pH对日本沼虾存活及肝功能相关酶活性的影响

为揭示日本沼虾(Macrobrachium nipponense)对水体pH的适应性,分析了不同pH胁迫下日本沼虾在不同时段的存活率以及96 h后蜕壳率,免疫、肝功能相关酶活性的变化。结果显示,pH胁迫处理96 h时,不同pH处理组日本沼虾的存活率显著低于对照组,除pH 7.0组的蜕壳率与对照组差异不显著外,其余pH处理组蜕壳率显著高于对照组;暴露在弱酸性水(pH 6.0)、弱碱性水(pH 8.0)、碱性水(PH9.0)中的成活率不同,其中PH6.0组虾的成活率在36 h时显著低于PH8.0组,24 h时显著低于pH 9.0组;pH 5.0酸性处理组日本沼虾在试验期间存活率始终最低,上述结果表明日本沼虾对碱性水体的适应性强于酸性水体。比较不同pH值对日本沼虾肝功能相关酶活性的影响程度时发现,日本沼虾T-SOD、ACP、GOT、T-AOC酶的耐受pH生态幅较窄,AKP酶的耐受pH生态幅较宽。通过96 h的pH值与相关酶回归分析得出,日本沼虾的最适pH值范围为7.3~7.6。     

Toxicity of Chelated Copper to Juvenile Red Drum Sciaenops ocellatus1

Acute toxicity of chelated copper to juvenile red drum (x?= 3.1 g) was determined in a static test at 25 C and 8 ppt salinity. The 12, 24, 48, 72, and 96 h LC₅₀s were 1.90, 0.84, 0.75, 0.64, and 0.52 mg/L copper, respectively. Effects of temperature and salinity on the 96 h LC₅₀ (0.5 mg/L copper) for juvenile red drum (x?= 5.0 g) were tested at two temperatures, 25 and 30 C, and three salinities, 0.5, 8, and 30 ppt. Temperature significantly affected mortality; mortality in 0.5 and 8 ppt salinities was significantly higher at 30 C than at 25 C. An increase in salinity significantly reduced the mortality of juvenile red drum. Total mortality occurred in 0.5 ppt salinity within 48 h at 25 C and within 12 h at 30 C. Total mortality occurred in 8 ppt salinity within 72 h at 25 C and within 48 h at 30 C. No mortality occurred during 96 h in 30 ppt salinity at 25 C or 30 C.     

Temperature and feed rate effects on Chinese catfish, Clarias fuscus (Lacepède), growth

Abstract. Chinese catfish, Clarias fuscus (Lacepède), within three size ranges were evaluated for growth, survival and feed conversion ratios (FCR). A 4 × 3 factorial design was used during year-long trials which included four temperatures (20,25,30 and 35 °C) and three feeding rates with commercially formulated salmon/trout feed. Specific growth rates of juvenile fish (1–60g) were highest, ranging from 1–64% body weight/day at 20°C (2%/day feed rate), to 4–94%/day at 25°C (6%/day feed rate). Specific growth rates of sub-adult fish (60–150g) averaged 0–65%/day, with no significant difference between temperature-feed rate treatments. Specific growth rates of adult fish (>150g) were lowest, averaging 0–30%/day for grouped feed rate treatments at 25°C, and 0–16%/day at 30°C. Most mortalities occurred during the juvenile stage, with survival ranging from 0% at 35°C(2% feed rate) to 96% at 30°C(6% feed rate). Survival was 95–100% with sub-adults and adults. FCR were 1 to 4 with juveniles, 2 to 12 with sub-adults, and 3 to 22 with adults. These trials suggest that optimal growth and FCRs were obtained at 25°C; with feed rates of 6%/day with juveniles, 2%/day with sub-adults, and 1%/day with adult fish. Final yields at 25 and 30°C indicate that even though growth and FCR are optimal at 25°C, survival was greater at 30°C, which compensated for reduced growth performance at this temperature. Yields at 25 and 30°C were almost double those at 20°C.     

