酸碱度和干露对墨西哥湾扇贝幼虫和稚贝的影响

为探讨酸碱度和干露对墨西哥湾扇贝不同发育阶段的影响,2000年4月和2001年4月在浙江省玉环县抛西水产育苗场用实验生态的方法研究了酸碱度和干露对墨西哥湾扇贝浮游幼虫和稚贝生长和存活的影响。结果表明:pH值7～8存活率最高,生长最好。稚贝的耐干露能力低下。     

Ca^2＋、Mg^2＋对凡纳滨对虾存活及生长的影响

通过单因子静态急性毒性试验和正交设计法,研究水环境中Ca~(2 )、Mg~(2 )、Ca~(2 ) Mg~(2 )总量及Ca~(2 )/Mg~(2 )比值对凡纳滨对虾存活及生长的影响。结果表明:(1)凡纳滨对虾48h的Ca~(2 )的LC_50为407.38mg·L~(-1)、Mg~(2 )的LC_(50)为741.31mg·L~(-1)。(2)在Ca~(2 )/Mg~(2 )比值为1:10时,对凡纳滨对虾生存没有影响;(3)凡纳滨对虾的生长与Ca~(2 )浓度有密切关系,其值过高或过低均会影响凡纳滨对虾的生长;在Ca~(2 )/Mg~(2 )比值为1:3时,凡纳滨对虾生长和存活率随着Ca~(2 ) Mg~(2 )质量浓度的增加而上升,但达到一定质量浓度后,又随着Ca~(2 ) Mg~(2 )质量浓度的继续增加而下降。     

Preliminary observations on the tank and pond culture of the glass eels of the Australian shortfin eel, Anguilla australis Richardson

There is expanding interest in the culture of the Australian shortfin eel Anguilla australis Richardson; however, there is a lack of fundamental biology and husbandry information necessary to further develop an industry within Australia. The present study was undertaken to gain a preliminary understanding of basic husbandry requirements for rearing of juvenile A. australis (glass eels and elvers) in tanks and earthen ponds. Newly caught glass eels were successfully acclimated to culture conditions. During tank culture trials, specific growth rates (SGR) and survival rates ranged from ?2.1 to 2.8% day^?1 and 52% to 100% respectively. Glass eels weaned onto a commercial eel diet exhibited a significantly greater SGR and survival rate than those weaned onto a commercial trout diet. Glass eels weaned onto an eel diet over a 15‐day period grew slightly faster than eels weaned over a 5‐day period, but survival rates were not significantly different for each treatment. SGRs (up to 2.8% day^?1) were significantly higher for glass eels fed at 9 and 12% day^?1 than at 6% day^?1. Stocking densities between 2.5 kg m^?3 and 30 kg m^?3 did not influence either SGR or survival rates. SGRs were significantly higher for glass eels cultured at 25 °C than at lower temperatures. During pond culture trials, SGRs and survival rates ranged from 1.36 to 1.65% day^?1 and 39% to 77% respectively. The SGR and survival rates of juvenile eels stocked into ponds receiving supplementary feeding with a commercial eel diet were not significantly different to those of eels stocked into ponds that did not receive supplementary feeding.     

Spatial and temporal trends in abundance of Atlantic salmon, Salmo salar, in Newfoundland with emphasis on impacts of the 1992 closure of the commercial fishery

Closure of the Newfoundland commercial Atlantic salmon, Salmo salar L., fishery in 1992 was the most restrictive measure introduced to help rebuild depressed local stocks of salmon. Here, the effects of the closure are evaluated by analysing trends in abundance since 1984, and estimates of survival in both freshwater and marine environments derived from enumeration of salmon at fish counting facilities. While freshwater production of smolts generally has been maintained, marine survival rates remain low (2–10%), and highly variable. Overall, total stock size differs little from that prior to the closure of the commercial salmon fishery. Spawning escapements have increased by a factor of 2 or 3 in some rivers, but in other areas total returns are lower on average than those prior to the fishery closure. Factors other than exploitation are contributing to lack of stock recovery, resulting in continued conservation concerns.     

Hatchery production of diploid and triploid clams, Tapes dorsatus (Lamarck 1818): a potential new species for aquaculture

To assess the potential for hatchery production of the venerid clam, Tapes dorsatus, diploid and triploid clams were produced and ongrown until the spat reached 5–8 mm in size. Triploidy percentages at metamorphosis that ranged from 56 to 85% were induced using a 15-min exposure to 1 mg/l cytochalasin B. No differences were observed in the growth rate of sibling diploid and triploid T. dorsatus larvae. Survival of diploid clams to pediveliger stage was however higher. Post-metamorphic growth and survival of diploid and triploid clams remained the same until the clams were removed from the hatchery to outdoor nurseries. Throughout the larval and early spat phases of production, T. dorsatus growth was similar to that reported for the Manila clam, Tapes philippinarum. Based upon its ease of culture, rapid growth and marketability, T. dorsatus are thought to have considerable aquaculture potential.     

