Fish Growth Research Articles

Selenium-enriched Lactobacillus plantarum alleviate of high alkalinity-induced microbiota-gut-blood systems affect by improving the gut microbiota

High alkalinity is the most important limiting factor in carbonate-type saline–alkali water aquaculture, and fish growth is slow and survival is low in highly alkaline environments. Selenium-enriched (Se-enriched) Lactobacillus plantarum (L. plantarum) has antioxidant and anti-inflammatory properties and can regulate the balance of the gut flora. However, the physiological regulatory mechanism of Se-enriched L. plantarum on common carp under high alkalinity stress is still unclear. In the present study, 360 common carp were randomly divided into a control group, a high alkalinity group, and a Se-enriched L. plantarum and high alkalinity group and fed for 56 days. High alkalinity stress induced growth inhibition in common carp. Histopathology revealed atrophy of the intestinal villi and damage to the intestinal microvilli and tight junction complexes. Serological parameters showed that the serum ammonia and LPS contents were significantly increased. Gut microbial disruption under high alkalinity stress increased the abundance of Bacteroidota (LPS-producing bacteria), Providencia sp. (ammonia-producing bacteria) and Vibrio (pathogenic bacteria) and significantly decreased the expression of the tight junction proteins Zonula occludens-1 (ZO-1) and Occludin, disrupting the gut barrier. However, Se-enriched L. plantarum decreased the abundance of Bacteroidota Providencia sp. and Vibrio, increased the expression of the tight junction proteins ZO-1 and Occludin, and alleviated intestinal damage caused by high alkalinity while reducing the content of lipopolysaccharides (LPS) and ammonia in the serum. In addition, metabolomic analysis of serum revealed that high alkalinity stress activated autophagy, glucocorticoids and mineralocorticoid receptor agonists/antagonists, ABC transporters, the phosphatidylinositol signalling system, and the Mammalian Target of Rapamycin (mTOR) signalling pathway and significantly increased creatine content and riboflavin. Se-enriched L. plantarum treatment significantly decreased the creatine and D-alanine contents. In summary, this study revealed that Se-enriched L. plantarum can alleviate the harmful effects of high alkalinity on common carp by regulating the balance of the intestinal microbiota, improving intestinal barrier function, reducing the amount of harmful substances entering the bloodstream, and regulating blood metabolites. This study demonstrates the physiological regulatory mechanism of Se-enriched L. plantarum in alleviating high alkalinity stress and provides ideas and a theoretical basis for the protection against high alkalinity poisoning of fish in saline–alkali waters.

Dietary algal-sourced zinc nanoparticles promote growth performance, intestinal integrity, and immune response of Nile tilapia (Oreochromis niloticus)

BackgroundTrace elements play a crucial role in fish nutrition, with zinc (Zn) being one of the most important elements. BIO-sourced zinc nanoparticles were synthesized using the green microalga Pediastrum boryanum (BIO-ZnNPs, 29.35 nm). 30 or 60 mg/ kg dry feed of the BIO-ZnNPs (BIO-ZnNPs30 and BIO-ZnNPs60) were mixed with the Nile tilapia (Oreochromis niloticus) basal diet and fed to the fish for 8 weeks to evaluate their impact on fish growth, digestion, intestinal integrity, antioxidative status, and immunity.ResultsA significant enhancement was observed in all investigated parameters, except for the serum protein profile. BIO-ZnNPs at 60 mg/kg feed elevated the activities of reduced glutathione (GSH) and catalase (CAT), enzymatic antioxidants, but did not induce oxidative stress as reflected by no change in MDA level. Fish intestinal immunity was improved in a dose-dependent manner, in terms of improved morphometry and a higher count of acid mucin-producing goblet cells. Interleukin-8 (IL-8) was upregulated in BIO-ZnNPs30 compared to BIO-ZnNPs60 and control fish groups, while no significant expressions were noted in tumor necrosis factor-alpha (TNFα), nuclear factor kappa B (NFkB), and Caspase3 genes.ConclusionOverall, BIO-ZnNPs inclusion at 60 mg/kg feed showed the most advantage in different scenarios, compared to BIO-ZnNPs at 30 mg/kg feed. The positive effects on growth and intestinal health suggest that BIO-ZnNPs supplementation of aquafeeds has many benefits for farmed fish.

