2013 Vol. 9 No. 6
Stichopus horrens is a tropical sea cucumber with high economic value, widely distributed in South China Sea.Due to unreasonable commercial exploitation, the wild population of S.horrens has reduced sharply so its artificial propagation and aquaculture are urgent.New breakthrough had been made in artificial propagation of S.horrens; however, there is insufficient research on S.horrens aquaculture.We investigate the possibility of culturing and releasing tropical sea cucumber by releasing juveniles and adults in cages in 3 areas at Xisha Islands from 2010 to 2011, and regularly monitoring the survival and growth rate.The results reveal that both juveniles and adults of S.horrens can be cultured in cage in the wild.For the released adults cultured in cages with low density, all survived after 7 months, although their weight decreased slightly.Survival and growth rate of the adults in region A were higher than those in region C.The aquaculture of adults in area A was superior to that in area C.The bigger sized (about 3 cm) juveniles had higher survival and growth rate than the smaller ones (about 1.5 cm).In area A and B, the contents of nutrient salts in seawater and organic compounds in the sediment were higher than those in area C.Therefore, cage culture of S.horrens in the wild is feasible with suitable area and size.
The tropical Pacific Ocean is the main tuna fishing area in the world. The impact of tuna longline fishery on pelagic shark populations has received considerable concerns recently. However, it is difficult to evaluate their population status using formal stock assessment models due to the lack of long-term fishery data. We conduct productivity-susceptibility analysis (PSA) to evaluate the vulnerability to overfishing for 10 pelagic shark species in the tropical Pacific Ocean. The 10 species with risk of overfishing suffered from longline fishery, in terms of vulnerability score, are as follows (in ascending order): smooth hammerhead (Sphyrna zygaena), scalloped hammerhead (S.lewini), great hammerhead (S.mokarran), shortfin mako (Isurus oxyrinchus), common thresher (Alopias vulpinus), oceanic whitetip shark (Carcharhinus longimanus), blue shark (Prionace glauca), silky shark (C.falciformis), pelagic thresher (A.pelagicus) and bigeye thresher (A.superciliosus). The results provide important information for conservation of pelagic sharks and pelagic ecosystem interacting with tuna longline fisheries in the tropical Pacific Ocean.
Grateloupia livida is a kind of commercial and scientific red alga with potential value in nutraceuticals and pharmaceuticals. We investigate the early development of G.livida at different temperatures (15 ℃, 20 ℃, 25 ℃ and 30 ℃) and light intensities (500 lx, 2 500 lx, 5 000 lx and 10 000 lx). The results show that the optimal conditions for the development of carpospores are temperature 25 ℃ and illumination 5 000 lx. The discoid crusts form were firstly at 25~30 ℃ and lastly at 15 ℃. Seedings cultured from discoid crusts were firstly observed at 25 ℃, then at 20 ℃, 15 ℃ and 30 ℃. The discoid crusts form firstly at 5 000~10 000 lx and then at 2 500 lx. In conclusion, high light intensity significantly accelerates the growth and development of discoid crusts. Low light intensity of 500 lx retards the growth and development of discoid crusts of G.livida.
To investigate the effects of different brands of commercial diets (D1, D2, D3, D4, D5 and D6) on the growth performance of black tiger shrimp (Penaeus monodon) and water quality, we fed the shrimps with 6 diets for 60 d.The results show that the weight gain and special growth rate of shrimps fed with D1, D5 and D6 are significantly higher than those with D2 and D4 (P < 0.05), and the feed conversion ratios of shrimps fed with D5 and D6 are significantly lower than those with D2 and D4 (P < 0.05).The apparent protein digestibility of shrimps fed with D4 and D5 is much higher than those with D1~D3 (P < 0.05).At 20th day, the chemical oxygen demand (COD) with D1 treatment is the lowest and significantly lower than that with D5 and D6 (P < 0.05).At 40th day, the COD with D5 and D6 treatments are significantly lower than that with D1~D4 treatments (P < 0.05).The NH4+-N with D2 treatment is the lowest and significantly lower than that with D4~D6 treatments (P < 0.05), and the total nitrogen (TN) and total phosphorus (TP) are the lowest with D4 and D6 treatments.At 60th day, the NH4+-N with D1 treatment is the lowest and significantly lower than that with the other treatments except D2 treatment (P < 0.05), and the TN with D5 and D6 treatments are significantly lower than that with D1~D4 treatments (P < 0.05), but the TP with D2 treatment is the lowest and significantly lower than that with D1 and D4 treatments (P < 0.05).The excretion rates of nitrogen with D1 and D6 treatments are the lowest and significantly lower than that with the other diet treatments (P < 0.05).The minimum excretion rate of phosphorus is with D1 treatment.In conclusion, the shrimps fed with D1, D5 and D6 perform better in growth, and D1, D5 and D6 diets have minimal pollution to the water.
