许氏平鲉幼鱼对饲料中维生素B6需求量的研究

本实验旨在研究饲料中维生素B6含量对许氏平鲉(Sebastes schlegeli)幼鱼生长、体成分、肝脏酶活和转氨酶基因表达的影响,以确定其对维生素B6的需求量。配制6组维生素B6实际含量分别为2.08(对照组)、3.25、4.16、6.32、10.17和31.14 mg/kg的实验饲料,饲喂初始体重为(36.35± 0.06) g的许氏平鲉幼鱼63 d。结果显示,随着维生素B6含量的增加,实验鱼的增重率(WGR)和特定生长率(SGR)均呈先升高后降低的趋势,4.16 mg/kg组达到最高。4.16 mg/kg组脏体比(VSI)显著高于对照组(P<0.05),3.25?10.17 mg/kg组的肝体比(HSI)和肠体比(ISI)显著高于对照组(P<0.05)。3.25?31.14 mg/kg组的肌肉水分含量显著低于对照组(P<0.05),全鱼和肌肉的粗蛋白和粗脂肪均呈先升后降的趋势。肝脏超氧化物歧化酶(SOD)活力先升高后降低,4.16?10.17 mg/kg组显著高于对照组(P<0.05);丙二醛含量(MDA)先降低后升高,3.25?31.14 mg/kg组显著低于对照组(P<0.05);肝脏维生素B6含量先升高后平稳;3.25?31.14 mg/kg组谷草转氨酶(GOT)和谷丙转氨酶(GPT)活力显著高于对照组(P<0.05)。谷草转氨酶(GOT1和GOT2)基因相对表达量先升后降,3.25?31.14 mg/kg组显著高于对照组(P<0.05);谷丙转氨酶(GPT1和GPT2)基因相对表达量先升后降,均在6.32 mg/kg组达到最大值;酪氨酸转氨酶(TAT)基因相对表达量先升后降,4.16?10.17 mg/kg组显著高于其他组(P<0.05);丝氨酸转氨酶(SerC)基因相对表达量呈下降趋势,4.16?31.14 mg/kg组显著低于对照组和3.25 mg/kg组(P<0.05)。以WGR、肝脏维生素B6含量和GPT为评价指标,经折线回归分析表明,体重36 g的许氏平鲉幼鱼维生素B6的需求量为3.53?6.32 mg/kg饲料。     

Effects of Dietary Recombinant Bovine Somatotropin Levels on Growth, Plasma Recombinant Bovine Somatotropin Concentrations, and Body Composition of Juvenile Korean Rockfish, Sebastes schlegeli

This experiment was conducted to study the effects of the graded recombinant bovine somatotropin (rBST) levels on growth, plasma rBST concentrations, and body composition of Korean rockfish, Sebastes schlegeli, and to estimate the optimum oral dosage of rBST. Seven experimental diets were formulated to be isonitrogenous and isocaloric and to contain 49.0% crude protein and 16.7 kJ available energy/g, with 0, 5, 10, 15, 20, 25, or 50 mg rBST/kg body weight (BW)/wk (rBST₀, rBST₅, rBST₁₀, rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀, respectively). After the feeding trial, fish fed all the diets supplemented with rBST showed higher weight gain (WG), feed efficiency (FE), specific growth rate (SGR), and protein efficiency ratio (PER) than those fed the rBST₀ diet (P < 0.05). WG of fish fed rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀ diets was significantly higher than that of fish fed rBST₀ and rBST₅ diets (P < 0.05); however, there were no significant differences among fish fed rBST₁₀, rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀ diets. FE of fish fed rBST₁₅ and rBST₂₀ diets was significantly higher than that of fish fed rBST₀, rBST₅, rBST₁₀, and rBST₅₀ diets, and fish fed rBST₁₀, rBST₂₅, and rBST₅₀ diets had significantly higher FE than those fed rBST₀ and rBST₅ diets (P < 0.05). SGR of fish fed all the diets supplemented with rBST was significantly higher than that of fish fed rBST₀ diet (P < 0.05); however, there were no significant differences among fish fed all the diets supplemented with rBST. PER of fish fed rBST₁₅ and rBST₂₀ diets was significantly higher than that of fish fed rBST₀, rBST₅, and rBST₅₀ diets, and fish fed rBST₁₀, rBST₂₅, and rBST₅₀ diets had significantly higher PER than those fed rBST₀ and rBST₅ diets (P < 0.05). Whole‐body protein of fish fed rBST₁₅ diet was significantly higher than that of fish fed rBST₀, rBST₅, and rBST₁₀ diets (P < 0.05); however, there were no significant differences among fish fed rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀ diets. Plasma rBST concentrations of fish fed all the diets began to rise at 3 h after oral administration of rBST; the maximum plasma rBST concentration peaked at 12 h and returned to the basal level at 24 h. Broken‐line model analyses of WG and FE were 12.8 and 13.2 mg rBST/kg BW/wk, respectively. These results indicated that the optimum oral dosage could be greater than 12.8 mg rBST/kg BW/wk but less than 13.2 mg rBST/kg BW/wk in juvenile Korean rockfish.     