Effect of Replacing Fishmeal with Algal Meal on Growth Parameters and Meat Composition in Rainbow Trout (Oncorhynchus mykiss W.)

Aquafarms should reduce the use of fishmeal and fish oil in nutritional feed. One such accessible and relatively inexpensive food component that could successfully meet the challenge posed by aquaculture is algae. The objective of the present study was to evaluate the algae meal inclusion of Chlorella and Spirulina sp. in a diet for rainbow trout, evaluating its effects on fish growth, histological parameters and fillet quality. Experiments were carried out to replace 50% and 100% of fishmeal with Spirulina sp. and Chlorella vulgaris in feed for rainbow trout (Oncorhynchus mykiss W.) cultured in a recirculation system. At the end of the experimental period, the highest mean live weight was measured in rainbow trout fed a feed containing 50% algal meal in the feed. The absorptive vacuolization of cells was increased the most and lamina propria was average thickened when fed 50% algae diets. Fat droplets in the hepatocytes were larger in the 50% algae meal fed group, and their nuclei were replaced in the peripheral zone of the cells. Substitution of fishmeal with 50% algal meal in fish feed resulted in a 36.44% reduction in the lipid content of rainbow trout fillets compared to control fish.

Growth of Patin Fish (Pangasius hypophthalmus) Using Kasgot (Black Soldier Fly Larvae) Media as the Basic Ingredient for Fertilization

Growth of Patin Fish (Pangasius hypophthalmus) Using Kasgot (Black Soldier Fly Larvae) Media as the Basic Ingredient for Fertilization

Peningkatan Produksi Melalui Formulasi Pakan Berbasis Potensi Lokal Sebagai Alternatif Pakan Buatan Pada Budidaya Ikan Lele

Doktor Mengabdi (DM) activities develop partnerships in orderto overcome the problem of higher feed prices, which have a small profit or even a loss. This is exacerbated if, during harvest, the price of catfish per kilogram decreases. The urgency needed to solve these problems is then met by training on the formulation and manufacture of self-sufficient feed based on the potential of local ingredients. The activity partners were BUMDES of Labruk Lor Village and the "Mina Agung Mandiri" Fish Farming Group, which was further assisted by the Lumajang District FisheriesService. The results that have been applied to this activity include: 1) socialization with approaches and providing understanding to activity partners; 2) counseling and training to increase knowledge about good and correct fish farming and making fish feed independently by utilizing abundant raw materials in the surrounding area; and 3) The practice or direct application of making fish feed includes flouring the raw materials for making fish feed, mixing all the raw material compositions for making fish feed, and printing using a fish feed pellet printing machine. 4). Evaluation and monitoring of the implementation of activities 5). Evaluating the impact of activities, both the impact on the economy and fish growth, This activity provides farmers with theability to make feed independently and shows an increase in the profit yields of fish farming production by up to 40%. Furthermore, based on the measurements carried out, it showthat the water quality of each partner's pond is still in optimal conditionfor fish growth and does not indicate any diseases that attack the growth and development of the fish being cultivated.

Co-incorporation of Black Soldier Fly (Hermetia illucens) Larvae and Moringa (Moringa oleifera) Leaves in the Diet Increase African Catfish Profitability (Clarias gariepinus)