野生哲罗鱼的采捕及运输技术

两次对采捕的野生哲罗鱼从虎林市虎头镇至宁安市渤安镇进行长途运输。运输时间是9h，运输成活率分别是76％和94．4％。     

Effects of four egg desticking procedures on hatching rate and further survival and growth of larvae in the tench (Tinca tinca L.)

Four desticking procedures for tench eggs (A: tannic acid solution (1 g L⁻¹) for 15 s; B: alcalase enzyme solution (8 mL L⁻¹) for 60 s; C: alcalase enzyme solution (15 mL L⁻¹) for 120 s; D: Woynarovich and Woynarovich (1980) solution for 58 min followed by tannic acid solution (1 g L⁻¹) for 15 s) were tested to obtain data about influence on embryo survival to hatching stage and further survival and growth of the larvae. In the tannic acid and Woynarovich and Woynarovich (1980) treatment (A and D) few eggs stuck together and some were adhered to the incubator walls, whereas in the alcalase treatments (B and C) eggs neither stuck together nor adhered to the incubator walls. Percentages of hatched larvae did not show significant differences (mean values ranged between 47.4% in treatment A to 37.0% in treatment C). Larvae deformities observed were <0.5% in all cases. There were no significant differences among survival and growth rates of the larvae from different egg desticking origin, reaching, after 30 days, mean survival values around 90% and total length and weight of 12.5 mm and 19 mg respectively.     

乙酰甲喹对刺参幼参非特异性免疫、生长及抗应激能力的影响

选用初始体重为0.6 g左右的幼参,水体中分别添加0(对照组)、0.5、1.0、2.0、4.0和6.0 mg/L的乙酰甲喹。前69天每两天全部换水后,按照用药浓度泼洒药物一次。停药两周后经长途运输,考察其抗应激能力。实验结果表明:前30 d,各组刺参体壁中SOD酶活性都呈现增高趋势,2.0 mg/L组SOD活性达到最高,之后又呈现降低趋势;随着乙酰甲喹浓度的增加,各实验组刺参体壁中AKP和ACP酶活性呈现先增加后降低的趋势,2.0 mg/L和4.0mg/L组刺参酶活性最高;40 d后各实验组刺参体壁酶活性逐渐与对照组持平。所有实验组刺参的末体重、增重率和特定生长率均显著高于对照组(P0.05),4.0 mg/L组刺参末体重、增重率和特定生长率最高,显著高于其他各组(P0.05);4.0 mg/L组成活率为90.6%,显著高于其他各组(P0.05)。高浓度(6.0 mg/L)的乙酰甲喹导致幼参抗应激能力差。综合以上分析,认为刺参保苗期间,乙酰甲喹的适宜添加量为2.0~4.0 mg/L。     

温度、湿度和氧气对海湾扇贝无水保活的影响

在实验室条件下,研究了温度、湿度和氧气对海湾扇贝Argopecten irradias无水保活的存活率和失重率的影响,进而研究其无水保活关键技术。对体质量为29~33 g的海湾扇贝采用普通、保湿、充氧和充氧保湿4种处理方式,并分别置于-2、0、4、10、15~18、20~25℃下进行无水保活试验。结果表明：海湾扇贝生态冰温区为-2.8~0℃;随着温度的升高,海湾扇贝的存活率逐渐降低;海湾扇贝在-2、0℃条件下保活效果最好,其次是4℃;保湿组比未保湿组、充氧组比未充氧组的存活率均有显著提高( P<0.05);低温条件下,保湿充氧处理的海湾扇贝存活率显著高于保湿组和充氧组(P<0.05),保活效果最好,保活10 d后其存活率依然达95%以上;低温无水条件下,采用保湿充氧处理的海湾扇贝失重率较小。研究表明,温度、湿度和氧气对海湾扇贝无水保活有较大影响,在-2~4℃的低温条件下采用保湿充氧处理方式对海湾扇贝进行无水保活,效果最佳。     

影响刺参幼参成活和生长的几个因素的研究

在刺参人工育苗过程中，从稚参到幼参阶段极易受外界综合因子影响，成活率很低。本文采用数理统计的方法，选择四种因子对此阶段死亡率进行试验。从方差和直观分析看到稚参的附着密度和饵料品种对其成活率和生长的影响大于水温和换水方式。稚参附着密度以0．2头／cm^2为最佳，0．5头／cm^2次之；饵料以鼠尾藻磨碎液为最佳，其次是鼠尾藻液和叉鞭金藻的混合液．