Aquaculture Research最新文献

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.

This study investigated the impacts of various inclusion levels of dietary potential of fish protein hydrolysate (FPH) on the growth and reproductive performance, biochemical composition, blood parameters, and liver histology of Ompok pabda broodstock. About 600 pabda broods (11.00 ± 0.05 g) were distributed into 12 cages and fed twice in a day. For this, four experimental diets (crude protein: 30%; crude lipid: 9%) were prepared by incorporating FPH at different percentages (0%, 5%, 7%, and 9%). The FPH positively impacted (p < 0.05) the durability index, water stability, and swelling rates of the experimental diets. Furthermore, significantly higher palatability (p < 0.05) was recorded for pabda diets incorporated with 5% and 7% FPH. After 90 days, the growth performance of pabda in final weight, live weight gain, total biomass, specific growth rate, hepatosomatic index, visceral somatic index, and nutrient utilization indices, feed conversion ratio and protein efficiency ratio, was significantly (p < 0.05) improved when fed with 7% FPH diet. Additionally, the ovipositor diameter (5.10 ± 0.05 mm), spawning response (98.48 ± 2.4%), fecundity (13.28 ± 0.23 × 10⁴ eggs/kg), and egg fertilization rate (87.09% ± 0.14%) were significantly higher (p < 0.05) for the 7% FPH dietary group than other treatments. The fish group that received control diet experienced a marked (p < 0.05) reduction in egg hatching rates, coupled with longer ovulation period as compared to FPH-treated groups. Dietary FPH inclusion at different levels also caused notable improvements (p < 0.05) in most hematological and serum biochemical indices of pabda broodfish. The 7% FPH group also exhibited enhanced liver health, characterized by superior nuclei, erythrocyte, and cytoplasmic structure and boosted the farm economics efficiency. In summary, 7% dietary FPH is suitable and beneficial for O. pabda broodstock development in captivity by improving growth and reproductive performance, overall health, and farm economics.

This study characterized four cholesterol transport-related genes, namely, lcat, acat1, acat2, and mttp, in juvenile tiger puffer in terms of tissue distribution (eye, heart, brain, skin, liver, spleen, muscle, and intestine) and nutritional regulation. Three feeding trials were conducted: (i) using diets with different cholesterol levels (0.11%, 0.65%, 1.10%, 2.32%, and 4.59% of dry matter); (ii) using diets with different lipid levels (8.05%, 12.02%, and 16.36% of dry matter); and (iii) a 1-month starvation experiment with different sampling times (Days 1, 4, 9, 16, and 31). The lcat, acat1, and acat2 were the most abundantly expressed in the liver, while mttp was the most abundantly expressed in the intestine. The lcat had a medium expression level in the muscle and skin but the lowest expression level in the spleen and intestine. The acat1 and acat2 had similar tissue distribution patterns, except that acat2 had a lower expression level in the heart but a higher level in the intestine than acat1. The mttp had medium expression levels in the liver and spleen but had the lowest level in the eye and skin. Different dietary cholesterol levels did not significantly affect the expression of these cholesterol transport genes in the liver and intestine, except that higher cholesterol levels (1.10%–4.59%) significantly downregulated the acat2 expression in the liver. Dietary lipid levels also had a mild influence on the hepatic expression of these genes, except that the diet with 12.02% lipid resulted in significantly higher acat1 expression than the one with 16.36% lipid. The starvation time significantly affected the hepatic expression of these genes. Long-term starvation (16 and 31 days) generally upregulated the hepatic gene expression of lcat, acat1, and mttp but generally downregulated that of acat2. This study provided preliminary knowledge about the tissue distribution and nutritional regulation of cholesterol transport-related genes in marine teleost.

