Novel droplet vitrification combined with fish antifreeze protein type III enhances cryoprotection of semen in wild endangered Persian sturgeon Acipenser persicus (Borodin, 1897)

In this study, the efficiency of a novel droplet vitrification technique along with different doses of fish antifreeze protein (AFP) type III on Persian sturgeon thawed spermatozoa quality (motility duration and motility percentage) was investigated. Semen of seven male individuals was pooled in equal volumes and diluted with 4°C Tris‐Hcl (100 mM), pH = 8 extenders containing 0, 5, 10, 15 μM of AFP type III in a ratio of 1:1 (semen/extenders). Treated semen was dropped into liquid nitrogen. Solidified droplets were stored for 2, 60 and 120 days and thawed by plunging them into a tube containing 5 mL Tris‐Hcl (100 mM), pH=8 with 1% BSA at 37°C. Motility duration in all treatments had no significant difference comparing to fresh sperm (P > 0.05), but their motility percentage was significantly lower. Treatment with 10 μM of AFP had significantly higher motility percentage (16.11 ± 0.5%) comparing to other treatments (P < 0.05). There was no significant difference between 0, 5, 15 μM of antifreeze protein treatments (P > 0.05), suggesting that antifreeze protein effectiveness are highly dose dependent, and dose of 10 μM is appropriate in Persian sturgeon spermatozoa droplet vitrification. Besides, the present technique obtained higher quality of spermatozoa comparing to its analogue techniques.     

High fry production rates using post-thaw silver carp (Hypophthalmichthys molitrix) spermatozoa under farming conditions

Silver carp (Hypophthalmichthys molitrix) is not endemic to Cuba, and egg fertilization is totally artificial; males produce spermatozoa only between March and October. Cryopreservation of silver carp spermatozoa would reduce the number of males needed, minimize handling stress through less frequent stripping, and facilitate artificial propagation when eggs are available. The effects on motility and fry production from eggs fertilized with thawed sperm under farm-conditions were examined in this study. Five, seven and ten percent of dimethyl sulfoxide (DMSO), glycerol and methanol were tested as cryoprotectants. DMSO was a more suitable cryoprotectant than methanol or glycerol. The effect of equilibration time on the motility rate at 10% DMSO was evaluated. Hatching rates equal to the control (P>0.01) were obtained under farm conditions with frozen spermatozoa, stored even for a year in liquid nitrogen, with a final DMSO concentration of 10%. Cryopreservation offers a useful routine method for sperm storage and silver carp handling. To our knowledge, this is the first report on the production of fry from post-thaw silver carp spermatozoa under farming conditions.     

Comparative evaluation of heat-processed Winged bean (Psophocarpus tetragonolobus) meals as partial replacement for fish meal in diets for the African catfish (Clarias gariepinus)

Mature winged bean (Psophocarpus tetragonolobus) (cultivar Tpt26) seeds were roasted or autoclaved and their meals evaluated as a dietary protein source for the African catfish. Five dry practical diets (400 g protein/kg and 17.5 kJ gross energy/g dry diet) containing menhaden fish meal or each of the heat-processed winged bean meals as partial replacement (80%), (with or without 5 g -methionine/kg diet supplementation) for menhaden fish meal, were prepared and fed to triplicate groups of catfish fingerlings (5.8±1.2 g) to satiation for 70 days. No mortality occurred throughout the study and satisfactory diet acceptance was observed when the heat-processed winged bean meals replaced menhaden fish meal. Differences were found in weight gain, specific growth rate, feed and protein efficiency ratios, but were not significant (P>0.05). Digestibility of crude protein and gross energy content of the diets were high (>85%) and comparable to that of menhaden fish meal. Carcass composition of catfish did not vary significantly (P>0.05) between diet treatments. Results indicate that both autoclaved and roasted winged bean meals were acceptable as protein sources and can replace 80% of menhaden fish meal in catfish diets.     

