Growth,body composition,intestinal enzyme activities and microflora of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary valine

This study investigated the effects of valine on growth, intestinal enzyme activities and microflora in juvenile Jian carp (Cyprinus carpio var. Jian). A total of 1200 fish with an average initial weight of 9.67 ± 0.03 g were fed diets containing 5.3 (unsupplemented control), 8.7, 11.8, 14.9, 18.7 and 20.1 g valine kg^?1 diet for 60 days. Results indicated that the specific growth rate, feed efficiency, body protein and lipid content of fish were significantly improved by the dietary valine (P < 0.05). The hepatopancreas weight and activities of trypsin, amylase, lipase, chymotrypsin, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) took the similar trends. Similarly, the optimum levels of dietary valine induced increases in the intestinal length, weight, folds height and activities of alkaline phosphatase, gamma‐glutamyl transpeptidase and creatine kinase. In contrast, the trends of muscle GOT activity and plasma ammonia content were opposite. Intestinal Aeromonas, Escherichia coli, Lactobacillus and Bacillus were changed by dietary valine supplementations. The dietary valine requirement for Jian carp (9.67–76.4 g) based on SGR was 13.7 g valine kg^?1 diet (4.0 g valine 100 g^?1 CP). Together, these results indicated that valine improved fish growth, digestive and absorptive ability.     

Effect of dietary riboflavin on growth,feed utilization,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1050 Jian carp, Cyprinus carpio var. Jian (23.39 ± 0.06 g) were randomly divided into seven groups of each three replicates, which were fed respectively with seven semi‐purified diets contained 1.25, 2.71, 4.22, 5.78, 7.23, 8.83 and 11.44 mg riboflavin kg^?1 diet for 6 weeks. The results showed that riboflavin significantly improved percent weight gain, specific growth rate, feed efficiency and protein efficiency ratio at the level of 4.22 mg kg^?1 diet. Gross protein retention efficiency and lipid production value improved with increasing dietary riboflavin levels from 1.25 to 5.78 mg kg^?1. Activities of trypsin, lipase, α‐amylase, Na⁺,K⁺‐ATPase and alkaline phosphatase in the intestinal tract were significantly improved with increasing riboflavin levels. Weight and protein content of hepatopancreas, intestine protein and intestine length index were also significantly improved.     

Effect of replacement of dietary fish meal with silkworm pupae meal on growth performance,body composition,intestinal protease activity and health status in juvenile Jian carp (Cyprinus carpio var. Jian)

This study investigated the effect of replacement of graded dietary fish meal (FM) protein (0, 50%, 60%, 70% and 80%) with silkworm pupae meal (SP) in juvenile Jian carp. Triplicate groups comprising 18 fish (15.96 ± 0.66 g) were fed one of five isonitrogenous and isocaloric diets (designated SP0, SP50, SP60, SP70 or SP80) for 8 weeks. The final body weight and specific growth rate of fish in the SP60, SP70 and SP80 groups were significantly lower than those for fish in the SP0 group (P < 0.05). The muscle protein content in the SP50 group was significantly higher than in the SP80 group (P < 0.05). With increasing FM replacement levels, the hepatic superoxide dismutase (SOD) activity decreased and the malondialdehyde (MDA) content increased among the groups, with the significant difference appeared in SP80 group. The gene expression level of heat shock protein 70 in the SP70 group was significantly higher than in the SP0 group (P < 0.05), while that in the SP80 group was significantly less than in the SP70 group (P < 0.05). Significantly decreased intestinal protease activity, increased serum ALT and AST activities, irregular‐shaped hepatocytes and intestinal microvilli were found in the SP80 group. The study demonstrates that it is practical to replace 50% of the Jian carp dietary FM protein with SP, higher SP levels are not recommended and that oxidation status of the SP should be carefully assessed.     