Aquaculture is a fast-growing activity in Cameroon and required substantial quantities of affordable protein-rich feed. In this study, we co-incorporated Moringa leaves (MOL) and black soldier fly larvae meal (BSFLM) in catfish diet, and the effect was evaluated on feed floatation, fish growth, flesh organoleptic qualities and profitability. 450 juvenile`s catfish weighing averagely 10 g, were subjected to five dietary treatments consisting of: T0 (0% BSFLM and 0% MOL); T1 (6.25% BSFLM and 5% MOL); T2 (12.5% BSFLM and 10% MOL); T3 (18.75% BSFLM and 15% MOL) and T4 (25% BSFLM and 20% MOL) for 119 days. The treatment T3 containing 18.75% BSFLM and 15% MOL recorded the highest floatation duration, fish weight (113.83±17.31 g) and weight gain (103.25±17.8 g), and the lowest feed conversion ratio (1.60±0.37). The flesh tasted good and was acceptable in all treatments. Incorporating BSFLM and MOL in the diets reduced the cost per kg of feed from 18 to 23%, thus increasing the system's profitability from 45.91 to 60.84%. We concluded that BSFLM and MOL can partially substitute fish meal in catfish diet and improve the profitability and offers insights into the development more profitable and sustainable aquaculture in Cameroon and globally.

Aqua drugs and chemicals used in commercial aquaculture in Mymensingh, Bangladesh

Mymensingh is a division in north-central Bangladesh renowned for its lush landscapes and agricultural productivity, with a strong focus on aquaculture as a key part of its economy. The study was performed to investigate the aqua drugs companies and their products used in commercial aquaculture farms in Mymensingh division. Questionnaire based data were collected from representatives of various aqua drug companies, district and upazila fisheries offices, chemical vendors, farmers, and hatchery owners of the Mymensingh division. The present study found aquaculture practices in Mymensingh rely heavily on various antibiotics, probiotics, disinfectants, and feed additives to prevent the spread of diseases, maintain water quality, and increase growth of culture fishes. Drugs from various companies are widely utilized across the Mymensingh division. Fishtech BD contributing the highest percentage (12%), followed by Eon Pharmaceutical Ltd. (11%) and ACI Animal Health (10%), while AVON Animal Health made the lowest contribution (2%). Among the various drugs from different companies, Renamycin (antibiotic), Timsen and Emsen (disinfectants), Pond Care (probiotics), Zeolite Gold, Gasonex, and Mega Zeo Plus (zeolite) are commonly preferred by the farmers. The study also found that many farmers lack knowledge about chemical ingredients, proper dosages, and appropriate application methods. Therefore, adequate training and implementation of government rules and regulations are necessary to ensure responsible use.

Effects of puerarin on growth, liver immunity and antioxidant capacity of yellowfin seabream (Acanthopagrus latus) under oxidized fish oil stress

Puerarin, an isoflavone, exhibits protective effects against liver damage. This study investigated the effects of puerarin on the growth, liver immunity, and antioxidant capacity of yellowfin seabream fed with oxidized fish oil. A total of 135 yellowfin seabream (13.00±0.05 g) were randomly divided into nine tanks (15 fish per tank), and fed with three types of diets for 56 days: a normal control fed with 6 % fresh fish oil (NC), an experimental control fed with 6 % oxidized fish oil (OFO), and a treatment fed with 6 % oxidized fish oil and supplemented with 400 mg/kg puerarin (OFP). Results showed, oxidized fish oil decreased the growth of fish, caused liver damage, and suppressed the fish's immunity. Compared to the NC group, the weight gain (WG) and specific growth rate (SGR) of the fish in the OFO group were significantly reduced; the activities of superoxide dismutase (SOD) and catalase (CAT) in serum were significantly decreased; liver morphology showed loose cytoplasm with a large amount of fatty degeneration; the lysozyme (LZM) activity in serum and liver was significantly reduced. On the other hand, compared to the NC and OFO groups, the WG and SGR of fish in the OFP group were significantly improved. Additionally, compared to the OFO group, the serum SOD and liver CAT activities in the fish of the OFP group were significantly increased, and the MDA content in serum and liver was significantly reduced. The extensive fatty degeneration in the liver was alleviated. The LZM activity in the serum and liver of fish in the OFP group was significantly higher than that in the OFO group, returning to the levels of the NC group. Meanwhile, puerarin significantly enhanced the expression of Nrf2. In conclusion, puerarin alleviated the adverse reactions induced by oxidized fish oil and promoted the growth of yellowfin seabream.