Almost total replacement of fish meal by plant protein sources in the diet of a marine teleost, the European seabass, Dicentrarchus labrax

Five practical diets in which the supply of protein from fish meal was decreased gradually from 100% to about 2% and replaced by plant protein sources were formulated. European seabass weighing about 190 g were fed these diets for 12 weeks at a water temperature of 22 °C. Feed was dispensed using automatic self-feeders and voluntary feed intake (VFI) was closely monitored. We did not find any significant difference among diets in the apparent digestibility coefficients (ADC) of dry matter (80–82%), protein (94–96%), energy (88–92%) or phosphorus (49–58%). Replacement of fish meal by plant protein ingredients did not influence VFI. All groups had very good growth rates (DGI above 1.3%/day) and there were no significant differences in growth rate, feed efficiency or in daily nitrogen gains among groups. There was, however, a slight increase in fat deposition in fish fed diets with plant protein sources. Ammonia nitrogen and soluble phosphorus excretion rates were measured. Nitrogen and phosphorus balance studies indicated that fish meal replacement by plant ingredients led to a slight increase in nitrogen losses (from 83 to 103 g N/kg weight gain) but led to a significant reduction in total phosphorus losses (from 13 to 5 g P/kg weight gain). These results combined with the remarkable acceptability of diets containing high levels of plant protein ingredients with identical growth performances of European seabass show clearly that dietary fish meal levels can be considerably reduced without any adverse consequence in terms of somatic growth or nitrogen utilisation.     

大菱鲆利用水解鱼蛋白和牛蛙蛋白的差异

为探究大菱鲆对不同来源水解蛋白的利用效率,实验选取太平洋狭鳕和牛蛙下脚料为蛋白来源,分别制备水解鱼蛋白和水解牛蛙蛋白,以初始体重为(8.00±0.01) g的大菱鲆为研究对象,进行为期56 d的养殖实验。实验设2个对照组,正对照组(PC)鱼粉含量为35.0%,负对照组(NC)鱼粉含量为26.5%;设2个实验组,水解鱼组(FPH)为26.5%的鱼粉和8.0%的水解鱼蛋白,水解牛蛙组(BPH)为26.5%的鱼粉和9.5%的水解牛蛙蛋白。结果显示,FPH组的终末体重、增重率和特定生长率显著高于BPH组和NC组,与PC组无显著差异。摄食6 h后,食糜必需氨基酸中赖氨酸、精氨酸、苏氨酸和缬氨酸在BPH组的含量显著高于PC组;多数非必需氨基酸在BPH组含量最高,但无显著差异。质子偶联氨基酸转运载体PAT1和小肽转运载体PepT1的mRNA表达量分别在FPH组和BPH组都显著高于PC组和NC组;碱性氨基酸转运载体CAT1和y⁺L型氨基酸转运载体y⁺LAT2的mRNA表达量在各处理组中无显著差异。研究表明,在饲料中添加鳕和牛蛙蛋白水解物均能提高大菱鲆的生长性...     

Effect of oral administration of l -thyroxine (T4) on growth performance, digestibility, and nutrient retention in Channa punctatus (Bloch) and Heteropneustes fossilis (Bloch)

Effects of oral administration of l-thyroxine (T₄) on growth performance, body composition, and some aspects of nutritional physiology were investigated in two slow-growing air-breathing fish (Channa punctatus and Heteropneustes fossilis) under laboratory conditions (LD 12:12 at 25°C). The results indicate that irrespective of the species, fish fed diets containing lower doses of T₄ (up to 50 mg kg⁻¹ of diet in C. punctatus and up to 100 mg kg⁻¹ of diet in H. fossilis) showed significantly (P < 0.05) higher growth (in terms of live weight and length gain, specific growth rate, percentage gain in body weight and condition factor), low feed conversion ratio, high nutrient retention, high apparent protein digestibility, and high digestive enzyme activity. Viscero-somatic (VSI) and hepato-somatic (HSI) values were also high in fish fed on low dietary T₄ levels. Liver glycogen levels decreased with the increase in the dietary T₄ levels, indicating its utilization during growth. Muscle glycogen levels in H. fossilis coincided with high growth at 100 mg of T₄. Observation of the postprandial excretion of metabolites (N–NH₄ ⁺ and o-PO₄ ⁻) indicated significantly (P < 0.05) low levels in aquaria water where the fish were fed diets with low T₄ levels. These studies further revealed that feeding fishes on higher T₄ levels (above 50 mg in C. punctatus and above 100 mg in H. fossilis) not only repressed growth performance and nutrient retention, but also affected carcass composition by lowering protein accumulation (muscle and carcass protein) and energy assimilation. These studies revealed a biphasic action of thyroxine, i.e., the hormone at lower doses is anabolic, while at higher doses it acts as a catabolic agent, indicating that feeding fishes on higher doses can be detrimental to their growth and metabolism. In summary, the results of the present study show that feeding H. fossilis and C. punctatus on low doses of T₄ enhances growth, decreases excretion of metabolites, and increases nitrogen retention. These observations suggest that T₄ supplementation of the diet may have practical utility in the culture of slow-growing fish species.     