The freshwater microalga, strain C67, was isolated from a freshwater lake in Hainan and selected as a high lipid producer. The biomass productivity and lipid content of the microalgal strain were analyzed under different trophic cultivation modes including autophototrophic, mixotrophic and heterotrophic cultivations. The strain was tentatively identified as Micractinium reisseri C67 based on microscopic examination and Lsu (large subunit) rDNA sequence analysis. Major fatty acids in the microalgae were C18:1, C16:0, C18:3 and C18:2, comprising 33%, 26%, 18% and 11% of the total fatty acids, respectively. The biomass productivity and lipid content of M.reisseri C67 under mixotrophic cultivation were higher than those of under autotrophic and heterotrophic cultivations. The maximum biomass productivity (7.0 g·L-1) and the maximum lipid content (40.2%) of M.reisseri C67 were achieved under mixotrophic cultivation with glucose and glycine (Gly), respectively. The lipid productivity of M.reisseri C67 was 2.2 g·L-1, 7.3 and 7.9 folds of those obtained under autophototrophic and heterotrophic conditions, respectively.
We analyze the expression stability of the housekeeping genes in Pinctada fucata, including Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH), beta-actin (β-actin) and 18S rRNA (18S), by quantitative real-time polymerase chain reaction (qRT-PCR) in different tissues, at different stages of gonadal development and embryonic development.Besides, we select the suitable reference genes by using softwares of BestKeeper, geNorm and NormFinder algorithms.The results indicate that β-actin is the most stable reference gene for different tissues and different embryonic developmental stages, while 18S is the most stable reference gene for different gonadal developmental stages.
The study explores the effect of Fenpropathrin on the acute toxicity and Na+-K+-ATPase activity and histopathological changes of carp (Cyprinus carpio) gills.According to the acute toxicity result, the 96 hour lethal concentration (96 h LC50) is 8.53 μg·L-1and the safe concentration (SC) is 0.853 μg·L-1.Exposed to Fenpropathrin at concentrations of 0, 0.43 μg·L-1, 0.85 μg·L-1, 1.70 μg·L-1 and 4.27 μg·L-1, the gill tissue of carp were collected at the 1st, 3rd, 7th, 14th, 21st day, respectively.Results indicate that the activities of Na+-K+-ATP enzyme in gill tissue during different exposure periods vary in a wave shape, i.e., first decrease, then increase, and decrease again as the exposing time progresses at the same concentration.The ATPase activities reach the lowest at 3rd day, which are very significantly different from the control (P < 0.01), with inhibition rates of 42.49%, 27.48%, 59.03% and 46.31%, respectively.The enzyme activities of all concentration groups reach the highest at 14th day, which are significantly (P < 0.05) or very significantly (P < 0.01) higher than that of the control. At 21st day, the enzyme activities of the highest concentration group are significantly lower than that of the control except the other 3 concentration groups.The HE staining histological changes in the gills include gill-amells distortion, epithelial cell and pillar cell shedding, blood capillary of gill-amells expanding and hyperaemia, mucilage cell and basal cell hyperplasia, sometimes even gill-amells adhesion and gill filament becoming club-shape.The damages of gill are related to concentration and effect of time accumulation.
Intestine and gonad of sea cucumber (Apostichopus japonicus) are by-products during its processing process.In order to utilize them better, we analyze the changes in contents of soluble protein and amino acid nitrogen during enzymatic hydrolyzation as well as study their free radical scavenging effects against 1, 1-Diphenyl-2-picrylhydrazyl radical (DPPH·), hydroxyl free radical (·OH) and superoxide anion free radical (O2-·) in vitro.Results show that the degree of hydrolysis (DH%) of intestine and gonad after enzymatic hydrolyzation are 53.63% and 63.40% respectively; the contents of soluble protein are 4.62 mg·mL-1 and 5.01 mg·mL-1, respectively; the contents of amino acid nitrogen are 0.43 mg·mL-1 and 0.56 mg·mL-1, respectively.The half maximal inhibition concentrations (IC50) of polypeptides prepared from intestine and gonad are 3.31 mg·mL-1 and 0.88 mg·mL-1 against DPPH·, respectively, 9.53 mg·mL-1 and 8.81 mg·mL-1 against ·OH, respectively, 6.42 mg·mL-1 and 3.22 mg·mL-1 against O2-·, respectively.The polypeptides from intestine and gonad of sea cucumber have remarkable antioxidation functions with good application prospects.
To investigate the accumulation and elimination rules of avermectin in perch (Lateolabrax japonicus) muscle during actual breeding process, we determined the median lethal concentration in 96 h as 4 ng·mL-1 based on a toxicity test, and exposed the perch to 4 ng·mL-1 of avermectin for 72 h, and then transfered the solution into seawater. Thus, we develop a method by high performance liquid chromatography-tandem mass spectrometry to determine avermectin in perch muscle. The results show that the avermectin concentration in perch muscle gradually increases with passing medicated bath time, and reaches the peak of 8.767 ·kg-1 at the end of the medicated bath. Later, the avermectin in perch muscle gradually decreases and reduces below the detection limit at 528th hour.