氨、亚硝酸盐和硝酸盐对凡纳滨对虾幼虾的毒性作用

研究了 NH₃-N、NO₂ ^- -N与 NO₃ ^- -N对凡纳滨对虾幼虾的毒性作用。获得了 NH₃-N_t(NH₃-N_m) 与 NO₂ ^- -N对体长2．4cm幼虾的 24h、48h、72h、96h之 LC₅₀值，两者对幼虾的安全质量分数分别为1．30 (0．101)mg/L和3．80mg/L。当 NH₃-N_t(NH₃-N_m)质量分数在1．3(0．101)~4．3(0．333)mg/L时，存活率为71．4% ~92．9%，体长增长率为36．3% ~57．1%，体重增长率为188．5% ~322．3%。当 NO₂ ^- -N质量分数在3．00~21．00mg/L时，成活率为75．0% ~91．7%，体长增长率为21．2% ~59．2%，体重增长率为72．0% ~311．9%。NO₃ ^- -N对体长7．37cm幼虾的亚急性毒性效应：NO₃ ^- -N的质量分数在 30~195mg/L时，成活率为 35% ~100%，体长增长率为8．5% ~20．5%，体重增长率为29．6% ~56．8% 。三态氮在一定质量分数范围内均对幼虾的存活率和生长率产生影响。     

Survival of silver catfish fingerlings exposed to acute changes of water pH and hardness

Theaim of this study was to examine the survival of fingerlings of silver catfish,Rhamdia quelen, in water with different pH and hardnessvalues. Fingerlings (1.60 ± 0.14 g; 5.67 ± 0.15cm) were randomly assigned to 35 treatments (in triplicate) andmaintained in 44 L polyethylene tanks (10 fingerlings/tank) for 96h. Fingerlings were exposed to seven solutions of varying pH (3.5,3.75, 4.0, 7.0, 9.5, 10.0, and 10.5) and five solutions of varying hardness(30,70, 150, 300, and 600 mg.l^–1 CaCO₃).Survival was assessed at 12, 24, 48, 72, and 96 h. Fingerlingmortality was 100% after 12 h exposure to pH 3.5 at all hardnesslevels, whereas mortality at pH 3.75, 10.0, and 10.5 decreased with increasinghardness. There was no mortality of fingerlings exposed to pH 4.0, 7.0, and 9.5at all hardness levels. The results allow us to conclude that the hardnesslevels studied do not affect the survival of silver catfish fingerlings exposedto pH 3.5, 4.0, 7.0, and 9.5 for 96 h. However, the increase ofwater hardness improved survival of fingerlings of this species exposed to pH3.75, 10.0, and 10.5.     

Survival of silver catfish fingerlings exposed to acute changes of water pH and hardness

Theaim of this study was to examine the survival of fingerlings of silver catfish,Rhamdia quelen, in water with different pH and hardnessvalues. Fingerlings (1.60 ± 0.14 g; 5.67 ± 0.15cm) were randomly assigned to 35 treatments (in triplicate) andmaintained in 44 L polyethylene tanks (10 fingerlings/tank) for 96h. Fingerlings were exposed to seven solutions of varying pH (3.5,3.75, 4.0, 7.0, 9.5, 10.0, and 10.5) and five solutions of varying hardness(30,70, 150, 300, and 600 mg.l^?1 CaCO₃).Survival was assessed at 12, 24, 48, 72, and 96 h. Fingerlingmortality was 100% after 12 h exposure to pH 3.5 at all hardnesslevels, whereas mortality at pH 3.75, 10.0, and 10.5 decreased with increasinghardness. There was no mortality of fingerlings exposed to pH 4.0, 7.0, and 9.5at all hardness levels. The results allow us to conclude that the hardnesslevels studied do not affect the survival of silver catfish fingerlings exposedto pH 3.5, 4.0, 7.0, and 9.5 for 96 h. However, the increase ofwater hardness improved survival of fingerlings of this species exposed to pH3.75, 10.0, and 10.5.     