Biological parameters of the endangered fish Chitala chitala (Osteoglossiformes: Notopteridae) from some Indian rivers

Age, growth and maturity data of the freshwater feather back Chitala chitala (Hamilton-Buchanan, 1822) were collected from ten different geographical locations. Out of ten populations, maximum 6+ ages were recorded from four river basins namely river Bhagirathi, Koshi, Saryu and Ganga and the back calculated lengths at 6+ ages ranged from 1033.36–1073.63 mm. In rest of the locations, however, only 3+ age classes were recorded. Specific rate of linear growth (C_l) and specific rate of weight increase (C_w) showed decreases except in two locations. The specific rate of linear growth (C_l) and the specific rate of weight increase (C_w) increased at 3+ age class in the river Bhagirathi. Among other growth parameters, three distinct life stages of C. chitala were observed based on analysis of growth constant data. Analysis of variance (ANOVA) of the back-calculated length data of 10 populations indicated a significant difference (p < 0.05). Out of ten populations studied, six showed significant variation of growth in 1+ age class and two showed significant variation in 2+ to 6+ age classes. Length-weight relationship of the species from all the population was calculated and the coefficient of correlation (r) was at the significant level where the value of ‘b’ was almost 3 for all the locations studied. Male C. chitala attained maturity earlier (2+ age) whereas females matured at age 3+. The percentages of mature individuals also varied between river basins. Based on this study strategies can be proposed for sustainable exploitation of the species from wild populations.     

辅酶渣替代鱼粉对中华绒螯蟹生长及肠道菌群的影响

为探究饲料中辅酶渣替代鱼粉对中华绒螯蟹生长性能、健康情况和肠道菌群的影响,以中华绒螯蟹幼蟹(0.70±0.01g)为研究对象,分别以等蛋白的辅酶渣替代基础饲料中鱼粉的0%(对照组,含20%鱼粉)、20%、40%、60%、80%、100%(记为C、T20、T40、T60、T80、T100)的饲料投喂8周。结果显示,与C组相比,T40组生长性能无显著改变,T60组肌肉粗蛋白含量显著降低。T80组、T100组生长性能、体粗蛋白和粗脂肪含量显著降低;与C组相比,替代组血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、碱性磷酸酶(AKP)、甘油三酯(TG)水平未见显著差异,总蛋白水平(TP)在T100组显著降低。血清葡萄糖(Glu)在替代组中显著降低。T60、T80、T100组的血清总胆固醇(T-CHO)、高密度脂蛋白胆固醇(HDL-C)含量显著降低,T80、T100组的血清低密度脂蛋白胆固醇(LDL-C)含量显著降低;与C组相比,各替代组肝胰腺超氧化物歧化酶(SOD)活性无显著差异,谷胱甘肽过氧化物酶(GSH-Px)活性显著上升,T100组丙二醛(MDA)含量显著降低;C、T40、T80组肠道菌...     