许氏平鲉幼鱼对饲料中精氨酸需求量的研究

本实验旨在研究饲料中不同精氨酸含量对许氏平鲉(Sebastes schlegelii)幼鱼生长、体组成、血清生化指标及肝脏相关酶活力的影响,以确定其对精氨酸的最适需求量。在基础饲料中添加晶体L-精氨酸配制精氨酸含量分别为1.39%、1.83%、2.34%、2.80%、3.39%和4.08%的6组等氮等脂的实验饲料(D1、D2、D3、D4、D5和D6)。饲喂初始体重为(12.03±0.03) g的许氏平鲉幼鱼56 d。结果显示,随着饲料中精氨酸含量的升高,实验鱼的增重率(WGR)、特定生长率(SGR)和蛋白质效率(PER)均先升高后降低,在D3组达到最高值,显著高于D1、D2、D5和D6组(P<0.05);饲料系数(FCR)先降低后升高,在D3组达到最低值,显著低于D1、D2、D5和D6组(P<0.05);D3组肌肉粗蛋白含量最高且显著高于其他组(P<0.05),肌肉水分、粗脂肪、粗灰分和全鱼水分、粗蛋白、粗脂肪和粗灰分无显著性差异;全鱼和肌肉总必需氨基酸(ΣEAA)和总氨基酸(ΣAA)含量均先升高后降低;血清谷丙转氨酶(ALT)活力先降低后升高,D3组显著小于其他组(P<0.05),一氧化氮(NO)含量先升高后降低,D3和D4组显著高于其他组(P<0.05),尿素氮(BUN)含量先升高后趋于平缓;肝脏超氧化物歧化酶(SOD)、溶菌酶(LZM)、总一氧化氮合酶(TNOS)和诱导型一氧化氮合酶(iNOS)活力均先升高后降低,丙二醛(MDA)含量先降低后升高,D2~D4组显著低于D1、D5和D6组(P<0.05)。在本研究条件下,以WGR为评价指标,经一元二次回归分析得出,许氏平鲉幼鱼[(12.03±0.03) g]饲料中精氨酸适宜需求量为2.78% (占5.56%饲料粗蛋白)。     

Effects of Different Dietary Lipid Sources on Growth Performance,Fatty Acid Composition,and Antioxidant Enzyme Activity of Juvenile Rockfish,Sebastes schlegeli

This study was carried out to investigate and compare the effects of various dietary lipid sources on growth performance, body composition, fatty acid profiles, and hepatic and plasma antioxidant enzyme activities of juvenile rockfish, Sebastes schlegeli. Three replicate groups of fish (initial mean weight, 1.7 ± 0.04 g) were fed four isonitrogenous and isolipidic diets containing either fish oil (FO), soybean oil (SO), linseed oil (LO), or a mixture of SO and LO (SO + LO) for 8 wk. There were no significant differences in survival, weight gain, feed efficiency, and protein efficiency ratios of fish fed the diets containing different lipid sources (P > 0.05). The fatty acids compositions of the liver and muscle tissues reflected the dietary fatty acid compositions. Liver and muscle of fish fed the SO diet had high concentration of linoleic acid, whereas those of fish fed the LO diet were rich in linolenic acid. Liver and muscle of fish fed the FO diet had significantly (P < 0.05) higher levels of eicosapentaenoic acid and docosahexaenoic acid than those of fish fed the SO and LO diets. Dietary lipid source had no significant effect on the hepatic and plasma enzyme activities of superoxide dismutase and glutathione peroxidase. The results of this study suggest that SO and LO can be used as a replacement for FO in the diets of juvenile rockfish without incurring any negative effects on growth, feed utilization, and antioxidant enzyme activity, when the dietary essential fatty acid requirements are satisfied for rockfish.     

