Observation on Behavior of Procambarus clarkii and Eriocheir sinensis in Polyculture System

[Objective] This study aimed to observe and explore the behavior of Procambarus clarkii and Eriocheir sinensis in polyculture system. [Method] P. clarkii and E. sinensis with the same weight were used for the experiment in a relatively small polyculture system. The agonistic behavior of P. clarkii and E. sinensis in the first 30 min of the initial encounter and the fighting results were observed and recorded; the approach-avoidance behavior of P. clarkii to bigger E. sinensis in a relatively large space （the ＂Y＂ maze） was observed and recorded. [Result] The re- sults showed that the times of first aggressions and approaches and the total times of active aggressions and approaches of P. clarkii in the initial period of polyculture experiment were all significantly more than E. sinensis （/：＇〈0.05）; after 30 d of poly- culture, P. clarkfi died in 30% of the groups while E. sinensis died in only 10% of the groups, and they coexisted in 60% of the groups. In the experiment of ap- proach-avoidance behavior of P. clarkii to bigger E. sinensis, with the increase of experiment times, the tendency of approach and avoidance of P. clarkii to the con- trol and E. sinensis became control-prefer （P〈0.05） from insignificantly different （P〉 0.05）, which indicated that the recognition ability of P. clarkii for E. sinensis was sig- nificantly improved, and the selection behavior of E. sinensis was obviously inhibited. [Conclusion] Presumably, polyculture of crayfishes and crabs can achieve better effi- ciency when under appropriate habitat conditions.

POLYCULTURE OF SCALLOP CHLAMYS FARRERI AND KELP LAMINRIA JAPONICA IN SUNGO BAY

Several polyculture models of scallop Chlamys farreri and kelp Laminaria japonica currently employedin Sungo Bay and other parts of northern China are described in this paper. Economic benefits of differ-ent polyculture models are analysed based on the growth rate, culture density and market price. In addi-tion, site selection, critical environmental conditions and polyculture problems are discussed in detail.

SUMMARY OF STUDIES ON CLOSED-POLYCULTURE OF PENAEID SHRIMP WITH FISHES AND MOLUSCANS

Closed polyculture of Chinese penaeid shrimp,Taiwan red tilapia ,and molluscans(constricted tagelus and bay scallop) was studied from 1995 to 1997 with the enclosure experiment method, on a shrimp farm in Haiyang County,Shandong Province. Four structure optimized closed polyculture systems, i.e., the “shrimp tagelus" system, the “shrimp scallop" system,the “shrimp tilapia" system and the “shrimp tilapia tagelus" system,were worked out. All these polyculture systems were superior to shrimp monoculture system in economic and ecological efficiencies. The order of these polyculture systems in efficiencies was “shrimp tilapia tagelus">“shrimp tagelus">“shrimp tilapia">“shrimp scallop". The “shrimp tilapia tagelus" system raised the production by 28% and the utilization efficiency of input nitrogen by 85%.These closed polyculture systems reduced the nitrogen discharge ratio to 6%-8%, instead of 40%-90% in the usual open culture systems. The ecological features of the systems were also investigated and many meaningful results have been obtained. The mechanism enhancing the efficiencies of these systems, the ways to enhance the efficiencies further and those to reuse the sedimented materials are disscussed.

Nitrogen and Phosphorus Budget of a Polyculture System of Sea Cucumber(Apostichopus japonicus), Jellyfish(Rhopilema esculenta) and Shrimp(Fenneropenaeus chinensis)

The nitrogen(N) and phosphorus(P) budget and the ecological efficiency of a polyculture system of sea cucumber(Apostichopus japonicus), jellyfish(Rhopilema esculenta) and shrimp(Fenneropenaeus chinensis) were studied in a cofferdam, 120.2 ha in size. The nutrients were supplied by spring tide inflow. In total, 139600 kg N yr-1 and 9730 kg P yr-1 input to the system; while 118900 kg N yr-1 and 2840 kg P yr-1 outflowed from the system concurrently, thus the outflow was 85.7%(N) and 29.2%(P) of inflow. The production of N and P was 889.5 kg yr-1 and 49.28 kg yr-1(sea cucumber) and 204 kg yr-1 and 18.03 kg yr-1(jellyfish and shrimp), respectively. The utilization rate of N and P by polycultured animals was 7.8‰ and 6.9‰, respectively, 21.9% and 38% higher than that of monocultured sea cucumber. Our results indicated that the polyculture system was an efficient culture system of animals and a remediation system of coastal environment as well; it scavenged 14.3% and 70.8% of N and P, respectively. Such an ecological efficiency may be improved further by increasing either the stocking density or the size of sea cucumber or both.