Enhancing aquaculture using nanotechnology: a review

The advent of nanotechnology is a laudable discovery, and to a large extent, it has potentials to solve many nagging problems in aquaculture industry. For instance, the challenge of recurring resistance of bacteria to antibiotics, and the myriad of different antibiotics in the market coupled with their toxic effect on fish and water is a serious concern. Nanotechnology provides new tools (Nanomaterials) which can find applications in various aspect of aquaculture with little or no risk of toxicity. These include: Nanosensors, DNA nanovaccines, nanogene delivery, smart drug delivery, nanobarcoding, fish growth enhancement using nanoselenite, nanodelivery of nutraceuticals, nanofilteration, nanopolymers, nanocoating, nanofeed to improve buoyancy and availability of feed during feeding, and nanonet treatment and so on. These products are readily available in the market. They can also be synthesized for application in the areas highlighted above. This paper presents a review on nanotechnology and its application to enhance various aspects of aquaculture with a view to finding effective management strategy to solve hydra-headed challenges bedevilling aquaculture industry by maximizing the full potential of nanomaterials

Integrating of the domestic goat into the rice-fish coculture systems: Rice paddy yield, diet, growth parameters, and intestine microbiota of common carp Cyprinus carpio (Linnaeus, 1758)

Feeding the World while ensuring food security and biodiversity conservation is one of the sustainable development challenges. Integrating farming systems holds great promise for enhancing agricultural sustainability. To reach this goal, the domestic goat (Capra hircus) was integrated into the rice fish system. Four plots each 5 m × 10.65 m were made in two experimental systems, goat-rice-fish (GRF) and rice-fish (RF). We compared the impacts on rice productivity, fish growth performance, water quality, dietary patterns, and gut microbiota composition between both systems. On the one hand, the rice yield indicators, survival rate (SR), specific growth rate (SGR), pH temperature, dissolved oxygen (DO), total nitrogen (TN), and total phosphorus (TP) were compared. On the other hand, the frequency of occurrence (FOC) of food items of fish (Cyprinus carpio), and the microbiota communities in goat faeces (GoFe) and fish intestines were also examined and compared among both systems. The results showed that the rice yield, the number of filled spikelets per panicle, the number of panicles per land area, and the 1000-grain weight were significantly increased with the integration of goat in the rice-fish coculture system. The SR of fish under the goat-rice-fish system was 12.12% significantly higher than that of the fish under the rice-fish system, as well as the SGR of fish in the GRF system was 21.85% significantly higher than that of the rice-fish system. However, the water quality analyses indicated that the integration of goats significantly increased the concentration of TN and TP. The DO concentration in the GRF system was 25.93% lower than that in the RF system. Dietary analysis of the common carp in goat-rice fish systems revealed shifts in foraging behaviors and diet composition compared to the rice-fish system. Furthermore, the study showed higher diversity in the gut microbiota communities of fish in response to goat-rice-fish integration. In conclusion, this comprehensive investigation underscores the complex and interconnected dynamics within the goat-rice-fish integrated system. It highlights the importance of balanced management practices to harness the system's potential for improved rice yield, fish ecology, and water quality. The findings contribute to a deeper understanding of sustainable integrated farming practices and inform strategies for optimizing the productivity and ecological resilience of this integrated agroecosystem.

The Effect of Exposure to Microplastic Polystyrene (PS) in Feed on the Haematology of Tilapia (Oreochromis niloticus)

Indonesia is one of the countries that has the largest archipelago area in the world. Indonesia's vast territorial waters also present major challenges in terms of environmental management. One problem that is getting worse is plastic waste. Over time, plastic waste scattered in the environment will degrade into small particles which are usually called microplastics. Tilapia (Oreochromis niloticus) is one of the economically and ecologically important freshwater fish species. This fish is not only an important source of protein for humans, but also plays a role in the balance of the marine ecosystem. Exposure to microplastics in fish can occur in various ways, including through contaminated feed. The aim of this study was to determine the effect of exposure to polystyrene (PS) microplastics in feed on the blood profile of tilapia (Oreochromis niloticus). The treatments given were P1 without exposure to microplastics, P2 with 0.01 mg/0.75 g, P3 with 0.1 mg/0.75 g, and P4 with 1 mg/0.75 g. The parameters measured in the study were blood profiles, including hematocrit, hemoglobin, erythrocytes, leukocytes, leukocyte differential and survival rate. The results obtained in this study were that hematocrit levels and survival rates had an effect on fish growth, while erythrocyte, leukocyte and leukocyte differential values had no significant effect on the blood profile of Nile fish exposed to polystyrene microplastics.