Growth and Hematological Changes of Rockfish, Sebastes schlegeli (Hilgendorf) Exposed to Dietary Cu and Cd

Cd and Cu toxicological effect on growth and hematological parameters was investigated in juvenile rockfish Sebasres schlegeli after sub-chronic dietary Cd (0, 0.5, 5, 25, and 125 mg/kg) and Cu exposure (0, 50, 125, 250, and 500 mg/kg) for 60 d. In the experiment of dietary Cd exposure, weight and length SGR of the rockfish were significantly different from control, and a significant inverse relationship was observed between weight gain and the exposure concentration of dietary Cd at 25, 125 mg/kg ( P > 0.05). Hematwrit and hemoglobin decreased significantly and were dose dependently in all Cd exposure. Glucose in serum was also increased significantly ( P < 0.05). The concentration of total protein in serum was significantly lower than control at 5, 25, and 125 mgkg. No differences were observed in serum calcium concentration. Magnesium concentration in serum was increased signillcantly with dietary Cd concentration. In the experiment of dietary Cu exposure, Cu was inhibited weight gain and growth rate. No differences were observed in hematocrit, hemoglobin and RBCs compared to control. Contents of total protein, glucose, and Ca in serum remained stable. Mg concentration in serum was increased significantly at 500 mg/kg.     

饥饿不同时间后投喂对许氏平鮋生长及体成分的影响

在室内水温21.8~25℃条件下,将初始体质量为(8.87±0.16)g的许氏平鮋Sebastes schlegeli放养在50cm×50cm×100cm网箱中,饥饿0(S0)、3(S3)、6(S6)、9(S9)和12d(S12)后分别投喂30d、27d、24d、21d和18d,每组3个重复,测定其体质量、肥满度、脏体指数、肝体指数、摄食率、食物转化率及全鱼和肝脏主要生化组成的变化。结果表明:随着饥饿时间的延长,幼鱼体质量逐渐降低,各饥饿组鱼体质量显著低于同期对照组(P0.05)。恢复投喂后,S3组体质量、增重率(WGR)和特定生长率(SGR)显著高于对照组S0(P0.05),S6与S0组无显著差异(P0.05),而S9与S12组未能达到S0水平(P0.05)。S3组食物转化率(FCE)显著高于其余各组(P0.05),S9、S12组则显著低于对照组(P0.05)。饥饿状态下,各饥饿组鱼肝体指数与脏体指数显著小于S0组(P0.05));恢复投喂后各组肝体指数、脏体指数与对照组无显著差异。随着饥饿时间的延长,鱼体粗灰分含量显著升高(P0.05),水分与粗蛋白含量呈上升趋势(P0.05)。饥饿6d后,鱼体粗脂肪含量显著低于对照组,饥饿12d时粗脂肪含量比饥饿前降低了19.33%(P0.05)。恢复投喂后,各试验组间鱼体水分、粗蛋白、粗脂肪和粗灰分含量差异不显著(P0.05)。S9和S12组中肝脏粗脂肪含量显著低于S0组(P0.05)。     

Optimum Dietary Protein Level and Protein‐to‐energy Ratio for Growth of Juvenile Parrot Fish,Oplegnathus fasciatus

