Showing papers in "Aquaculture International in 2010"

Herbal biomedicines: a new opportunity for aquaculture industry

Abstract: Hormones, antibiotics, vitamins and several other chemicals have been tested in aquaculture operations for various remedies Even though they give positive effects, they cannot be recommended due to their residual and other side effects The alternative herbal bio-medicinal products in the aquacultural operations, that have the characteristics of growth promoting ability and tonic to improve the immune system, act as appetite stimulators They increase consumption, induce maturation, and have antimicrobial capability and also antistress characteristics that will be of immense use in the culture of shrimps and other fin fishes without any environmental and hazardous problems Herbal compounds such as phenolics, polyphenols, alkaloids, quinones, terpenoids, lectines and polypeptides have been shown to be very effective alternatives to antibiotics and other synthetic compounds The present paper is presented after a careful review of more than 50 herbal plants for their biological effects such as growth promotion, immunostimulation, antistress, antibacterial, antifungal, antivirals, appetite stimulators and aphrodisiac

Are compensatory growth and catch-up growth two sides of the same coin?

Abstract: Compensatory growth refers to an animal’s ability to grow extremely rapidly after it has experienced a period of reduced growth. It is also widely held that the growth trajectories of animals showing compensatory growth converge towards those followed by conspecifics that have experienced favorable growth conditions throughout their lives. In other words, it is often assumed that animals undergoing compensatory growth also show some recovery, and thereby exhibit catch-up growth. This belief has resulted in the terms compensatory growth, recovery growth, and catch-up growth being used as synonyms, and has also created some problems with regard to data analysis and interpretation. Following a discussion of methods of analysis and their limitations, a series of growth simulations is presented to illustrate why the terms should not be used as synonyms. The simulations, based upon the assumption that compensatory growth results in a restoration of body composition (using condition index as a surrogate), show that compensatory growth is not always accompanied by a convergence of growth trajectories. Compensatory growth can occur in the absence of catch-up growth, and the simultaneous observation of compensatory growth and a recovery of body mass is a special combination of events. Further, it is possible for growth trajectories to converge even when animals that have experienced a period of reduced growth do not display compensatory growth. Definitions are proposed that distinguish between the terms compensatory growth, recovery growth, and catch-up growth, and guidelines are given relating to the analysis of the results of fish compensatory growth studies.

Social aspects of the sustainability of integrated multi-trophic aquaculture

Abstract: A pilot project in the Bay of Fundy, Canada, is growing kelps, mussels, and salmon in an integrated multi-trophic aquaculture (IMTA) system. Biological and economic results are positive, but social acceptability is also a critical component of aquaculture sustainability. Focus group sessions with several segments of the population (restaurateurs, residents of communities near aquaculture facilities, and the general population) were held and the participants’ knowledge of, and opinions on, IMTA were recorded. Most participants felt that IMTA had the potential to reduce the environmental impacts of salmon farming, benefit community economies, and improve industry competitiveness and sustainability. All felt that seafood produced in IMTA systems would be safe to eat and 50% of the participants were willing to pay 10% more for these products if labelled as such. The participants felt that IMTA appears to be an improvement over current monoculture practices and would be cautiously welcomed in the marketplace. A promotional campaign educating the general public, food distributors, and other industry stakeholders about the positive benefits of IMTA would go a long way in gaining mainstream acceptance of this aquaculture practice.

Rice fields to prawn farms:a blue revolution in southwest Bangladesh?

Abstract: This paper examines freshwater prawn (Macrobrachium rosenbergii) farming in southwest Bangladesh where a large number of farmers have converted their rice fields to export oriented prawn farms, locally known as gher. The gher design potentially provides good opportunities for diversified production of prawn, fish, rice and dike crops, that has brought about a ‘blue revolution’. The average annual yield of prawn, fish and rice was estimated at 467, 986 and 2,257 kg ha−1, respectively. Large farmers produced higher production due to more inputs, larger farm size and longer experience of prawn farming than others. All farmers in different gher size categories (i.e., small, medium and large) made a profit, with seed and feed dominating variable costs. Despite a higher production costs per hectare, the average annual net return was higher in large farms (US$2,426), compared with medium (US$1,798) and small (US$1,420) farms. Prawn production in gher systems has been accompanied by a great deal of social and economic benefits. Most farmers associate the blue revolution with increases in income and living standards. Socio-economic benefits of the households of prawn farmers depend on resource ownership (i.e., farm size) and are very apparent. Nevertheless, a number of significant challenges, particularly social and environmental issues, are vital in translating its benefits effectively to the thousands of rural poor.

