不同盐度海水对锯缘青蟹生长变态的影响

实验室条件下比较了盐度为0、3.38‰，6.76‰,13.52‰,16.9‰条件下锯缘青蟹由二期幼蟹至六期幼蟹的生长变态情况，初步结果表明：青蟹幼蟹在变态为四期幼蟹之前，对环境盐度条件有较高的要求；盐度低于10‰，将延长其变态周期和降低成活率；四期幼蟹以后对盐度的适应能力明显增强，此阶段适当降低盐度，钭有助于缩短其蜕壳周期。     

盐度骤变和渐变对三疣梭子蟹幼蟹发育和摄食的影响

为探讨三疣梭子蟹幼蟹对盐度的适应性,设置盐度骤变和渐变2组试验.骤变试验以27为基础盐度,幼蟹直接转入7、11、15、19、23、31、35、39、43、47、51盐度水体中;渐变试验盐度从27开始,以4/d的日变幅逐渐升至51和降至7,分析不同处理下幼蟹存活率、变态率及摄食量的变化.试验结果表明,I期幼蟹盐度从27骤变为11～23后,120 h存活率≥50%,骤变为35～47,72 h存活率均降至10%,96 h内幼蟹全部死亡.Ⅱ期幼蟹盐度骤变为7、47、51后,96 h存活率分别为40%、20%、0%,其他处理存活率≥50%.I期幼蟹盐度骤变为11～31时,变态率≥40%,其他处理均为0%;Ⅱ期幼蟹盐度骤变为11～39时,变态率≥40%,其他变态率为10%～30%(51处理组除外,为0%).盐度骤变试验组存活幼蟹平均摄食卤虫成体1～3.17个.盐度突降＜16或突升＜8时,幼蟹的摄食量高于其他盐度骤变组.盐度渐变对幼蟹存活率、变态率和摄食量的影响均小于相应盐度下的骤变组.幼蟹适应盐度渐变的能力强于骤变;在盐度的降低或升高变化中,幼蟹能较好的适应盐度降低;幼蟹的盐度适应能力随发育呈增强趋势.15～31为三疣梭子蟹幼蟹生长发育的适宜盐度.     

盐度对河蟹仔蟹培育的影响

研究了盐度对河蟹仔蟹培育的影响以及不同盐度中培育的仔蟹对淡水的适应能力。结果表明 :大眼幼体适宜在 5‰～ 15‰盐度的水体中生活在淡水中培育会降低其变态成活率 ,早期仔蟹可以适应 0～ 15‰盐度 ,2 0‰的高盐度会明显影响仔蟹的变态成活率 ;仔蟹对淡水的适应能力与培育仔蟹的水体盐度呈明显的负相关 ,15‰以上盐度水体中育成的仔蟹不能完全适应在淡水中进行后续养殖。考虑到仔蟹培育过程中早期成活率和仔蟹对淡水的适应能力两方面的因素 ,仔蟹培育的盐度应控制在 5‰左右为宜。     

环境因子变化对锯缘青蟹后期幼体及仔蟹变态存活率的影响

通过实验对锯缘青蟹Z、M、C1～C4仔蟹在不同温度、盐度及干露时间的条件下，观察变态及存活率的差异。结果表明：1．温度改变对Z5变态率有影响，30—26℃温度突变其变态率为53％，30-28～25℃温度渐变变态率为60％，对照组(30℃)为57％；温度改变对M的变态存活率和变态时间间隔无影响．但C1变态为C2的时间间隔比对照组延长24～48h。2．盐度改变对青蟹Z5及C1-C4。仔蟹存活和变态的影响不同,在直接由盐度33移至28、21、15、8的不同条件下，Z5和M的盐度忍耐下限分别为21和15；C1-C4仔蟹在以上的盐度变化条件下均能成活、变态，但C4仔蟹在28、33高盐度下部分个体蜕壳不遂或蜕壳后死亡。3．蟹苗及仔蟹耐干露能力随着个体长大而增强；同规格蟹苗在干露6～18h条件下，变态时间间隔随着干露时间的增加延长24．48h；M在潮湿海绵和不透风的条件下放置12h，可正常变态，离开海绵则在6h内全部死亡；但C1-C4仔蟹即便离开海绵18h，也能正常存活变态。     

