Length-based Beverton and Holt spawning stock biomass per-recruit-models, with application to the Lates stappersii (Boulenger) stock in Lake Tanganyika

Two kinds of length-based Beverton and Holt spawning stock biomass per-recruit ( SSB/R )-models are presented. The first allows the computation of the absolute value of SSB/R . The second estimates the index of SSB/R , also called 'relative SSB/R '. Both models are extensions of the original age-based Beverton and Holt SSB/R -models. The SSB/R and its index can be assessed with reference to variations in the exploitation characteristics. These models were applied to the Lates stappersii (Boulenger) stock in Lake Tanganyika using fishing mortality as the independent variable. They produce an absolute value of SSB/R of 12.95 g, representing 22.4% of that of the 'virgin' stock for the 1993–1994 equilibrium-fishing regime. This level is indicative of an unsafe state of the stock in question. Moreover, the SSB for L. stappersii seems to be fragile under increased fishing pressure as, for example, doubling or tripling the current fishing regime would reduce the current SSB/R by 57.3 and 77.4%, respectively. In general, the use of length-based Beverton and Holt SSB/R -models is handicapped by underlying hypotheses and sub-models which are restrictive.     

Immune responses of barramundi, Lates calcarifer (Bloch), after administration of an experimental Vibrio harveyi bacterin by intraperitoneal injection, anal intubation and immersion

Barramundi, Lates calcarifer (Bloch), were immunized with an experimental Vibrio harveyi bacterin via intraperitoneal injection, immersion and anal intubation. Both specific and non-specific immune parameters were measured to compare responses to bacterin after delivery by various methods. Elevated antibody activities in sera were found in all treatment groups with barramundi injected intraperitoneally displaying significantly higher antibody activity than the other groups. In addition, there was evidence of memory induction with a heightened antibody response in the intraperitoneally injected group only. Bacteriostatic assays indicated activity against V. harveyi in the sera of all bacterin-treated groups; again this activity was significantly higher in the intraperitoneally injected groups. There was no enhancement noted in head kidney macrophage phagocytic activity or in serum lysozyme levels.     

湛江港区底泥悬浮物对2种海洋动物的致死效应研究

为评价湛江沿海涉海工程建设过程中引起的悬浮物质对附近海区海洋动物的影响,研究了底泥液相及不同浓度底泥悬浮物对川纹笛鲷和尖吻鲈的致死效应。试验结果表明,在8d的试验时间里,底泥水相对川纹笛鲷和尖吻鲈均无致死效应。底泥悬浮物浓度≤160mg/L时,川纹笛鲷和尖吻鲈的死亡率均处于较低水平。底泥悬浮物浓度≥2560 mg/L时,川纹笛鲷死亡率达75%,尖吻鲈死亡率达70%。通过概率单位法计算得出川纹笛鲷的8d半致死浓度为716.14 mg/L,尖吻鲈的8d半致死浓度为1105.096 mg/L。     

Combined or individual effects of dietary magnesium and selenium nanoparticles on growth performance,immunity, blood biochemistry and antioxidant status of Asian seabass (Lates calcarifer) reared in freshwater

This study was conducted to investigate effects of and interactions between nanoselenium (NanoSe) and nanomagnesium (NanoMg) on growth, humoral immunity, serum biochemistry and antioxidant capacity of juvenile Asian seabass Lates calcarifer reared in freshwater. Four groups of fish with an average weight of 32.78 ± 2.23 g were fed one of the experimental diets for 6 weeks: (a) control (basal diet); (b) NanoSe (basal diet + 4 mg NanoSe/kg diet); (c) NanoMg (basal diet + 500 mg NanoMg/kg diet); and (d) combination (basal diet + 4 mg NanoSe/kg diet + 500 mg NanoMg/kg diet). Fish fed with NanoSe‐supplemented diets (NanoSe and combination) showed higher weight gain, specific growth rate and feed intake. The combination of NanoSe and NanoMg enhanced the immune response. Also, fish fed on combination diet showed higher serum alanine aminotransferase and aspartate transaminase levels but lower glucose concentration. The activities of liver superoxide dismutase, glutathione peroxidase and catalase were not different among all groups, but liver malondialdehyde level was lower in fish fed diets supplemented with NanoSe and/or NanoMg. It could be concluded that NanoSe improved growth performance; the combination of both NanoSe and NanoMg enhanced humoral immunity; and NanoSe and/or NanoMg improved antioxidant capacity in Asian seabass.     

Genetic variation of Lates calcarifer in Peninsular Malaysia based on the cytochrome b gene

A 312 bp segment of the mitochondrial cytochrome b gene was sequenced from 132 sea bass Lates calcarifer individuals from nine populations across Peninsular Malaysia. Phylogenetic analysis and analysis of molecular variance within and among populations showed no significant geographical structuring. Several populations formed discrete units while others were of mixed populations. The former group suggests a low gene flow among some populations while the latter suggests that widespread translocations have impacted the other wild and cultured local populations. The data from this study have important implications for fishery management, conservation of sea bass stocks and translocation policy for aquaculture and stock enhancement in Peninsular Malaysia.     

