军曹鱼养殖水体及其肠道弧菌的耐药性研究

选用常用的10种抗生素,通过纸片扩散法(Kirby-Bauer纸片扩散法,简称K-B法),参照NCCLS抗生素敏感试验操作标准,并以金黄色葡萄球菌Staphylococcus aureus ATCC25923和大肠埃希菌Esсheriсhia coliATCC25922为质控菌株,对周年监测分离自养殖军曹鱼水体及肠道的41株优势弧菌(水体菌18株,肠道菌23株)进行了药物敏感性研究。结果显示,抑制弧菌效果最好的药物是氯霉素(100%敏感)、庆大霉素(水体菌100%敏感,肠道菌敏感率超过90%),其次是诺氟沙星、复方新诺明和多粘菌素B。青霉素类抑菌效果则较差,如试验肠道弧菌对青霉素G的耐药率超过78%,对氨苄青霉素的耐药率超过60%。不同来源(即分别来自养殖水体和鱼肠道)的弧菌菌株对同种抗生素的敏感情况存在一定程度的差异。     

Pond Culture of Larval and Juvenile Cobia,Rachycentron canadum,in the Southeastern United States

Abstract

The potential of growing larval and juvenile cobia, Rach-ycentron canadum, in ponds was investigated. Larval cobia, obtained from tank spawning of wild-caught adults, were stocked 48-72-h post-hatch at a rate of 700,000/ha into three fertilized 0.25-ha ponds. At one week post-stocking (WPS), fish were observed consuming formulated feed. Growth was rapid, with specific growth rates (SGR) ranging from 12.5-19.2% body weight/day. At harvest (5 WPS) fish reared in two ponds weighed 7.9 and 9.3 g and total length (TL) was 118.9 and 129.3 mm, respectively (all fish reared in remaining pond died the night prior to harvest due to aerator failure). Feed conversion ratio (FCR) was 3.8 for both ponds and survival was 5.3 and 8.5%. Low survival rates were thought to be due primarily to cannibalism. Immediately after harvest, fish were restocked into two 0.25-ha ponds at a stocking rate of 14,400/ ha. Fish were fed formulated, pelleted feeds. Growth was rapid up to ～9 WPS, after which pond water temperatures declined. Ponds were harvested at 13 and 15 WPS, respectively. Final weight of fish was 309.9 and 362.5 g. Final TL was 343.1 and 355.7 mm. FCR was 3.8 and 4.5 and survival was 27.5 and 30.5%. Major losses of fish were associated with avian predators and possibly a toxic algal bloom. Results of trials indicate that cobia larvae and juveniles can be reared in pond-based culture systems, however additional research is needed to refine this approach.     

Evaluation of egg quality in broodstock cobia Rachycentron canadum L.

Twenty egg batches spawned naturally from 17 different females over two spawning seasons were used to evaluate the egg quality of cobia Rachycentron canadum. A reduction in egg size was observed towards the end of the spawning season for both years. The proportion of floating eggs demonstrated a positive linear relationship with both yolk‐sac larval survival (r²=0.91, P<0.05) and batch larval production (r²=0.80, P<0.01). Viable egg batches (i.e. fertilization success >50%) were of higher batch fecundity, had larger eggs and a higher proportion of floating eggs than non‐viable batches (i.e. 0% fertilization success). Also, biochemical analyses revealed that these viable eggs had significantly higher protein and amino acid contents. A multiple regression model based on the proportion of floating eggs, batch fecundity and fertilization success provided the most accurate predictions of batch larval production (r²=0.95, P<0.001). Similarly, using the egg content of arginine/glycine and methionine significantly increased the correlation coefficient in the multiple regression model predicting larval deformity (r²=0.92, P=0.002). This study reveals that accurate determination of egg quality in cobia can be improved using a combination of several variables rather than a single variable.     