刺参“参优1号”苗种在不同pH条件下的代谢特征和适应性研究

为研究刺参(Apostichopus japonicus)"参优1号"苗种的适宜pH及耐受范围并解析其对水体的酸碱性适应机制,本研究测定了pH 6.5~10.0条件下该良种苗种的生长、存活、呼吸代谢以及非特异性免疫酶活性的差异。结果显示,在pH 6.5~9.5范围内,30 d实验周期内苗种的存活率均为100%,而在pH 10.0条件下苗种全部死亡。在pH 7.5~8.5范围内,苗种特定生长率(SGR)为正值,且在pH为8.0时SGR最高,达到0.541%/d,而在pH低于7.0和高于9.0时,SGR为负值,苗种为负生长。对不同pH条件下的耗氧率(R_O)和排氨率(R_N)的测定结果显示,随pH的变化,R_O和R_N均呈现以pH 8.0为波谷的"V"型变化,在pH 8.0条件下的R_O和R_N分别为19.07和1.34μg/(g·h)。不同pH实验组刺参苗种的氧氮比(O/N)均在11左右,O/N随pH变化无显著差异(P>0.05)。pH的升高和降低会引起刺参体腔液中酸性磷酸酶、碱性磷酸酶、溶菌酶和超氧化物歧化酶的活性显著升高(P<0.05),在苗种适应pH胁迫过程中,各pH组超氧化物歧化酶活性的峰值一般在第0天出现,而溶菌酶的活性峰值在第10天出现。研究表明,刺参"参优1号"可存活的pH范围为6.5~9.5,适宜生长的pH范围为7.5~8.5,pH变化会导致苗种呼吸代谢和免疫酶活性的改变。本研究结果将为刺参"参优1号"苗种的科学化推广提供依据。     

Effect of Fish Density During Transportation on Stress and Mortality of Juvenile Tambaqui Colossoma macropomum

The increased demand for juvenile tambaqui Colossoma macropomum for grow-out ponds and stocking programs in the Amazon state of Brazil has increased the transportation of this species. This study was designed to determine the optimum density of juvenile tambaqui during transportation in closed containers. Fish (51.9 ± 3.3 g and 14.9 ± 0.4 cm) were packed in sealed plastic bags and transported for 10 h at four densities: 78, 156, 234, and 312 kg/m³. After transportation, fish from each density were kept in separate 500-L tanks for 96 h. Mortality, 96-h cumulative mortality, water quality, and blood parameters (hematocrit, plasma cortisol, and glucose) were monitored. Fish mortality after transportation was significantly lower at densities of 78 and 156 kg/m³ than at 234 and 312 kg/m³. Cumulative mortality was significantly lower at a density of 78 kg/m³. Dissolved oxygen after 10 h of transportation remained high at a density of 78 kg/m³, but reached critically low values at all other densities. Ammonia concentration was highest at the lowest density and was lower at higher densities. Carbon dioxide concentration was lowest at the density of 78 kg/m³ but higher in the other treatments. Plasma glucose and cortisol increased significantly immediately after transportation at densities of 156, 234, and 312 kg/m³, returning to control values by 24 h. The best density for juvenile tambaqui during a 10-h transportation haul in a closed container was 78 kg/m³. At this density there was no fish mortality, water quality was kept within acceptable values, and fish were not stressed.     

Effects of different photoperiods on growth, stress and haematological parameters in juvenile great sturgeon Huso huso

The effects of constant light (24L:00D), no light (00L:24D) and two light–dark periods (18L:06D;12L:12D) on the growth, stress and haematological variables were assessed in juvenile great sturgeon, Huso huso . During the 8-week experimental period, juveniles (22.5 ± 0.6 g) were kept under a 150 lx light intensity in fibreglass tanks (0.8 m², 500 L). Differences in growth were insignificant during the experiment, but lactate levels were higher in the 00L:24D and 24L:00D photoperiods compared with 12L:12D and 18L:06D photoperiods. Cortisol levels did not show differences among the various photoperiods. At the end of the experimental period, fish reared under a 12L:12D photoperiod had higher haemoglobin values and erythrocyte numbers than in the other photoperiods, while no differences were found between groups with regard to haematocrit values or leucocyte numbers. The highest survival rate (89%) was observed in the 12L:12D period in which the levels of lactate and cortisol as stress indicators were minimal. The results indicate that various photoperiods cause different stress levels in juvenile great sturgeon and have no significant effects on growth, at least in short time periods.     