An 8‐wk feeding trial was conducted to estimate the optimum dietary protein level and protein‐to‐energy (P/E) ratio in juvenile parrot fish, Oplegnathus fasciatus. Eight experimental diets were formulated with two energy levels and four protein levels for each energy level. Diets containing crude protein (CP) at 35, 40, 45, and 50% had either 12.5 or 14.6 kJ/g of energy. Fish averaging 7.1 ± 0.06 g (mean ± SD) were fed one of the experimental diets for 8 wk. At the end of the feeding trial, weight gain (WG) of fish fed 45 and 50% CP in the 12.5 kJ/g diet was significantly higher than fish fed the 35% CP diet (P < 0.05). WG of the fish fed 45 and 50% CP in the 14.6 kJ/g diet was significantly higher than fish fed the 35 and 40% CP diets (P < 0.05). Fish fed the 14.6 kJ/g diet had a higher WG compared with fish fed the 12.5 kJ/g diet at all CP levels. Feed efficiency (FE) and specific growth rate (SGR) showed a similar trend to the WG. WG, FE, and SGR improved with increasing dietary protein levels up to 45% and remained constant at 50% CP for both energy levels. However, protein efficiency ratio was negatively related to dietary protein levels. The results suggested that the optimum level of protein and the optimum P/E ratio for juvenile parrot fish should be 45% and 31.1 mg protein/kJ, respectively, in a diet containing 14.6 kJ/g energy.     

Genetic Diversity and Population Structure in the Heavily Exploited Korean Rockfish,Sebastes schlegeli,in Korea

The Korean rockfish, Sebastes schlegeli, is a valuable and intensively exploited species in Korea. We discuss the genetic diversity and genetic structure of four Korean rockfish populations using eight microsatellite loci. In total, 161 different alleles from 138 individuals were observed. Average allele number per locus ranged from 2.5 to 23 and allelic richness varied from 13.38 to 14.63 within a population. Despite a long history of stocking practices, we found very high levels of polymorphism (mean heterozygosity = 0.810), which is comparable to other congeneric species. No significant difference in genetic diversity and molecular genetic variance (F_ST and R_ST) was observed among four local samples (P > 0.1). Little indication of contemporary inbreeding (F_IS= 0.051) or population structure (K = 1) was detected. This absence of differentiation may reflect high levels of gene flow along the coast of Korea. Our study demonstrates that rockfish in Korea should be managed as a single unit. Currently, the species does not appear to be genetically threatened, but the potential for a rapid loss of genetic diversity remains. This information on the genetic characteristics of Korean rockfish populations has important implications for fisheries management and conservation efforts, and will aid in the sustainable exploitation of the fishing resources and the preservation of biodiversity.     

Development of Thyroid Follicles and Changes in Thyroid Hormones During the Early Development of Korean Rockfish Sebastes schlegeli

The development of thyroid follicles and the change of thyroid hormone concentrations in whole body were examined, and the relationship between thyroid follicle differentiation and growth were also studied during early development of Korean rockfish Sebastes schlegeli . Total length (TL) and body weight (BW) of larva at parturition were 6.3 ± 0.1 mm and 3.6 ± 0.1 mg respectively. The larvae transformed to juveniles from 20 to 30 d after parturition with continuous growth. The thyroid primordium of the rockfish was observed histologically in newly born larvae, suggesting that the thyroid primordium may have been formed during yolk-sac larval stage after hatching as with other marine telosts. In addition, although the Korean rockfish is a viviparous fish, the developmental features of the thyroid gland in number, size and shape are very similar to the general development features of marine oviparous fish. As the larvae grew, the thyroid follicles of Korean rockfish increased in number, became variable in size, and changed from the normal spheroid/ovoid shape to more irregular forms in shape after parturition, and then concentrated mostly along the areas immediately adjacent to the ventral aorta. In addition, thyroid cell height and thyroid hormone concentrations were related with physiological activity at a specific developmental stage.     