Estimate by means of flow cytometry of variation in composition of fatty acids from Tetraselmis suecica in response to culture conditions

Abstract: The present work shows the possibility of determining variations in the lipid composition in Tetraselmis suecica under different conditions of culture by means of flow cytometry in cells marked with Nile Red (NR) A significant correlation was observed between the cellular contents in polar and neutral lipids and the cytometric signal of the marked cells Likewise, there was a significant correlation between the ratio of polar and neutral lipids, estimated by cytometry, and the relative composition of polyunsaturated fatty acids (PUFAs) in Tetraselmis, which corresponded to the greater content of PUFAs detected in the polar lipid fraction of this microalgae This relationship between the polar/neutral ratio and the relative contents of PUFAs, together with the flow cytometry and the marking by means of NR, would make it possible to have an effective indicator of the abundance of PUFAs in Tetraselmis, as well as the development of techniques of massive screening of strains which are hyperproductive of PUFAs and of rapid checking of the variations in lipid composition in response to cultivation conditions, which are much simpler and more rapid than traditional techniques

Effects of stocking density, temperature, and salinity on larval survival and growth of the red race of the sea cucumber Apostichopus japonicus (Selenka)

Abstract: The red race of the sea cucumber Apostichopus japonicus was introduced into China from Japan for large-scale seed production because of its economic value. This paper reports the effects of stocking density, temperature, and salinity on survival and growth of early larvae before and after feeding, in order to establish conditions for optimal larval growth and production. To maximize the yield per unit of space, densities of 0.5–1 larvae/ml are recommended for non-feeding larvae, while 0.1–0.2 larvae/ml are best for feeding larvae. Higher survival and growth values were obtained for both non-feeding and feeding larvae at temperature ranges from 21 to 24°C. Larvae reared at a salinity of 30‰ always showed maximum growth and survival. Based on results of this study, a temperature range from 21 to 24°C and a salinity of 30 are considered optimal for early development of the red A. japonicus.

Use of shrimp protein hydrolysate in Nile tilapia ( Oreochromis niloticus , L.) feeds

Abstract: A 45-day feeding trial was carried out to evaluate the use of shrimp protein hydrolysate (SPH) in diets for Oreochromis niloticus, L. SPH was included in isonitrogenous diets replacing fish meal protein by 0, 5, 10, and 20% and offered to Nile tilapia juveniles (1.7 ± 0.4 g) stocked in 40-L glass aquaria. The inclusion of SPH produced no significant differences (P ≥ 0.05) in final weight, survival, weight gain, average daily gain, specific growth rate, feed conversion ratio, protein efficiency ratio, or apparent net protein utilization. The inclusion of SPH Nile tilapia diets significantly affected (P < 0.05) the final fish body composition. Protein and ash contents decreased and fat content increased slightly with the increase in SPH. This study has demonstrated that SPH is a promising protein feedstuff and could account for as much as 6% of Nile tilapia diets with no adverse effects on growth and nutrient utilization.

Lipid composition of the mantle and digestive gland of Octopus vulgaris juveniles (Cuvier, 1797) exposed to prolonged starvation

Abstract: Lipid composition of the mantle and digestive gland of Octopus vulgaris that were not fed for 27 days were determined. Every 3 days, three octopuses were killed and samples of the mantle and the digestive gland (DG) were taken, in order to determine total lipids as well as lipid classes and fatty acids. Composition in total lipids (TL) for the mantle was similar until day 21, then decreased and remained similar until the end of the experiment. Composition in total lipids for the DG decreased significantly after 3 days, then remained similar until day 21, and then decreased until the end of the experiment. As for the lipid classes, in the DG the main components were triglycerides and sterol esters. Sterol esters suffered strong reductions after 10 days of starvation, while triglycerides remained similar until day 21 and then decreased until the end of the experiment. Cholesterol decreased gradually throughout the experimental period. For polar lipids, phosphatidylcholine and phosphatidylethanolamine increased during the first 3 days and then decreased throughout the experiment. In the mantle, the only neutral classes that decrease were triacylglycerols and sterol esters, while no polar lipid classes decreased in this organ. It was noticeable the decrease in almost all fatty acids in the DG after 3 days of starvation, while in the mantle there were no differences in fatty acid concentrations during the experiment.

Economic analysis of tiger grouper Epinephelus fuscoguttatus and humpback grouper Cromileptes altivelis commercial cage culture in Indonesia

Abstract: This study presents an economic analysis of tiger and humpback grouper at different production scales in Indonesia. The results highlight the non-viability of small-scale tiger grouper farming, with a 5-year projected negative cumulative cash flow of −IDR 18,102,650.00 and a negative net present value (NPV) of −IDR 22,059,576.28. An increased production scale of tiger grouper highlights a marginal viability for medium-scale farms (with a 5-year projected cumulative cash flow of IDR 198,320,673.00, a positive NPV of IDR 105,578,440.42; a benefit cost ratio of 1.25; an internal rate of return (IRR) of 88% and a payback period of 0.99 years), and an economically viable large-scale cage culture (with a 5-year projected cumulative cash of IDR 707,746,923.00; a NPV of IDR 406,801,749.07; a benefit cost ratio of 1.33; an internal rate of return of 157%; and a payback period of 0.57 years). The economic analysis of humpback grouper at different production scales highlighted a positive cumulative cash and NPV, a benefit cost ratio over 2, an internal rate of return over 300% and a payback period <1 year. A sensitivity analysis revealed that increased survival rate up to 80% would increase cumulative cash and NPV of small-scale tiger grouper cage culture. Additionally, improved profitability performance was associated with decreasing major production costs, increasing production and price of the product.