Effects of dietary thiamin supplement on growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1050 juvenile Jian carp (Cyprinus carpio var. Jian) (8.20 ± 0.02 g) were fed diets containing seven graded levels of thiamin (0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg kg^?1) for 60 days to investigate the effects of thiamin on growth, body composition and digestive enzyme activities. Percent weight gain (PWG), feed intake and feed efficiency (FE) were the lowest in fish fed the basal diet (P < 0.05). Protein productive value and lipid productive value increased with increasing dietary thiamin levels up to 1.06 and 0.79 mg kg^?1 diet, respectively (P < 0.05). Body protein and lipid increased with increasing dietary thiamin levels (P < 0.05), while moisture and ash of fish carcasses decreased with the increase in dietary thiamin supplementation (P < 0.05). Intestinal folds height had a similar trend to PWG (P < 0.05). Activities of α‐amylase, lipase, trypsin, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase in intestine were all affected by the dietary thiamin (P < 0.05). In conclusion, thiamin could improve growth and intestinal enzyme activities of juvenile Jian carp. The dietary thiamin requirement of juvenile Jian carp (8.0–60.2 g) based on PWG was 1.02 mg kg^?1 diet.     

Reaction of common carp (Cyprinus carpio, L.) to oxygen deficiency in winter as an example for the suitability of radio telemetry for monitoring the reaction of fish to stress factors in pond aquaculture

The reaction of common carp (Cyprinus carpio L.) in an ice‐ and snow‐covered pond to depletion of dissolved oxygen (DO) in winter was recorded using radio telemetry. The carp moved from the deeper parts of the pond to the shallow areas near the tributary in search of better oxygenated water. Evidence was found that feeding occurred until December but ceased with the oxygen crisis. After the carp farmer started aeration to improve the oxygen supply, carp returned towards the deeper parts of the pond. The gross activity was significantly correlated with DO (P<0.001) and was not influenced by water temperature (P>0.05). The clear documentation of the carp's reaction to oxygen depletion suggests, that radio telemetry may be useful for investigating the effects of various stress factors on fish in pond aquaculture.     

Effect of dietary pantothenic acid supplement on growth, body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A 9-week feeding trial was carried out with juvenile Jian carp to study the effect of dietary pantothenic acid (PA) on growth, body composition and intestinal enzyme activities. Semi-purified diets with seven levels (4.0, 15.5, 25.6, 36.1, 45.9, 56.1 and 65.9 mg PA kg⁻¹) of supplemental calcium d -pantothenate were fed to Jian carp (13.0 ± 0.0 g). PA improved specific growth rate (SGR), protein productive value (PPV), protein efficiency ratio (PER) and lipid production value (LPV) ( P <  0.05). Fish fed the control diet had significantly lower feed efficiency (FE) than that in any other group ( P <  0.05). Body protein content increased with increasing PA levels ( P <  0.05), but moisture, lipid and ash of fish carcasses were negatively related to the graded PA levels ( P <  0.05). Intestine protein content (IPC), hepatopancreas protein content (HPC) and activity of α-amylase, lipase, trypsin, Na⁺,K⁺-ATPase, alkaline phosphatase (AKP) and gamma-glutamyl transpeptidase (γ-GT) were all positively affected by the dietary PA levels ( P <  0.05), while intestine index (ISI) and hepatopancreas index (HSI) decreased with the increment of supplemental levels of PA ( P <  0.05). These results suggested that PA could enhance fish growth and intestinal enzyme activities. The dietary PA requirement of juvenile Jian carp, Cyprinus carpio var . Jian (13.0–73.0 g), for optimal growth estimated by the broken-line analysis was 23.0 mg PA kg⁻¹ diet.     