影响锯缘青蟹溞状幼体成活率的多因素试验

用正交试验法研究了盐度、光照强度、换水量和抗菌素用量4个因素对锯缘青蟹幼体从Z1变态至Z3的成活率和变态时间的影响．并从试验组合中选出最佳条件。结果表明各因素对锯缘青蟹Z1-Z3期潘状幼体成活率影响的大小顺序为：光照强度〉盐度〉换水量〉抗菌素用量，对锯缘青蟹Z2-Z3期潘状幼体变态时间影响的大小顺序为：盐度〉光照强度〉抗菌素用量〉换水量．并得出培育锯缘青蟹前期潘状幼体的最佳条件为：盐庹为25‰；光照强度为170lx；换水量为1／3；抗菌素的用量为0．5×10^-6。在此条件下，54％的锯缘膏蟹幼体可以从五变态至Z3。     

影响锯缘青蟹涵状幼体成活率的多因素试验

用正交试验法研究了盐度、光照强度、换水量和抗菌素用量4个因素对锯缘青蟹幼体从Z1变态至Z3的成活率和变态时间的影响．并从试验组合中选出最佳条件。结果表明各因素对锯缘青蟹Z1-Z3期潘状幼体成活率影响的大小顺序为：光照强度〉盐度〉换水量〉抗菌素用量，对锯缘青蟹Z2-Z3期潘状幼体变态时间影响的大小顺序为：盐度〉光照强度〉抗菌素用量〉换水量．并得出培育锯缘青蟹前期潘状幼体的最佳条件为：盐庹为25‰；光照强度为170lx；换水量为1／3；抗菌素的用量为0．5×10^-6。在此条件下，54％的锯缘膏蟹幼体可以从五变态至Z3。     

拟穴青蟹幼蟹耗氧率和窒息点的研究

在盐度20、温度28.0±0.2℃条件下,采用密封流水方法进行了拟穴青蟹幼蟹耗氧率和窒息点的研究。结果表明:拟穴青蟹Ⅴ期幼蟹的平均耗氧率高于Ⅵ期幼蟹,Ⅴ期幼蟹的窒息点也高于Ⅵ期幼蟹。其中,当蟹苗体质量为1.00±0.22 g时,耗氧率为0.437 2±0.083 mg/(g.h),耗氧量0.423 7±0.080 mg/(ind.h),窒息点为0.716 0±0.017 mg/L;当蟹苗体质量为1.81±0.30 g时,耗氧率为0.381 6±0.081 mg/(g.h),耗氧量0.671 7±0.140 mg/(ind.h),窒息点为0.698 7±0.011 mg/L。实验发现,拟穴青蟹幼蟹的耗氧率和耗氧量具有比较明显的昼夜变化规律,其峰值出现在20∶00及02∶00左右,谷值出现在08∶00及16∶00。研究结果可为拟穴青蟹养殖生产中制定合理的苗种放养密度和养殖工艺提供参考依据。     

北方低盐度池塘锯缘青蟹养殖技术要点

锯缘青蟹俗称青蟹,是一种经济价值很高的食用蟹,为广盐性的海水经济甲壳动物,具有生长快、适应性强的特点,自然海区最大个体可达1公斤以上。该蟹在我国主要分布于浙江、广东、海南和广西等地为多,而在北方尚没有自然分布。2004年,天津从福建漳州市引进2000只锯缘青蟹淡化苗种,在盐度2.5‰的池塘试养,从6月28日放苗至10月8日出池,共产成蟹215kg,成蟹平均个体为0.2kg,最大个体为0.8kg,获得了初步成功。初步探索出了适合于北方地区低盐度池塘锯缘青蟹养殖的关键技术。现将低盐度池塘锯缘青蟹养殖技术要点总结如下:一、蟹池条件蟹池水源充足、无…     