Genome-wide identification of Fgfr genes and function analysis of Fgfr4 in myoblasts differentiation of Lateolabrax maculatus

Fibroblast growth factor receptors (Fgfrs) are involved in cell proliferation, differentiation, and migration via complex signaling pathways in different tissues. Our previous studies showed that fibroblast growth factor receptor 4 (fgfr4) was detected in the most significant quantitative trait loci (QTL) for growth traits. However, studies focusing on the function of fgfr4 on the growth of bony fish are still limited. In this study, we identified seven fgfr genes in spotted sea bass (Lateolabrax maculatus) genome, namely fgfr1a, fgfr1b, fgfr2, fgfr3, fgfr4, fgfr5a, and fgfr5b. Phylogenetic analysis, syntenic analysis and gene structure analysis were conducted to further support the accuracy of our annotation and classification results. Additionally, fgfr4 showed the highest expression levels among fgfrs during the proliferation and differentiation stages of spotted sea bass myoblasts. To further study the function of fgfr4 in myogenesis, dual-fluorescence in situ hybridization (ISH) assay was conducted, and the results showed co-localization of fgfr4 with marker gene of skeletal muscle satellite cells. By treating differentiating myoblasts cultured in vitro with BLU-554, the mRNA expressions of myogenin (myog) and the numbers of myotubes formed by myoblasts increased significantly compared to negative control group. These results indicated that Fgfr4 inhibits the differentiation of myoblasts in spotted sea bass. Our findings contributed to filling a research gap on fgfr4 in bony fish myogenesis and the theoretical understanding of growth trait regulation of spotted sea bass.

Gckr depletion leads to growth retardation and diet-dependent visceral obesity in red crucian carp (Carassius auratus red var.)

There exists a notable contrast in the carbohydrate utilization capacity between fish and mammals. In mammals, the glucokinase regulatory protein (GCKR) is known to exert inhibitory effects on glycolysis by binding to glucokinase (GCK), but its role in fish remains unexplored. In this study, the function of gckr in red crucian carp (Carassius auratus red var.), hereafter referred to as RCC, was investigated through its knockout. Under normal dietary conditions, the growth rate of gckr knockout RCC was significantly lower compared to wild-type (WT) RCC reared in the same environment. Subsequent analysis found that gckr knockout RCC exhibited significantly higher serum glucose levels at 1 h post-feeding or glucose injection (hpi), while the difference was abolished at 3 h. Therefore, the metabolic characteristics at 1 and 3 hpi were evaluated between WT and gckr knockout RCC. The results revealed that gckr knockout led to impaired insulin signaling and glycolysis, as evidenced by a reduction in serum insulin level, hepatic insulin receptor a and pyruvate kinase expression, GCK contents, and pyruvate levels at 1 hpi. Additionally, gckr knockout resulted in compromised gluconeogenesis, as indicated by a significant decrease in hepatic expression of fructose-1,6-bisphosphatase 1 and glucose-6-phosphatase at 1 hpi, while it did not affect glycogen accumulation after glucose injection. Regarding lipid metabolism, gckr knockout caused a transient decrease in triglyceride level and reduced expression of fatty acid synthase after glucose injection. Moreover, decreased hepatic peroxisome proliferator activated receptor alpha (ppara) transcripts and proteins were observed in gckr knockout RCC at 1 dpi, indicating a reduced capacity for β-oxidation due to Gckr deficiency. Interestingly, when fed a high-lipid diet, gckr knockout resulted in a significant increase in visceral mass with higher triglyceride level, accompanied by attenuated PPARα signaling. Taken together, this study provides evidence that Gckr-mediated maintenance of Gck contributes to the facilitation of postprandial glycolysis, gluconeogenesis, lipogenesis, and fatty acid β-oxidation in RCC. This study further suggests that enhancing glycolysis may promote growth and liver health in fish under high lipid dietary conditions.

