Urea and ammonia excretion by embryos and larvae of the African catfish Clarias gariepinus (Burchell 1822)

Yolk-sac larvae and starved larvae of Clarias gariepinus (Burchell 1822), reared at 28°C, were predominantly ammonotelic, but urea excretion contributed about 19±7% to the total nitrogen excretion. Exogenously feeding larvae of C. gariepinus were mainly ammonotelic until 180-205 h post fertilization, but from then on the relative urea excretion stabilized at 44±13%. The contents of total free amino acids (FAA) and ammonia in C. gariepinus peaked around complete yolk absorption. During the first period after hatching 64% of the FAA and 60% of the total ammonia were located in the yolk compartment. The body compartment contained the highest amount of FAA and total ammonia at the end of the yolk-sac period (65 and 77%, respectively). The amount of nitrogen originating from catabolism of amino acids was balanced within 6% by the excreted sum of ammonia and urea. The high degree of ureotelism in C. gariepinus larvae may constitute an adaptive mechanism to a habitat of temporal water shortage.     

饵料卤虫的营养强化对黑斑口虾蛄(Oratosquilla kempi) 幼体消化酶活力及其抗逆性的影响

用扁藻、酵母和"鱼油 酵母"强化3种方式处理的卤虫无节幼体投喂黑斑口虾蛄幼体,对各组黑斑口虾蛄幼体消化酶活力和抗逆性差别分析。结果显示,经过"鱼油 酵母"强化的幼体对氨氮、福尔马林、饥饿和盐度的耐受性均强于对照组。经过扁藻和"鱼油 酵母"强化的第Ⅲ相幼体脂肪酶活力是对照组的3倍,经过酵母和"鱼油 酵母"强化的仔虾蛄幼体脂肪酶活力较高。在第Ⅲ相幼体中淀粉酶活力为扁藻>酵母>对照>"鱼油 酵母"强化,仔虾蛄中酶活力为扁藻>对照>酵母>"鱼油 酵母"强化。在酵母强化第Ⅲ相幼体和对照组仔虾蛄中纤维素酶活力最高。第Ⅲ相幼体对照组的胃蛋白酶和类胰蛋白酶活力均为最高,而"鱼油 酵母"强化仔虾蛄幼体的胃蛋白酶和类胰蛋白酶活力均高于对照组。黑斑口虾蛄幼体消化酶活性和抗逆性能力的变化趋势与其成活率、变态率、生长速度、EPA和DHA含量变化趋势相同,可以作为评价饵料质量好坏的重要指标。     

Effect of stocking density and addition of proteins on larval survival in Japanese flounder, Paralichthys olivaceus

The effects of larval density, rearing media, and protein additions on fish larval survival were tested by rearing larvae in small containers. Yolk-sac larvae of Japanese flounder, Paralichthys olivaceus, were transferred 1 day after hatching to plastic dishes and cell-culture microplates by Pasture pipette at densities ranging from 0.3 to 30 individuals/ml and incubated at 16 °C without food. Dead larvae were removed and counted every 12 h. Three peaks of larval mortality were observed: the first peak appeared just after the transfer, the second corresponded to the completion of yolk absorption, and the third occurred 10–12 days after the transfer. Since about 50% of larvae survived until the third peak, it was clear that mortality at the second peak (completion of yolk absorption; equivalent to the first feeding) was not due to starvation. At the first mortality peak, better survival was unexpectedly recorded at higher larval densities (30 individuals/ml), suggesting that some material beneficial for survival is derived from the larvae. This idea was further supported by the improved survival in media previously used to rear larvae at high densities. The addition of bovine serum albumin (BSA) at 10 μg/ml effectively reduced mortality in microplates and in 30-l tanks. To reduce the larval mortality just after handling, addition of egg white at a dilution rate of 1/30,000 (vol/vol) or less is recommended as a practical alternative to BSA. Since the addition of polyethylene glycol 6000 (1 μg/ml) also effectively reduced mortality, reduction in mortality could not be attributed to a specific mechanism. The precise determination of the magnitude and timing of larval mortality was attained through the use of small containers, and a method to prevent mortality due to handling was identified in this study. These types of tests may allow the logical evaluation and establishment of better rearing procedures for seed production in aquaculture.     

Larval growth of turbot, Scophthalmus maximus (L.) produced with fresh and cryopreserved sperm

The present paper assesses the fertilization and hatching rates, as well as the growth, of larvae obtained from four artificial fertilizations (AF) using fresh and cryopreserved sperm of the turbot Scophthalmus maximus (L.). Larvae growth in both sperm groups, measured in terms of length and weight at culture days 0, 7, 14 and 31, are compared, as well as their growth rates. The two groups' fertilization and hatching rates were not significantly different. Likewise, no significant differences in length and wet weight of 7‐ and 14‐day‐old larvae were found using fresh and cryopreserved sperm; however, significant differences were found in 31‐day‐old larvae, which were more attributable to the variability inherent in larval turbot culture, and to variability in the reproductive specimens used in our study, than to the type of sperm employed. These results indicate that the type of sperm used in artificial fertilization, i.e. fresh or cryopreserved, is not a determining factor, either for fertilization and hatching, or for subsequent larval development. Our results also confirm once again the high quality of cryopreserved turbot sperm, and its usefulness in commercial hatcheries.     