三疣梭子蟹“黄选1号”盐度耐受性分析

通过盐度突变和渐变两种方法测定了三疣梭子蟹"黄选1号"的盐度耐受性。盐度突变条件下,Ⅱ期幼蟹24、48、72h低盐半致死浓度分别为21.655、22.109、23.184;高盐半致死浓度分别为50.711、50.061、49.612。80日龄成蟹24、48、72h低盐半致死浓度分别为5.13、7.49、8.56;高盐半致死浓度分别为54.49、52.74、52.21。在逐渐降低盐度条件下,Ⅱ期幼蟹可在盐度6.7的海水中存活,而80日龄成蟹可在盐度为5.7的海水中存活;随着盐度逐渐升高,Ⅱ期幼蟹和80日零成蟹均可在盐度47.7的海水中存活。三疣梭子蟹"黄选1号"具有较宽的盐度耐受范围。     

调整盐度对河蟹Z_1～Z_2幼体变态大量死亡的控制作用

1999年4月底以后,河北省黄骅地区河蟹育苗生产中普遍出现Z_1—Z_2幼体变态大量死亡的问题,为此我们采用大幅调整用水盐度,改善微生态环境的方法,进行了控制Z_1幼体变态大量死亡的实验,结果发现,当池水盐度较大幅度地偏离常用盐度的情况下,如在18‰和32‰的盐度条件下Z_1幼体均能顺利变态为Z_2幼体,而当盐度在最适盐度24‰左右时Z_1幼体在第三日几乎全部死亡。     

Effects of Stocking Density, Salinity, and Light Intensity on Growth and Survival of Southern Flounder Paralichthys lethostigma Larvae

Four separate studies were done on Southern flounder Paralichthys lethostigma larvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different ( P > 0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect ( P > 0.05) on growth or survival, but fish stocked at 3/L had significantly lower ( P < 0.05) survival than fish at 1/L. Complete mortality of larvae occurred at 0 ppt. Growth and survival past metamorphosis were not significantly different ( P > 0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two-step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 ppt.     

Effect of Salinity on Embryonic Development,Hatchability, and Growth of African Catfish,Clarias gariepinus,Eggs and Larvae

Abstract

Effects of salinity on embryonic development and growth of African catfish, Clarias gariepinus, eggs and larvae were studied. Eggs were incubated at 27-29°C in 2,4,6,8, and 10 ppt sodium chloride. Rate of embryonic development was delayed in all salt solutions by 15, 15,28 and 30 minutes, in 2,4,6, and 8 ppt sodium chloride, respectively, when compared with the control group (0% salt); total mortality occurred at 12 hours after gastrula stage in the 10 ppt concentration. Percentage hatching was 45.1,47.7, 59.5,49.2, and 26.6% while percentage deformity was 10.4, 16.1, 52.0, 28.6, and 71.6% in 0, 2, 4, 6, 8, and 10 ppt salt treatments, respectively. There were significant differences (P <0.05) in the hatching percentage and in deformity percentage between 4, 6, and 8 ppt. Rate of yolk absorption was significantly faster in the control and 2 ppt salt treatments, but slower in 4, 6, and 8 ppt. Rate of increase in length was slower with increasing salinity. The optimum salinity for African catfish eggs and was between 0-2 ppt and acceptable up to 6 ppt. The results suggest that increasing salinity delayed hatching and development of African catfish eggs and larvae, respectively, as well as increased the deformity of the larvae.     

OPTIMAL SALINITY-TEMPERATURE COMBINATIONS FOR THE EARLY LIFE STAGES OF GILTHEAD BREAM,Sparus auratus L.