Proteomic Blueprint of Atlantic Cod (Gadus morhua) Otoliths Revealing Environmental Stress Insights through Label-Free Quantitative Shotgun Proteomics

Otoliths of the fish’s inner ear serve as a natural chronological recorder because of their continuous formation marked by daily, monthly, and annual increments. Despite their importance, the comprehensive protein content of otoliths remains not fully identified. Using the label-free shotgun proteomics method with one-dimensional liquid chromatography coupled to electrospray ionization-orbitrap tandem mass spectrometry, we quantified a broad range of proteins, with individual otoliths containing between 1341 and 1839 proteins. The identified proteins could potentially serve as a blueprint for fish growth from embryo to adult. We quantified eleven heat-shock proteins (HSPs) in both sexes and several proteins impacted by endocrine disruptors, indicating the otolith’s capacity to reflect environmental stress, potentially linked to climate change effects and altering of hormonal and neuroendocrine functions. Our bioinformatic ontology analysis confirmed the presence of proteins critical for various biological processes, including structural and enzymatic proteins. Protein–protein interaction (PPI) mapping also identified key interactions between the identified proteins. These findings significantly advance our understanding of otolith proteomics, offering a solid foundation for future work. Most of the identified proteins deposited daily and influenced by the environment were not implicated in the biomineralization of otolith, raising the potential for the otolith proteome to recreate details of fish life history at previously unrealized levels.

Integrated organismal responses induced by projected levels of CO2 and temperature exposures in the early life stages of lake sturgeon.

Atmospheric CO2 and temperature are rising concurrently, and may have profound impacts on the transcriptional, physiological and behavioural responses of aquatic organisms. Further, spring snowmelt may cause transient increases of pCO2 in many freshwater systems. We examined the behavioural, physiological and transcriptomic responses of an ancient fish, the lake sturgeon (Acipenser fulvescens) to projected levels of warming and pCO2 during its most vulnerable period of life, the first year. Specifically, larval fish were raised in either low (16°C) or high (22°C) temperature, and/or low (1000 μatm) or high (2500 μatm) pCO2 in a crossed experimental design over approximately 8 months. Following overwintering, lake sturgeon were exposed to a transient increase in pCO2 of 10,000 μatm, simulating a spring melt based on data in freshwater systems. Transcriptional analyses revealed potential connections to otolith formation and reduced growth in fish exposed to high pCO2 and temperature in combination. Network analyses of differential gene expression revealed different biological processes among the different treatments on the edges of transcriptional networks. Na+/K+-ATPase activity increased in fish not exposed to elevated pCO2 during development, and mRNA abundance of the β subunit was most strongly predictive of enzyme activity. Behavioural assays revealed a decrease in total activity following an acute CO2 exposure. These results demonstrate compensatory and compounding mechanisms of pCO2 and warming dependent on developmental conditions in lake sturgeon. Conserved elements of the cellular stress response across all organisms provide key information for how other freshwater organisms may respond to future climate change.

Bentonite-supplemented diets improved fish performance ammonia excretion haemato-biochemical analyses immunity antioxidants and histological characteristics of European seabass Dicentrarchus labrax