Effects of various feed supplements containing fish protein hydrolysate or fish processing by-products on the innate immune functions of juvenile coho salmon (Oncorhynchus kisutch)

Immunomodulators administered to fish in the diet have been shown in some cases to enhance innate immune defense mechanisms. Recent studies have suggested that polypeptide fractions found in fish protein hydrolysates may stimulate factors in fish important for disease resistance. For the current study, groups of coho salmon were reared on practical feeds that contained either fish meal (Control diet), fish meal supplemented with cooked fish by-products, or fish meal supplemented with hydrolyzed fish protein alone, or with hydrolyzed fish protein and processed fish bones. For each diet group, three replicate tanks of fish were fed the experimental diets for 6 weeks. Morphometric measurements, and serologic and cellular assays were used to evaluate the general health and immunocompetence of fish in the various feed groups. Whereas the experimental diets had no effect on the morphometric and cellular measurements, fish fed cooked by-products had increased leucocrit levels and lower hematocrit levels than fish from the other feed groups. Innate cellular responses were increased in all feed groups after feeding the four experimental diets compared with pre-feed results. Subgroups of fish from each diet group were also challenged with Vibrio anguillarum (ca. 7.71×10⁵ bacteria ml⁻¹) at 15 °C by immersion. No differences were found in survival among the various feed groups.     

Guidance of groups of guppies (Poecilia reticulata) to allow sorting by computer vision

Prior to marketing, ornamental tropical fish are currently sorted, graded and counted manually; a process that is labor intensive, stressful to fish and inaccurate. Manipulation of fish movements at our will is a key element in the development of a device for automatically sorting, grading and counting fish by a computer vision system, and the present study is one step towards the development of such a fish-friendly sorting device. The positive phototactic and rheotactic innate responses of guppies (Poecilia reticulata) were exploited to induce them to swim through transparent pipes or narrow channels, to render them ready for inspection by a computer vision system. Water flow direction and velocity, water level, and illumination were effective in inducing fish to move from one container into the other via a narrow transparent pipe. It was attempted to separate guppies moving in groups into individually spaced fish, by introducing an obstacle into a narrow channel or narrowing the transparent pipe.     

Comparing geometric morphometrics and outline fitting methods to monitor fish shape variability of Diplodus puntazzo (Teleostea: Sparidae)

The definition of a remote system in the monitoring of fin fish shape variability relies on the appropriate shape analysis tools. In this paper, different methods are proposed and compared. Growth trajectories, computed using geometric morphometrics, allow the pattern of size-related shape change and visualize growth allometry to be analyse. Geometric morphometrics is used to describe shape change in three samples (507 5100 days after hatching) of 119 individuals of the Sparid Diplodus puntazzo. The results are potentially interesting but the method still relies on the manual detection of homologous landmarks (coordinates of points located unambiguously on each specimen’s profile or structure) which are basic for such analysis. In an attempt to proceed towards the remote estimation and the automation of data collection, two alternative approaches are tested. In particular, Elliptic Fourier analysis and Bezier function were applied to the same samples, and results compared with geometric morphometrics. Fourier analysis’ growth curves are very similar to geometric morphometrics’ ones and allows for an appropriate visualisation of global shape changes. At the same time, Fourier methods can be applied to remotely and automatically detected profiles. This method is thus considered as the best candidate in the context of automated fish shape monitoring. The Bezier method performed poorly, both in terms of statistical output and shape visualization.     

Size-fractionated fish hydrolysate as feed ingredient for rainbow trout (Oncorhynchus mykiss) fed high plant protein diets. I: Growth, growth regulation and feed utilization