High larval mortalities during rearing of gilthead bream, Sparus auratus L., led to experiments on the influence of salinity and temperature on eggs and yolk-sac larvae. Test salinities ranged from 5 to 70 ppt for eggs and from 15 to 45 ppt for larvae; experimental temperatures were 18–20°C for eggs and 18, 23 and 26°C for larvae. Spawning conditions were 18–20°C and 33–35 ppt salinity; the yolk-sac larvae were chosen from hatches obtained under similar conditions (18°C and 35 ppt salinity). For eggs the optimum survival range was found to be 30–50 ppt at 18°C and 15–60 ppt at 23°C, while that for yolk-sac larvae was 15–25 ppt at all three temperatures. Choosing normal development (no dorsal curvature) as the decisive criterion, the optimum salinity range for egg incubation was reduced to 30–40 ppt at 18°C and to 35–45 ppt at 23°C, while that for the yolk-sac stage remained 15–25 ppt at all test temperatures. Egg incubation was most successful at salinity-temperature combinations close to those during spawning, whereas salinity had to be reduced by at least 10 ppt for yolk-sac larvae.     

The Effects of Temperature, Age, and Acclimation to Salinity on the Survival of Farfantepenaeus paulensis Postlarvae

Abstract.— Salinity tolerance limits during the ontogenetic development of Farfantepenaeus paulensis postlarvae (PL) were determined at different temperatures. Initially, PL 10, 20, 30, 40, 60 and 80 maintained in 30 ppt (parts per thousand) salinity, 22‐25 C, were directly transferred to 15 combinations of salinity (2, 5, 10, 20 and 30 ppt) and temperature (15, 20 and 30 C) for 96 h. Irrespective of age or salinity, higher survival rates were registered at 25 C. PL 10 suffered high mortality, especially at low salinities combined with low (15 C) or high (30 C) temperatures. From PL 20 to PL 40, an increase in survival was observed in all combinations. For PL 60 and 80, tolerance to low salinity was reduced, suggesting that PL have a maximum age by which they are able to develop adaptability to low salinities. In general, the effect of temperature contributed more significantly to mortality in PL 10 and PL 30, but its influence decreased afterwards. From PL 40, salinity becomes the main factor determining mortality. In order to examine the effects of acclimation to salinity on the tolerance limits, a second set of experiments was performed with PL 5, 10, 15 and 25 acclimated to 2, 5, 10, 20 and 30 ppt, 25 C, over a 5‐d period. Postlarvae were then transferred to different salinity levels (2, 5, 10, 20 and 30 ppt) and kept for 96 h. High mortality of PL 10 occurred after direct transfer from high to intermediate/low salinity levels. Although the acclimation to salinity increased survival, it was still poor. An increase in the salinity tolerance was observed from PL 15 to 30, even with no acclimation. Results indicate that PL 10 do not have a fully developed osmoregulatory capacity to cope with low and/or abrupt changes of salinity. It is recommended that non‐acclimated PL 10 should only be released in environments with salinity at or above 20 ppt. If acclimation is carried out, PL may be released in salinities above 10 ppt. The release of PL 10 in salinities below 5 ppt may result in mortality rates of up to 70%. The best age for the release of non‐acclimated F. paulensis PL in environments with low and/ or wide fluctuations of salinity would he PL 15‐30.     

The effects of salinity on the fertilization rate and rearing of the Persian sturgeon (Acipenser persicus) larvae

Persian sturgeon eggs were fertilized with different levels of salinities (0.5, 2, 4, 6, 8, 10, 12?ppt), and then each group was incubated in the same salinity until hatch. The fertility (%), hatching rate as well as larvae cumulative mortality rate and abnormality (%) were measured. Our Results revealed that Persian surgeon eggs could be fertilized in the different salinity concentrations but not more than 4?ppt. Moreover, hatching rate decreased with increase in salinities more than 2 and 4?ppt, respectively, and no larvae hatched in 6?ppt salinity. According to these results, the salinity tolerance threshold for Persian sturgeon larvae hatching in brackish water is less than 4?ppt.     