We evaluate the nutritional quality of Antarctic krill (Euphausia superba)meals: meal A (freeze-dried Antarctic krill meal), meal B (steam cooked Antarctic krill meal, processed on board without adding anti-oxidant) and meal C (steam cooked Antarctic krill meal, processed on board with adding anti-oxidant). Results show that all the 3 samples have good nutritional quality, with high content of crude protein (61.73%~68.48%), total content of amino acids (ΣAA) (51.46%~66.32%), total content of 10 essential amino acids for shrimp and fish (ΣEAA) (23.69%~31.78%), respectively. Moreover, the contents of poly-unsaturated fatty acids (ΣPUFA) is 44.05%~52.74%, and a high proportion of EPA and DHA is also found in the 3 samples (38.55%~46.38%). Based on the results of ΣAA, ΣEAA, the essential amino acids index (EAAI), score of ratio coefficient of amino acid (SRC), ΣPUFA, and the total contents of EPA and DHA, Antarctic krill meal C has the highest nutritional quality compared with the other two, and has high nutritional value for further development and utilization.
In order to study the sterilization and quality effects of ozone water on cobia fillets, flowing ozone water at various concentrations of 4 mg·L-1, 5 mg·L-1, 6 mg·L-1 and 7 mg·L-1 was experimented to screen the optimal condition at 15 ℃. Comparing the effects of sterilization ratio, sensory evaluation and color difference in different groups, we find that the treatment with 7 mg·L-1 flowing ozone water for 10 min on cobia fillets gets a better sterilization ratio of 81.12% without reducing the quality.
Taking ordinary refrigerator freezing as control group, we explore the quality changes of immersion freezing Pseudosciaena crocea during storage by using quality evaluation indices such as protein content, frozen denaturation degree of protein, water holding capacity, muscle tissue structure and springiness. In the first 2 months, the immersion freezing P.crocea had slow protein denaturation, less protein lost, more uniform ice crystal, less destroyed tissue structure, better water holding capacity and springiness than the control, maintaining better quality. The quality decreased faster after 2 months; at the 6th month, the immersion freezing P.crocea had no obvious advantages in quality. We suggest the frozen storage time of P.crocea should not be too long (no more than 2 months is appropriate).
We discuss the mechanism of corrosion in steel fishing vessel mainly caused by electrochemical corrosion, and the primary cause is voltage gradient producing electric current.Besides, we compare sacrificial anodes protection method and impressed current protection method in the aspects of technology, installation, system maintenance and economy.Based on the numerical simulation conducted for impressed current protection in the case of fishing vessel berthing, we establish an electrostatic field numerical model by the software ANSYS, and use boundary element method (BEM) to solve potential distribution problem.Thus, new strategies are proposed to eliminate electrochemical corrosion in berthing steel fishing vessel.
We randomly assigned 360 juvenile yellow catfish(Peltobagrus fulvidraco) with average body weight 2.48 g to 4 groups, and fed the control (G0) with basal diet, the other 3 groups (G100, G200 and G400) with basal diet supplemented with 100 mg·kg-1, 200 mg·kg-1 and 400 mg·kg-1 complete enzyme preparation (CEP), respectively. After feeding for 8 weeks, the weight gain rate (WGR), specific growth rate (SGR) and feed intake (FI) increased with the CEP concentration. Besides, the WGR, SGR and FI of G400 were higher than those of the control by 15.4%, 7.5% and 20.3%(P < 0.05), respectively. No significant difference was found among all the treatments in body moisture, crude protein, crude lipid and ash content (P > 0.05). Serum urea content decreased with increasing CEP in diets, while glutamic-pyruvic transaminase (ALT), glutamic-oxalacetic transaminase (AST) activities and total protein(TP)content increased (P > 0.05). The activity of lysozyme(LSZ)increased and then decreased(P < 0.05). In conclusion, the feed added with 400 mg·kg-1 CEP can promote the growth and ALT activities of yellow catfish, and decrease its urea content; the feed added with 200 mg·kg-1CEP can significantly increase the TP content and LSZ and AST activities of the fish.
Immune prevention, especially developing new effective vaccine, is important in preventing and controlling streptococcosis outbreak in tilapia.Currently, the developing sreptococcosis vaccines for tilapia include inactivated vaccine, attenuated vaccine, subunit vaccine, DNA vaccine, passive immunization vaccine, etc..However, the inoculating way, adjuvants, physiological status of fish and environment factors also have great impact on the effects of vaccine.The paper reviews the research progress on vaccines of streptococcosis in tilapia, so as to provide scientific solutions for the design and application of those vaccines.