Optimisation of larval culture of the mussel Mytilus edulis (L.)

Abstract: The blue mussel Mytilus edulis is a commercially important species whose fishery and culture generally relies on natural spat collection. Hatchery-production could provide an alternative source of seed, enabling reliable expansion of the industry. Mussel spawning and larval rearing trials were carried out to optimise elements of hatchery production. Culturing fertilised eggs at low density (20–200 eggs cm−2) rather than high density (400–720 eggs cm−2) significantly improved the quality of first veliger larvae and differences in this improvement were evident between the eggs from different females (maternal effects). Veliger larval growth at 17 or 21°C was significantly faster than growth at 14°C. Feeding veliger larvae an identical total ration either daily or at 2–3 day intervals did not significantly affect their growth. Different microalgal diets (1: Isochrysis sp. (clone T-ISO), 2: Chaetoceros calcitrans forma pumilus, 3: C. muelleri, 4: mixed Isochrysis sp. (clone T-ISO) and C. calcitrans f. pumilus, and 5: mixed Isochrysis sp. (clone T-ISO) and C. muelleri) were tested on veliger larval growth and mixed diets outperformed single-species diets.

Dietary total phosphorus requirement of juvenile yellow catfish Pelteobagrus fulvidraco.

Abstract: The present experiment was conducted to determine the dietary total phosphorus requirement of juvenile yellow catfish Pelteobagrus fulvidraco. Six diets with increasing dietary phosphorus concentration (0.43, 0.55, 0.78, 0.90, 1.05 and 1.18% of dry matter, respectively) were fed to triplicate groups of 20 fish each (mean initial body weight, 2.68 ± 0.08 g, mean ± SD) to apparent satiation for 7 weeks. Weight gain and specific growth rate (SGR) increased with increasing dietary phosphorus level from 0.43 to 0.90% and then declined over dietary phosphorus level of 0.90% (P 0.05). Vertebrae phosphorus content increased with dietary phosphorus level from 0.43 to 0.78% (P 0.05). Dietary phosphorus level significantly influenced condition factor, viscerosomatic index and hepatosomatic index (P < 0.05). The relationship between SGR and whole body ash content against dietary phosphorus levels could be expressed as a second-order polynomial equation and the points of 0.89 and 0.85% were considered to be the optimal dietary total phosphorus level, respectively. Based on broken-line analysis of vertebrae phosphorus content, the minimal dietary total phosphorus requirements for maintaining maximum phosphorus storages were estimated to be 0.76% phosphorus.

Effect of triploidization on juvenile African catfish (Clarias gariepinus)

Abstract: Triploid African catfish (Clarias gariepinus) produced through cold shock 3 min post fertilization were compared to diploid offspring of the same parentage at 66 days of age. Triploid fish were significantly shorter (11%) and weighed less (18%) than diploids but showed no significant difference in mortality or cannibalism, which can be an important source of losses under aquaculture conditions. Erythrocytes of triploid fish were more oval shaped than the normal spherical shape of diploid erythrocytes, were significantly larger (38%) and had nuclei that were significantly larger (25%) than observed in diploid fish. Erythrocyte morphological characteristics show potential as an indicator for the detection of triploidy in African catfish.

Effects of dietary l-carnitine and chromium picolinate supplementations on performance and some serum parameters in rainbow trout (Oncorhynchus mykiss)

Abstract: An experiment was conducted to determine the effects of supplemental dietary l-carnitine, chromium picolinate (Cr-Pic) and their combination on growth performance and serum total protein, cholesterol, triglyceride and glucose of rainbow trout (Oncorhynchus mykiss) A total of 276 rainbow trout were randomly allocated to four groups Fish (average initial body weight = 151 ± 169 g) were fed a basal diet without supplemental l-carnitine and chromium picolinate in the control group The basal diet was supplemented with either 500 mg/kg l-carnitine, 16 mg/kg chromium picolinate or 500 mg/kg l-carnitine plus 16 mg/kg chromium picolinate for experimental groups 1 (C), 2 (Cr-Pic) and 3 (C + Cr-Pic), respectively Fish were fed twice a day to apparent satiation for 58 days Weight gain, growth rate, feed consumption and feed conversion ratio (feed/gain) were calculated for the whole period At the end of the study, six fish were chosen randomly from each tank to represent the experiment and frozen at −20°C for subsequent dorsal muscle analysis The results showed no significant differences in final body weight, weight gain or feed conversion ratio among groups There were also no significant differences in serum total protein, cholesterol, triglyceride or glucose concentrations among groups Significantly higher lipid concentration of dorsal muscle was observed in experimental groups 1 and 3 In conclusion, supplemental dietary l-carnitine, chromium picolinate and their combination have no beneficial effects on improving growth performance and feed conversion ratio in rainbow trout However, dietary l-carnitine slightly increased lipid concentration in dorsal muscle of rainbow trout

