桑沟湾多元养殖生态模型研究：Ⅲ海带养殖容量的数值研究

基于已建立的桑沟湾多元养殖生态模型,模拟得到桑沟湾海带的生长情况和最终的产量分布。并且运用数值实验的方法,通过改变海带养殖密度,探寻桑沟湾海带的养殖容量。结果表明,养殖密度越大,对海水流动的阻碍作用越强,海带生长期间由外海补充到湾内的无机氮营养盐就越少。因此,提高养殖密度,最终海带产量并非相应增加。由模型实验得到,0.9倍于现有养殖密度为最适养养殖密度,对应的最大海带养殖产出为7.21万t淡干重。     

桑沟湾多元养殖生态模型研究：Ⅱ生态环境模拟与生源要素循环

运用桑沟湾多元养殖生态模型,模拟得到了桑沟湾浮游植物和无机氮营养盐的年变化规律、水平分布的季节变化。结果表明,浮游植物生物量和无机氮营养盐浓度存在明显的季节变化,养殖活动的季节性增大了二者的季节变化幅度;桑沟湾浮游植物和无机氮营养盐的分布受大面积海带和贝类养殖的影响;外海营养盐补充是桑沟湾内无机氮营养盐的主要来源。     

桑沟湾海带标准化养殖模式的优势探析

针对桑沟湾养殖海区海带(Laminaria japonica)的超容量养殖现象,研究了该海区中标准化养殖模式和传统养殖模式的海带生长差异。结果显示,在标准化养殖模式下,海带长、宽、平均厚度、湿重、投影面积和特定生长率均高于传统养殖模式,单棵海带重量显著提高,且海带的碳、氮和蛋白质含量明显高于传统养殖模式,海带品质大大提升。养殖后期,标准化养殖海区养殖海带垂直投影面积之和与对应养殖海区面积之比为6.33,而传统养殖模式的比值为9.15;标准化养殖海区海带所处水层下方的光照强度显著高于传统养殖区,海带所处水层的海流流速也高于传统养殖区。研究表明,桑沟湾海带标准化养殖模式使海带养殖密度降低,海带生长速度和品质均得以提高;在标准化养殖模式下,海带重叠较小,接受的光照比传统养殖模式充足;较快的海流使标准化养殖海区营养盐更新速度更快,这两方面可能是导致2种养殖模式下海带生长和品质产生差异的原因。     

桑沟湾水域叶绿素a在海带收获前后的变化及其影响因素

依据2014年5月和8月2个航次走航和定点连续调查资料,分析了桑沟湾水域叶绿素a的空间分布及海带养殖区叶绿素a(Chl.a)的昼夜变化特征,同时结合所调查的温度、盐度 、pH和营养盐等分布特征,分析了桑沟湾水域Chl.a浓度与理化因子的关系,探讨了海带收获前后Chl.a的变化及其影响因素。(1)走航调查的结果显示,桑沟湾夏季Chl.a浓度显著高于春季。桑沟湾春季表、底层总Chl.a浓度均值分别为(0.67±0.39)和(0.50±0.31)μg/L,表层Chl.a浓度高于底层,春季表层整体表现出自湾内向湾外逐渐降低的趋势;夏季表、底层总Chl.a浓度均值分别为(3.39±1.53)和(3.12±1.43)μg/L,表层Chl.a浓度高于底层。桑沟湾夏季表层Chl.a高值区出现在海带养殖区,低值区出现在贝类养殖区,夏季底层Chl.a高值区出现在贝类和海带养殖区,低值区出现在外海区。(2)定点连续监测结果显示,春季海带养殖区Chl.a浓度变化范围在0.24~0.95 μg/L,均值为(0.70±0.19)μg/L,昼夜波动较小。而夏季海带养殖区Chl.a浓度变化范围在2.01~4.66 μg/L,均值为(3.04±0.82)μg/L,昼夜波动较大。桑沟湾海带养殖区夏季Chl.a浓度显著高于春季。春季海带养殖区营养盐平均浓度及硅磷比、氮磷、硅氮比均显著低于夏季。(3)桑沟湾春季表层Chl.a浓度主要与温度、硅酸盐呈显著正相关,而夏季底层Chl.a浓度与盐度呈显著正相关。桑沟湾海带收获前后Chl.a的变化及分布受温度、硅酸盐、盐度、养殖环境状况和水文环境的共同影响,多元的贝藻养殖模式是影响Chl.a变化及分布的重要因素。     

桑沟湾海带养殖容量的研究

首次对桑沟湾的海带养殖容量进行了调查研究。采用了无机氮作为估算桑沟湾海带养殖容量的关键因子，通过无机氮的供需平衡估算海带养殖容量。结果显示，海底沉积物中释放的无机氮为该湾无机氮的主要来源，而由海水交换所带入的无机氮次之。海带生长期间海水交换周期为３９ｄ，比８０年代中期延长了近１倍。桑沟湾在海带生长期间由海水交换、陆地径流、动物排泄和海底沉积物中释放所进入该湾的无机氮总供应量为１２２８ｔ；而浮游植物     

桑沟湾多元养殖生态模型研究：Ⅰ养殖生态模型的建立和参数敏感性分析

建立了一个与考虑养殖阻力的水动力模型耦合的、以浮游植物生物量、无机氮浓度、悬浮有机颗粒物浓度、海带生物量为变量的桑沟湾三维多元养殖生态模型。模型考虑了养殖生物海带对海水流动的阻碍作用随其生长的动态变化,以及养殖生物和浮游植物之间对无机氮营养盐的竞争。最后,分别以浮游植物生物量和海带产量为目标变量,对参数的敏感性进行了分析。     

