Aquaculture Research最新文献

The carnivorous marine gastropod, Rapana venosa, also known as the veined rapa whelk, has recently gained considerable attention due to its dual significance as both a valuable commercial seafood resource and a biological invader with widespread ecological implications. Significant efforts have been made to investigate the molecular pathways governing the specific adaptations in R. venosa. However, the regulatory mechanisms of these pathways remain largely unclear. Circular RNA (circRNA), a newly-recognized class of non-coding molecules, plays crucial roles in post-transcriptional regulation, impacting various fundamental bioprocesses including development, cell cycle, immunity and disease pathogenesis. In this study, we conducted a comprehensive genome wide profiling of circRNAs across 11 tissues of R. venosa. We identified a total of 1214 circRNA genes across tissues, with 640 regarded as high-confidence candidates. circRNAs displayed overall low expression levels, diverse isoform types and dynamic expression patterns across various tissues. Our comparative analyses revealed a few circRNA genes with a great diversity of isoforms and abundant expression in the salivary gland, suggesting potential roles in the feeding process of R. venosa. Furthermore, Gene Ontology (GO) enrichment analysis indicated the potential involvement of commonly expressed circRNAs in fundamental cellular processes, including cell division, amide biosynthesis and cellular response to hormone stimuli. Our study describes a preliminary examination of circRNAs across various tissues of R. venosa, offering a foundation for future research into the molecular mechanisms that influence the biology, ecology and behaviour of marine gastropods.

Mariculture has not fundamentally reduced its dependence on resources and the environment; ecological and economic efficiency has become an important target of concern for the sustainable and healthy development of China’s mariculture industry. Environmental regulation (ER) is a core tool to realize the synergistic development of economic development and environmental resource protection in mariculture. In this paper, the provincial panel data of China’s coastal areas from 2007 to 2020 was selected, and the level of ecological and economic efficiency of mariculture in different provinces of China was measured by using the super slacks-based measurement–data envelopment analysis model considering the undesirable output of mariculture, and the impact of different ERs on ecological and economic efficiency was explored. It was found that the impacts of different ER methods on the eco-economic efficiency (EEF) of mariculture may be non-linearized, and there is also regional heterogeneity in the optimal choice and combination of ER methods to improve the EEF of mariculture.

Fish feed is critical in aquaculture production, accounting for over 60% of operational costs, with protein being the most expensive component. Traditionally, fish meal (FM) has been the primary protein source. However, due to declining capture fisheries and high demand, FM has become scarce and costly, necessitating the search for alternative, low-cost, and nutritionally balanced protein sources. A 180-day feeding experiment was conducted to evaluate the effects of replacing FM with a combination of cottonseed and sunflower meal (SFM) in Nile tilapia diets on growth performance, protein digestibility, and economic returns. Freshwater shrimp meal was replaced at 25%, 50%, 75%, and 100% (diets D1, D2, D3, and D4) and compared to the control diet (D0) containing only FM. Monosex Nile tilapia fingerlings (25 ± 0.01 g) were allocated to 15 cages within an 800 m² earthen pond. Fish on diets D0 and D1 showed superior growth performance metrics, including final mean body weight, weight gain, daily weight gain, specific growth rate, feed conversion ratio, and survival rate (p > 0.05), compared to diets D2, D3, and D4. Growth performance declined significantly with increasing levels of the plant protein mixture (p < 0.05). Diet D0 had the highest apparent protein digestibility, while D4 had the lowest. Cost-benefit analysis revealed that diet D0 had the highest production cost, followed by diets D1, D2, D3, and D4, with no significant cost difference between D0 and D1 (p > 0.05). Thus, the plant protein mixture can effectively replace FM at a 25% inclusion level in Nile tilapia diets.

To address the growing demand for optimization strategies in recirculating aquaculture systems (RAS), this study investigates the impact of stocking density and feeding levels on barramundi (Lates calcarifer). A total of 3510 fish with an initial weight of 50.2 ± 1.1 g were allocated into 27 tanks, each with a volume of 1 m³. The fish were grown at three stocking densities: low (LD, 5.6 kg m⁻³) with 110 fish per tank, medium (MD, 6.7 kg m⁻³) with 130 fish per tank, and high (HD, 7.7 kg m⁻³) with 150 fish per tank. All fish were fed to satiation but were offered three feeding levels that varied according to fish body weight (BW): standard (SF, 20.6 × BW^−0.418), high (HF, 11.4 × BW^−0.242), and very high (VHF, 7.0 × BW^−0.094). After 8 weeks, the stocking density had increased to 24.9, 29.3, and 33.0 kg m⁻³ in the LD, MD, and HD groups, respectively. The biomass gain increased with both stocking density and feeding levels (P < 0.001), reaching 23.6 kg in both HD-HF and HD-MF groups. Higher stocking density was found to reduce fish BW gain (P < 0.05) and total feed intake (P < 0.05), while lower feeding levels significantly improved the feed conversion ratio (P < 0.001). The consistency of daily feed intake (DFI, as a proportion of BW) was dependent on feeding level in all groups. Subsatiation feeding levels maintained consistent feed intake, whereas exceeding satiation levels led to irregular feed intake patterns and a significant increase in day-to-day and tank-to-tank variabilities. The DFI 1 day before the first feed refusal was used to propose an optimized feeding table for barramundi. This study emphasizes the tradeoff between overall tank productivity and individual fish performance and showed that slightly underfeeding barramundi can be beneficial for day-to-day farm management.