冰点调节剂对军曹鱼冰点的控制研究

研究几种冰点调节剂对于军曹鱼（Rachycentroncanadum）冰点的影响。选取氯化钙（CaCl2）、氯化钠（NaCl）和维生素C（Vc）3种冰点调节剂,利用单因素比较法得出使用4％CaCl2浸泡处理60min可使军曹鱼冰点降至-1．21oC;用2％NaCl浸泡处理军曹鱼90min可使军曹鱼冰点由-1．01cC降至-1．36℃;使用0．5％V,溶液浸泡处理30min可使其冰点降至-1．30℃。因此选取NaCl和Vc 2种较好的冰点调节剂进行复配,再通过正交试验确定两者结合使用的最佳配比。结果显示,使用3％NaCl和0．3％V。共同处理军曹鱼60min为最佳,可使其冰点降至-1．62℃,下降了60．4％。     

军曹鱼的营养需要研究进展

本文就军曹鱼的各种营养,包括蛋白质、氨基酸、脂肪、必需脂肪酸及矿物质和维生素的需要进行综述.     

Effect of dietary carbohydrate level on growth performance,body composition,apparent digestibility coefficient and digestive enzyme activities of juvenile cobia,Rachycentron canadum L

A 9‐week feeding trial was conducted to investigate the effect of dietary carbohydrate level on the growth performance, body composition and apparent digestibility coefficient and digestive enzyme activities of juvenile cobia. Six isonitrogenous and isolipidic diets containing graded levels of starch (1.3%, 6.5%, 12.5%, 18.4%, 24.2% and 30.4%) were fed to juvenile cobia. Specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) increased with increasing dietary starch up to 18.4% (P<0.05), and thereafter SGR declined but FER and PER remained nearly the same. Apparent digestibility coefficient of starch reduced significantly when dietary starch up to 30.4%. Fish fed the diets with starch from 18.4% to 30.4% showed higher amylase activities in intestinal tract than those fed diets containing starch 1.3% and 6.5% (P<0.05). Significantly higher whole‐body lipid contents were observed in fish fed the diets containing higher starch. Whole‐body moisture content was inversely correlated with whole‐body lipid content, while protein and ash showed no significant differences. Plasma glucose, hepatosomatic index, liver glycogen and liver lipid increased with an increasing dietary starch. Based on SGR and FER, the appropriate dietary starch supplementations of juvenile cobia were estimated to be 21.1% and 18.0 % of diet respectively.     

摄食水平对几种重要海水养殖鱼类生长和氮收支的影响

本文研究了不同摄食水平（从饥饿至饱食）军曹鱼幼鱼（平均初始体重10.0g）、青石斑鱼幼鱼（平均初始体重5.5g）和卵形鲳鲹幼鱼（平均初始体重7.7g）的生长和氮收支,建立了生长和氮排泄与摄食水平的回归方程。结果表明,军曹鱼幼鱼特定生长率随摄食水平的增加呈显著增长趋势,在9%和饱食两个摄食水平之间无显著性差异,而青石斑鱼和卵形鲳鲹幼鱼的特定生长率随摄食水平增加呈线性增长趋势;饱食时,青石斑鱼和卵形鲳鲹幼鱼的生长速率接近而明显低于军曹鱼幼鱼的。军曹鱼幼鱼食物转化效率随摄食水平的增加呈先增长后下降的趋势,在9%/d摄食水平组有最大值,而青石斑鱼和卵形鲳鲹幼鱼食物转化效率随摄食水平的增加而持续增长,在饱食摄食水平时有最大值;饱食时,军曹鱼和青石斑鱼幼鱼的食物转化效率接近而明显高于卵形鲳鲹幼鱼的。3种海水鱼摄食氮、排粪氮、生长氮和氮排泄均随摄食水平的增加呈显著增长趋势;比较可知,军曹鱼幼鱼的摄食氮和氮排泄均最大,而青石斑鱼幼鱼的最小。军曹鱼、青石斑鱼和卵形鲳鲹幼鱼饱食和次饱食摄食水平时的氮收支方程分别为100CN = 7.7(6.0)FN + 22.6(31.31)GN + 69.7(62.68)UN、100CN = 2.7(2.8)FN + 20.9(8.4)GN + 76.4(88.8)UN和100CN = 1.8(1.4)FN + 12.8(9.3)GN + 85.4(89.3)UN（氮收支方程括号中的为次饱食数据）;3种海水鱼饱时和次饱食时摄食氮中用于排粪的比例较小且变化不大,军曹鱼次饱食时摄食氮中用于生长的比例较饱食时的大而用于排泄的比例较饱食时的小,青石斑鱼和卵形鲳鲹幼鱼的则相反。因此,鱼类的氮排泄率和氮收支方程存在种间差异,而当食物中氮含量较为接近时,摄食量增大是导致鱼类氮排泄增加的主要原因之一。综合考虑生长、食物转化效率、氮排泄和氮收支方程各因素,可得出在实验的生长阶段,3种海水养殖鱼中,军曹鱼幼鱼的最佳摄食水平为次饱食摄食水平（9%/d或约为饱食摄食水平的70%）,而青石斑鱼和卵形鲳鲹幼鱼的最佳摄食水平为饱食摄食水平。     