Using Efinol®L during transportation of marbled hatchetfish, Carnegiella strigata (Günther)

The objective of this experiment was to test the efficacy of a probiotic (Efinol^®L) during transportation of marbled hatchetfish, Carnegiella strigata . Wild specimens were captured from a small stream and transported for 24 h in plastic fish boxes with a probiotic (10 mg L⁻¹) and probiotic-free water. The boxes were sampled at 3, 12 and 24 h of transport. At the end of the experiment, the survival rate was close to 100% in both treatments. Dissolved oxygen diminished with time in both treatments, but the probiotic group had significantly higher levels. Conductivity, pH and ammonia increased significantly during the transport, demonstrating higher levels in the probiotic-free group. Fish from both treatments presented very high net Na⁺ and K⁺ effluxes after 3 h of transport. At 24 h, net K⁺ effluxes in fish of the probiotic treatment reached values close to zero and a significantly lower Na⁺ efflux was observed. Cortisol levels in both treatments at 3 and 12 h were significantly higher than that in control samples. Higher body cortisol levels were observed in the probiotic-free group than that in the probiotic group at 3 and 12 h. The results demonstrate that addition of a probiotic during fish transport improves water quality and leads to fish presenting a lower stress response intensity.     

Effect of vitamin E and highly unsaturated fatty acid-enriched Artemia urmiana on growth performance, survival and stress resistance of Beluga (Huso huso) larvae

A 44-day rearing trial was conducted to examine the enrichment of Artemia urmiana nauplii with vitamin E and highly unsaturated fatty acid (HUFA) and its effects on the growth performance, survival and stress resistance of great sturgeon, Huso huso , larvae. Cod liver oil (EPA 18% and DHA 12%) and α-tocopherol acetate were used as lipid and vitamin E sources. Beluga larvae at the first exogenous feeding with 69±5.9 mg body weight were randomly distributed into four treatments and three tanks were assigned to each diet. The test treatments were as follows: larvae fed with HUFA+20% and HUFA+50% (w/w) vitamin E-enriched Artemia nauplii (E1 and E2 groups, respectively), HUFA without vitamin E (HUFA group) and non-enriched Artemia (control group). All treatments fed non-enriched Artemia for the initial 5 days after first feeding and then fed enriched Artemia for 7 days. After the period of enrichment, larvae were fed with daphnia from the 13th to the 40th day. At day 40, submersion in salt water (6 ppt for 4 days and 12 ppt for 2 days) and warm water (33 °C for 2 days) was performed to evaluate larvae resistance to salinity and temperature stress. Final weight, daily growth rate, specific growth rate and weight gain were higher in beluga fed with enriched Artemia . The highest growth rates were observed in E1, whereas survival was not significantly different between groups. Use of vitamin E and HUFA significantly increased fish resistance to a salinity of 12 ppt and the lowest stress resistance was observed in the control group. Stress tolerance was not significantly different at 6 ppt and 33 °C between groups. There was no comparable difference in the haematocrit index under stress conditions. These results indicated that the enrichment of Artemia with essential fatty acids and vitamin E can affect some growth and stress tolerance factors in great sturgeon, Huso huso , larvae.     

Post-transport recovery of cultured scallop (<Emphasis Type="Italic">Pecten maximus</Emphasis>) spat,juveniles and adults

High mortality associated with transport operations in scallop culture has been a major problem faced by European farmers. Simulated transport with Pecten maximus L. spat <2 mm, spat 15–30 mm, juveniles 30–50 mm and adults >100 mm were carried out in Spain, Ireland and Norway. Different time and temperature combinations were studied in order to maximise post-transport survival and establish best practices. Out-of-water transport could result in 100% survival if conditions were right, but the response to emersion stress depended on size, season and location. Post-transport recovery decreased with emersion time and was strongly influenced by temperature. Air exposure was tolerated for a longer time by adult scallops than spat and juveniles, but the results differed among trials in the different countries. The maximum emersion time that gave post-transport survival ≥80% was 12 h for the smallest spat, 18 h for larger spat and 24 h for juvenile and adult scallops. Adults were less affected by transport temperatures that deviated from ambient seawater temperature than spat and juveniles. In general post-transport recovery was high when sea temperature was <10°C, but during warm-water seasons special care should be taken to avoid stressful and lethal transport conditions. A transport temperature <12°C was recommended, though not more than 10°C below ambient culture temperature. A maximum transport time of 9 h was suggested for spat and juveniles to attain post-transport survival close to 100%, but 12–24 h was feasible during the cold-water season or at favourable transport temperatures.     