Development and distribution of the non-indigenous Pacific oyster ( Crassostrea gigas ) in the Dutch Wadden Sea

Abstract: Pacific oysters (Crassostrea gigas) were first observed in the Dutch Wadden Sea near Texel in 1983. The population increased slowly in the beginning but grew exponentially from the mid-1990s onwards, although now some stabilisation seems to be occurring. They occur on a variety of substrates such as mussel beds (Mytilus edulis), shell banks, dikes and poles. After initial settlement spat may fall on older individuals and congregate to dense clumps and subsequently form reefs. Individual Pacific oysters grow 3–4 cm long in their first year and 2–3 cm in their second year. Many mussel beds (Mytilus edulis) are slowly taken over by Pacific oysters, but there are also several reports of mussel spat settling on Pacific oyster reefs. This might in the end result in combined reefs. Successful Pacific oyster spat fall seems to be related to high summer temperatures, but also after mild summers much spat can be found on old (Pacific oyster) shells. Predation is of limited importance. Mortality factors are unknown, but every now and then unexplained mass mortality occurs. The gradual spread of the Pacific oyster in the Dutch Wadden Sea is documented in the first instance based on historical and anecdotal information. At the start of the more in-depth investigation in 2002, Pacific oysters of all size classes were already present near Texel. Near Ameland the development could be followed from the first observed settlement. On dense reefs each square metre may contain more than 500 adult Pacific oysters, weighing more than 100 kg per m² fresh weight.

From fright to anticipation: using aversive light stimuli to investigate reward conditioning in large groups of Atlantic salmon ( Salmo salar )

Abstract: In this study, we demonstrate how an event that is initially frightening to Atlantic salmon is turned to a positive stimulus through habituation and associative learning. The study was carried out in four commercial sized tanks (5 m3) with near industry densities (>550 fish, 16 kg m−3), using a delay conditioning procedure with an aversive flashing light as the conditioned stimulus and food reward as the unconditioned stimulus. By using video image analysis of the distribution of the fish in the tanks, the changes in behaviour from trial to trial could be documented in great detail. The current study documents the change in behaviour across the individual conditioning trials, clearly showing the step-by-step nature of the transition. The salmon needed more than 26 trials to become fully habituated to the flashing light but showed clear anticipatory behaviour already after about 19 trials. This demonstrates that the learning process is a combination of habituation and associative learning.

Stocking density for the intensive rearing of juvenile crayfish, Pacifastacus leniusculus (Astacidae), using Artemia nauplii to supplement a dry diet from the onset of exogenous feeding

Abstract: Recent advances in intensive rearing of astacid juvenile crayfish have greatly improved the results. This challenges the current application possibilities of the studies performed previously, and new research on density is required. A 100-day experiment was carried out under controlled conditions to evaluate density effects on survival and growth rates of juvenile crayfish in optimal conditions of feeding. Juvenile stage 2 Pacifastacus leniusculus were stocked in fibreglass tanks (1 m2, 200 l water) at 20 ± 1°C and fed a dry diet for salmonids supplemented with restricted amounts of Artemia nauplii. Stocking densities were 100, 300, 600 and 1,000 crayfish m−2. Mean survival rate was reduced significantly with increased stocking density, ranging from 86.33% (100 m−2) to 39.13% (1,000 m−2). All checks showed that at the lowest initial density (100 m−2) animals grew significantly faster those at higher densities, recording a final carapace length of 15.28 mm and weight of 1.08 g. Among the treatments of 300, 600 and 1,000 m−2 no differences were found either in carapace length or in weight throughout the experimental period, with a final mean growth of 14 mm carapace length and 0.72 g weight. The final proportion of animals with chelae autotomy rose significantly with increasing stocking density, ranging from 14.44% (100 m−2) to 41.45% (1,000 m−2). This study shows that diet is a decisive factor for stocking successfully high densities under controlled conditions and provides useful information to set adequate densities in accordance with the production objectives.

Fuzzy-logic-based feeder system for intensive tilapia production (Oreochromis niloticus)

Abstract: In high-fish-density aquaculture systems, tilapia producers are compelled to provide 100% of food required to obtain profitable growth rates. It is well known that fish have a low food conversion rate and feeding represents the most important expenditure, approximately 40% of total production cost. Therefore, precise quantities of food should be provided to avoid water pollution and economic losses due to food waste when water conditions are inadequate for fish feeding. A way to control food provisions in this work was determined by the conditions of temperature, dissolved oxygen, fish age, and body weight, since these variables have a direct effect on fish metabolism and growth. Thus, a change in metabolism is reflected in a modification of energy requirements and, as a consequence, in variations of food consumption. In this work, a new feeder with fuzzy-logic control algorithms is proposed for fish feeding; this technique allows farmer knowledge to be taken into account in a series of if–then-type rules. To define these rules the temperature and dissolve oxygen were considered in order to provide precise food quantities. The results show minimal differences in growth (P > 0.05) between treatments, important food saving of 29.12% (equivalent to 105.3 kg), and lower water pollution (reduced water dissolved solids and ammonium components) compared with timed feeders. This system provides an important contribution to sustainability of intensive aquaculture systems, increasing productivity and profitability, and optimizing water use.