Trophic Interaction in a Portunus rituberculatus Polyculture Ecosystem Based on Carbon and Nitrogen Stable Isotope Analysis

Trophic interaction among various biomass groups in a swimming crab Portunus trituberculatus polyculture pond was investigated using carbon and nitrogen stable isotope analysis. The polycultured animal species also included white shrimp Litopenaeus vannamei, short-necked clam Ruditapes philippinarum, and redlip mullet Liza haematochila. The mean δ^(13)C value for all the biomass groups in polyculture ecosystem ranged from -25.61‰ to -16.60‰, and the mean δ^(15)N value ranged from 6.80‰ to 13.09‰. Significant difference in the δ^(13)C value was found between particulate organic matter(POM) and sediment organic matter(SOM)(P < 0.05), indicating that these two organic matter pools have different material sources. Assuming that a ^(13)C-enrichment factor of 1.00‰ and a ^(15)N-enrichment factor of 2.70‰ existed between consumer and prey, diets of the four cultured animals were estimated using a stable isotope mixing model. The estimated model results indicated that P. trituberculatus mainly feed on Aloidis laevis; L. vannamei mainly feed on shrimp feed; while A. laevis, R. philippinarum and L. haematochelia mainly feed on POM. Shrimp feed was also an important food source of R. philippinarum and L. haematochelia. The diets of P. trituberculatus, L. vannamei, R. philippinarum, and L. haematochila showed complementary effects in this polyculture ecosystem. Our finding indicated that the polyculture of these four organisms with suitable farming density could make an effective use of most of the food sources, which can make a highly efficient polyculture ecosystem.

COMPARATIVE STUDIES ON NITROGEN BUDGETS OF CLOSED SHRIMP POLYCULTURE SYSTEMS

April to October, 1997 comparative studies on the nitrogen budgets of closed shrimp polyculture systems showed that, in all the studied polyculture systems, nitrogen from feeds and fertilizers were the main input items, which comprised 70.7%-83.9% of the total input nitrogen, 3.2%-7.4% of which was provided by nitrogen fixation. It was in monoculture enclosures (Y 4, Y 11 and Y 12) that the percentage reached the maximum value. The output nitrogen in harvested products comprised 10.8%-24.6% of total input nitrogen, and the highest percentage, 24.6%, was found in shrimp fish tagelus polyculture systems. In shrimp monoculture and shrimp fish polyculture systems, they were 19.1% and 21.9%, respectively. The nitrogen utilization efficiency was different and varied from 12.2% to 20.1%. The highest, 20.1%, was found in shrimp fish tagelus polyculture systems, and the average of 20.0% was found in shrimp tagelus polyculture systems. The lowest, 12.2%, was found in shrimp monoculture systems. All the nitrogen utilization efficiencies in shrimp fish systems or shrimp scallop systems seemed to be higher than that of the monoculture system, but they showed little statistical difference. The main outputs of nitrogen were found in sediment mud, and comprised 48.2%-60.8% of the total input, the lowest percentage was found in shrimp fish tagelus polyculture systems, and the highest percentage in shrimp scallop systems. During the experiment, nitrogen lost through denitrification and ammonia volatilization comprised 1.9%-6.2%, averaged 2.8%, of the total input, and the loss through seepage comprised 5.9%-8.9% of the total. The estimated nitrogen attached to the enclosure wall comprised 3.7%-13.3% of the total, and was highest in shrimp monoculture systems. Compared with the classic shrimp farming industry, the closed shrimp polyculture systems may improve the nitrogen utilization efficiency, and hence reduce the environmental impacts on coastal waters. The nitrogen discharging rates for all the studied polyculture systems ranged from 3.0% to 6.0% of total input nitrogen.

