Metformin attenuates high-carbohydrate diet-induced redox imbalance, inflammation, and mitochondrial dysfunction in Megalobrama amblycephala.

This study aimed to investigate the effects of dietary metformin supplementation on the redox balance, inflammation, mitochondrial biogenesis, and function in blunt snout bream fed a high-carbohydrate (HC) diet. Fish (45.12 ± 0.36 g) were randomly offered four diets, including a control diet (33% carbohydrate), an HC diet (45% carbohydrate), and the HC diet supplemented with 0.06% (HCM1) and 0.12% (HCM2) metformin respectively for 12 weeks. Compared with the control, feeding the HC diet significantly increased the hepatosomatic index (HSI), the mesenteric fat index, liver and muscle glycogen contents, liver and adipose tissue lipid contents, plasma glucose and glycation end products (AGES) levels and aspartate transaminase activity, plasma and liver malondialdehyde (MDA) contents, hepatic adenosine triphosphate (ATP) and adenosine monophosphate (AMP) contents, mitochondrial cytochrome c content, mitochondrial complex IV activity and ATP 6 transcription, but decreased plasma catalase (CAT) activity, muscle superoxide dismutase (SOD) activity, hepatic antioxidant enzymes activities, and the transcriptions of transforming growth factor ß (tgfß) and interleukin 10 (il10). Compared with the HC group, metformin treatment (especially the HCM2 group) significantly elevated tissue glycogen contents, muscle SOD activity, plasma and liver antioxidant enzymes activities, the transcriptions of tgfß and il10, the sodium/potassium ATPase activity, the contents of mitochondrial protein and AMP, the level of p-AMP activated protein kinase (AMPK), and the p-AMPK/t-AMPK ratio, but lowered the HSI, tissue lipid contents, plasma levels of glucose, AGES and glycated serum protein, plasma, and liver MDA contents, the transcriptions of il1ß, NADH dehydrogenase subunit 1 and ATP 6, the contents of ATP and cytochrome c, the ATP/AMP ratio, and the activities of complexes I and IV. In conclusion, metformin could attenuate the HC diet-induced redox imbalance, inflammation, and mitochondrial dysfunction in blunt snout bream.

Phosphatidylserine Counteracts the High Stocking Density-Induced Stress Response, Redox Imbalance and Immunosuppression in Fish Megalobrama ambylsephala.

This study was conducted to investigate the effects of dietary phosphatidylserine (PS) supplementation on the growth performance, stress response, non-specific immunity and antioxidant capacity of juvenile blunt snout bream (Megalobrama ambylcephala) cultured under a high stocking density. A 2 × 2 two-factorial design was adopted, including two stocking densities (10 and 20 fish/m3) and two dietary PS levels (0 and 50 mg/kg). After the 12-week feeding trial, the high stocking density significantly decreased the final weight; weight gain rate; specific growth rate; feed intake; nitrogen retention efficiency; plasma complement 3 (C3) level; albumin/globulin (ALB/GLB, A/G) ratio; activity of myeloperoxidase, lysozyme (LZM) and glutathione peroxidase (GPX); gpx transcription; and abundance of sirtuin3 (Sirt3) and nuclear factor erythroid-2-related factor 2 (Nrf2). However, it significantly increased the plasma levels of cortisol, glucose (GLU), lactic acid (LD), total protein and GLB; hepatic malondialdehyde (MDA) content; and sirt1 transcription. PS supplementation significantly increased the plasma ALB and C4 levels; the A/G ratio; the activity of LZM, CAT and GPX; the transcription of sirt1, nrf2, manganese-containing superoxide dismutase and catalase; and the Nrf2 abundance. However, it significantly decreased the plasma levels of cortisol, GLU and GLB, as well as the hepatic MDA content. In addition, there was a significant interaction between the stocking density and PS supplementation regarding the effects on the plasma LD, ALB, GLB and C3 levels; A/G ratio; hepatic CAT activity; and protein abundance of Sod2. In conclusion, PS supplementation can counteract the high stocking density-induced stress response, redox imbalance and immunosuppression in blunt snout bream.

Oral feed-based administration of phage cocktail protects rohu fish (Labeo rohita) against Aeromonas hydrophila infection.