Growth and fatty acid composition of Octopus vulgaris paralarvae fed with enriched Artemia or co-fed with an inert diet

Abstract: The rearing of Octopus vulgaris paralarvae during its planktonic life stage is a major challenge, as mortality is currently very high and unpredictable. In this study, we examined the survival and growth rates, as well as the fatty acid composition, of O. vulgaris paralarvae fed on three different dietary treatments: group ArDHA was offered juvenile Artemia enriched with a lipid emulsion (Easy DHA-Selco®); group ArMA was fed with juvenile Artemia enriched with a mixture of microalgae (Rhodomonas lens and Isochrysis galbana); and group ArMA+ID received the same Artemia as group ArMA complemented with an inert diet. Dietary treatments were tested in triplicate with homogenous groups of paralarvae (25 individuals l−1) established in 50-l tanks, and the experiment was conducted for 15 days. The survival rate of 15-day post-hatch (-dph) paralarvae from groups ArMA (20 ± 8%) and ArMA+ID (17 ± 4%) tended to be higher than in group ArDHA (13 ± 5%), though these differences were not statistically different. The dry weight (DW) of 15-dph paralarvae increased by almost 60% in groups ArMA and ArMA+ID, and nearly 40% in group ArDHA, with respect to hatchlings. The fatty acid (FA) composition of paralarvae revealed a remarkable drop of docosahexaenoic acid (22:6n-3, DHA) from hatchlings to 15-dph paralarvae of all groups (P < 0.05). However, paralarvae from group ArDHA contained higher levels of DHA than those from ArMA and ArMA+ID (P < 0.05). Despite Artemia enriched with DHA-Selco® contained three-times more DHA than Artemia enriched with microalgae, no beneficial effects of this dietary treatment were observed on the performance of paralarvae.

Optimum ration level for better growth, conversion efficiencies and body composition of fingerling Heteropneustes fossilis (Bloch)

Abstract: The effects of ration levels on growth, conversion efficiencies and body composition of fingerling Heteropneustes fossilis (6.8 ± 0.04 cm, 5.0 ± 0.02 g) were studied by feeding isonitrogenous (40% crude protein) and isocaloric (19.06 MJ kg−1 gross energy) diets representing 1, 3, 5, 7 and 9% of the body weight (BW) day−1 to triplicate groups of fish . Growth performance of the fish fed at the various ration levels was evaluated on the basis of live weight gain percentage (LWG%), feed conversion ratio (FCR), specific growth rate percentage (SGR%), protein retention efficiency (PRE%) and energy retention efficiency (ERE%) data. Maximum LWG% and SGR were obtained at a feeding rate of 7% BW day−1, whereas best FCR (1.6), PRE% and ERE% were recorded at a feeding rate of 5% BW day−1. Maximum body protein was also obtained for the group receiving the diet representing 5% of their body weight. However, a linear increase in fat content was noted with the increase in ration levels up to 7% BW day−1. The SGR, FCR, PRE and ERE data were also analyzed using second-degree polynomial regression analysis to obtain more precise information on ration level, with the results showing that the optimal ration for these parameters was 6.8, 6.1, 5.9 and 6.2% BW day−1, respectively. Based on the above second-degree polynomial regression analysis, the optimum ration level for better growth, conversion efficiencies and body composition of fingerling H. fossilis was found to be in the range of 5.9–6.8% of the BW day−1, corresponding to 2.36–2.72 g protein and 88.20–101.66 MJ digestible energy kg−1 diet day−1.

Effect of dietary protein reduction with synthetic amino acids supplementation on growth performance, digestibility, and body composition of juvenile Pacific white shrimp, Litopenaeus vannamei

Abstract: Two experiments were conducted to evaluate the effect of lowering crude protein level and fish-meal inclusion rate by using commercially available synthetic amino acid supplements in practical diets on the growth performance of Litopenaeus vannamei. In experiment 1, three diets were formulated to assess whether 50% of fish meal could be replaced by soybean meal with synthetic amino acid supplementation. Diet 1 was formulated as the normal control with 20% fish meal and 36% crude protein; diet 2 was the negative control with 34% crude protein and half of the fish meal was replaced with soybean meal; and diet 3 was similar to diet 2 but was supplemented with amino acids to ensure the level of lysine, methionine plus cystine, and threonine similar to that in the diet 1. After a 70-day feeding trial, weight gain and specific growth rate of shrimps fed diet 2 were significantly lower than those fed diet 3, and numerically lower than those fed diet 1. Feed intake of shrimps fed diet 3 was significantly higher than those fed diets 1 and 2. There were no significant differences in feed conversion ratio among shrimps fed different diets. In experiment 2, four diets were prepared with diet 1 as the normal control with 41.26% crude protein, diets 2–4 were formulated to contain 39.81, 38.40, and 35.52% of crude protein with synthetic amino acids were added to simulate the amino acid levels of the diet 1. After a 70-day feeding trial, it was found that reducing dietary crude protein from 41.26 to 35.52% did not affect weight gain or feed conversion ratio. The survival of crude protein 35.52% treatment was significantly lower than other treatments. No difference was observed in body protein, lipid composition, and apparent digestibility coefficient among dietary treatments. Results of this study suggested that dietary crude protein could be reduced from 41.26 to 35.52% in the diets of L. vannamei as long as synthetic amino acids were supplemented.