Production of Pacific White Shrimp Polycultured with Swimming Crab at Different Densities, and Nutrient Budget in the Enclosure System

This study was to evaluate the effect of stocking densities on the nitrogen and phosphorus budgets for a polyculture of the crab Portunus trituberculatus and the Pacific white shrimp Litopenaeus vannamei.The shrimps(initial weight,0.012 g)were cultured at a density of 45 shrimp m^(-2),and juvenile crabs(initial weight,0.024 g)were cultured at five densities of 0,3,6,9,and 12 crabs m^(-2).The treatments were grouped as C0S45,C3S45,C6S45,C9S45,and C12S45,respectively.Water quality parameters,growth of shrimp and crabs,and nitrogen and phosphorus budget were measured.The results indicated that the shrimp performances in polyculture treatments C3S45 and C6S45 were superior to those in the crab-free treatment(C0S45).The crab in treatments C3S45 and C6S45 exhibited a significantly higher final mean weight and carapace width/length than those in treatments C9S45 and C12S45.The final size and survival of crabs had a negative correlation with the increasing crab stocking density.The contents of total phos-phorus and total nitrogen and the comprehensive contamination index values were higher in the C9S45 and C12S45 treatments than in the other treatments.The conversion ratios of nitrogen for crab and shrimp growth in treatment C3S45 were significantly higher than those in the crab-free treatment.These findings indicate that polyculturing shrimp with crabs at suitable densities can improve productivity,profitability,nutrient utilization,and the environmental quality.From the 60-day treatments,the optimal culture densi-ties were 3-6 crabs m^(-2) and 45 shrimps m^(-2).

Closed recirculating system for shrimp-mollusk polyculture

This paper deals with a new system of aquaculture, i.e., a closed recirculating system for shrimp-mollusk polyculture. The culture system consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir. During the production cycle, water circulated between the shrimp and mollusk ponds, and the reservoir compensated for water loss from seepage and evaporation. Constricted tagelus, Sinonovacula con- stricta, was selected as the cultured mollusk, and Pacific white shrimp, Litopenaeus vannamei, as the cultured shrimp. The main managing measures during the production cycle were: setting and using the aerators; introduc- ing the probiotic products timely into the shrimp ponds; adopting a "pen-closing" method for controlling shrimp viral epidemics; setting the flow diversion barriers in the mollusk pond to keep the circulating water flowing through the pond along a sine-like curve and serve as substrate for biofilm; no direct feeding was necessary for the cultured mollusk until the co-cultured shrimp was harvested; natural foods in the water from the shrimp ponds was used for their foods. Two sets of the system were used in the experiment in 2002 and satisfactory re- sults were achieved. The average yield of the shrimp was 11 943.5 kg/hm2, and that of the mollusk was 16 965 kg/hm2. After converting the mollusk yield into shrimp yield at their market price ratio, the food coefficient of the entire system averaged at as low as 0.81. The water quality in the ponds was maintained at a desirable level and no viral epidemics were discovered during the production cycle.

CARBON CYCLE IN SHRIMP POLYCULTURE MESOCOSM

The carbon cycle in shrimp polyculture mesocosm ecosystems was studied in the shrimp farm of the Huanghai Fisheries Group Corporation in Shandong Province from May to August, 1997. The results showed that the plankton community respiration rate fluctuated between 0.07 and 2.28 mgC/(L·d), average of 0.82±0.42 mgC/(L·d), which was 49 percent of the rate of phytoplankton gross production;that the average respiration rates (mgC/(L·d)) of micro , nano and pico plankton were 0.07, 0.38 and 0.31, which were 175, 30 and 207 percent of the corresponding sized phytoplankton production rates; that the sediment respiration rate (mgC/(m 2·d)) varied from 178.64 to 373.23, average of 262.60±48.68, and increased gradually with the lapse of culture time; and that the organic carbon accumulation and the respiration in the sediment of the shrimp monoculture mesocosm was higher than that in the polyculture mesocosms. The total sediment respiration per 25 m 2 mesocosm in the culture period averaged 571.16 gC, which was 10 percent of the total organic carbon input of the mesocosm.