不同糖脂比对建鲤幼鱼生长、体组成、消化及糖酵解能力的影响

本试验研究了饲料中不同糖脂比对建鲤幼鱼生长、体组成、消化及糖酵解的影响。试验共配制6组等氮等能的半纯合饲料,对应糖脂比分别为2.3,3.0,4.0,5.6,7.7和12.1。将鱼饱食投喂8周,每日投喂3次。试验结果表明,当饲料糖脂比从2.3升高至7.7时,增重率、特定生长率、蛋白质效率和蛋白保留率均显著升高(P < 0.05);而当糖脂比进一步升高时,其均呈下降趋势,但差异不显著(P > 0.05);饲料系数的变化趋势与其相反。建鲤幼鱼的脏体比以及全鱼、胴体和肝脏脂肪含量随着饲料糖脂比的降低均显著升高(P < 0.05),而全鱼、胴体和肝脏的蛋白质含量无显著差异(P > 0.05)。肠道淀粉酶活性随着糖脂比的升高显著升高(P < 0.05),而脂肪酶的变化趋势则相反(P < 0.05)。此外,血糖和胰岛素水平、肝糖原含量及肝脏葡萄糖激酶和丙酮酸激酶活性随饲料糖脂比的升高均显著升高(P < 0.05),血液中总胆固醇和甘油三酯含量则随着糖脂比的降低显著升高(P < 0.05)。根据二次回归模型得出,在等氮等能的饲料条件下,建鲤幼鱼最适宜的糖水平和脂肪水平分别为38.21%和4.69%,对应的糖脂比为8.14。     

Effect of dietary iron levels on growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A 60‐day feeding trial was carried out to investigate the effect of iron on growth, body composition and digestive enzyme activities. Diets with seven levels of iron (53.9, 90.0, 115.6, 146.1, 176.0, 215.8 and 266.0 mg iron kg^?1 diet) were fed to Jian carp (initial weight 11.4 ± 0.0 g). Per cent weight gain (PWG), feed efficiency (FE) and protein efficiency ratio were the lowest in fish fed the basal diet (P < 0.05). Body protein content was increased with the increasing iron levels (P < 0.05), but moisture, lipid and ash of fish were not significantly affected by dietary iron levels (P > 0.05). Activities of trypsin, lipase, α‐amylase, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase were improved with increasing dietary iron levels. Serum iron were significantly enhanced with dietary iron levels up to 146.1 mg iron kg^?1 diet, and plateaued. In conclusion, iron improved digestive enzyme activities of juvenile Jian carp and the dietary iron requirement for serum iron of juvenile Jian carp (11.4–64.0 g) was 147.4 mg iron kg^?1 diet with ferrous fumarate as the iron source.     

Growth,body composition,intestinal enzyme activities and microflora of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary phosphorus

A 9‐week feeding trial was carried out with juvenile Jian carp (Cyprinus carpio var. Jian) to study the effects of dietary phosphorus on growth, body composition, intestinal enzyme activities and microflora. Quadruple groups of juvenile Jian carp (7.17 ± 0.01 g) were fed practical diets containing available phosphorus 1.7 (unsupplemented control), 3.6, 5.5, 7.3, 9.2 and 11.0 g kg^?1 diet to satiation. Feed intake, specific growth ratio and feed efficiency were the lowest in fish fed the basal diet (P < 0.05). Body moisture, protein, lipid content and ash were all significantly affected by dietary available phosphorus levels (P < 0.05). Activities of trypsin, amylase, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase were improved with increasing dietary phosphorus levels. Intestinal Aeromonas and Escherichia coli decreased with increasing dietary phosphorus up to 3.6 and 5.5 g kg^?1 diet respectively (P < 0.05), while Lactobacillus increased with the increasing dietary phosphorus up to 9.2 g kg^?1 diet (P < 0.05). These results suggested that phosphorus could enhance intestinal enzyme activities of juvenile Jian carp and the minimum dietary available phosphorus requirement for SGR of juvenile Jian carp (7.2–63.8 g) was 5.2 g kg^?1 diet.     

Influence of replacing fish meal with enzymatic hydrolysates of defatted silkworm pupa (Bombyx mori L.) on growth performance,body composition and non‐specific immunity of juvenile mirror carp (Cyprinus carpio var. specularis)