Application of synthetic hormone LHRH-A2 on the artificial propagation of Persian sturgeon Acipenser persicus.

Abstract: For studying the effect of LHRH-A2 hormone on the induction of final maturation and ovulation of Persian sturgeon, 71 matured females and 20 matured males were used. Five groups of breeders were injected with sturgeon pituitary gland hormone (50 mg per fish) and LHRH-A2 in dosages of 3.5, 7, 8 and 10 μg kg−1 for females and 3 and 5 μg kg−1 for males. Results showed that LHRH-A2 successfully induced final maturation and ovulation in females, and there was no significant difference between five groups of breeders in ovulation proportion, fertilization rate, survival rate of incubation, survival of yolk-sac absorption period and active feeding period of larvae. It can be concluded that the LHRH-A2 is a proper alternative for pituitary gland hormone in artificial propagation of Persian sturgeon.

Effect of refeeding on the growth and digestive enzyme activities of Fenneropenaeus chinensis juveniles exposed to different periods of food deprivation

Abstract: The changes in the specific growth rate (SGR), feed intake (FI), feed conversion efficiency (FCE), and digestive enzyme activities (protease, amylase, and lipase in the hepatopancreas) of Fenneropenaeus chinensis juveniles (0.753 ± 0.041 g, wet weight) exposed to different periods of food deprivation were investigated during the period of refeeding in a controlled laboratory experiment. The starvation-refeeding cycles consisted of the following seven regimes of 24-day duration: satiate feeding (control, SC); no feeding for 4 (S4), 8 (S8), 12 (S12), 16 (S16), 20 (S20), and 24 (S24) days; then feeding to apparent satiation for the next 20, 16, 12, 8, 4, and 0 days, respectively. The various starvation-refeeding cycles have significant influences on the growth of the test shrimps. The SGR of the shrimps exposed to S4 and S8 treatments exceeded the controls, and no significant differences in SGR (P > 0.05) were found between the SC and S12 or S16 treatments at the end of the refeeding. These changes may have resulted from the significant increase in FI and FCE. The protease activities of test shrimps exposed to different periods of food deprivation were significantly lower (P < 0.05) than those of shrimps under SC treatment at the end of food deprivation then showed a tendency to rapidly increase during refeeding. However, nearly the exact opposite occurred for amylase activities and lipase activities. Lipid and carbohydrate reserves in the hepatopancreas are preferentially mobilized with protein-sparing effect at the beginning of food deprivation. Proteins are the main nutritional store during the refeeding. The findings of the research will be beneficial in the design of feeding regimes and will improve our knowledge on some aspects of the nutrition physiology of F. chinensis related to their biology.

Influence of natural diet on growth and biochemical composition of Octopus vulgaris Cuvier, 1797

Abstract: The influence of diet on growth and biochemical composition of cultured Octopus vulgaris was investigated. Octopuses were reared in a open recirculation seawater system and during the experiment were kept apart in cages. Experiment lasted 30 days. Three experimental dietary groups were established: group I (mixed diet: Carcinus mediterraneus, Boops boops and Mytilus galloprovincialis), group II (monodiet on B. boops) and group III (monodiet on M. galloprovincialis). The best results were obtained with the monodiet based on bogue that gave a weight gain of 390.65 ± 37.54, an absolute growth rate of 13.02 g day−1 and feed efficiency of 44.79 ± 0.96%. Regarding to biochemical composition, the mussel-fed and bogue-fed groups showed the highest protein content. Animals fed on bogue also showed the highest carbohydrate content, while the lowest value was observed in the mussels-fed group. The lipid content was found to be very low in all dietary groups. Saturated fatty acids were the most abundant fatty acid class, ranging from 58.22% in wild octopuses to 46.83% in bogues-fed octopuses. Polyunsaturated fatty acids (PUFAs) were the second most abundant fatty acids class in all dietary treatments (25.65–37.00% as a per cent of total FAs) except in octopuses fed with mussels. MUFAs ranged from 11.44 to 26.93% of total FAs. Although it is empirically known that a varied diet better covers the nutritional requirements than a monodiet, the results of this study reveal that a monodiet of B. boops may be used.