Effect of high temperature on survival,oxygen consumption,behavior, ammonia-N excretion,and related immune indicators of the Japanese scallop Mizuhopecten yessoensis

In this study, two experiments were conducted to test the effect of high temperature on survival, behavior, oxygen consumption, ammonia-N excretion, and enzyme activities related to oxidative stress of the Japanese scallop Mizuhopecten yessoensis. In the first test, we abruptly transferred scallops from the rearing temperature (15 °C, control temperature) to 20, 22, 24, and 26 °C. Scallops exposed to 26 °C were significantly affected by temperature, with 100 % mortality after 12 h. The 8-, 12-, 24-, 48-, and 96-h lethal temperatures for 50 % mortality (LT₅₀) were 27.5, 24.4, 24.3, 24.2, and 23.8 °C, respectively. The activities of CAT and SOD and the T-AOC in the coelomic fluid of M. yessoensis changed significantly after high-temperature stress (P < 0.05). They reached to the highest levels after 8 h of stress in the 22, 24, and 26 °C treatment groups then returned to the control group level. The content of MDA reached the highest level after 12 h in each temperature treatment. In the second test, scallops were acclimatized to the different temperature levels (20, 22, 24, and 26 °C) and then maintained for 30 days. Survival was significantly lower at 26 °C than at the other temperatures, and the highest survival occurred in the 15 °C treatment. High temperature also significantly influenced the oxygen consumption rates and ammonia-N excretion rates (P < 0.05). As the temperature increased, the CAT and SOD activities and the T-AOC in the coelomic fluid of M. yessoensis declined significantly, whereas the MDA content increased. These results illustrate that high temperature can significantly affect the survival, behavior, oxygen consumption, ammonia-N excretion, and enzyme activities related to oxidative stress of M. yessoensis.     

敌百虫对奥尼罗非鱼幼鱼的急性毒性及安全浓度评价

为研究敌百虫对奥尼罗非鱼幼鱼的急性毒性效应,采用96 h半静水式生物毒性试验方法,在水温(23.5±2.0)℃,溶解氧>5 mg/L的条件下,分别检测在曝气自来水(pH为6.5)和池塘水(pH为8.5)中敌百虫对奥尼罗非鱼幼鱼的急性毒性效应。结果显示:在曝气自来水中,敌百虫对奥尼罗非鱼幼鱼24、48、72、96 h的半致死质量浓度分别为3.68、3.31、2.05、1.57 mg/L,安全质量浓度为0.157 mg/L;在池塘水中,敌百虫对奥尼罗非鱼幼鱼24、48、72、96 h的半致死质量浓度分别为0.35、0.29、0.17、0.13 mg/L,安全质量浓度为0.013 mg/L。试验结果表明,在池塘水中敌百虫对奥尼罗非鱼幼鱼的毒性比在曝气自来水条件下强。     

Effect of Stocking Density on the Growth and Survival of Spotted Sand Bass Paralabrax maculatofasciatus Larvae in a Closed Recirculating System