双抗对紫彩血蛤幼虫发育的影响

本文研究了青霉素钾盐和硫酸链霉素(双抗)混合使用对紫彩血蛤(Nutallia olivacea)幼虫发育的影响。结果表明:1～80ppm的双抗均有很好的抑菌效果,均可显著地提高幼虫的存活率,最高可提高52％,最低也可提高38％,同时对幼虫生长和变态均有明显的促进作用。其中以2～4ppm效果最好,幼虫生长最快,变态率最高;高浓度组对幼虫也无明显的副作用,幼虫生长速度、变态率和存活率也都高于对照组。     

南美白对虾室外育苗的初步试验

在4个室外水泥池和2个室内水泥池进行南美白对虾育苗试验,室外池总育苗水体为40 0m3,室内池总育苗水体为20 0m3。直接在室外育苗池培养单胞藻;白天日照时间为8h以上,光照强度为500～8000lx;室外育苗池共放入南美白对虾无节幼体600万尾,培育至体长1 0cm的虾苗,出苗354 4万尾,总成活率为59 1%。室外育出的虾苗规格整齐,体质强壮;比室内池育苗的时间缩短3～4d。     

盐度对赤点石斑鱼受精卵发育的影响及仔鱼活力的判断

观察比较了10个盐度梯度（44.0,41.0,38.0,35.0，自然海水盐度30.5-32.5,27.0,24.0,21.0,18.0,15.0)下赤点石斑鱼受精卵的孵化率和畸形率，对12批初孵仔鱼进行耐饥饿试验。并测定其不投饵存活系数SAI值。结果表明，赤点石斑鱼受精卵孵化的适宜盐度为38.0-24.0，最适盐度为35.0-27.0。盐度高于35.0，孵化率随盐度的升高而降低，仔鱼畸形率则随之升高。盐度低于24.0，孵化率随盐度的降低而降低，仔鱼畸形率则随之升高，从盐度38.0到41.0以及24.0到21.0是2个对受精卵孵化率和仔鱼畸形率影响很大的盐度梯度，高于或低于这2个盐度梯度，孵化率即明显大幅度降低，畸形率则大幅度升高，赤点石斑鱼仔鱼的SAI值为3.19-12.42，低于长吻Sheng和黄条Shi的SAI值，仔鱼的SAI值与卵的受精率，孵化率呈正相关关系。只有SAI值大于5的仔鱼才有可能被进一步培育成苗，低于5的将在数天内死亡。     

The effect of dietary vitamin K (phylloquinone and menadione) levels on the vertebral formation in mummichog Fundulus heteroclitus

SUMMARY: The effect of different dosages of vitamin K, either as phylloquinone or menadione sodium bisulfite (MSB), on vertebrae formation during growth of mummichog Fundulus heteroclitus was investigated. Diets without vitamin K caused a significantly higher incidence of bone deformity in fish than diets supplemented with MSB or phylloquinone ( P < 0.01). These results indicate that vitamin K is essential for mummichog. A massive dose of MSB caused a high incidence of bone deformity compared with a lower dose, while an increased dose of phylloquinone brought about no significant difference in deformity incidence. The vertebral deformity was significantly higher ( P < 0.01) in fish fed a vitamin K-free diet (Control Group) and MSB-supplemented diet (Group MSB25) compared to fish fed a phylloquinone-supplemented diet (Group PK1). These results indicate that phylloquinone is more suitable than MSB as a vitamin K source in fish feed.     

Evaluation of various diets for the optimum growth and survival of larvae of the penaeid prawn Penaeus japonicus Bate

Four types of food were tested to determine their effects on the growth and survival of larvae of the penaeid shrimp Penaeus japonicus Bate. The food types were live cells of Candida utilis (yeast), freeze-dried Candida utilis, microparticulate diet, and microencapsulated diet (commercial product). The diatom Chaetoceros gracilis was fed to larvae as a control. Two sets of experiments were carried out; the first was run in outdoor 1.5 ton tanks, and the second in indoor 1.2 ton tanks. In the outdoor experiment, the best survival and growth from nauplius to postlarva stage were obtained using microparticulate diet. During the first week of culture, freeze-dried Candida utilis resulted in the highest growth and survival among examined diets, but both factors dropped dramatically after the mysis stage. In the indoor experiment, the best growth and survival were obtained using live cells of Candida utilis from nauplius stage to end of mysis stage followed by brine shrimp. Tested diets were analysed for their contents of crude protein, total lipids, total carbohydrates, amino acid profiles and fatty acid contents.     

赤点石斑鱼早期仔鱼轮虫日摄食量的研究

赤点石斑鱼早期仔鱼轮虫日摄食量的研究王涵生（福建省水产研究所，厦门３６１００５）关键词赤点石斑鱼，仔鱼，轮虫，日摄食量ＳＴＵＤＩＥＳＯＮＴＨＥＤＡＩＬＹＣＯＮＳＵＭＥＤＮＵＭＢＥＲＳＯＦＲＯＴＩＦＥＲＦＥＤＢＹＴＨＥＥＡＲＬＹＬＡＲＶＡＥＯＦＥＰＩＮ...