Six experimental diets were fed to rainbow trout to examine the effect of fish hydrolysate and ultra filtered fish hydrolysate on growth performance, feed utilization and growth regulation using diets low in dietary fish meal inclusion. One diet contained a high level of plant protein sources (90.6% of total dietary protein) and a low level of fish meal (9.4% of dietary protein). Two diets contained different levels of hydrolysate in exchange for the plant protein sources, reducing the plant protein level to 73.9% and 57.2%, respectively. Two further diets were identical in composition except that the hydrolysate was ultra filtered to remove low molecular weight compounds. A moderate level of fish meal was used in the sixth diet which had a dietary plant protein level of 57.0%. All diets were made equal in protein, lipid, energy and lysine. The feeding trial lasted for 90 days and for the fastest growing group, fed moderate level of fish meal, the fish increased in weight from 149 g at start to a final weight of 443 g. All groups showed significant differences in growth and feed utilizations. Specific growth rates were; 0.30% day^− 1 for the plant protein diet, 0.98% day^− 1 for the high hydrolysate diet, 0.72% day^− 1 for the group containing the high level of ultra filtered hydrolysate, and 1.21% day^− 1 for the moderate fish meal diet. Feed efficiencies (g fish weight gain per g feed intake) were found to be 0.57 for plant protein diet, 0.97 for high level of hydrolysate, 0.83 for ultra filtered hydrolysate and 1.03 for the moderate fish meal diet. Half dietary inclusions of hydrolysate and ultra filtered hydrolysate revealed values between the plant protein diets and high levels of these ingredients, respectively. Feed consumption in percentage of average fish weight per day, correlated with the feed efficiency for all groups. PER, PPV and BV correlated with the differences in growth. Protein digestibilities were equal for all groups, while the moderate fish meal diet showed higher lipid and energy digestibilities than the plant protein diets. Although some of the differences may be due to growth inhibitors in plant resources other explanations may be relevant. Plasma growth hormone (GH) levels were significantly higher in fish fed the plant protein diet than fish fed the fish meal or high hydrolysate diet, which is most likely a result of their poor feeding status. Plasma IGF-I levels were not affected by diet. Comparisons of groups with similar inclusion of plant ingredients, and thus equal level of growth inhibitors, show that in removing small molecular weight compounds from fish hydrolysate, the growth and feed efficiency were significantly reduced. Some of these small compounds in fish hydrolysate thus seem to be essential for biological performance. Further, as fish meal revealed the best performance, fish muscle protein is not the only nutrient that makes fish meal an essential ingredient in aqua feed for carnivorous fish. This information is important in the work to find replacement of fish meal in a sustainable growing global aquaculture industry.     

Feed preferences of Salminus brasiliensis (Pisces, Characidae) larvae in fish ponds

Feed preferences of dorado, Salminus brasiliensis, in the early stages of life was studied in larvae, stocked 5 days after hatching in three earthen commercial ponds (810 m², 900 m² and 1480 m²) at a density of 30 m^− 2. Larvae were fed on natural food from ponds supplemented with a commercial ration (40% crude protein), and for 12 days fish samples were taken daily in the morning and in the afternoon from each pond to analyze the food items present in the diet. Zooplankton available in the environment was also analyzed. Feeding was intensive since 94% of the larvae guts examined contained food. Since the commercial diet was not found in the dorado guts, the natural diet dominated the artificial food, but the cannibalistic behavior typically found in laboratory conditions was not observed. Insect larvae and cladocerans were the main prey items found in the gut of the larvae. In fish ponds dorado larvae can be considered a generalist feeder, since small amounts of different food items were consumed, but they tend to specialize in some items, according to their developmental stage.     

Replacement of fish meal by meat and bone meal in diets for large yellow croaker, Pseudosciaena crocea

A growth experiment was conducted to investigate the effects of replacement of fish meal (FM) by meat and bone meal (MBM) in diets on the growth and body composition of large yellow croaker (Pseudosciaena crocea). Six isonitrogenous (43% crude protein) and isoenergetic (20 kJ g^− 1) diets replacing 0, 15, 30, 45, 60 and 75% FM protein by MBM protein were formulated. Each diet was randomly allocated to triplicate groups of fish in sea floating cages (1.0 × 1.0 × 1.5 m), and each cage was stocked with 180 fish (initial average weight of 1.88 ± 0.02 g). Fish were fed twice daily (05:00 and 17:30) to apparent satiation for 8 weeks. The water temperature ranged from 26.5 to 32.5 °C, salinity from 32 to 36‰, and dissolved oxygen content was approximately 7 mg l^− 1 during the experimental period. Survival decreased with increasing dietary MBM and the survival in the fish fed the diet with 75% protein from MBM was significantly lower than other groups (P < 0.05). There were no significant differences in specific growth rate (SGR) among the fish fed the diets with 0 (the control group), 15, 30 and 45% protein from MBM. However, SGR in the fish fed the diets with 60 and 75% protein from MBM were significantly lower than other groups (P < 0.05). No significant differences in feeding rate were observed among dietary treatments. The digestibility experiment showed that the apparent digestibility coefficients (ADC) of dry matter, protein, lipid and energy of MBM were significantly lower compared with those of FM (P < 0.05). Essential amino acid index was found to be correlated positively with SGR in the present study, suggesting that essential amino acid balance was important. Body composition analysis showed that the carcass protein and essential amino acids were not significantly affected by dietary MBM. The lipid and n-3 highly unsaturated fatty acid (n-3 HUFA) in fish muscle, however, significantly decreased with increasing dietary MBM. These results showed that 45% of FM protein could be replaced by MBM protein in diets of large yellow croaker without significantly reducing growth. It was suggested that the reduced growth with higher MBM was due to lower digestibility and imbalance of essential amino acids.     