The purpose of this research was to examine the potential effects of bentonite (BN) supplemented diets on growth, feed utilization, blood biochemistry, and histomorphology of Dicentrarchus labrax. Six treatments in triplicate were tested: B0, B0.5, B1.0, B1.5, B3.0, and B4.5, which represented fish groups fed diets supplemented with 0, 0.5, 1, 1.5, 3, and 4.5% BN, respectively. For 84 days, juveniles’ seabass (initial weight = 32.73 g) were fed diets containing 46% protein, three times daily at 3% of body weight. With a 5% daily water exchange, underground seawater (32 ppt) was used. Findings revealed significant improvements in water quality (TAN and NH3), growth (FW, WG and SGR) and feed utilization (FCR, PER and PPV) in fish fed BN-supplemented diets, with the best values in favor of the B1.5 group. Additional enhancements in kidney function indicators (urea and uric acid) and liver enzymes were observed in fish of the BN-treated groups along with a decrease in cholesterol level in the B1.5 group. Further improvements in fish innate immunity (hemoglobin, red blood cells, glucose, total protein, globulin, and immunoglobulin IgM), antioxidant activity (total antioxidative capacity and catalase), and decreased cortisol levels in fish of the BN-treated groups. Histological examinations of the anterior and posterior intestines and liver in groups B1.5 and B3 revealed the healthiest organs. This study recommends BN at a concentration of 1.5% as a feed additive in the Dicentrarchus labrax diet.

Flood Pulse Effects on the Growth of Pseudoplatystoma fasciatum in the Amazon Basin

Fish growth is a fundamental biological process driven by a multitude of intrinsic (within-individual) and extrinsic (environmental) factors that underpin individual fitness and population dynamics. Interannual variability in river hydrology regarding the intensity and duration of floods and droughts can induce interannual variations in the biotic and abiotic variables that regulate fish growth. However, the understanding of how interannual variability in river hydrology affects fish growth remains limited for most species and ecosystems. We evaluated how inter-annual hydrological variations within the Amazon River basin influence the growth of the catfish Pseudoplaystoma fasciatum. Our research questions were as follows: Do floods lead to the faster growth of P. fasciatum and droughts lead to the slower growth? And do floods and droughts affect all age classes in the same manner? We sampled 364 specimens of P. fasciatum from five sites in the Amazon basin, estimated their growth rates, and related the growth rates to indices of the intensity of floods and droughts. We fitted linear mixed-effects models to test the relationship between growth increments and hydrological indices (with F and D quantifying the intensities of floods and droughts, respectively), age as fixed effects, and basins and Fish ID as random effects. We found an inverse relationship between the increment width in the fish hard parts and hydrological indices. That is, intense floods and droughts negatively affected the growth rates. We also found that the growth of P. fasciatum was no different in years with intense and mild floods across age classes 1–5, although was different for age class 6. However, the growth of P. fasciatum was faster in years of mild droughts for all age classes. Our results showing that the growth of P. fasciatum was slower in years of intense droughts are supported by those of previous studies in the Amazon basin and elsewhere. However, our results showing for the first time that the growth of P. fasciatum is slower in years of intense flooding is the opposite of patterns found in other studies. These results thus suggest that the growth of P. fasciatum is maximized within an optimum range of hydrological conditions, where neither floods nor droughts are intense.

Two pathways regulate insulin-like growth factor genes in the brain and liver of the tropical damselfish Chrysiptera cyanea: A possible role for melatonin in the actions of growth and thyroid hormones

External and internal factors are involved in controlling the growth of fishes. However, little is known about the mechanisms by which external factors trigger stimulus signals. This study explored the physiological roles of melatonin in the transcription of growth-related genes in the brain and liver of Chrysiptera cyanea, a tropical damselfish with long-day preference. In brain samples of this species collected at 4-h intervals, the transcript levels of arylalkylamine N-acetyltransferase2 (aanat2), the rate-limiting enzyme of melatonin synthesis, and growth hormone (gh) peaked at 20:00 and 00:00, respectively. Concomitantly, the transcript levels of insulin-like growth factors (igf1 and igf2) in the brain and liver were upregulated during the scotophase. Levels of iodothyronine deiodinases (dio2 and dio3), enzymes that convert thyroxine (T4) to triiodothyronine (T3) and reverse T3, respectively, increased in the brain (dio2 and dio3) and liver (dio2) during the photophase, whereas dio3 levels in the liver showed the opposite trend. Fish reared in melatonin-containing water exhibited significant increases in the transcription levels of gh and igf1 in the brain and igf1 in the liver, suggesting that growth in this fish is positively regulated by the GH/IGF pathway on a daily basis. Melatonin treatment also stimulated the transcript levels of dio2 and dio3 in the liver, but not in the brain. Fish consuming pellets containing T3, but not T4, showed significant increases in gh and igf1 in the brain and igf1 and igf2 in the liver, suggesting that the intercellular actions of the TH/IGF pathway have an impact on growth on a daily basis. In summary, IGF synthesis and action in the brain and liver undergo dual regulation by distinct hormone networks, which may also be affected by daily, seasonal, or nutritional factors.