Organic carbon budget in shrimp polyculture enclosure ecosystems

The organic carbon budget in shrimp polyculture ecosystems was studied with five experimental enclosures. The results showed that: (l ) the total Organic carbon income of the ecosystems varied from 4 847. 46 to 6 154. 67 g, averaged (5 646. 94 t 551.09) g, the average ratio among its components, i. e., (phytoplankton production ): (periphyte production ): (feed casted) was 0. 73: 0. 11: 0. 16; (2) the total output of organic carbon varied from 3 310. 28 to 3 974. 79 g, averaged (3 644. 21 281. 44) g, the average ratio among its components, i. e., (plankton community respiration): (periphyton respiration): (benthic community): (culture animal production): (culture animal respiration) was 0. 53: 0. 19: 0. 15: 0. 04:0. 09; (3) the organic carbon accumulation varied from 1 383. 45 to 2 707. 31 g, averaged (2 002. 73 546. 76) g, which was 26% --44 % of the total organic carbon income; the sequence of organic carbon accumulation in the ecosystems of different polyculture types was Y5 (Penaeus chinensis -- Argopecten irradians) > Y7 (P. chinensis -- Taiwan red tilapia) > Y4 (P. chinensis ) > T5 (P. chinensis -- Taiwan red tilapia -- Sinonovacula constricta ) > Y6 (P. chinensis S. constricta ); (4) the average conversion rate of organic carbon income to P. chinensis was (l. 77 0. 62) % (Y6>T5 > Y4 >YS > Y7), and that to total culture animals was (2. 18 0. 79) % (T5 >Y6 > Y5 > Y4 > Y7).

A study on the polyculture of the algae, the shrimp and the crab

A study was made on the polyculture of the red algae Gracilaria tenuistipitata Chang et Xia f. Liui Zhang et Xia, f. nov. , the shrimp Penaeus penicillatus Alcock and the mud crab Scylla serrata (Forskal) . The photosynthesis of the algae produces the oxygen on which the shrimp and the crab breathe. The algae are the reproductive place of the organism for the food of the shrimp and the carb, also is the shelter of the shrimp and the crab. The shrimp and the crab regard the algae as the vegetable

Effects of Ionic Concentrations on Survival and Growth in Polyculture of Litopenaeus vannamei with Oreochromis niloticus in Low Salinity Water

A study comparative of rearing of the Pacific white shrimp （Litopenaeus vannamei） with the Nile tilapia （Oreochromis niloticus） in three earthen ponds （5,600 m^2） with the salinity ranged from 0.5-1.2 ppt and three treatment ponds with salinity of 2-4 ppt by adding brine water into the ponds. Postlarvae 12 （PL12） of L. vannamei were stocked at density of 9 PL/m^2 and after one week the Nile tilapia fingerlings were stocked at density of I fish/m^2. Only pelleted feed were given to the fish during the 196-day rearing period. Shrimps were partially harvested by sieve net at day 80 and 120, and five days later PLI2 were stocked at the rate of 3 PL/m^2. After final harvesting at day 196, the production, body weight and survival from the treatment group were significantly higher （P 〈 0.05） than those of the control group. While the fish production body weight and survival rate from both groups were not significant differences （P 〉 0.051）. The ionic concentration of six major ions （CI, SO42, Ca^2＋, Na^＋, Mg^2＋ and K^＋）, salinity and hardness in the treatment ponds were significantly higher than those of the control ponds （P 〈 0.05）. Moreover, the ionic profiles of the treatment ponds were similar to seawater at the salinity of 2 ppt while only 1 ppt in the control ponds. Results from the study indicated that in order to achieve good growth and survival rate of L. vannamei, brine water should be added into grow-out ponds prior to stocking and during the rearing： period to obtain and maintain the salinity not less than 2 ppt.