卵形鲳鲹幼鱼饲料中适宜蛋白能量比的研究

以鱼粉、豆粕为蛋白源,豆油、鱼油为脂肪源,配制9种不同蛋白能量水平的饲料,蛋白质3个水平(38%、43%、49%),每个蛋白水平设3个脂肪梯度(6%、10%、14%),其蛋白能量比为19.3～27.4mg/kJ。卵形鲳鲹初始质量为(25.02±0.16)g,每个处理设3个重复,每个网箱(1.5 m×1.0 m×2.0m)放养卵形鲳鲹苗20尾,养殖试验持续8周。结果显示,卵形鲳鲹特定生长率随饲料蛋白水平的升高而显著升高(P<0.05)。投喂含43%或49%蛋白质、6%脂肪饲料的卵形鲳鲹表现出较好的特定生长率。饲料中不同的脂肪水平未表现出蛋白质节约效应,较高的脂肪水平反而抑制了卵形鲳鲹的特定生长率、饲料效率和蛋白质效率。卵形鲳鲹鱼体蛋白和脂肪含量分别随饲料蛋白质和脂肪水平的上升而显著升高(P<0.05)。在该试验条件下,卵形鲳鲹幼鱼饲料中最适蛋白质、脂肪水平和蛋白能量比分别为43%、6%和24.4 mg/kJ。     

Dietary methionine requirement for juvenile rockfish, Sebastes schlegeli

A 65‐day growth trial was conducted at 19.5 °C to determine the optimal dietary methionine for juvenile rockfish, Sebastes schlegeli. Semipurified diets were formulated to be isonitrogenous and isoenergetic. Fish meal was used as intact protein source and crystal amino acid was used as a part of dietary protein. Six experimental diets were formulated to contain 5.8, 10.8, 15.8, 20.8, 25.8 and 30.8 g kg⁻¹ dietary methionine. The results showed that dietary methionine significantly affected specific growth rate, weight gain, food conversion ratio, protein productive value (PPV), energy retention efficiency, carcass index and body composition. No significant difference was found in hepatosomatic index. The dietary methionine requirement for maximum growth was 13.7 g kg⁻¹ dry matter or 28.0 g kg⁻¹ of dietary protein when cystine content was 1.2 g kg⁻¹ dry matter.     

Dietary microbial phytase increased the phosphorus digestibility in juvenile Korean rockfish Sebastes schlegeli fed diets containing soybean meal

This study was conducted to evaluate the effects of dietary microbial phytase supplementation on nutrient digestibility, growth performance and body composition in juvenile Korean rockfish fed soybean meal-based diets.Nine experimental diets were formulated to be isonitrogenous and isocaloric to contain 48.6% crude protein (CP) and 15.9 kJ of available energy/g with or without dietary phytase (Natuphos-5000™, BASF, NJ, USA) supplementation. White fish meal (FM) provided 89.1% of the total protein in the basal diet (S₀), in the other eight diets, 30 or 40% FM protein was replaced by soybean meal: 70% FM+30% soybean meal (S₃₀); 70% FM+30% 1000 U phytase pretreated SM (S₃₀PP₁₀₀₀); 70% FM+30% SM+1000 U phytase/kg diet (S₃₀P₁₀₀₀); 70% FM+30% SM+2000 U phytase/kg diet (S₃₀P₂₀₀₀); 60% FM+40% SM (S₄₀); 60% FM+40% 1000 U P_tre SM (S₄₀PP₁₀₀₀); 60% FM+40% SM+1000 U phytase/kg diet (S₄₀P₁₀₀₀); and 60% FM+40% SM+2000 U phytase/kg diet (S₄₀P₂₀₀₀). After 2 weeks of the adaptation, triplicate groups of 20 fish initially averaging 7.25±0.04 g (mean±S.D.) were randomly distributed into the aquarium and were fed one of the experimental diets for 8 weeks.By the end of the 8-week feeding trial, supplementation of phytase significantly improved the apparent digestibility coefficient (ADC) of phosphorus in rockfish diets (P<0.05) containing 30% and 40% soybean meal regardless of the level and method of phytase supplementation. Supplementation of phytase significantly increased the ADC of dry matter in diets containing 30% soybean meal (P<0.05). However, phytase had no influence on growth performance and whole body composition of fish. The pretreatment of soybean meal with 1000 U phytase improved weight gain (WG) when 30% fish meal protein was replaced by soybean meal. Based on the experimental results, we conclude that supplementation of phytase can improve the apparent digestibility coefficient of phosphorus in Korean rockfish.     