This study was conducted to investigate the effects of dietary supplementation of enzymatic hydrolysates of defatted silkworm pupa (EHDSP) on growth performance, body composition and non‐specific immunity of juvenile mirror carp (Cyprinus carpio var. specularis). The control diet (EHDSP0) was produced using fish meal (FM) as the main protein source and the other four diets were formulated by substitution of 25% (EHDSP25), 50% (EHDSP50), 75% (EHDSP75) and 100% (EHDSP100) FM with EHDSP. Five groups containing 270 juvenile mirror carp (14.51 ± 0.03 g) were fed to apparent satiation for 8 weeks. The results indicated that the special growth rate, weight gain, protein efficiency ratio and feed conversion rate of experimental fish in EHDSP25 and EHDSP50 groups were not significantly different from EHDSP0 group (p > .05). The spleen index of experimental fish in EHDSP25 group was significantly higher than that of EHDSP0 group (p < .05). The muscle protein content of experimental fish in EHDSP25 and EHDSP50 groups was significantly higher than that of EHDSP0 group (p < .05). Serum alanine aminotransferase and total cholesterol of experimental fish fed with the EHDSP were significantly lower than that of control (p < .05). The activity of serum superoxide dismutase of experimental fish in EHDSP25, EHDSP50 groups was significantly higher than that of EHDSP0 group (p < .05). Intestinal trypsin activity of EHDSP25 group was significantly higher than that of EHDSP0 (p < .05). In conclusion, EHDSP can be included into diet to replace 50% FM of juvenile mirror carp without negative effect on growth, furthermore, it can improve the non‐specific immunity and function of intestinal tract.     

Effects of dietary histidine levels on growth performance,body composition and intestinal enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1200 juvenile Jian carp (Cyprinus carpio var. Jian) (8.76 ± 0.02 g) were fed diets containing graded levels of histidine at 2.3 (unsupplemented control), 4.4, 6.3, 8.6, 10.8 and 12.7 g kg^?1 diet for 60 days to investigate the effects of histidine levels on growth performance, body composition, intestinal enzymes activities and microflora. Specific growth rate (SGR), feed efficiency, protein efficiency ratio, protein productive value, body protein content and lipid content of fish were lowest in fish fed the basal diet (P < 0.05). Activities of glutamate‐pyruvate transaminase in muscle and hepatopancreas, trypsin, chymotrypsin, amylase, lipase activities in intestine and hepatopancreas, and Na⁺, K⁺‐ATPase, creatine kinase, alkaline phosphatase, γ‐glutamyl transpeptidase activities in three intestinal segments were improved by dietary histidine (P < 0.05), whereas glutamate‐oxaloacetate transaminase activities and plasma ammonia content followed an opposite trend. The amounts of Lactobacillus, Escherichia coli and Aeromonas were significantly affected by dietary histidine levels (P < 0.05). These results suggested that histidine could improve growth and enhance intestinal enzymes activities of juvenile Jian carp. The dietary histidine requirement of juvenile Jian carp (8.76–68.02 g) based on SGR was 7.8 g kg^?1 diet or 2.38 g 100 g^?1 protein by quadratic regression analysis.     

Effects of dietary Lactobacillus delbrueckii on growth performance,body composition,digestive and absorptive capacity,and gene expression of common carp (Cyprinus carpio Huanghe var)

The present study aimed to investigate the effects of dietary supplementation of Lactobacillus delbrueckii (L. delbrueckii) on growth performance, body composition, intestinal enzyme activities and gene expression of Cyprinus carpio Huanghe var. Fish (mean 1.05 ± 0.03 g in triplicate) were conducted for 8 weeks with five treatments in triplicate. The fish in the control were fed a basal diet, and those in D2, D3, D4 and D5 were fed basal diet containing L. delbrueckii at 1 × 10 CFU/g, 1 × 10 CFU/g, 1 × 10 CFU/g and 1 × 10 CFU/g. The growth performance and the hepatic IGF‐I expression of fish increased significantly as L. delbrueckii level increased from 0 to 1 × 10 CFU/g, but decreased significantly with further increasing L. delbrueckii levels. The whole body protein, lipid contents, intestinal digestive and absorptive enzyme activities were significantly affected by dietary L. delbrueckii levels with the highest values observed in fish fed diet containing 1 × 10⁶ CFU/g L. delbrueckii. The carbohydrate content showed the opposite trend. The results suggest that supplementation of L. delbrueckii as probiotic in the diet at approximately 1 × 10 CFU/g can improve growth performance, intestinal enzyme activities and the growth‐related gene expression in Cyprinus carpio Huanghe var.     

Growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary zinc

A 6‐week trial was carried out with 900 juvenile Jian carp (Cyprinus carpio var. Jian) to investigate the effects of dietary zinc on growth, body composition and intestinal enzyme activities. Diets supplemented with increasing levels (15.3, 26.9, 40.8, 58.2, 68.9 and 92.5 mg Zn kg^?1) of zinc lactate were fed to Jian carp (mean initial weight 15.7 ± 0.01 g). Results indicated that per cent weight gain (PWG), feed efficiency (FE), protein efficiency ratio (PER) and lipid productive value (LPV) enhanced with dietary zinc levels up to 40.8 mg kg^?1 diet (P < 0.05), and plateaued thereafter (P > 0.05). Feed intake (FI) was similar to that observed for PWG. Intestosomatic index (ISI), relative gut length (RGL), hepatopancreas protein content (HPC), intestine protein content (IPC), trypsin, chymotrypsin, lipase, amylase, alkaline phosphatase (AKP), Na⁺, K⁺‐ATPase and γ‐glutamyl transpeptidase (γ‐GT) activities were all higher by dietary zinc supplementation than zinc un‐supplementation (P < 0.05). These results suggested that zinc could promote growth and increase nutrient deposition and intestinal enzyme activities. The dietary zinc requirements (use zinc lactate as zinc source) of juvenile Jian carp (15.7–42.2 g) based on PWG and serum zinc were 48.7 and 43.2 mg Zn kg^?1 diet, respectively.     

Breeding and larval rearing of threatened, endemic fish stonesucker, Garra ceylonensis (Bleeker)

This study was aimed to develop captive breeding and nurture the young of stonesucker (Garra ceylonensis, Bleeker), a small threatened freshwater fish species endemic to Sri Lanka. Breeding of stonesucker was possible under indoor conditions without hormonal stimulation. They were single spawners having a fecundity of 562±176 eggs per fish (total length of 7.9±0.6 cm) with an egg size of 770–1877 μm. Duration of development stages were, egg to hatchling 36–48 h, hatchling to postlarva stage 3–4 days, postlarva to juvenile stage 5–64 days and adult stage in 300–365 days at 26–28°C. Juveniles exhibited bottom dwelling habit in 70–75 days. Postlarva fed with formulated feed exhibited the highest growth (P<0.05) compared with live diets, Artemia and microworm (Anguillula sp.). Although the juveniles revealed a significantly high growth performance (P<0.05) with swine liver diet up to day 45 compared with formulated feed and combination of detritus and plankton, formulated feed exhibited an increase in growth from day 50. Therefore, formulated feed could be used for rearing of postlarva and juvenile stages without any live feeds.     

肌醇对胭脂鱼生长、体成分和部分血清生化指标的影响

为了探讨不同方法制备的肌醇及其添加量对建鲤生长性能、生理生化以及抗氧化能力的影响,实验以蛋白含量34.64%和脂肪含量7.86%制备基础日粮 (C),通过在基础日粮中分别添加400 mg/kg酶促法肌醇 (C+400E-MI)和400 mg/kg化工法肌醇 (C+400C-MI)配制3种实验日粮,选取当年繁育的健康的建鲤幼鱼 [(1.5±0.01) g]进行为期10周的养殖实验。养殖结束后,测定其生长性能、肝脏抗氧化酶活性和炎症相关基因的表达。结果显示,与对照组相比,基础日粮中添加不同制备方法的肌醇均具有提高建鲤幼鱼的特定生长率、蛋白质效率和蛋白质沉积率的作用;能降低血浆中乳酸脱氢酶的含量,有效保护肝细胞。与对照组相比,添加400 mg/kg酶促法肌醇可以显著提高建鲤幼鱼肝脏总超氧化物歧化酶 (T-SOD)和谷胱甘肽过氧化物酶 (GPX)活性,增加谷胱甘肽 (GSH)的含量。添加400 mg/kg化工法肌醇能够显著提高建鲤幼鱼肝脏GPX的活性,但同时也显著提高了丙二醛 (MDA)的含量。进一步对基因表达的分析发现,2种肌醇的添加均显著降低了建鲤幼鱼肠道中促炎因子IL-6、TNF-α和IL-12在mRNA水平的表达,同时,添加400 mg/kg酶促法肌醇还显著降低了肠道中抗炎因子TGF-β1和IL-10在mRNA水平的表达。总体而言,饲料中添加400 mg/kg 化工法和酶促法制备获得的肌醇均可以提高建鲤幼鱼的生长和饲料利用,抑制了肠道炎症反应,而酶促法肌醇对建鲤幼鱼的生长促进和抗氧化能力增强效果更优,因此,酶促法肌醇是一种符合绿色发展要求的水产动物营养添加剂。本实验可为不同方法制备的肌醇作为饲料添加剂在水产养殖中的应用提供参考依据。     