地衣芽孢杆菌对尖吻鲈血液生理生化指标的影响

以初始体重为(17.47±0.19)g的尖吻鲈(Lates calarifer)为试验对象,在基础饲料中分别添加0(对照)、1.0、2.0、3.0、4.0、5.0和6.0 g·kg-1饲料的地衣芽孢杆菌(Bacillus licheniformis)粉状制剂,研究地衣芽孢杆菌对尖吻鲈的生理生化指标的影响.摄食不同地衣芽孢杆菌含量的尖吻鲈血液中红细胞和白细胞数量、血红蛋白和无机盐离子等没有显著性差异(P>0.05),但显著降低了尖吻鲈的血糖和尿素氮水平(P<0.05),血糖在2.0 g·kg-1饲料组达到最小值,尿素氮在1.0 g·kg-1饲料组达到最小值.血清总蛋白均高于对照组,并在4.0 g·kg-1饲料组显著升高(P<0.05);胆固醇除了3.0 g·kg-1饲料组显著低于对照组外,其他各试验组均与对照组差异不显著.地衣芽孢杆菌也降低了血清谷丙转氨酶及乳酸脱氢酶的活性,谷丙转氨酶在1.0、4.0、5.0和6.0 g·kg-1饲料组显著低于对照组(P<0.05),而乳酸脱氢酶只在1.0 g·kg-1饲料组显著低于对照组(P<0.05).     

Anti-oxidant status in embryonic,post-hatch and larval stages of Asian seabass (<Emphasis Type="Italic">Lates calcarifer</Emphasis>)

The concentrations of anti-oxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (SeGPx), and low molecular weight free-radical scavengers such as reduced glutathione (GSH) and ascorbic acid (vitamin C) were evaluated during the period from gastrulation (GS) to 25 days post-hatch (dph) in the larvae of Asian Seabass, Lates calcarifer. Oxidative damage due to lipid peroxidation (LPO) was also assessed, by evaluation of the formation of malondialdehyde (MDA). All the three anti-oxidant enzymes, SOD, CAT and GPx, showed high activities during gastrulation, suggesting an increased metabolic rate during the period of embryonic development. Though the SOD activity apparently decreased progressively during 3–20 dph of larval development, the difference was not significant. CAT showed high activity during gastrulation and remained constant up to 3 dph, suggesting an increased need to metabolise hydrogen peroxide (H₂O₂) and organic peroxides. In contrast, SeGPx activity increased progressively from 5 dph to 25 dph during larval development, indicating an increased need to detoxify lipid peroxides. This is evident from the observation of increased lipid peroxidation from 10 dph to 25 dph during larval development. GSH levels were low at gastrulation, indicating increased metabolic rate and formation of lipid radicals during this period, corresponding to the decrease in the level of ascorbic acid, which is consumed for regeneration of GSH.     

尖吻鲈幼鱼运输密度和时长对运输水质及其复苏率和抗氧化能力的影响

该试验采用塑料袋密闭充氧运输方式,探讨3种运输密度(D1=14 kg·m-3、D2=21 kg·m-3、D3=28 kg·m-3)下模拟运输24 h和运输密度7 kg·m-3下模拟6个不同运输时长(T1=4 h、T2=8 h、T3=12 h、T4=16 h、T5=20 h、T6=24 h)对运输水质、尖吻鲈(Lates...     

Detection of nodavirus in barramundi, Lates calcarifer (Bloch), using recombinant coat protein-based ELISA and RT–PCR

The coat protein encoded by the nodavirus RNA2 gene originally isolated from greasy grouper, Epinephelus tauvina , was cloned, expressed as a recombinant polyhistidine-tailed fusion protein and characterized by immunoblot analysis. The purified recombinant protein was used to develop an indirect enzyme-linked immunosorbent assay (ELISA) to detect body exudate and plasma antibodies against the coat protein in both experimentally infected and commercial barramundi. In addition, the nucleotide sequence was employed to develop a RT–PCR detection assay based on the T4 region. The results showed that the virus could be detected as early as 3 days post-infection by RT–PCR while antibodies against the recombinant coat protein were detectable on day 6 post-infection. Among 112 commercial barramundi samples collected from October 1999 to April 2000, 9% showed positive ELISA results which were further verified by Western blot.     

Growth trials for polyculture of hatchery-reared juvenile spotted babylon (Babylonia areolata) and sea bass (Lates calcarifer) in a flow-through sea water system

Juvenile spotted babylon (Babylonia areolata) and sea bass (Lates calcarifer) were cultured in 11.5‐m³ indoor rearing tanks supplied with flow‐through of ambient natural sea water over a 120‐day experiment. Each species, stocked at the following densities for the following treatments, was tested with three replicates per treatment: 5000 B. areolata per tank (Treatment 1); 200 L. calcarifer per tank (Treatment 2); and 5000 B. areolata plus 200 L. calcarifer per tank (Treatment 3),. The average growth (length and weight), feed conversion ratio and total production of spotted babylon and sea bass from Treatment 3 were not significantly different from those of Treatment 1 and 2 (P > 0.05). Average survival rates for both spotted babylon and sea bass exceeded 95% for all treatments.