Optimal Conditions for Long-distance Transportation of Live Black Rockfish (Sebastes schlegeli) and Changes in their Characteristics during Transport

Optimal transport conditions for the live black rockfish and changes in their characteristics during long-distance transport were investigated. Oxygen consumption by black rockfish was lowest at 4°C and increased as the water temperature increased up to a maximum at 10°C. At a water temperature of 8°C and 10°C, the plasma glucose concentration of the fish was 36.2 and 38.2 mg/dL, respectively. The mean weight of the fish reduced to approximately 2.8% of initial weight after 16 days of storage at 8°C. The fish did not feed, and the survival rate of fish stored for 16 days at 8°C was 98.4%. The longer the live fish were stored in the container, the quicker the onset of rigor mortis after the slaughter was reached. Compared with fillets from control fish, the chewiness of fillets was somewhat lower (17.3%) after storage of fish for 16 days, but the softness of the fillets was slightly higher (21.6%). From these results, it was suggested that the optimum temperature for long-distance transport of the live fish was 8°C and that the long transport period of live fishes decreased their fillet quality more rapidly after fish death.     

2-苯氧乙醇和丁香酚对许氏平鲉幼鱼麻醉效果的实验研究

研究了2-苯氧乙醇、丁香酚麻醉两个规格许氏平鲉幼鱼的效果。幼鱼呼吸频率随麻醉剂浓度的上升而显著下降(P0.001),在高浓度液(2-苯氧乙醇:500、600、800μl/L;丁香酚:60、80μl/L)中可在短时间内降低为0(休克),在中浓度液(2-苯氧乙醇:400μl/L;丁香酚:30、40μl/L)中存在不同程度下降,而低浓度液(2-苯氧乙醇:200、300μl/L;丁香酚:10、20μl/L)对呼吸频率总体影响较小。同等浓度麻醉剂对小规格幼鱼呼吸频率的影响(P0.01)高于大规格幼鱼。2-苯氧乙醇中大规格幼鱼的入麻、休克和复苏时间均长于小规格幼鱼(P0.05)。大规格幼鱼对麻醉剂的耐受能力强于小规格幼鱼;复苏能力方面,丁香酚麻醉的大规格幼鱼复苏迟于小规格幼鱼,但2-苯氧乙醇麻醉的大、小规格幼鱼复苏时间无差异。综合考虑入麻、休克、复苏时间和死亡率,认为使用2-苯氧乙醇、丁香酚麻醉许氏平鲉幼鱼的理想浓度分别为300、20μl/L。     

Optimum Dietary Level of Chlorella Powder as a Feed Additive for Growth Performance of Juvenile Olive Flounder,Paralichthys olivaceus

ABSTRACT

The present study was conducted toestimate the optimum dietary supplementation level of Chlorella powder as a feed additive to optimize growth of juvenile olive flounder, Paralichthys olivaceus. Four experimental diets supplemented with Chlorella powder (CHP) at 0, 1, 2 and 4% (CHP₀, CHP₁, CHP₂, and CHP₄, respectively) of diet as a dry-matter (DM) basis were prepared. Three replicate groups of fish averaging 1.1±0.02 g were fed one of the four experimental diets for 12 weeks. After the feeding trial, fish fed the CHP₂ diet had a higher (P < 0.05) weight gain (819%) than did fish fed CHP₀ (707%) and CHP₁(712%); however, there was no significant difference between fish fed CHP₂ (8197%) and CHP₄ (7559%) as among fish fed CHP₀, CHP₁, and CHP₄ (P > 0.05). Fish fed CHP₂ had a higher (P < 0.05) feed efficiency (134%) than did fish fed CHP₀ (123%); however, there was no significant difference (P > 0.05) among fish fed CHP₀ (123%), CHP₁ (125%), and CHP₄ (125%) as among fish fed CHP1 (125%), CHP₂ (134%), and CHP₄ (125%). Fish fed CHP₂ and CHP₄ had a lower (P < 0.05) serum glucose level (average 32.9 mg/dL) than did fish fed CHP₀ and CHP1 (average 34.8 mg/dL). Fish fed CHP1 and CHP₂ had a lower (P < 0.05) serum glutamic oxaloacetic transaminase (GOT) level than did fish fed CHP0 and CHP₄. Glutamic pyruvic transaminase (GPT) levels significantly (P < 0.05) deceased as dietary CHP increased. Fish fed CHP₂ and CHP₄ had a less (P < 0.05) whole-body fat than did fish fed CHP₀. These results indicate that the optimum dietary supplementation level of Chlorella powder as a feed additive in juvenile olive flounder could be approximately 2% of diet.     