The impact of dietary fenugreek (FN) supplementation on growth performance, physio-metabolic enzyme response, and antioxidant enzyme activities in hybrid African catfish (Clarias gariepinus ♀ × Heterobranchus bidorsalis ♂) was investigated in this study. Five isonitrogenous diets (38% crude protein) were developed and fed to the fish for 60 days. The FN was incorporated into the diets at 0%, 0.5%, 1.0%, 1.5%, and 2%. Two hundred twenty-five fingerlings of hybrid African catfish (average weight 4.01 g ± 0.02) were used for the study and randomly distributed to five dietary groups in triplicate. FN supplementation improved growth responses and survival rates; the dietary groups considerably (p < 0.05) outperformed the control group. FN-based diets considerably increased the carcass protein content (p = 0.020) and improved protein retention (p = 0.015). FN supplementation markedly (p < 0.001) and dose-dependently reduced the carcass’s lipid content and substantially (p < 0.001) increased the levels of metabolic enzymes. The fish antioxidant capacity was significantly enhanced (p < 0.001), and hepatic stress enzymes were greatly (p < 0.001) lowered in FN-based diets. In summary, the second-order polynomial regression analysis indicates that the optimal dose of FN supplementation to improve hybrid catfish growth without negatively affecting the fish’s physio-metabolic response or overall wellbeing is 1% dietary inclusion level.

Grass carp (Ctenopharyngodon idella), a freshwater nonnative fish species, is a potential aquaculture candidate in Bangladesh. The seed of the species is produced in the hatcheries by hypophysation, but the quality of seedstock of grass carp is deteriorated due to inbreeding, negative selection, and interspecific introgression among fishes. To increase the availability of quality seed and best genetic traits of grass carp, this study dealt with finding suitable conditions of sperm cryopreservation protocols and evaluated the effectiveness of cryopreserved sperm through breeding trials of C. idella. A broodstock population was developed from fingerlings imported from China by the Bangladesh Department of Fisheries. Sperm was collected from hormone-induced mature males, with an estimated concentration of 2.4 ± 0.3× 10¹⁰ cells/mL and a pH of 8.3 ± 0.2. Sperm motility was evaluated in different concentrations of NaCl solution. The highest motility (96% ± 1%) and longest motility duration (22 ± 1 min) were achieved at 0.4% of NaCl (128 mOsmol/kg). The toxicity of DMSO and methanol at concentrations of 5%, 10%, and 15% was evaluated for 5–40 min using Alsever’s solution and egg yolk citrate. The highest motility was achieved during 5 and 10 min of incubation with cryoprotectants at 5% and 10%. Alsever’s solution with 10% DMSO at 1:9 dilution with sperm produced the highest equilibration motility (93% ± 2%) and when cooled at 10°C/min yielded the highest postthaw motility (85% ± 3%). Fertilization of 24% ± 3% to 51% ± 2% and hatching of 18% ± 2% to 41% ± 2% were achieved by using cryopreserved sperm in six selected private hatcheries. The fertilization rate for fresh sperm sourced from hatchery-reared males was 64% ± 5% to 85% ± 3%, and the hatching rate ranged from 53% ± 6% to 74% ± 5%. Thus, the cryopreservation protocol of C. idella sperm was found to be feasible for fry production at commercial hatcheries, but further research is needed to improve the fertilization and hatching rates.

The present experiment was performed to reveal the mechanisms of toxic effects of ammonia nitrogen on Chinese hook snout carp (Opsariichthys bidens) based on the levels of antioxidant enzyme activities and the expression of 70-kDa heat shock protein gene (HSP70) and tumor necrosis factor-α (TNF-α) after 96 h of acute toxic ammonia exposure to investigate its adaptability. The result showed that activities of antioxidant enzymes and lipid peroxidation in the intestine, liver, brain, and gills showed a general trend of increasing and then decreasing when exposed to ammonia nitrogen. The intestinal tissue structure was damaged to varying degrees, the expression of the HSP70 in the brain and gills increased at 0–12 h, and the expression of the TNF-α in brain tissues decreased at 0–12 h. The expression of TNF-α in the liver was continuously upregulated in the late stages of stress, and it did not decrease until the stress was released. The above results indicate that high concentrations of ammonia nitrogen caused varying degrees of damage to the neurological, respiratory, and metabolic-related organs of the O. bidens.