基于GIS的桑沟湾及周围海域海带养殖适宜性评价

目前水产养殖面临用海冲突、单位面积和人均生产率偏低、养殖业的生态和经济成本较高等问题。为充分利用海区的自然生产力,提高养殖效率和效益,需要对海区进行适宜性评价,选择最适宜的水域进行养殖。以桑沟湾及周围海域主要的养殖品种海带(Saccharina japonica)作为评价对象,选取光照、温度、流速、无机氮、盐度、深度作为适宜性评价指标,利用遥感技术确定海区养殖布局,通过野外调查和数据模拟获取养殖海区环境参数数据,根据动态能量学(Dynamic energy budget, DEB)模型——STELLA模型敏感性分析结果,并结合层次分析法计算评价指标权重,海带生长相关环境因子的强制函数拟合得到单因子评分曲线进行评分。最后,采用线性加权叠加分析方法得到海带养殖适宜性评价结果。适宜性评价过程以地理信息系统(Geographical information systems, GIS)作为技术支持,利用GIS空间插值功能生成光照、温度、流速、无机氮、盐度、深度专题图层,采用栅格计算功能对各专题图层进行叠加,得到综合多因素的海带养殖适宜性评分和适宜性等级。评价结果显示,在不考虑用海冲突的情况下,桑沟湾及周围海域海带养殖适宜性分数分布在0~6.7范围内,分值主要集中在4~6分,属于中等适宜,占研究区总面积的67%,最适宜和不适宜分别占研究区总面积的23%和10%,无一般适宜区。评分较高的区域主要分布在北部爱莲湾和楮岛东部海域周围,适宜性评分较低的区域主要位于近岸水深较浅的海域。根据适宜性评价结果可进行水域空间规划和安排养殖生产计划,为管理部门开展养殖分区和海洋功能区划提供参考。     

桑沟湾筏式养殖鼠尾藻(Sargassum thunbergii)的生长特性

2014年4–6月在桑沟湾海区进行鼠尾藻(Sargassum thunbergii)海上筏式养殖实验,分析了鼠尾藻在桑沟湾的生长特性,调查了藻体上的附着生物。结果显示,(1)鼠尾藻在桑沟湾海域生长迅速,水温为10–17℃时特定生长率最高,可达6.10%/d;根据特定生长率与水温的关系,获得了鼠尾藻的最佳生长温度为14.9℃;(2)5月10日开始有生殖托形成,水温达到20.4℃时,鼠尾藻生殖托大量成熟,并有放散;(3)养殖期间,鼠尾藻最大长度达187.05 cm,均长可达112.31 cm;干湿比由0.147(4月)上升至0.189(6月);每公顷产量可达43.95 t(湿重),相当于干重为8.25 t;(4)藻体上有大型附着生物16种,主要优势种为尖嘴扁颌针鱼鱼卵、玻璃海鞘和海绵;附着生物的生物量随着水温升高而增加。研究表明,海区的附着生物对鼠尾藻的生长影响不大,在桑沟湾大规模养殖鼠尾藻是可行的。     

桑沟湾养殖海域营养状况及其影响因素分析

桑沟湾营养现状调查结果表明，桑沟湾营养状况不仅受沿岸排放水的影响，而且大面积的海带和扇贝养殖对于营养盐的补充与消耗也有较大的影响，特别是在扇贝养殖区水域，富营养化水平较高。由Ｎ／Ｐ比值计算结果表明，从整个海湾看，冬季无机氮显得相对紧缺，而其他季节无机磷则显得相对紧缺。但从局部海域看，各季节扇贝养殖区无机磷显得相对紧缺。而在扇贝和海带混养区的１月，以及在海带单养区养殖海带期间的１月和４月无机氮显得相     

莱州湾和桑沟湾养殖海区浮游植物的研究Ⅱ.

系统研究了桑沟湾浮游植物的周年变动,并对中国北方两个典型养殖海湾——莱州湾和桑沟湾的养殖模式及其与浮游植物数量变动的相互关系进行了比较。桑沟湾浮游植物数量在3月份达到高峰,此时的主要物种是中肋骨条藻(Skeletonema costatum (Grev．)Cleve)和海链藻(Thalassiosira sp.)等。在桑沟湾,浮游植物的群落演替不明显,硅藻在全年都是主要类群。在实验进行的12个月当中,始终都是硅藻占绝对优势,其中10个月很难见到其他藻类,只有两个月发现水中有极少量的甲藻。通过对莱州湾和桑沟湾具体情况的比较,作者发现：海带对浮游植物的压制作用强于扇贝,扇贝的代谢作用有可能促进浮游植物的繁殖。从浮游植物的年际变化也可以看出,养殖模式对浮游植物的数量和种类组成都有或多或少的影响。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

Vitamin D3 and the renal handling of phosphate in American eels

Cholecalciferol (Vitamin D₃) increased plasma inorganic phosphate concentration in American eels,Anguilla rostrata, in a dose-dependent fashion. This response was more marked in phosphate loaded fish. In control as well as phosphate loaded eels the hyperphosphatemic response to D₃ was associated with a sharp reduction in renal phosphate clearance relative to¹⁴C-polyethelene glycol (PEG) clearance. Glomerular filtration and urine flow rates were not affected by D₃. As renal phosphate clearance, even in phosphate loaded eels, never significantly exceeded that of PEG, it is suggested that D₃ reduced the relative clearance rate of phosphate by increasing renal phosphate reabsorption rather than by reducing the tubular secretion of phosphate.