Optimum dietary protein and lipid levels for juvenile rockfish (Sebastes schlegeli,Hilgendorf 1880)

Optimum dietary protein and lipid levels for juvenile rockfish were determined. Eight hundred and ten juvenile fish averaging 3.22 g were randomly chosen and distributed into 27 flow‐through tanks of 50 L (30 fish per tank). Nine experimental diets were prepared according to a 3 × 3 factorial experimental design: three crude protein levels (45%, 50% and 55%) × three crude lipid levels (11%, 15% and 19%). Crude protein and crude lipid levels increased at the expense of dextrin and cellulose in the experimental diets. Survival of fish was not affected by either dietary protein or lipid level. Weight gain of fish was affected by dietary protein level, but not by dietary lipid level. Weight gain of fish fed the 50P‐15L (50% protein and 15% lipid) diet was higher than that of fish fed the 45% protein diets regardless of lipid level, but not different from that of fish fed the 50P‐11L (50% protein and 11% lipid), 50P‐19L (50% protein and 19% lipid), 55P‐11L (55% protein and 11% lipid), 55P‐15L (55% protein and 15% lipid) and 55P‐19L (55% protein and 19% lipid) diets. Feed consumption of fish was affected by dietary protein level, but not by dietary lipid levels. Feed efficiency ratio (FER) of fish was affected by dietary protein level, but not by dietary lipid level. Protein efficiency ratio (PER) of fish was affected by dietary protein level, but not by dietary lipid level. Nitrogen retention efficiency (NRE) of fish fed the 45P‐19L diet was higher than that of fish fed the 45P‐11L, 50P‐11L, 50P‐15L, 50P‐19L, 55P‐11L, 55P‐15L and 55P‐19L diets, but not different from that of fish fed the 45P‐15L diet. Moisture, crude protein and crude lipid contents of fish was affected by dietary protein and/or lipid level. Plasma triglyceride of fish was affected by dietary lipid level, but not by dietary protein level. In conclusion, optimum protein and lipid levels for growth and feed utilization (PER and NRE) for juvenile rockfish were 50% and 15%, and 45% and 19%, respectively, and the optimum dietary protein‐to‐energy ratio of 27.4 and 23.9 mg protein kJ^?1.     

Optimum Dietary Protein and Lipid Levels in Juvenile Filefish,Stephanolepis cirrhifer,Feed

A feeding trial was designed to assess the effects of dietary protein and lipid content on growth, feed utilization efficiency, body composition, and hematological indices of juvenile filefish, Stephanolepis cirrhifer. Eight experimental diets were formulated with a combination of four protein (35, 40, 45, and 50%) and two dietary lipid levels (7 and 14%). Each diet was fed to triplicate groups of fish (3.2 ± 0.06 g) to apparent satiation for 8 wk. Fish growth performance and feed utilization were significantly affected by increasing dietary protein and lipid levels, with no significant interactions between factors. The highest growth performance value, in terms of weight gain, was observed in groups fed the diets with 50% protein (399%). However, fish fed the diet containing 45% protein had comparable growth (357%) while achieving relatively higher protein efficiency ratio. Hepatosomatic index was significantly affected by interaction of dietary lipid and protein with the highest values observed in those fish fed the highest protein (45–50%) and lipid (14%) diets. There was a significant increase in body lipid content (5.1 to 6.6%) and a decrease in body protein (15.8 to 14.8%) and ash (2.47 to 2.16%) with increasing dietary lipid levels from 7 to 14%. Muscle lipid content was significantly affected by both dietary protein and lipid levels and tended to increase with increasing dietary protein and lipid levels, ranging from 0.13 to 1.20%. Liver lipid content (65.9 to 68.7%) was significantly increased with the increase in dietary lipid levels while liver moisture content (28.9 to 25.9%) showed a clear decreasing trend. Hematological values were also altered with the increase in either dietary protein or lipid levels. These findings may suggest that a diet containing 45% protein and 7% lipid, with a protein to energy ratio of 23.8 mg/kJ, could deliver sufficient nutrient and energy to support acceptable growth and feed utilization and avoid excessive fat deposition in juvenile filefish.     