The southern scallop (Austrochlamys natans) and the Patagonian scallop (Zygochlamys patagonica) are vital species in the fisheries of Chilean Patagonia. However, overfishing has led to stock depletion, necessitating research for stock restoration and commercial production. This study aimed to evaluate the growth and survival of these scallops in suspended systems and land-based tanks across various Patagonian regions. Eight experiments were conducted, three with southern scallops and five with Patagonian scallops. For southern scallops, two experiments involved suspended systems at different shell heights and three tested land-based tanks at various temperatures (9, 11, and 13°C). Patagonian scallop experiments included one suspended system in an endemic area, land-based tanks with different temperatures (9, 11, and 13°C), and three suspended systems outside the species’ endemic zone. In suspended systems, southern scallops grew from 15.1 to 42.7 mm (shell height) in 322 days, with a rate of 0.085 mm/day and a survival rate of 43.7%. Patagonian scallops reached 46.0 mm shell height in 466 days, with a growth rate of 0.079 mm/day and a survival rate of 57.2%. Experiments in controlled-temperature tanks revealed that 13°C was the lethal temperature for southern scallops. Notably, higher growth rates occurred at temperatures between 9 and 11°C. Both species show potential for future commercial cultivation, contributing to Chilean aquaculture diversification.

The aim of the current study was to assess the impacts of tank color on the growth, stress, biochemical, hematological, and immunological responses, and expression of growth-related genes in juvenile Oscar (Astronotus ocellatus). Therefore, a total of 120 fish (9.14 ± 0.34 g) were distributed into 12 aquariums (60 × 50 × 35 cm) and divided into four treatments (aquariums with blue, white, yellow, and red colors) in three replicates (10 fish per aquarium). The fish were daily hand-fed ad libitum in three meals at 7:00, 12:00, and 17:00 hr for 56 days. Results showed that Oscar fish cultured in the red aquariums had higher final weight and weight gain and lower feed conversion ratio. Plasma cortisol, glucose, and lactate values of fish were significantly higher, and the amount of white blood cells was lower in the blue aquariums compared to other tank colors. Plasma triglyceride values were significantly higher in the white and yellow groups than the blue aquariums. Moreover, fish cultured in yellow and red aquariums had significantly higher melatonin levels than the blue aquariums. Plasma cholesterol, total protein, albumin, complement 3, and total immunoglobulin values were highest in Oscar fish cultured in the red aquariums. Also, lysozyme and alternative complement (ACH50) activities and complement 4 values of fish cultured in yellow and red aquariums were meaningfully higher compared to blue and white groups. Growth hormone relative gene expression levels were meaningfully higher in Oscar fish cultured in white, yellow, and red aquariums than the blue aquariums. Furthermore, insulin-like growth factor-1 (IGF-1) relative gene expression levels were significantly higher in fish cultured in yellow and red aquariums compared to those cultured in blue and white tank colors. Thus, the most suitable tank color for rearing juvenile A. ocellatus is red, while blue tank color is unsuitable.

The use of herbicides has risen considerably in order to increase agricultural production, and Ronstar® is one of the popular organochlorine herbicides with oxadiazon as its active component. This herbicide has a wide range of effects on fish, including physiological, genetic, neurological, and hemato-immunological impacts. In the current study, p-Coumaric acid (P-CA) was used as a feed additive for its potential benefits in rainbow trout (Oncorhynchus mykiss) exposed to Ronstar using hematological, immunological, and biochemical analyses. The fish (16.02 ± 0.27 g) was divided into eight treatments as follows: C (negative control), P1, P2, and P3 (0.5, 1, and 1.5 g P-CA/kg, respectively, with no toxin), R1, P1R1, P2R1, and P3R1 (12.5% Ronstar toxin with 0, 0.5, 1, and 1.5 g P-CA/kg, respectively), each with a replicate of three. According to the two-way ANOVA test (P < 0.05), the overall trend of changes were growth, antioxidant enzyme activity (superoxide dismutase, catalase, glutathione peroxidase), and malondialdehyde level, humoral immune system (total immunoglobulin levels (total Ig)), lysozyme, complement 3 (C3), complement 4 (C4), ACH₅₀, serum nitroblue tetrazolium, and myeloperoxid. The only parameters that were unaffected by P-CA were globulin, albumin, and cortisol; however, Ronstar had negative effects on all three of these measures as well. It was found that the positive effects of dietary P-CA may ameliorate the negative effects of Ronstar in rainbow trout in a dose-dependent manner, with the best performance for the treatment P-CA + Ronstar. However, it is crucial to evaluate the mitigating effects of dietary P-CA against Ronstar on some vital organs of rainbow trout, especially the liver, at histological levels in future studies.