Antibiotics,Penicillin and Sreptomycin improve semen quality indices of endangered Caspian brown trout,Salmo trutta caspius (Kessler, 1870) during in vitro short‐term storage

In this study, we examined the effects of 500 IU mL^?1 penicillin + 500 μg mL^?1 streptomycin sulphate on semen quality indices of endangered caspian brown during 12 days short‐term storage at 4°C. Twenty‐four millilitre semen samples with good quality were considered for the experiment. The semen samples were then stored in the presence and absence of 500 IU mL^?1 penicillin + 500 μg mL^?1 streptomycin sulphate. The semen quality parameters including percentage and duration of sperm motility were measured 0, 3, 6, 9 and 12 days after storage. In the antibiotic receiving group, the values of percentage and duration of sperm motility reduced 3 and 6 days after storage respectively and reduced to lowest levels at day 12. In the antibiotic‐free group, the duration and percentage of sperm motility decreased significantly after 3 days of storage and reached to lowest values at day 12. Also, percentage and duration of sperm motility in each storage time were significantly higher in the antibiotic receiving group than in the antibiotic‐free group. The overall values of percentage and duration of sperm motility for all storage periods were higher in the antibiotic receiving group than in the antibiotic‐free group. In conclusion, our results demonstrated that 500 IU mL^?1 penicillin + 500 μg mL^?1 streptomycin sulphate improves the viability of caspian brown trout during short‐term storage.     

Economic efficiency and optimum stocking densities in fish polyculture: an application of data envelopment analysis (DEA) to Chinese fish farms

Polyculture is commonly practiced in pond aquaculture where several fish species are reared together, creating a multi-output production structure. This study applied a nonparametric data envelopment analysis (DEA) technique for multiple outputs to: (1) measure economic or ‘revenue' efficiency and its technical and allocative components for a sample of Chinese polyculture fish farms; and (2) derive the optimum stocking densities for different fish species. The mean economic efficiency was estimated to be 0.74. Technical inefficiencies accounted for most of the production inefficiencies in Chinese fish farms. On average, farmers should increase grass carp and decrease black carp stocking rates. Smaller farms and those from the developed regions were found to be relatively more technically and economically efficient.     

Larval feeding behaviour of the endangered fish golden bubblebee goodeid, Allotoca dugesi, implications for conservation of an endangered species

Abstract To improve survival of cultured juvenile fishes, it is important to understand prey preferences and predation behaviour of fish larvae. In this study, the feeding behaviour and prey preference of Allotoca dugesi (Bean), a small fish species endemic to Mexico and currently threatened with extinction are presented. Three zooplanktonic prey, viz. Brachionus calyciflorus (Pallas) , Moina macrocopa (Goulden) and Daphnia pulex (Leydig) were tested. The mean size (standard length ± SE, mm) of the larvae ranged from 9.0 ± 0.1 mm at week 1 to 18 ± 2 mm at the end of the experimental period (8 weeks). The gape size (mean ± SE) increased from 0.125 ± 0.002 mm at the first week to 2.300 ± 0.361 mm by the eighth week. Capture success (capture/attack) ranged from 0.80 to 0.98 with Brachionus , 0.72–0.94 with Moina and 0.17–0.46 with Daphnia . Prey preference experiments were conducted using B. calyciflorus, M. macrocopa and D. pulex at a fixed ratio of 5 : 2 : 2 ind. mL⁻¹, respectively, and revealed a positive selection for rotifers and Moina , but avoidance of Daphnia . The results are discussed with reference to conservation efforts for Allotoca dugesi .     