Temperature and Salinity Tolerances of the Tropical Spiny Lobster,Panulirus ornatus

Interest in the development of aquaculture of the tropical spiny lobster, Panulirus ornatus, has increased markedly over the past 10 yr because of strong market demand and high prices. In Australia, economic conditions will necessitate that a semi‐intensive approach be taken, possibly involving managed environmental conditions. Identification of optimal temperature and salinity levels will be necessary, and therefore two experiments were performed to examine these two parameters. Juvenile lobsters were grown in tanks at five temperatures (19, 22, 25, 28 and 31 C). Growth was significantly affected by temperature (P < 0.01), and maximal growth occurred at 25–31 C. Examination of the temperature effect on molt increment and intermolt period indicated that 27 C was the optimal temperature, at which molt increment was greatest and intermolt period the least. Temperature also had a significant (P < 0.01) positive effect on apparent feed intake (AFI). Juvenile lobsters were also exposed to four different salinities (20, 25, 30 and 35 ppt) over a period of 91 d. Significant differences (P < 0.01) were apparent for both survival and growth. Lowest survival occurred at 35 ppt which may be attributable to higher cannibalism at that salinity. Growth was highest at 35 ppt and progressively less at lower salinities. Although full marine salinity (35 ppt) will generate best performance of P. ornatus, its capacity to tolerate reduced salinity will provide greater opportunity to develop commercial aquaculture.     

Effects of Temperature and Salinity on Weight Gain, Oxygen Consumption Rate, and Growth Efficiency in Juvenile Red-Claw Crayfish Cherax quadricarinatus

Abstract.— Weight gain and metabolic rates, as determined by oxygen consumption rates, were examined in juvenile Australian red-claw crayfish Cherax quadricarinatus exposed to different temperatures (16–32 C in 2 C increments) or salinities (0–30 ppt in 5 ppt increments). Mean weight gain, molting frequency, and survival (%) were dependent on temperature and salinity. In freshwater (0 ppt), maximal weight gain and molting frequency were observed at 28 C with maximal survival observed over the temperature range of 24–30 C. Metabolic rates in freshwater were temperature dependent (mean Q₁₀= 2.44). Maximal weight gain and molting frequency were observed at salinities of 0 and 5 ppt (28 C); however, survival was reduced at salinities ≥ 5 ppt. Metabolic rates were not salinity dependent and did not differ significantly over the salinity range from 0–20 ppt. Growth efficiencies, calculated by dividing weight gain by total metabolic energy expenditure (i.e., weight gain + metabolic rate), were highest at a temperature of 20 C (0 ppt) and at salinities of 0 and 5 ppt (28 C). These data suggest that, at higher culture temperatures, maximal weight gain of red-claw juveniles may be reduced when food resources are limited. Maximal weight gain, at optimal temperatures (28 C) with unlimited food supply, does not appear to be effected by low salinity conditions. Because of the potential commercial value of red-claw, culturists, should be aware of the relationship between environmental condition and metabolic energy requirements to ensure maximal weight gain and survival of juveniles.     

Effects of temperature and salinity on oxygen consumption and ammonia excretion of juvenile miiuy croaker, <Emphasis Type="Italic">Miichthys miiuy</Emphasis> (Basilewsky)

The metabolic responses of the juvenile Miichthys miiuy in terms of oxygen consumption and ammonia excretion to changes in temperature (6–25°C) and salinity (16–31 ppt) were investigated. At a constant salinity of 26 ppt, the oxygen consumption rate (OCR) of the fish increased with an increase in temperature and ranged between 133.38 and 594.96 μg O₂ h⁻¹ g⁻¹ DW. The effect of temperature on OCR was significant (P < 0.01). Q₁₀ coefficients were 6.80, 1.41, 1.29 and 2.36 at temperatures of 6–10, 10–15, 15–20 and 20–25°C, respectively, suggesting that the juveniles of M. miiuy will be well adapted to the field temperature in the summer, but not in the winter. The ammonium excretion rates (AER) of the fish were also affected significantly by temperature (P < 0.01). The O:N ratio at temperatures of 6, 10, 15 and 20°C ranged from 13.12 to 20.91, which was indicative of a protein-dominated metabolism, whereas the O:N at a temperature of 25°C was 51.37, suggesting that protein-lipids were used as an energy substrate. At a constant temperature of 15°C, the OCRs of the fish ranged between 334.14 (at 31 ppt) and 409.68 (at 16 ppt) μg O₂ h⁻¹ g⁻¹ DW. No significant differences were observed in the OCR and AER of the juveniles between salinities of 26 and 31 ppt (P > 0.05). The OCR and AER at 16 ppt were, however, significantly higher than those at 26 and 31 ppt (P < 0.05), indicating salinity lower than 16 ppt is presumably stressful to M. miiuy juveniles.     