Isolation, partial characterization and localization of integumental peroxidase, a stress-related enzyme in the skin of a teleostean fish (Cyprinus carpio L.)

Biochemical and immunological characteristics of peroxidase activity of the skin epithelium of common carp (Cyprinus carpio) were investigated and compared with peroxidase activity of blood cells. Skin as well as blood-borne peroxidases eluted from the Superdex column as a 135 kDa protein and both probably are tetrameric molecules. Skin peroxidase activity was characterized by a V_max of 51.5 ± 1.3 U mg^-1 min^-1 and a K_M of 1.64 ± 0.18 mM ortho-phenylenediamine (OPD), whereas blood-borne peroxidase was characterized by a 1,000 fold higher specific activity (V_max = 30.5 103 ± 2.5 103 U mg^-1 min^-1) and a higher affinity (K_M = 0.875 ± 0.003 mM OPD). Polyclonal antibodies were raised against concanavalin-A purified skin peroxidase as well as blood-borne peroxidase. Immunocytochemical labelling showed that peroxidase is present in mucous cells and in mucus covering the skin and gill epithelia, as well as in erythrocytes and leucocytes. We conclude that the mucous cells of the skin produce a biochemically distinct peroxidase that is released in the mucus and may contribute to the antimicrobial properties of the mucous layer covering the skin. After exposure of the fish to cadmium the kinetic characteristics of the enzyme activity, as determined in skin homogenates, changed considerably. The V_max increased significantly to 61.9 ± 1.1 U mg^-1 min^-1, and the affinity for OPD increased to the value demonstrated for blood-borne peroxidase (K_M = 0.888 ± 0.045 mM OPD). Increased peroxidase levels after cadmium exposure were also demonstrated immunochemically in a dotblot assay. However, no significant changes were observed when the circulatory system of the fish was perfused prior to sampling, indicating that erythrocytes are a major contributor to the increased peroxidase activity in carp skin during cadmium exposure. This likely reflects the increased vascularization of the connective tissue layer underlying the skin epithelium, which takes place when the fish are exposed to chronic stressors including cadmium. In the cadmium-exposed fish this effect prevented the biochemical detection of stressor-related changes in epithelial peroxidase reported earlier with cytochemical methods.     

Growth testing of two breeds of common carp, Cyprinus carpio L. (Hungarian mirror and Třeboň scaly carp), in ponds with low and high stocking density

The growth of two breeds of common carp, Cyprinus carpio L., was tested in ponds under the climatic conditions of South Bohemia. T?eboň scaly carp (TR) and Hungarian mirror carp (M2) were kept in both low and high stocking densities during the second growing season and then stocked together for communal testing during the third growing season. Before the communal testing, the mean initial weights of fish from low‐ and high‐density stocks differed significantly (374.1 vs. 227.7 g for the TR breed and 766.7 vs. 317.3 g for the M2 breed respectively, P<0.01). After communal testing, mean weights of fish from low‐ and high‐density stocks gained 761.8 vs. 543.8 g for the TR breed and 1339.7 vs. 706.7 g for the M2 breed respectively. These observed weights were also significantly different (P<0.01). However, the test of corrected weight gain, i.e. gain not related to the initial weight of fish, revealed insignificant differences (P>0.01) between the weight gains after correction, i.e. the effect of different initial weights was successfully eliminated. These results seem to confirm the applicability of this method for the assessment of growth of purebred common carp under the climatic conditions of Central European fish farms.     

