Aquaculture Research最新文献

The study aimed to investigate body parameters and the process of spermatogenesis from April to September. In addition, it sought to test the applicability of sperm cryopreservation for conservation purposes in a razorfish (Pelecus cultratus) population of Lake Balaton, the largest shallow lake in Central Europe. During the aforementioned period, measurements were taken for the standard length (SL, cm) and body weight (BW, g), and the sex of specimens was determined. Cells at different stages of spermatogenesis (spermatogonia-SG, spermatocytes-SC, spermatids-ST, and spermatozoa-SZ) were quantified monthly for each male sample. Sperm samples collected at the end of May were cryopreserved using a method designed for common carp. No significant differences were found between males (SL: 25 ± 2 cm and BW: 146 ± 38 g) and females (SL: 26 ± 3 cm and BW: 168 ± 53 g) in terms of measured body parameters. No significant correlations were found between the sex, SL, and BW. High standard deviations were observed for all mean values in all sampling periods, possibly due to the low number of individual samples per month. A significantly higher proportion of SC compared to SZ was found in April. In May, no differences were observed between the four groups. Significantly more SG and SZ than SC and ST were observed in June. In August and September, a slight dominance in the number of SG was recorded, with no differences measured among the cells in different developmental stages. The males studied exhibited a low gonadosomatic index (0.92% ± 0.27%). A significant reduction was recorded in motility (MOT), progressive motility (pMOT), and in most of the kinetic parameters (distance curved line-DCL, curvilinear velocity-VCL, straight line velocity-VSL, and beat cross frequency-BCF). The spermiation of males could have started in May and conceivably lasted until the end of June. It is recommended to increase sperm quality and quantity before cryopreservation.

To reduce the negative impact of fish oil substitutes on the fatty acid composition of farmed fish, this experiment utilized different types of oils as dietary lipid sources for GIFT tilapia. Tilapia oil (FO) was used as the control, along with corn oil (CO), linseed oil (LO), algae oil (AO), and a mixture of linseed oil and algae oil in various ratios of 1 : 2, 1 : 1, and 2 : 1 (LA12, LA11, and LA21) to reshape the fatty acid profile of GIFT tilapia (0.205 ± 0.005 g) in the muscle. The weight gain and specific growth rate of tilapia in the LO and control groups were significantly higher than in other treatments (P < 0.05). Meanwhile, despite the AO group exhibited the highest docosahexaenoic acid (DHA) content (P < 0.05), it also exhibited the highest levels of malondialdehyde content and superoxide dismutase activity (P < 0.05). The mRNA expression levels of Δ6/Δ5 fatty acyl desaturase 2 (Δ6/Δ5FADs2), Δ4 fatty acyl desaturase 2 (Δ4FADs2), acetyl-CoA carboxylase α (ACCα), and elongase of very long chain fatty acids 5 (ELOVL5) in the hepatopancreas of LO group were exhibited a significant upregulation compared to the control (P < 0.05). The synthesis of DHA and eicosapentaenoic acid (EPA) in the muscles of LA12, LA11, and LA21 groups increased as the proportion of DHA decreased in the diets. In conclusion, the edible value of fatty acids of tilapia muscle, especially n-3 long-chain polyunsaturated fatty acids, can be significantly improved by adjusting the oil source in the diet through lipid metabolism.

This research aimed to evaluate the impact of hydrolyzable tannin on immune responses, intestinal morphology, and resistance to Vibrio alginolyticus in whiteleg shrimp (Penaeus vannamei). In preliminary in vitro experiments, shrimp hemocytes were exposed to different concentrations of hydrolyzable tannin. The findings indicated that hydrolyzable tannin exhibited nontoxic characteristics and could stimulate respiratory burst activity. For the subsequent in vivo trial, shrimp (11.83 ± 0.98 g) were subjected to a 28-day oral administration of diets containing diverse hydrolyzable tannin concentrations (0, 1, 2, 4, and 8 g/kg denoted as control, T1, T2, T4, and T8, respectively). Immune parameters, antimicrobial peptide genes, and intestinal morphology were measured. Significant enhancements were observed in total hemocyte count (THC), phagocytic activity, respiratory burst activity, and phenoloxidase activity (PO) across all treatment groups compared to the control group, particularly in T2 and T4 groups (p < 0.05). The gene expressions of Penaeidin-2, Penaeidin-3, Penaeidin-4, crustin, and lysozyme were markedly higher in the treatment groups, especially in T2 (p < 0.05). Additionally, hydrolyzable tannin contributed to increased intestinal wall thickness after the 28-day feeding trial (p  < 0.05). In a separate challenge experiment, shrimps (11.36 ± 0.66 g) were exposed to V. alginolyticus after 7 days of culture. Notably, T2 and T4 exhibited enhanced resistance, resulting in survival rates of 66.67% and 69.70%, respectively. To conclude, administering 4 g of hydrolyzable tannin per kilogram of feed proved effective in enhancing nonspecific immune responses, improving intestinal morphology, and augmenting resistance to V. alginolyticus in whiteleg shrimp.