Aeromonas hydrophila is one of the major freshwater fish pathogens. In the current study, a cocktail of D6 and CF7 phages was given orally to Labeo rohita to assess phage survival in fish organs as well as to determine the therapeutic efficacy of phage treatment against fish mortality caused by A. hydrophila. In the phage-coated feed, prepared by simple spraying method, phage counts were quite stable for up to 2 months with a decline of ≤ 0.23 log10 and ≤ 1.66 log10 PFU/g feed during 4 oC and room temperature storage. Throughout the experimental period of 7 days, both phages could be detected in the gut of fish fed with phage-coated feed. Besides, both CF7 and D6 phages were also detected in fish kidneys indicating the ability of both the phage to cross the intestinal barrier. During challenge studies with LD50 dose of A. hydrophila, phage cocktail doses of 1 × 106 - 1 × 108 PFU/g feed prevented the mortality in L. rohita with relative percentage survival (RPS) of 8.7-65.2. When challenged with LD90 dose of A. hydrophila, an RPS value of 28.6 was obtained at a phage cocktail dose of 1 × 108 PFU/g feed. The RPS data showed that orally-fed phage cocktail protected the fish against the mortality caused by A. hydrophila in a dose-dependent manner. Simple practical approaches for phage cocktail development, medicated feed preparation and oral administration along with phage survival and protection data make the current study useful for farmer-level application.

Grass carp reovirus VP56 and VP35 induce formation of viral inclusion bodies for replication.

Viral inclusion bodies (VIBs) are subcellular structures required for efficient viral replication. How type II grass carp reovirus (GCRV-II), the mainly prevalent strain, forms VIBs is unknown. In this study, we found that GCRV-II infection induced punctate VIBs in grass carp ovary (GCO) cells and that non-structural protein 38 (NS38) functioned as a participant in VIB formation. Furthermore, VP56 and VP35 induced VIBs and recruited other viral proteins via the N-terminal of VP56 and the middle domain of VP35. Additionally, we found that the newly synthesized viral RNAs co-localized with VP56 and VP35 in VIBs during infection. Taken together, VP56 and VP35 induce VIB formation and recruit other viral proteins and viral RNAs to the VIBs for viral replication, which helps identify new targets for developing anti-GCRV-II drugs to disrupt viral replication.

Teleost IgD+IgM- B cells in gills and skin have a plasmablast profile, but functionally and phenotypically differ from IgM+IgD- B cells in these sites.

Although most B cells in teleost systemic compartments co-express IgM and IgD on the surface, cells exclusively expressing either of the two Igs are common in fish mucosal tissues, providing us with a unique opportunity to further characterize IgD+IgM- B cells, an intriguing B cell subset. Hence, we compared the phenotype of IgD+IgM- cells to that of IgM+IgD- B cells in rainbow trout gills and skin, also establishing the response of these subsets to immune stimulation. The transcriptional profile and secreting capacity of IgD+IgM- B cells corresponded to that of cells that have started a differentiation program toward plasmablasts, similarly to IgM+IgD- B cells. Yet, IgM+IgD- B cells retained high levels of surface MHC II and antigen-processing abilities, while these were much lower in IgD+IgM- cells, suggesting important differences in their antigen-presenting capacities. Our findings contribute to a deeper understanding of the enigmatic role of IgD in mucosal surfaces.

In-feed emamectin benzoate abuse affects the biological responses and erythrocytes of Nile tilapia Oreochromis niloticus.

In aquaculture, drugs are often abused to accomplish disease control without considering the negative effects on fish health. This study aimed at elucidating the pernicious effects of in-feed antiparasitic drug emamectin benzoate (EB) abuse on the haemato-biochemistry and erythro-morphometry of healthy Nile tilapia Oreochromis niloticus. The fish were fed EB at 50 µg (1×) and 150 µg/kg biomass/d (3×) for 14 d as against the recommended 7 d and periodically assessed the blood parameters. A significant dose- and time-dependent reduction in feed intake, survival, total erythrocytes (TEC), monocytes (MC), hemoglobin (Hb), hematocrit (Ht) and mean corpuscular Hb concentration were noted. The total leukocytes (TLC), thrombocytes (TC), lymphocytes (LC) and neutrophils (NC) markedly augmented. The EB-dosing altered the fish physiology by enhancing the glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and creatinine and reducing the calcium, chloride and acetylcholinesterase (AChE) levels dose-dependently. The fish recovered within 4 weeks in the 1× group post-dosing but persevered in the overdosed group. The erythro-cellular and nuclear dimensions were reduced with the increase in dose and normalized after the cessation of dosing, except for nuclear volume. The erythro-morphological alterations were more prominent in the overdosed group. The results implied the pernicious effect of oral EB medication on the biological responses of fish if abused.