Lack of essential fatty acids in live feed during larval and post-larval rearing: effect on the performance of juvenile Solea senegalensis

Abstract: Despite the large progress obtained in recent years, Senegalese sole (Solea senegalensis) production of high quality juveniles is still a bottleneck. This paper examines the effect of larval and post-larval lipid nutrition on juvenile performance and quality. Four dietary treatments were tested: A—enriched Artemia spp. (EA); B—non-enriched Artemia spp. (NEA); C—EA during the pelagic larval period and NEA after larval settlement; D—50% EA and 50% NEA. Juvenile fatty acid profile at 60 days after hatching (DAH) clearly reflected the larval and post-larval diet composition. Feeding sole larvae on NEA (poor in lipids and essential fatty acids-EFA) had a negative effect, reducing growth (total length and dry weight) after 30 DAH and decreasing digestive enzyme activity at the end of the rearing period (60 DAH). However, relatively good performance compared to the EFA-richest treatment (A) was obtained when larvae were fed 50% EA and 50% NEA (D) or even EA only during the pelagic larval period followed by NEA after larval settlement (C). Malpigmentation was not affected by the dietary regimes and its incidence was very low. However, skeletal deformities were prevalent, particularly in the caudal complex, independently of diet. The results confirm that Senegalese sole appear to have lower larval EFA requirements than most cultured marine species and potentially even lower requirements during the post-larval stage. The importance of studying the impact of early nutrition on later juvenile stages was clearly highlighted in this study.

Sex reversal and growth performance in juvenile females of the freshwater crayfish Cherax quadricarinatus (Parastacidae): effect of increasing temperature and androgenic gland extract in the diet

Abstract: Monosex male culture of C. quadricarinatus is proposed for increasing yields because males reach a larger size at harvest than females. An experiment was done to evaluate the effects of androgenic gland extract and temperature on sex reversal and somatic growth in early juvenile females. Females were exposed to the following experimental conditions: C: control food and temperature maintained at 26 ± 1°C; HT (high temperature): control food and temperature maintained at 28.5 ± 1°C; VHT (very high temperature): control food and temperature maintained at 31 ± 1°C; AG: food with enriched with androgenic gland (1/10 dose for each juvenile per day) and temperature maintained at (26 ± 1)°C. The juveniles were weighed, sexed, and growth increment (GI) and growth rate (GR) were calculated twice a month. The HT and AG groups differed from the C group in GI and GR indicating a greater somatic growth. At the end of the experiment, the HT and AG groups had similar weight but only the HT group had enhanced oocyte diameter, with some vitellogenic oocytes compared to the C group. In the HT group, there was significant sex reversal, as indicated by development of male and intersex male characteristics in different individuals. Both temperature and AG diet have a high potential for culture of this species because of their enhancement of somatic growth; higher temperature increases the proportion of males, a desirable characteristic of cultured populations.

Effect of VP28 DNA vaccine on white spot syndrome virus in Litopenaeus vannamei

Abstract: White spot syndrome virus (WSSV) occurs worldwide and causes high mortality and considerable economic damage to the shrimp farming industry. Considering the global environmental, the economic and sociological importance of shrimp farming, and the constraints of high intensity cultivation, development of novel control measures against the outbreak of WSSV become inevitable. In this study, we have explored the protective efficacy of DNA vaccination and tissue distribution of the recombinant plasmid in immunized Litopenaeus vannamei. The VP28 gene was cloned in the eukaryotic expression vector pVAX1, and the construct vector was named as lpv28. The protective effect of lpv28 against WSSV was evaluated in L. vannamei by injecting lpv28 construct and later challenging with WSSV. Expression of these proteins from the recombinant plasmids was confirmed in vitro by RT-PCR and Western blot analysis. The result of vaccination trials showed that a survival rate in shrimp vaccinated with lpv28 was 52.5% at most compared to control groups (100% mortality). The immunological parameters analyzed in the vaccinated and control groups showed that the vaccinated groups owned a high level of lysozyme, alkaline phosphatase, and total superoxide dismutase when compared to the control group. Furthermore, protein expression analysis indicated that VP28 can be detected in gill, muscle and head soft tissue of the shrimps in the immunized group after 14th day injection. Thus, the result indicated that DNA vaccination strategy has a potential utility against WSSV.

Effect of altering linoleic acid and linolenic acid dietary levels and ratios on the performance and tissue fatty acid profiles of Nile tilapia Oreochromis niloticus fry

