe food-grade quick-freezing liquid formulation suitable for rapid freezing of aquatic products, we designed a low-temperature quick freezing liquid which composed of ethanol, oligofructose, citric acid, calcium chloride and propylene glycol. Then, we analyzed the variation of freezing point with different mass fractions of that composition by single factor test. Based on that, taking the freezing point and viscosity as response values, we optimized the addition amount of the refrigerants in the quick freezing liquid by Box-Behnken response surface method. The optimum formula of quick-freezing liquid was 19.9% ethanol, 9.5% fructooligosaccharide, 3% citric acid, 5% calcium chloride and 10% propylene glycol. The quick-freezing liquid prepared by the formula had a freezing point of –63.50 ℃ and a viscosity of 4.64 mPa·s, characterized by low freezing temperature, small viscosity, low formulation cost and convenient operation, suitable for rapid freezing of aquatic products and frozen convenience foods.
We investigated the changes of tyrosinase and cystinase activities, as well as the expressions of tyr, mitf, agouti and mc1r mRNAs at the early developmental stage of Kohaku and Hi-Utsuri koi carp (Cyprinus carpio) by using histological observation, enzyme-linked immunoassay and quantitative reverse transcription-polymerase chain reaction methods. The results show that the hatched carps became light yellow and translucent. The melanocytes occurred on 8 dph (day-post-hatching). The activity of cystinase increased with the koi carp development, and no significant difference was observed between Kohaku and Hi-Utsuri groups before 7 dph (P>0.05), while Hi-Utsuri group showed significantly higher enzyme activity than Kohaku group at the same stages after 7 dph (P<0.05). Tyrosinase activity showed an up-regulation trend with slight fluctuation during the development of koi carp, and peaked at the ocular pigment stage and on 23 dph (P<0.05). The enzyme activity was significantly higher in Hi-Utsuri group than in Kohaku group at each developmental stage (P<0.05), which indicates that tyrosinase and cystinase activities were closely associated with pigment cell development of koi carp. The expressions of agouti, mc1r, mitf and tyr mRNAs peaked in gastrula and blastula periods (P<0.01), then decreased. Thus, agouti, mc1r, mitf and tyr mRNAs might play an important role in the formation of body colors in early embryonic development.
In this study, two strains of lactic acid bacteria [Lactobacillus casei (S60) and L. plantarum (S72)] were tested by aseptic technique, including routine biochemical detection, susceptibility test, in vitro bacteriostasis test and animal experiment. Their feasibility and safety as probiotics for fishing were also verified. Results show that the two lactic acid bacteria could tolerate acid (pH 4.0) and bile salt (0.1%), and exhibit different antibacterial activities against six pathogens including Aeromonas hydrophila. The results of antimicrobial substances analysis shows that the effective antimicrobial substances were related to the organic acids produced in metabolic process. The results of safety evaluation shows that the two strains of lactic acid bacteria had no ability to decompose gelatin and hemolysis. The results of death statistics and blood biochemical indicators show that the intraperitoneal injection of live bacteria as high as 1.0×109 CFU·mL−1 did not cause serious death and body injury in experimental fish. It is included that the two strains of lactic acid bacteria have high safety as oral probiotics. Drug resistance studies show that the two strains of lactic acid bacteria had strong tolerance to aminoglycosides and sulfamethoxazole, and were sensitive to ampicillin, enrofloxacin, florfenicol and doxycycline. Therefore, the application of the two strains of lactic acid bacteria should pay attention to the selection of drugs in management process.
As a notorious environmental issue, harmful algal blooms (HABs) severely threat the marine ecosystem, aquaculture and human health around the world. Therefore, it has been a research hotspot to develop a more environment-friendly and effective agents to control the HABs. In recent years, a lot of marine bacteria have been found to inhibit algal growth or lyse the algae through direct or indirect attacking. Utilizing marine algicidal bacteria to control HABs can maintain balance of water ecosystem. The algicidal bacteria show broad application prospects in HABs control because of its secure and high efficiency. In this paper, the development of algicidal bacteria, algicidal mechanism and their applications are summarized, and the future prospects in theoretical research and application fields are discussed.