Impact of Stocking Density on the Polyculture of C/arias gariepinus and Oreochromis niloticus

Knowledge on stocking density enables the farmer decide on the density limits that will enhance fish yield when intuition and experience are used as guide. Twelve weeks experiment conducted in concrete tanks assessed the growth performance and survival rate at different stocking densities of test specimens. Data analysis revealed that the highest stocking density produced the highest （157.85 ±36.54a） mean weight gain for C. gariepinus. Mean weight gain for O. niloticus in the same tank as just mentioned, took the reverse order. Specific growth data recorded for C. gariepinus revealed an intermediate value at the highest （4.25 ±1.3ab） and lowest （4.23 ±1.2ab） stocking densities, while the highest value was recorded at the intermediate stocking density （4.41 ± 1.34a）. Data on performance index revealed significant differences between the lowest （339.24 ± 86.95b） and intermediate （397.07±103.81a） and also between the lowest （339.24 ± 86.95b） and the highest （397.81±113.14a） stocking densities. The lowest stocking density recorded the highest food conversion efficiency, while the least was recorded at the highest stocking density. Clarias gariepinus recorded 98.3% survival at the highest stocking density, whereas O. niloticus in the same tank recorded 70.83%. The authors therefore conclude that since the highest stocking density gave the best yield in most of the output parameters, it should be recommended to farmers.

The Potential for Homestead Pond Polyculture of Tilapia and Carps in Coastal Bangladesh

A fishers’women-led Participatory Action Research(PAR)was conducted in 30 homestead ponds to assess the potential for polyculture of Tilapia(Oreochromis niloticus)and major carps Rohu(Labeo rohita)and Catla(Catla catla)in two coastal fishing villages of Bangladesh.Three treatments,namely T1(Tilapia 200 fish per decimal;1 decimal=40 m^2),T2(Tilapia 200+Rohu 32+Catla 8 fish per decimal)and T3(Tilapia 200+Rohu 8+Catla 32 fish per decimal),each with 5 replicates,were tried in Hossainpur and Anipara villages.Formulated commercial Mega-feed was applied to the ponds twice daily at an initial rate of 10%body weight(bw)/day of Tilapia down to 4%bw/day throughout the culture period.The water quality parameters of ponds including transparency,salinity and dissolved oxygen significantly varied among treatments except temperature and pH and remained within optimum range for carp polyculture except salinity.The survival rate,harvesting weight and yield of Tilapia were significantly highest in T1(85.63±05%,258.59±18.76 g&11073±805 kg/ha,respectively)in Anipara and lowest in T3(75.63±0.37%,136.97±10.63 g&5180±406 kg/ha,respectively)in Hossainpur.The gross fish production was the significantly highest in T1(11354±806 kg/ha)of Anipara and lowest in T1(6325±227 kg/ha)of Hossainpur.Statistically,the highest net return(866,627±84874 BDT/ha)was found in T1 of Anipara and lowest in T3(279,389±46104 BDT/ha)of Hossainpur with a significantly higher benefit-cost ratio(BCR)obtained in T1(3.26±0.20)for Tilapia and lower in T3(1.58±0.10)for polyculture Tilapia and carp of Hossainpur.Therefore,it may be concluded that Tilapia production in small homestead coastal ponds has a higher potential than its mix with carps in polyculture for generating food and supplemental income opportunity for coastal fishers’women in Bangladesh.