As an omnivorous fish, wild tilapia feed on both animal and plant foods, depending on what is available. To understand the nutritional function of the gut microbiota of tilapia, we used shotgun metagenomic sequencing, untargeted metabolomics analysis, and 16S rRNA gene sequencing to study the metabolites and gut microbial communities in tilapia eating different diets (artemia nauplii in the carnivorous diet; plant-based pelleted feed [PBP] in the herbivorous diet; and a mixture of these two in the omnivorous diet). A total of 225 Nile tilapia (Oreochromis niloticus) were cultured in nine 1500 L outdoor tanks, with three replicate tanks per diet and 25 fish per tank. β-diversity analysis revealed that there was no significant difference in microbial structure between the three diets. However, significant differences were detected in gut metabolites. The abundance of the core bacteria in tilapia intestine (genus Cetobacterium) increased significantly when an omnivorous diet was fed. Cetobacterium abundance was significantly correlated to some differential metabolites including glucose and amino acids, and significantly correlated to pathways of carbohydrate and amino acids metabolism, identified by metagenome analysis. Metagenomic binning produced seven Cetobacterium MAGs with the completeness >50% and contamination <10%, in which genes related to the above metabolites and metabolism pathways were identified. All seven MAGs contained CAZymes that could act on distinct carbohydrates, providing highly diversified capabilities to this genus to cope with both animal and plant glycans. These tilapia fed with an omnivorous diet also showed increased growth. The differential intestinal metabolites aspartate, isoleucine, ornithine, proline, nicotinate, and NAD+ could be related to the increased growth. Our results expanded the understanding of how tilapia have adapted to an omnivorous diet and may provide knowledge for improving aquaculture management.

Determination of protein and lipid requirements is crucial in prawn species aquaculture. The present study investigated the impact of six diets with different protein and lipid levels (T1, 30/08; T2, 30/12; T3, 35/08; T4, 35/12; T5, 40/08; and T6, 40/12), in triplicate, on the zootechnical performance and body composition of juvenile Macrobrachium macrobrachion over 56 days. These protein and lipid levels were chosen based on the requirements of other freshwater prawn species. The stocking density was one individual per liter. Results show that prawn survival was lower in T6 (with 40% protein and 8% lipid) compared to all others. The treatment T3 (35% protein and 8% lipid) shows higher survival (with 40.0 ± 24.0%) but not significantly different from other diets. The specific growth rate obtained in the present study was not different between diets. Negative values were recorded for treatments T2, T3, and T4 (30%, 35%, and 35% proteins and 12%, 8%, and 12% lipids, respectively) and positive values for treatments T1, T5, and T6 (30%, 40%, and 40% proteins and 8%, 8%, and 12% lipids, respectively). The protein efficiency coefficient (PEC) and the lipid efficiency coefficient (LEC) did not differ between treatments; however, there was a trend for these coefficients to be lower in T4, T5, and T6 (35%, 40%, and 40% proteins and 12%, 8%, and 12% lipids, respectively) compared with the other diets. The highest protein efficiency rates were recorded with the T3 and T4 treatments (35% proteins and 8% and 12% lipids, respectively), while the best lipid level was obtained with T4 (35% proteins and 12% lipids). According to dose–response models, the optimal protein/lipid ratio requirements for M. macrobrachion juveniles can be estimated at 35/8. This study is the first to provide relevant information on the nutritional needs of juveniles of African native freshwater prawn M. Macrobrachion. Further research is needed to optimize nutritional requirements at early stages of development.

Hybridization is a common technique in the breeding of new varieties. In this study, we obtained F₁ and F₂ hybrids through interspecific hybridization between Siniperca chuatsi and Siniperca scherzeri and backcross offspring by backcrossing between F₁ and Siniperca chuatsi. We analyzed the morphological traits and genetic diversity of the parents and their progeny. The results showed that although most morphological traits of the progeny were not significantly different from those of their parents, the F₁ hybrids exhibited the most pronounced morphological variations. The F₂ and backcross hybrids appeared morphological differentiation within their populations. The CPL/CPW ratio emerged as a reliable marker for identifying hybrids morphologically. The expected heterozygosity for F₁ (0.6264), F₂ (0.6677), and backcross offspring (0.5260) were intermediate between Siniperca chuatsi (0.7388) and Siniperca scherzeri (0.3910), indicating a relatively high level of genetic diversity in the offspring. Additionally, the private allele frequency of F₁ and F₂ was higher than backcross offspring. One SSR marker (G₅₂₂₀) was identified as a specific molecular marker to distinguish the hybrid F₁ population from the parents, hybrid F₂, and backcross F₁ populations by analyzing specific alleles. The result of Ne, He, I, and PIC confirmed that F₂ maintained the genetic diversity of F₁. We speculated that both F₁ and F₂ have higher breeding potential. This study provides essential baseline data for genetic breeding of mandarin fish that will be instrumental in the future.