Effect of prey type and size on the growth,survival and pigmentation of cod (Gadus morhua L.) larvae

The aim of this study was to investigate the effect of natural zooplankton versus rotifers and the effect of prey size on the growth and survival of cod larvae. At 20 days post hatch (DPH) myotome height, standard length and dry mass were significantly higher in larvae fed zooplankton compared to those fed rotifers. The dry mass at age 25 DPH was 135 μg (±45), 331 μg (±114), 391 μg (±121) for larvae fed rotifers, small size and large size plankton, respectively. At 25 days post hatch, the survival rates were 41.8% (±10.5), 90.7% (±2.3) and 91.4% (±1.7) for larvae reared on rotifers, small size and large size plankton, respectively. The limited growth and survival of cod larvae reared on rotifers were not mainly caused by the small size of rotifers. Large differences in skin coloration between larvae in the rotifer group and the two zooplankton groups were observed, probably caused by the large difference in astaxanthin levels in rotifers and natural zooplankton. We suggest that the nutritional composition of rotifers is a limiting factor for cod larvae growth and survival.     

Fish fauna in a Protected Greek lake: biodiversity, introduced fish species over a 80-year period and their impacts on the ecosystem

Abstract –  Lake Pamvotis is a tertiary natural shallow lake located in the NW of Greece. For biogeographical reasons, it historically contained only four fish species: two endemics ( Phoxinellus epiroticus , Squalius pamvoticus ), one native to the West Greece ( Barbus albanicus ) and the ubiquitous Anguilla anguilla . These species were almost exclusively present in the lake before 1920, forming remarkable commercially exploited populations. From the 1930s through the 1990s, 20 species were introduced into the lake for purposes of eutrophication control or to enhance the fishery. These introductions, some of them accidental have led to the apparent decline, even loss, of the native species. During the last three decades the fish fauna of the lake has shifted from the native, clear-water species to a predominance of introduced species, mainly those adapted for turbid eutrophic water ( Rutilus panosi , Cyprinus carpio and Carassius gibelio , and several Asian cyprinids). The current fish assemblage in the lake is dominated by introduced species particularly the Mosquitofish ( Gambusia affinis ) and the Lourogobios ( Economidichthys pygmaeus ) in the littoral zone, the benthopelagic allogynogenetic Prussian carp ( C. gibelio) , and the opportunistic Trichonis roach ( R. panosi ), in the pelagic zone.     

Combined effect of temperature,salinity and density on the growth and feed utilization of Nile tilapia juveniles (Oreochromis niloticus)

Based on Box–Behnken experimental design and response surface method, the joint effect of temperature (16–36°C), salinity (0–22 ppt) and rearing density (200–1000 fish.m^?3) on the specific growth rate (SGR) and feed conversion rate (FCR) of Nile tilapia juveniles were studied under laboratory conditions. The entire experiment lasted for 1 month (30 days). Results showed that the linear and quadratic effects of temperature, salinity on both growth and feed utilization were highly statistically significant (P < 0.01). The linear and quadratic effect of rearing density on the growth was highly significant (P < 0.01); the linear effect of rearing density on feed utilization was significant (P < 0.05), but the quadratic effect nonsignificant (P > 0.05). Interactions between temperature and salinity, and between salinity and rearing density on the growth statistically differed from zero (P < 0.05). Interactions between temperature and salinity, between temperature and density on feed utilization was significant (P < 0.05). Model equations of the growth and feed utilization on temperature, salinity and density were established, with the coefficient of determination being 98.34% for growth and 98.11% for feed utilization, and could be applied to projection. The optimal temperature/salinity/density combination was obtained utilizing statistical optimization approach: 29°C/6 ppt/500 fish.m^?3, at which the maximal specific growth and feed utilization reached 4.228%.d^?1 and 0.520 respectively, with the desirability being 0.989.