Resveratrol Modulates the Redox Response and Bile Acid Metabolism to Maintain the Cholesterol Homeostasis in Fish Megalobrama amblycephala Offered a High-Carbohydrate Diet.

This study aimed to characterize the effects of resveratrol on the redox balance, cholesterol homeostasis and bile acid metabolism of Megalobrama amblycephala offered a high-carbohydrate diet. Fish (35.0 ± 0.15 g) were fed four diets including one control diet (32% nitrogen-free extract), one high-carbohydrate diet (45% nitrogen-free extract, HC), and the HC diet supplemented with different levels (0.04%, HCR1; 0.08%, HCR2) of resveratrol for 12 weeks. The HC diet-induced redox imbalance is characterized by increased MDA content and decreased T-SOD and CAT activities in the liver. Resveratrol attenuated this by up-regulating the transcription of Cu/Zn-sod, and increasing the activities of T-SOD, CAT, and GPX. The HC diet enhanced the cholesterol synthesis, but decreased the bile acid synthesis via up-regulating both hmgcr and acat2, and down-regulating cyp7a1, thus resulting in excessive cholesterol accumulation. Resveratrol supplement decreased cholesterol synthesis, and increased cholesterol uptake in the liver by down-regulating both hmgcr and acat2, and up-regulating ldlr. It also increased bile acid synthesis and biliary excretion by up-regulating cyp7a1, and down-regulating mrp2, oatp1, and oatp4 in the hindgut, thereby decreasing cholesterol accumulation. In conclusion, resveratrol improves the cholesterol homeostasis of Megalobrama amblycephala fed a high-carbohydrate diet by modulating the redox response and bile acid metabolism.

Sodium oxamate reduces lactate production to improve the glucose homeostasis of Micropterus salmoides fed high-carbohydrate diets.

The study was performed to evaluate the effects of the reduced lactate production by sodium oxamate (SO) on growth performance, lactate and glucose and lipid metabolism, and glucose tolerance of Micropterus salmoides fed high-carbohydrate (CHO) diets. In in vitro study, primary hepatocytes were incubated for 48 h in a control medium (5.5 mM glucose), a high-glucose medium (25 mM glucose, HG), or a SO-containing high-glucose medium (25 mM glucose + 50 mM SO, HG-SO). Results indicated lactate and triglyceride (TG) levels, and lactate dehydrogenase a (LDH-a) expression in the HG-SO group were remarkably lower than those of the HG group. In in vivo study, M. salmoides (5.23 ± 0.03 g) were fed four diets containing a control diet (10% CHO, C) and three SO contents [0 (HC), 100 (HC-SO1), and 200 (HC-SO2) mg·kg-1, respectively] of high-CHO diets (20% CHO) for 11 wk. High-CHO diets significantly reduced weight gain rate (WGR), specific growth rate (SGR), p-AMPK-to-t-AMPK ratio, and expression of insulin receptor substrate 1 (IRS1), insulin-like growth factor I (IGF-I), insulin-like growth factor I receptor (IGF-IR), fructose-1,6-biphosphatase (FBPase), peroxisome proliferator-activated receptor α (PPARα), and carnitine palmitoyl transferase 1α (CPT1α) compared with the C group, whereas the opposite was true for plasma levels of glucose, TG, lactate, tissue glycogen, and lipid contents, and expression of LDH-a, monocarboxylate transporter 1 and 4 (MCT1 and MCT4), insulin, glucokinase (GK), pyruvate dehydrogenase E1 subunit (PDH), sterol-regulatory element-binding protein 1 (SREBP1), fatty acid synthase (FAS). The HC-SO2 diets remarkably increased WGR, SGR, p-AMPK-to-t-AMPK ratio, and expression of IRS1, IGF-I, IGF-IR, GK, PDHα, PDHß, FAS, acetyl-CoA carboxylase 1 (ACC1), PPARα, and CPT1α compared with the HC group. Besides, HC-SO2 diets also enhanced glucose tolerance of fish after a glucose loading. Overall, the reduced lactate production by SO benefits growth performance and glucose homeostasis of high-CHO-fed M. salmoides through the enhancement of glycolysis, lipogenesis, and fatty acid ß-oxidation coupled with the suppression of glycogenesis and gluconeogenesis.