海水多品种养殖池塘沉积物-水界面氮磷通量

为探明生源要素氮、磷在沉积物与水体间的迁移过程,比较3种不同养殖模式下、不同时间养殖池塘沉积物-水界面的氮、磷通量变化,2014年6—10月,在3种综合养殖池塘:海蜇+凡纳滨对虾+菲律宾蛤仔、海蜇+凡纳滨对虾+缢蛏和海蜇+凡纳滨对虾的整个养殖周期内,采集检测3口池塘沉积物-水界面样品中的亚硝态氮、硝态氮、氨氮和活性磷酸盐含量,分析沉积物-水界面的亚硝态氮+硝态氮、氨氮和活性磷酸盐的通量变化。试验结果显示,6—10月,3种综合养殖池塘沉积物上覆水中亚硝态氮和硝态氮均以向沉积物中扩散为主,仅10月海蜇+凡纳滨对虾池塘沉积物中亚硝态氮和硝态氮向上覆水释放。海蜇+凡纳滨对虾+菲律宾蛤仔、海蜇+凡纳滨对虾+缢蛏池塘沉积物上覆水中氨氮向沉积物扩散,6月海蜇+凡纳滨对虾+缢蛏池塘沉积物中氨氮向上覆水扩散;与海蜇+凡纳滨对虾+菲律宾蛤仔和海蜇+凡纳滨对虾+缢蛏池塘相比,海蜇+凡纳滨对虾池塘氨氮通量变化幅度较大,6—7月上覆水中氨氮向沉积物扩散,且扩散速率逐渐降低,9—10月沉积物中氨氮向上覆水释放,释放速率逐渐上升。6、7、10月海蜇+凡纳滨对虾+菲律宾蛤仔池塘沉积物中活性磷酸盐向上覆水释放,8—9月上覆水中活性磷酸盐向沉积物扩散;6—10月,海蜇+凡纳滨对虾+缢蛏池塘沉积物中活性磷酸盐向上覆水释放;海蜇+凡纳滨对虾池塘上覆水中活性磷酸盐向沉积物扩散,10月沉积物中活性磷酸盐向上覆水释放。试验结果表明,配养底栖贝类,可以通过改变综合养殖池塘沉积物-水界面的氮、磷通量,改善池塘的底质和水质环境。

基于Ecopath模型的硬壳蛤多元混养系统养殖容量评估

为优化硬壳蛤多元混养系统养殖模式,提高硬壳蛤池塘养殖技术水平,以硬壳蛤(Mercenaria mercenaria)-三疣梭子蟹(Portunus trituberculatus)-凡纳滨对虾(Litopenaeus vannamei)混养池塘生态系统为研究对象,利用Ecopath模型构建了由12个生物功能组组成的能量流动模型,并基于能流模型评价了生态系统中硬壳蛤养殖容量。研究表明,该生态系统中硬壳蛤生物量最高(134.99 g/m^(2)),其次是凡纳滨对虾(62.56 g/m^(2));底栖动物营养级最高(2.65)。由于生态系统中第Ⅱ、Ⅲ营养级间能流传递效率较低(5.20%),系统绝大部分能量流通量(98.37%)位于第Ⅰ、Ⅱ营养级;系统连接指数和杂食指数分别为0.37和0.05,表明生态系统食物网结构简单;系统总初级生产力/总呼吸量比值为2.13,系统净生产力为每30天715.18 g/m^(2),表明生态系统以自养为主。研究期间人工饵料投入量占初级生产力的71.60%,大量饵料投入使生态系统食物网以碎屑食物链为主;从生态系统能流平衡的角度评估硬壳蛤养殖容量,发现该系统中以硬壳蛤个体总湿重计的生态容量和生产容量分别为:854.46 g/m^(2)和1441.47 g/m^(2)。基于该系统中硬壳蛤生态、生产容量获取的硬壳蛤最大放养密度分别为73 ind./m^(2)和123 ind./m^(2)。由于Ecopath模型无法模拟生态系统无机环境因子对养殖容量的限制作用,在开展基于Ecopath模型的养殖容量评估结果应用时应保持谨慎。养殖期间水体、底质环境保持在养殖生物适宜范围是Ecopath模型评估结果可靠的一个重要前提。

北京混栽樱桃园果蝇物种组成及种群消长动态

果蝇是危害樱桃的重要害虫,为明确北京市混栽樱桃园果蝇物种组成和种群发生消长动态,以北京市农林科学院通州樱桃育种基地诱集的果蝇为研究对象,采用分子和形态相结合的方法进行种类鉴定,比较园内不同果树(樱桃、梨、苹果、桃、李)和果园杂草上果蝇的种类组成及种群消长动态,组建果蝇-寄主食物网,并通过主成分分析阐明果蝇种群发生与寄主植物的相关性。混栽樱桃园内共诱集到10种果蝇,其中巴氏果蝇(Drosophila busckii)、花果蝇属果蝇(Scaptodrosophila sp.)、叔白颜果蝇(Drosophila triauraria)、斑翅果蝇(Drosophila suzukii)为优势物种,分别占果蝇总数的27.7%、15.1%、14.7%、10.6%。果蝇物种在不同寄主植物上组成不同,巴氏果蝇种群数量在杂草上随生长季节持续下降,其他优势果蝇物种在不同寄主植物上种群波动情况相似。杂草上果蝇种类多样,种群丰富度最高,相关性分析表明,果园杂草是斑翅果蝇的主要虫源,是樱桃果实成熟期果蝇的主要孳生地。混栽樱桃园果蝇种类丰富,需重点关注叔白颜果蝇、黑腹/拟果蝇和斑翅果蝇的发生,同时,在果树生长前期清除园内杂草,减少果蝇在樱桃和杂草等寄主间相互转移,降低其混合发生频率,以减轻樱桃成熟期的危害。