Dietary inclusion of insect oil: Impact on growth, nutrient utilisation, lipid metabolism, antioxidant and immune-related responses in European catfish (Silurus glanis L)

In this study, we investigated the black soldier fly (Hermetia illucens) larvae oil (IO) as replacement of fish oil and vegetable oil in the diets of European catfish. The formulated diets included a control diet (CTR) containing fish oil (FO) and rapeseed oil (RO), and two experimental diets replacing FO and RO, with 50% and 100% IO, respectively. The nutritional trial comprising 630 European catfish juveniles (average initial body weight: 28.1 ± 0.17 g) randomly distributed into triplicated dietary groups (CTR, IO50, and IO100) was conducted for 8 weeks in a recirculation aquaculture system. The study was focused to evaluate the impact of IO on fish growth and nutrient utilisation, lipid metabolism, antioxidant, and immune-related responses in juvenile fish. Results obtained indicated that all the diets promoted adequate fish growth and feed utilisation, with no significant differences in these parameters between the dietary fish groups. It appears that the diets did not impact the activity of digestive enzymes, but a decrease in the apparent digestibility coefficients was observed. Significant differences were observed in tissue fatty acid (FA) composition. The significantly higher levels of whole-body total saturated fatty acids and arachidonic acid in fish fed IO-based diets relative to those fed CTR diet were accompanied by significantly lower levels of whole-body monounsaturated fatty acids and n-3 polyunsaturated fatty acids (n-3 PUFA). However, some deviations in this trend were observed in the liver highlighting the sparing effect for long chain polyunsaturated fatty acids (LC-PUFAs). Gene expression analysis showed a significant upregulation of genes encoding lipoprotein lipase (lpl), carnitine palmitoyl transferase (cpt1a), and hepatocyte nuclear factor 4 alpha (hnf4α) in the livers of fish fed the IO100 diet. Among the five immune-related genes examined in the spleen, only interferon regulatory factor 1 was significantly upregulated in fish fed IO50 relative to the CTR. These results indicated upregulated metabolic activities in fish fed the IO100 diet probably due to a higher level of dietary medium chain saturated fatty acids (MCSFA) and a lower level of LC-PUFA, creating the need for fish to oxidise more MCSFA and to deposit more LC-PUFA in the tissues in order to maintain fatty acid balance.

Mulberry (Morus alba) leaves improved the growth and intestinal health in largemouth bass (Micropterus salmoides) fed a cottonseed protein concentrate-based diet

Mulberry leaves (ML) have diverse biological activities and show potential as a functional additive. However, it is unclear whether ML can alleviate the adverse effects of high cottonseed protein concentrate (CPC) inclusion in carnivores. In this study, Micropterus salmoides were respectively fed six different diets over an 8-week period. Four experimental diets were formulated with varying levels of ML (0%, 2%, 4%, and 6%), designated as CG (basic diet), ML2, ML4, and ML6. Additionally, two diets replaced 75% of fishmeal (FM) protein with CPC in the CG diet, with or without 4% ML, named CPC and CM4 diet, respectively. Results showed that ML4 diet improved growth and feed utilization in largemouth bass compared with the control. The growth of fish fed with the CPC diet were significantly lower than those fed with the CG diet (P < 0.05). However, supplementing 4% ML in the CPC diet could improve the decreased growth and feed utilization, compromised intestinal barrier, and intestinal inflammation caused by high CPC in largemouth bass. Through 16S rDNA and intestinal transcriptome correlation analysis, it was revealed that ML could reduce non-homeostatic apoptosis by positively regulating intestinal microbiota to down-regulate the expression of pro-apoptosis genes in the PI3K-Akt pathway of the Apoptosis pathway.