Abstract: This experiment was conducted to study the effect of altering the linoleic acid (LA) and linolenic acid (LNA) levels and ratios in the diet of Nile tilapia (Oreochromis niloticus) on fry performance. Twelve diets were formulated to be isonitrogenous, isocaloric, and differed only in their main lipid source. An oil rich in n-3 fatty acids [linseed oil (L)] and two oils rich in n-6 fatty acids [soybean oil (S) and corn oil (C)] were added at 6% of the basal diet either separately or in equal combinations (L1:S1 or L1:C1 or S1:C1) or at ratio 2:1 (L2:S1 or L2:C1 or C2:L1 or C2:S1 or S2:L1 or S2:C1). The fish were fed twice daily (09 and 16 h) to apparent satiation throughout the duration of the trial (16 weeks). Survival rates increased in a linear pattern with increasing the LA level in the diets (R2 = 0.764). Final body weight was significantly higher in fish fed S, S2:L1, and L2:C1 diets, being 14.29, 14.14, and 14.09 g/fish, respectively. However, tilapia fed C, S1:C1, and C2:S1 diets exhibited low final body weight (11.41, 11.60, and 11.76 g/fish, respectively). The final body weight was negatively affected by increasing the LA/LNA ratios (R2 = 0.647). Either LA or arachidonic acid (%) in the whole body of fish increased in a linear patterns (R2 = 0.641 and 0.746, respectively) with increasing dietary LA. Besides, LNA, eicosapentaenoic, acid and docosahexaenoic acid (%) in the whole body increased in a linear pattern (R2 = 0.777, 0.501, and 0.8148, respectively) the increasing dietary LNA level. The present study indicated that LA/LNA ratio less than 13 is recommended for nutrition of tilapia fry.

Modelling the biomass yield and the impact of seabream mariculture in the Adriatic and Tyrrhenian Seas (Italy)

Abstract: An individual-based model for Sparus aurata was developed, taking into account the effects on the growth rate of water temperature, food availability and diet composition. The model was identified on the basis of the recent literature regarding the physiological ecology of this species. It was subsequently calibrated and validated by using original field data collected at two Italian fish farms located, respectively, in the Adriatic and Tyrrhenian Seas. The mass budget of uneaten food and faeces was computed using the model at each farm: the optimal ingestion rate of a fish was computed based on its wet weight and the temperature of the water, while the faeces estimation considered the different digestibility of lipids, carbohydrates and proteins in the diet. From an applied perspective, the future use of this growth model in relation to mariculture site selection and monitoring might typically be to estimate both the yield and the amount of uneaten food and faeces discharged from a fish cage. This second output represents a useful input for deposition models which are routinely used in the field of mariculture monitoring by different EU countries. The integration of growth and deposition models in a single system could provide a useful tool for the site-selection and monitoring of finfish mariculture operations in Mediterranean environments.

Growth and feed utilization of gilthead sea bream (Sparus aurata, L.) fed to satiation and restrictively at increasing dietary energy levels

Abstract: Three isoproteic (47% protein) diets were formulated to contain graded levels of crude fat (diet D16:16%, diet D24: 24% and diet D32: 32%). Each diet was fed to satiation in three and to 80% satiation in two replicate groups of gilthead sea bream (Sparus aurata), having an initial body weight of 72–74 g. The trial lasted 81 days. Groups fed to satiation showed higher final body weight (FBW; 238.8–252.3 g vs. 218.0–229.3 g) and daily growth index (DGI; 2.49–2.65%/day vs. 2.27–2.34%/day) than those fed to 80% satiation. Feed intake was significantly different both for feeding level and for diet composition. Fish fed to satiation had higher feed conversion rate (FCR) compared to the 80% satiation groups (1.33–1.44 vs. 1.13–1.17; P ≤ 0.001). Within satiation groups, FCR was significantly lower in fish fed D16 compared to fish fed D32 (1.33 vs. 1.44, P ≤ 0.05), whereas no statistical differences were found within the 80% satiation groups. The increase in dietary lipid level did not improve growth performance, feed efficiency and protein utilization but decreased gross lipid efficiency. Conversely, a reduction in ration from satiation to 80% satiation decreased DGI, thus improving FCR. Feed costs were influenced by dietary energy level and feeding ratio, the lowest energy diet at 80% satiation being the most profitable combination among the variables.

Some clinical, microbiological and molecular characteristics of Aeromonas hydrophila isolated from various naturally infected fishes

Abstract: Heat-stable cytotonic enterotoxin gene (Ast) was detected by polymerase chain reaction (PCR) of twenty isolates of Aeromonas hydrophila isolated from various naturally infected fishes collected from both fresh and brackish water These fishes were Nile tilapia and meagre, mullet and sea bream, respectively Antibiotic susceptibility, pathogenic characteristics of these isolates and histopathological alterations of liver from experimentally infected tilapia fish with A hydrophila which contained Ast gene were investigated PCR technique for the detection of Ast as specific gene for Ahydrophila genomes showed that 90% of tested A hydrophila (18/20) contained Ast gene, which is specific for A hydrophila(SSU)The in vitro susceptibility of 18 strains of A hydrophila (SSU) to 9 antibiotics was evaluated Oxytetracycline only was an effective antibiotic for all tested isolates On contrast, all these isolates were resistant to amoxicillin, ampicillin and penicillin Pathogenicity assay in this study proved that 333% of the tested A hydrophila (6/18) were pathogenic for tilapia in vitro with various levels of virulence where 2/6 were classified as strongly virulent according to the severity of mortality rate Microscopically, A hydrophila toxins apparently cause irreparable systemic damage to liver which leads to death