一株鹅-鱼养殖环境下罗非鱼无乳链球菌的分离鉴定及药物敏感性分析

【目的】为确定鹅-鱼立体养殖环境下引发罗非鱼疾病的病原菌,通过分析病原菌的生长特性、致病性与药物敏感性,为罗非鱼病的深入研究与精准防控提供科学依据。【方法】从患病罗非鱼组织中分离病原菌,采用形态观察、生理生化鉴定、16S rRNA序列分析等方法鉴定菌株;绘制菌株生长曲线,分析温度、盐度及pH值对病原菌生长的影响;通过腹腔注射和拌料口服投喂方式人工回归感染健康罗非鱼,分析病原菌的致病性;采用药敏纸片法测定病原菌对11类共26种抗菌药物的敏感性。【结果】从患病罗非鱼的脑组织中分离纯化得到一株优势菌株,编号为SAYJN,经形态学观察、生理生化鉴定、16S rRNA序列分析及回归感染试验,鉴定此菌株为无乳链球菌(Streptococcus agalactiae);SAYJN菌株的生长迟缓期为0~5 h,对数期为5~12 h;最适生长温度37℃、最适pH值7.0、最适盐度为5‰。腹腔注射和拌料口服投喂SAYJN菌株均可感染健康罗非鱼;水温为29(±1)℃时,腹腔注射SAYJN菌液对罗非鱼有较强的致病性,半致死浓度(LC_(50))为2.4×10^(8)CFU/mL;SAYJN菌株致病力与其浓度和水温密切相关。SAYJN菌株对甲氧苄啶、庆大霉素、新霉素等6种药物产生耐药性,对恩诺沙星、环丙沙星、阿米卡星等4种药物中度敏感,对多西环素、氟苯尼考、利福平等16种药物敏感。【结论】无乳链球菌SAYJN菌株是鹅-鱼立体养殖环境下罗非鱼疾病爆发的主要病原菌,该菌的致病力强弱与其浓度和水温密切相关。

南美白对虾与长吻鱼危生态混养试验

为研究新型的生态养殖模式,降低南美白对虾单一品种养殖风险,于2022年6—10月开展了南美白对虾与长吻鱼危生态混养试验,并与传统的南美白对虾池塘单养模式进行对比分析。结果显示:单养模式下南美白对虾的产量为(4011.3±1083.6)kg/hm^(2),规格70~90尾/kg,成活率为(69.4±7.9)%。混养模式下虾的产量为(3650.0±663.4)kg/hm^(2),规格40~70尾/kg,成活率为(45.4±5.0)%,单养模式和混养模式虾的成活率差异显著(P<0.05)。长吻鱼危放养规格(91.9±26.8)g/尾,放养密度1500尾/hm^(2),收获规格(449.3±103.7)g/尾,成活率(98.0±1.9)%,混养模式较单养模式获得了29170元/hm^(2)的增收。试验结果表明,混养相对于单养,在几乎没有增加其他养殖成本的情况下,保证了南美白对虾的养殖收益,同时收获了较好的长吻鱼危养殖效益,提高了养殖生产总收益。

唐山大清河盐场注水池三疣梭子蟹与日本对虾生态混养试验

为持续提高盐田养殖效益,在唐山大清河盐场注水池连续三年进行了三疣梭子蟹(Portunus trituberculatus)与日本对虾(Penaeus japonicus)生态混养,试验结果显示,该模式三疣梭子蟹雄蟹平均产量达到637.5 kg/hm^(2),雌蟹平均产量达到787.5 kg/hm^(2),日本对虾平均产量达到236.25 kg/hm^(2)。