Combined effects of a simulated marine heatwave and an algal toxin on a tropical marine aquaculture fish cobia (Rachycentron canadum)

Ongoing global warming is one of the major challenges for the development of aquaculture in the tropical regions where species are already cultured in the water temperature close to their upper physiological thresholds. Furthermore, warming can trigger blooms of toxic algae, yet we do not know how extreme warming such as a marine heatwave (MHW) and algal toxins may affect marine aquaculture species. To address this issue, we investigated the effects of a simulated MHW in combination with exposure to trans‐4‐trans‐decadienal (PUA), a diatom‐derived toxin, on survival, growth, development and biochemical composition of cobia larvae and juveniles. Cobia larvae were exposed for 48 hr to one of two temperatures (29 vs. 34°C) and two PUA treatments (0 vs. 0.5 µM). Surviving larvae from each treatment were divided into two subsets: three replicates were used for the feeding test and five replicates were used for the recovery test in a non‐contaminated environment at the respective temperatures of 29 or 34°C. Survival of cobia larvae was reduced by 16% in either MHW or PUA, but it dropped by 60% when both stressors were present, indicating a synergistic effect. MHW, but not PUA, reduced the feeding of cobia larvae. PUA had no delayed effects on growth rate and biochemical composition of the fish. MHW strongly reduced specific growth rate, body protein and lipid contents in cobia. Our results provide the first empirical evidence of how MHW and toxic algae may interact and challenge cobia and marine aquaculture production in tropical countries.     

不同饲料对军曹鱼组织消化酶活力的影响

比较研究了投喂冰鲜鱼和人工配合饲料的军曹鱼胃、前肠以及肝脏消化酶(蛋白酶、胰蛋白酶、淀粉酶和脂肪酶)活力.试验结果表明,(1)蛋白酶活力:前肠与肝脏的蛋白酶比活力,投喂配合饲料组显著高于冰鲜鱼组(P<0.05),而胃中的蛋白酶比活力以冰鲜鱼组显著高于配合饲料组(P<0.05);(2)胰蛋白酶活力:胃中胰蛋白酶比活力,冰鲜鱼组显著高于配合饲料组(P<0.05),前肠与肝脏的胰蛋白酶比活力配合饲料显著高于冰鲜鱼组(P<0.05);(3)淀粉酶活力:胃中的淀粉酶比活力,冰鲜鱼组显著高于配合饲料组(P <0.05),前肠的淀粉酶比活力则是配合饲料组显著高于冰鲜鱼组(P<0.05),两种饲料对军曹鱼肝脏淀粉酶比活力影响不显著(P>0.05);(4)脂肪酶活力:胃及前肠的脂肪酶比活力两种饲料间差异不显著(P>0.05),但肝脏的脂肪酶比活力则以配合饲料组显著高于冰鲜鱼组(P<0.05).