Brachionus plicatilis is considered an indispensable first live feed for many fish and crustacean larvae; the demand for the species has increased globally. The mass production of the rotifer involves quality microalga and a standard diet; this culture is expensive and needs a skilled workforce. The hatchery’s incubators are likely to have limited resources leading to sudden rotifer culture crashes that ultimately disrupt the larvae production. More recently, improved sustainable rotifer production has been achieved through biofloc technology (BFT) that uses fish wastes and wheat flour. However, various carbon sources, which are typically used in BFT-based systems need to be explored and tested for their efficacies. A 4-day rotifer, B. plicatilis batch culture, was conducted in BFT systems by adding four carbon sources: molasses, rice bran, maize starch, and palm kernel expeller versus a control (without any carbon source). Fifteen 125 L containing polyethylene tanks with a water volume of 100 L were used for this experiment, and each tank was stocked with 5 × 10⁶ rotifer (50 rotifers mL⁻¹). Different carbon sources in triplicates including a control were tested as treatments. The carbon : nitrogen ratio in the study was maintained at 10 : 1. The rotifers were fed with Baker’s yeast at 1.0, 0.50, and 0.25 g million^-−1 rotifers for the first, second, and third day and continued after that. Total ammonia–nitrogen (TAN) and pH values were found to be significantly (p < 0.05) lower in all four treatments of the BFT system than in the control. Significantly higher (p < 0.05) settleable solids were obtained in the molasses and rice bran treatments than those in the maize starch or palm kernel expeller. Likewise, the significantly (p < 0.05) higher density of B. plicatilis and their specific growth rate were obtained in the molasses and rice bran-adding treatments, followed by those in palm kernel expeller, maize starch, and the control. This study indicates that molasses and rice bran as carbon sources when added to BFT-based systems enhance B. plicatilis production.

Global interest in using duckweed (Lemna minor) as a substitute for fish, livestock, and human diets has spurred research on the mass culture of the species. There is a scarcity of information on the L. minor fatty acid composition in different aquaculture settings. A comparative study was carried out to investigate the fatty acid composition of L. minor cultured in indoor plastic tanks and outdoor earthen ponds for 30 days. During the culture period, culture facilities were fertilized using livestock manure. Fatty acid characterization was done using gas chromatography method. Fifteen fatty acids: five saturated (SAFAs), five monounsaturated (MUFAS), and five polyunsaturated (PUFAs) were identified. Fatty acid compositions varied between indoor and outdoor settings. Percentage composition of L. minor PUFAs cultured outdoor (37.13) was higher than that of indoor (21.96) settings. L. minor SAFAs percentage composition was higher in the indoor culture at 41.63% while that of outdoor was 33.75%. The composition of L. minor MUFAs in indoor tanks was higher (36.32%) than in outdoor earthen ponds (29.10%). This study indicated the presence of docosahexaenoic, eicosapentaenoic, linoelaidic, and eicosanoic acids in L. minor seldom reported in past studies. Paired Students’ t-test indicated that the means of the fatty acid composition were significantly different (p < 0.05) in both settings, with docosahexaenoic showing the highest paired mean difference.