Abstract.— The effect on growth and survival of the initial stocking density (50, 100, 150, and 200 larvae/ L) in larval rearing of spotted sand bass was evaluated over 30 d in a closed recirculating system. Larvae were fed with rotifers, copepods, nauplii and adult Artemia , and spotted sand bass yolk-sac larvae. Water quality was monitored daily. The notochordal or standard length of sampled larvae was measured by image analysis. Specific growth rates at each density were compared by covariance analysis. Survival was estimated from day 15 to the end of the experiment, when a resistance test was used to evaluate the juvenile quality among densities. At the end of the experiment, mean standard length of larvae at lower densities was significantly larger ( P < 0.05) than at higher densities. Higher specific growth rates were found at lower densities. Significantly higher survival ( P < 0.05) was recorded for the lowest density, but the highest number of harvested fish was obtained with the highest densities (150 and 200 larvae/L). The lowest density also showed the significantly ( P < 0.05) higher survival after using a resistance test. We conclude the highest density can be used in larval rearing of spotted sand bass. However, better survival, growth, and seed quality are obtained at the lowest density. To recommend an optimal density for this specie, it is necessary to improve the water quality in the culture system and to make a cost-benefit study.     

Natural spawning, early development and first feeding of the semicircle angelfish [Pomacanthus semicirculatus (Cuvier, 1831)] in captivity

Successful natural spawning of Pomacanthus semicirculatus in captivity from 11 September to 18 October, 2006 is described for the first time. Each female laid an average of 230 000 eggs during the spawning period. Fertilized eggs were spherical, transparent and buoyant and had a mean diameter of 0.61 ± 0.03 mm (mean ± SD). Embryonic development lasted 18–21 h at 28.5 °C. Newly hatched larvae were 1.35 ± 0.02 mm in total length (TL) with 27 (12+15) myomeres and had an oil globule in the ventroposterior area of the yolk sac. Larvae completed yolk absorption within 3 days post hatching at 2.37 ± 0.05 mm TL. Larvae were fed either 100% microalgae ( Nannochloropsis sp.), 100% s-type rotifers ( Brachionus rotundiformis ), 100% dinoflagellates ( Gonyaulax sp.) or different combinations of the three (50%:50%:0%, 30%:35%:35%) to determine the effect of live feed on the survival rate. The survival was significantly ( P <0.001) better in larvae fed a combination of diets (30%: 35%: 35%) than others. These results indicate that P. semicirculatus is a potential species for captive-breeding programmes and the use of a combination of diets (microalgae plus s-type rotifers and dinoflagellates) may be a suitable first food for fish larvae.     

Effects of Feed Application Rates on Growth, Survival, and Feed Conversion of Juvenile Snakehead Channa striatus

Growth, survival and feed conversion ratio of juvenile snakehead Channa striatus were evaluated when fed a dry, formulated feed (50% crude protein) at 24 ± 1 C. Six daily feed application rates were used (0%, 5%, 10%, 15%, 20%, and 30%), as a percentage of fish body weight, with three replicates per treatment. After 29 d, final weights were all significantly greater ( P < 0.01) than initial weights, except for the 0% application. Feed applications higher than 5% did not result in increased growth ( P > 0.05). Feed conversion ratio was 0.99 at 5% feed application, and 6.3 at 30% feed application. Fish survival was increased by providing formulated diet, but no further improvement was found when feed applications exceeded 5%. Cannibalism was reduced by providing formulated feed, but it was unavoidable when substantial differences in fish size existed, even when feeding ad libitum . Our results indicate that the optimal feed application rate is close to 5% body weight/d for juvenile snakehead.     

Effect of lignite fulvic acid on growth,antioxidant ability,and HSP70 of Pacific white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

This study was conducted to evaluate the effects of fulvic acid (0, 0.3, 0.6, 0.9, and 1.2%) as feed additive on growth, feed utilization, antioxidant ability, and HSP70 in hemolymph and hepatopancreas of juvenile white shrimp Litopenaeus vannamei (average weight 2.5 g) reared under experiment conditions. Shrimp were stocked at a density of 625 shrimps m^?3 for 60 days in net cages submerged in recirculating tanks. At the end of the experiment, specific growth rates and survival rates of shrimp in treatment groups fed with 0.6, 0.9, and 1.2% fulvic acid were higher compared to that of the control group. Shrimp fed 0.6, 0.9, and 1.2% fulvic acid had significantly lower feed conversion rates than those fed control diet. The optimum dietary fulvic acid requirement for juvenile shrimp based on weight gain was 0.897%. Furthermore, superoxide dismutase activity and peroxidase activity increased significantly, while malonaldehyde content decreased in the hemolymph and hepatopancreas of shrimp fed 0.9 and 1.2% dietary fulvic acid. Glutathione content increased obviously in hemolymph of shrimp fed 0.6, 0.9, and 1.2% fulvic acid. In hepatopancreas, glutathione content was significantly higher in shrimp supplemented with 1.2% fulvic acid. HSP70 decreased obviously in hemolymph of shrimp fed 0.9 and 1.2% fulvic acid, while shrimp fed with 0.6 and 0.9% fulvic acid showed lower HSP70 level in hepatopancreas. The results of this study demonstrated that dietary fulvic acid could improve survival rates, growth, feed utilization, antioxidant capability, and stress resistance of juvenile L. vannamei reared under intensive stocking conditions.     