A Preliminary Study on the Effects of Salinity on Growth and Survival of Mulloway Argyrosomus japonicus Larvae and Juveniles

Abstract.— Tko experiments were conducted to determine the effects of salinity on growth and survival of mulloway Argyrosomus japonicus larvae and juveniles. First, 6-d-old larvae were stocked into different salinities (5, 12.5, 20, 27.5 and 35 ppt) for 14 d. Larvae grew at all salinities, but based on results for growth and survival, the optimum range of salinity for 6-d-old to 20-d-old larvae is 5–12.5 ppt. During this experiment larvae held in all experimental salinities were infested by a dinoflagellate ectoparasite, Amyloodinium sp. Degree of infestation was affected by salinity. There were very low infestation rates at 5 ppt (0.2 parasites/larva). Infestation increased with salinity to 20 ppt (33.1 parasites/larva), then declined with salinity to 35 ppt (1.5 parasites/larva). For the second experiment, juveniles (6.1 ± 0.1 g/fish) were stocked into different salinities (0.6, 5, 10, 20 and 35 ppt) for 28 d. Juveniles were removed from freshwater 3 d after transfer as they did not feed, several fish died and many fish had lost equilibrium. However, when transferred directly to 5 ppt. these stressed fish recovered and behaved normally. Trends in final mean weight and food conversion ratio of juvenile mulloway suggest that fish performed best at 5 ppt. Although salinity (5 to 35 ppt) had no significant ( P > 0.05) effect on growth, survival, or food conversion ratio of juveniles, statistical power of the experiment was low (0.22). Based on these results we recommend that mulloway larvae older than 6 d be cultured at 5 to 12.5 ppt. Optimum growth of juveniles may also be achieved at low salinities.     

Acclimation of Litopenaeus vannamei Postlarvae to Low Salinity: Influence of Age, Salinity Endpoint, and Rate of Salinity Reduction

Abstract.— Inland culture of Liropenaeus vannarnei in low salinity well waters is currently conducted on a small scale in a few areas in the U.S. To successfully rear shrimp in low salinity water, postlarvae (PL) must be transferred from high-salinity larval rearing systems to low-salinity growout conditions. To determine effective transfer methods, a series of experiments were conducted under controlled conditions to evaluate the influence of PL age, rate of acclimation, and salinity endpoint on 48 h survival of shrimp. Three age classes of L. vannurnei PL (10, 15, and 20-d) were acclimated from a salinity of 23 ppt to treatment endpoint salinities of 0, 1, 2, 4, 8, and 12 ppt. Survival of PL₁₀ acclimated to 0, 1, or 2 ppt salinity was significantly lower than survival of PL acclimated to salinities of 4, 8, and 12 ppt. Survival of PL, and PL₂₀ shrimp was only reduced for the 0 ppt salinity treatment, thus indicating a clear effect of age on salinity tolerance. The same age classes of PL were acclimated from 23 ppt to final salinity endpoints of I or 4 ppt at three different rates of salinity reduction: low, 19%/h; medium, 258/h, and high, 478/h. Survival was not significantly influenced by the acclimation rates for any of the three PL age classes. As in the fixed rate experiments, survival of the 10-d-old PL was significantly lower for shrimp acclimated to the 1 ppt endpoint compared to the 4 ppt endpoint. Under the reported conditions, age appears to influence PL tolerance to a salinity end-point. A 10-d-old PL can be acclimated to 4 ppt with good survival, whereas 15- and 20-d-old PL can be acclimated to a salinity of 1 ppt with good survivals.