Biofloc technology (BFT) is one of the most sustainable aquaculture system, which is based on the principle of nutrient recycling and addition of carbon to enable heterotrophic microorganisms to the system. To evaluate the performance of the biofloc culture system for Cyprinus carpio fingerlings, a 60-day growth trial was conducted. The fingerlings (n = 600) of average body weight (4.92 g ± 0.14) were stocked in 12 circular fiberglass tanks (300 L, volume 10.59 cft) to form three biofloc treatments (T1, T2, and T3) along with one control group. The carbon sources for treatments were sugarcane molasses, tapioca, and wheat. The C/N ratio of 15 was maintained for all treatments. After 60 days of rearing, the fish were challenged with Aeromonas hydrophila, and the relative percentage survival (RPS) was observed over 14 days. A haematological, nonspecific immune, and stress parameters were analyzed using blood and serum samples collected at intervals of 20, 40, and 60 days. According to the results, the carbon sources affected the water quality parameters but were still adequate for fish welfare. An increased biofloc volume was observed with tapioca. Growth performance and better feed conversion ratio were recorded in biofloc with the tapioca group. The hematological parameters, including haemoglobin (Hb), hematocrit (HCT), white blood cells and lymphocytes were significantly (P  < 0.05) higher in biofloc-based tapioca group than in other treatments and control. Further, the serum protein, globulin, albumin, total immunoglobulin, and respiratory burst activity were also found significantly (P  < 0.05) higher in biofloc with tapioca as carbon source. However, the lysozyme activity was higher in biofloc with the wheat group. The RPS in tapioca was significantly higher, followed by biofloc with wheat. In conclusion, the tapioca-based biofloc can improve C. carpio growth, haematology, and nonspecific immune response under zero water exchange.

Replicated studies are advantageous for optimizing larval rearing of the Eastern oyster (Crassostrea virginica) and increasing the availability of high-quality seed for the continued expansion of the U.S. oyster aquaculture industry. Although small-scale systems using live algal feeds have been used successfully, rearing larvae on algae concentrate presents additional challenges. To determine the feasibility of rearing oyster larvae in small-scale systems using algae concentrate, oyster larvae were raised for 2 weeks in replicate control (1,000 L) and microcosm (17 L) tanks. Five aeration strategies were tested in the microcosms in two separate trials. Results of this study indicate similar survival in small systems compared to controls through the appearance of eyed larvae. Accumulated algae and pink biofilm formation in microcosms using polyvinyl chloride (PVC) airlifts suggest that this aeration strategy is undesirable. One- and 5-mL air injectors maintained higher overnight oxygen levels than controls. The recovery of more eyed larvae after 14 dpf in control systems may be the result of significant temperature fluctuations in microcosms. Overall, this study demonstrates that algae concentrate can be used to rear oyster larvae in small-scale systems, providing a live feed alternative that saves space and labor in replicated studies.

Conservation aquaculture provides a means for promoting environmental stewardship, useful both in the context of restoring native species and limiting the production of invasive species. Aquaculture of lampreys is a relatively recent endeavor aimed primarily at producing animals to support the restoration of declining native populations. However, in the Laurentian Great Lakes, where sea lamprey Petromyzon marinus are invasive, the ability to acquire a reliable source of certain life stages would be a significant benefit to those controlling their populations and studying the species. Here, we apply methodologies developed for Pacific lamprey Entosphenus tridentatus restoration to investigate the feasibility of rearing larval sea lamprey under laboratory conditions. In two experiments lasting 3 and 9 months, we tested the effects of different dietary sources and water temperature (ambient and controlled) on the survival and growth of wild-caught larvae. Rearing conditions had no effect on mortality, as larval survival was 100% in both experiments. Growth was significantly affected by water temperature, with the highest average daily growth rates observed at 22 and 15°C (0.14 mm day⁻¹) and lowest at 8°C (0.06 mm day⁻¹). Diets of yeast alone (0.19 and 0.21 g L⁻¹) performed better than those comprising a mixture of yeast and other material when fed 3 times weekly (rice flour, wheat flour, fish meal; 0.19 and 0.32 g L⁻¹). Averaged across the three constant temperatures (8, 15, and 22°C), larvae fed on yeast grew 0.13 mm day⁻¹ and 0.01 g day⁻¹, whereas on yeast + fish meal, they grew 0.09 mm day⁻¹ and 0.01 g day⁻¹. At ambient temperature (4–20°C), larvae fed on yeast grew 0.15 mm day⁻¹ and 0.01 g day⁻¹, whereas those fed on yeast + wheat flour grew 0.13 mm day⁻¹ and 0.008 g day⁻¹ and those fed on yeast + rice flour grew 0.12 mm day⁻¹ and 0.009 g day⁻¹. An experimental duration of 90 days was sufficient to detect significant changes to larval sea lamprey growth stemming from temperature variation. Overall, rearing of sea lamprey in captivity appears feasible at low density (31–32 g m⁻² and 17–25 larvae m⁻²), but uncertainties remain regarding the most appropriate means of providing adequate feed for these fish in high-density conditions.