Effect of Dietary Lipid Level and Protein Energy Ratio on Growth and Body Composition of Largemouth Bass Micropterus salmoides

A feeding trial was conducted in aquaria with juvenile largemouth bass Micropterus salmoides to examine the effects of increasing dietary lipid levels on growth and body composition. Feed‐trained largemouth bass fingerlings were graded to a similar size (16.3 ± 2.4 g) and randomly stocked into 15 113.6‐L glass aquaria at 25 fish/aquarium. Fingerlings were fed twice daily to apparent satiation with one of five isonitrogenous extruded experimental diets based on practical ingredients. Diets contained approximately 40% crude protein and either 0, 5, 10, 15, or 20% added lipid. Due to background lipids in the ingredients, this equated to total lipid levels of 7, 10, 16, 20, and 23%, respectively. These diets had protein to energy ratios of 137, 120, 106, 95, and 86 mg/kcal, respectively. There were three replicate aquaria per dietary treatment. After 12 wk, there were no statistically significant differences (P > 0.05) in average weight (g), specific growth rate (% body weight/d), survival (%), or protein efficiency ratio (PER, %) among fish fed the five diets, which averaged 79.3 ± 5.6, 1.9 ± 0.1, 99.5 ± 1.5, and 2.11 ± 0.19, respectively. Juvenile largemouth bass fed diets containing 15 and 20% added lipid had significantly lower (P± 0.05) feed conversion ratios (FCR) (1.1 ± 0.0 and 1.1 ± 0. 1, respectively) than fish fed diets containing 0, 5, and 10% added lipid (1.4 ± 0.1, 1.3 ± 0. 1, and 1.3 ± 0.2, respectively). Proximate analysis of whole body samples indicated a significantly higher (P ± 0.05) lipid content in fish fed 15 and 20% added lipid compared to fish fed lower lipid levels. While FCR was lowest in fish fed the 15 and 20% added lipid diets, increased whole body lipid deposition may indicate that these levels are above optimal levels for juvenile largemouth bass. It appears that 7–16% total dietary lipid (P/E:137–106 mg/kcal) is sufficient to support efficient growth without impacting body composition in juvenile largemouth bass when fed a diet containing 40% crude protein.     

许氏平鲉的食物组成及其食物选择性

 2009年8月和10月对渤海进行了底拖网调查, 对增殖放流种类之一的许氏平鲉(Sebates schlegeli)进行了胃含物分析和食物选择性的初步研究。结果表明许氏平鲉共摄食7类20余种饵料, 主要摄食虾类和鱼类, 属虾/鱼食性鱼类。8月摄食的主要饵料为日本鼓虾和虾虎鱼类, 10月摄食的主要饵料为疣背宽额虾和小黄鱼。与20世纪90年代的研究结果相比, 许氏平鲉的摄食发生了显著的年间变化, 摄食的虾类饵料增多, 鱼类饵料减少; 主要饵料种类发生改变, 鳀不再是其主要的饵料种类。食物选择性指数的计算表明许氏平鲉摄食的主要饵料种类与喜食的饵料种类有一定差别; 许氏平鲉的食物选择性并不完全是由环境中的饵料丰度决定的, 说明其对食物的选择具有较强的主动性。结论认为, 许氏平鲉的摄食和食物选择性的季节变化不仅受环境中饵料丰度的影响, 也受鱼类自身营养需求和主动选择性摄食的影响。