盐度与pH对花鲈孵化、初孵仔鱼成活及早期幼鱼生长性能的影响

为探究我国北方海域花鲈繁育适宜盐度和pH处理的设定,及促进早期花鲈苗种推广,本研究针对不同盐度(0、15、20、25、30、35和40)与pH(5.5、6.5、7.5、8.5和9.5)条件下,北方人工繁殖花鲈受精卵的孵化率、畸形率及饥饿10 d后的存活情况进行了分析,并对花鲈初孵仔鱼进行不投饵耐饥饿实验,记录每日存活率(SR)及最终生存活力指数(SAI)。最后观测低盐0、养殖盐度30与高盐45对花鲈早期幼鱼生长性能的影响。结果显示,北方海域花鲈受精卵适宜孵化盐度为20~35,以盐度25组孵化率最高,适宜pH为6.5~7.5,以pH 6.5组孵化率最高。低盐15组中,具最低的孵化率及最高的畸形率,但在最终饥饿SR的统计中,低盐15组的SR及SAI明显高于盐度30与35组,推测低盐15接近花鲈体液等渗点,降低了渗透调节中的能量消耗,更利于存活。初孵仔鱼饥饿实验中,盐度20组SR下降相对平缓,在第8天仍有12.66%的SR(其他组已为0)。饥饿1 d时,各pH组SR均小于90%,以pH 6.5组SR最高,为89.11%。与盐度处理组相比,花鲈初孵仔鱼对pH变化较为敏感,其孵化率及最终SR显著低于盐度处理组。花鲈早期幼鱼盐度处理组中,低盐0与高盐45将对此规格花鲈幼鱼产生较大损伤,以高盐45抑制最显著,应为苗种盐度推广的上限,而花鲈生长盐度30与各处理盐度相比,较适合花鲈早期幼鱼的生长。研究结果将为北方海域花鲈繁育适宜盐度和pH处理的设定,及提高花鲈孵化率、育苗成活率与早期苗种推广提供基础资料。     

Comparisons of Uptake and Depuration of 2-Methylisoborneol in Male, Female, Juvenile, and 3MC-induced Channel Catfish Ictalurus punctatus

The occurrence of off-flavors in farm-raised channel catfish is a major burden to the catfish culture industry, causing millions of dollars worth of market-ready fish to be rejected each year. Off-flavors are believed to be the result of exposure and subsequent accumulation of certain volatile microbial metabolites such as 2-methylisoborneol. In this study, the uptake and elimination of [¹⁴C]-2-methylisoborneol equivalents were examined in juvenile and mature channel catfish. The described method is presented as a simple and inexpensive procedure for comparing treatment effects on off-flavor elimination rates. In addition, the effects of the cytochrome P4501A inducing agent 3-methylcholanthrene on 2-methylisoborneol depuration was studied in juvenile fish. Uptake was determined during a 24–h static exposure to waterborne 2-methylisoborneol (7.6 ± 3.7 μg/L). Uptake equilibrium had been established in all groups by 12 h, with total uptake higher in juvenile fish. Depuration rates were not different between untreated groups (t_½ a = 12.r122.4 h; t_½β= 91.3–143.7 h); however, the depuration half-lives for 3-methylcholanthrene treated juveniles were significantly longer than those of controls.