Induced spawning of hatchery-raised Brazilian catfish, cachara Pseudoplatystoma fasciatum (Linnaeus, 1766)

In the months of January 2001 and 2002, female cachara Pseudoplatystoma fasciatum were selected during their first and second gonadal maturation (2 years and 7 months old and 3 years and 7 months old, respectively) with an of oocyte diameter of 937.5 μm (82.5% with central nuclei and 17.5% with peripheral nuclei). Nine females in first maturation received two doses of carp pituitary extract (CPE), 0.5 mg/kg and 5.0 mg/kg; seven received two doses of human chorionic gonadotropin (hCG), 5 and 10 IU/g; five received doses of 0.5 CPE mg/kg and 5 hCG IU/g (CPE+hCG); and four received 0.9% saline (saline). Nine females from CPE and seven from hCG presented oocytes with the same diameter at the moment of oocyte release (100% with germinal vesicle breakdown and fertilization rate of 53.44±18.3 and 54.81±11.8%; larvae number of 165,330±94.1 and 158,570±20.6, respectively). The five females from CPE+hCG did not respond to the hormonal treatment. The four females from the saline group did not ovulate. In January 2002, 6 of 15 selected females that were going through the second reproductive cycle received CPE (five received hCG and four received saline), showing oocyte diameters similar to the ones in the first maturation. At stripping, CPE females had an oocyte diameter of 1062.5 μm (the hCG females had oocyte diameters ranging from 937.5 to 1125.0 μm; fertilization rates of 56.08±30.9 and 81.90±17.3%; 364,547±244 and 633,129±190, larvae, respectively). The fertilization rates and larvae number were higher in the second gonad maturation, both for CPE and hCG.     

Evaluation of krill (Euphausia superba) meal as a partial replacement for fish meal in rainbow trout (Oncorhynchus mykiss) diets

We studied partial replacement of fish meal (FM) by krill meal (KM) and how fluoride from KM enriched-muscles and bones of rainbow trout reared in freshwater affected these fish. Diets that replaced FM with KM at proportions of 0, 7, 15 and 30% (control, KM7, KM15, and KM30) were fed to groups of rainbow trout for 92 days and growth was observed. In fish fed KM7 and KM15, weight gain (WG), feed intake (FI) and specific growth rate (SGR) were unchanged compared with fish fed the control diet, but in fish fed KM30, WG, FI and SGR significantly decreased. After the experiment, fluoride concentration in dorsal muscles of each experimental group was below the detected limit (1 mg/kg), but in vertebral bones, the fluoride concentration increased with each increase in KM inclusion in the diets: 490 mg/kg (control), 755 mg/kg (KM7), 1100 mg/kg (KM15), and 2400 mg/kg (KM30). Tissue specimens of liver of each experimental group had no histopathological changes. Therefore, accumulation of fluoride in vertebral bones apparently adversely affected growth of the vertebral bones thus affecting the growth performance as shown by the decrease in WG, FI and SGR.     

Effect of cryoprotectants, equilibration periods and freezing rates on cryopreservation of spermatozoa of mahseer, Tor khudree (Sykes) and T. putitora (Hamilton)

A study was conducted to standardize a protocol for cryopreservation of spermatozoa of the endangered mahseer, Tor khudree (Sykes) and T. putitora (Hamilton). The suitability of the cryoprotectants, dimethyl sulphoxide (DMSO) and glycerol, and the combination of the two were tested. Four equilibration periods and four freezing rates were also tested for their standardization. A combination of 9% DMSO and 11% glycerol gave significantly higher mean percentage of hatching in both T. khudree (45.59±1.86%) (control 71.08±0.59%) and T. putitora (45.00±1.25%) (control 73.48±1.19%) among the eight different treatments. Among the four different equilibration periods tested, the equilibration period of 30 min^?1 yielded the highest mean hatching percentage in T. khudree (39.46±1.94%) (control 71.70±0.61%) and T. putitora (38.28±1.06%) (control 73.11±0.82%). Freezing straws at a height of 8 cm above LN₂ surface for 10 min^?1 gave higher hatching percentages for both T. khudree (41.75±1.72%) (control 73.99±1.17%) and T. putitora (41.34±2.04%) (control 72.48±1.51%). The study reports the superior performance of the combination of DMSO and glycerol for the first time.