Application of limestone-molasses blends in Nile tilapia rearing tanks

The work aimed at determining the effects of applying different blends between liquid molasses and agricultural limestone on water quality and growth performance of Nile tilapia juveniles, Oreochromis niloticus. The study employed 24 indoor tanks of 100 L and 24 outdoor tanks of 250 L. Four control groups were set up (no product applied, only molasses, only limestone, molasses-limestone blend with 48% limestone but no fish) and two experimental groups (molasses-limestone blends with 32% and 48% molasses), with four replicates each. Over 11 weeks, the water quality was monitored systematically. The 24-h cycle monitoring of temperature, pH, specific conductance, dissolved O2 and total alkalinity were carried out at the 8th week. The blends between molasses and limestone accelerated the dissolution rate of the agricultural limestone in water. The blend containing 48% molasses led to greater increases in water alkalinity and pH in relation to tanks with only limestone applications. However, the molasses-limestone blend applications impaired the Nile tilapia growth performance, especially in the outdoor tanks. While the fish yield was 25.1 g m-3 day-1 in the molasses outdoor tanks, it was equal to 22.8 g m-3 day-1 in the molasses (32%)-limestone units (P<0.05). It has been concluded that the blending between limestone and molasses brings no clear benefits to Nile tilapia's rearing tanks when compared to the limestone-only tanks.

Feeding Strategies for Adapting Lake Sturgeon (Acipenser fulvescens) Larvae to Formulated Diets at Early Life Stages.

Cost-effective feeding management is required to support conservation hatcheries for lake sturgeon (Acipenser fulvescens), an ecologically important species in the Great Lakes region. This study investigated an approach to transition lake sturgeon larvae from live feed (Artemia) to formulated feed and its effect on growth performance, survival, and response to acute hypoxia stress. The first experiment showed that sturgeon had similar (p > 0.05) growth and survival when fed Artemia or the combined feeding of Artemia with the commercial diet (crude protein, 551 g/kg diet). Feeding solely on the commercial or lab-made (crude protein, 491 g/kg diet) diet significantly reduced growth and survival (p < 0.05). In the second experiment, the growth performance of sturgeon (14 days post-hatch, DPH) fed with either Artemia only or combined feeding different feeding durations of two, three, and four weeks followed by a complete transition to the commercial diet. At the end of six weeks, the 3- and 4-week combined feeding periods resulted in significantly higher body weight and survival compared to the 2-week combined and the Artemia only feeding treatments. In the last experiment, sturgeons (27 DPH) were fed only with Artemia or combined feeding of Artemia with the commercial diet for four weeks followed by the complete transition to the commercial diet for two weeks. Eighteen fish from each treatment were investigated the response to acute hypoxic conditions (gradual decrease in dissolved oxygen level from 8 to 2.3 mg/L at the rate of 1 mg/L per hour). When the dissolved oxygen was between 3 and 4 mg/L, the mortality rate of the combination-fed sturgeon (11.7%) was significantly lower than those fed only Artemia (83.3%). These results clearly demonstrate that a commercial diet can partially replace Artemia at early life stages to improve growth, survival, and hypoxia tolerance and thus its co-feeding with Artemia is recommended.

Uncertainty evaluation and performance assessment of water quality model for mariculture management.

Ecosystem based water quality models are important tools for prognostic site assessment and evaluation of ecosystem-performance of marine fish farms. We present the development and application of a comprehensive Fish Culture Zone Water Quality Model using continuous bi-weekly field data over a six-year period (2012-2017). The model simulates five interacting subsystems: phytoplankton, phosphorus and nitrogen cycles, and the dissolved oxygen (DO) and particulate organic carbon balance. The application of the model to two fish culture zones in Hong Kong shows the model captures the trends of nutrient and DO variation and the performance in quantitative prediction of algal biomass is challenging. The effect of errors in the specification of primary model inputs are evaluated using dimensionless sensitivity coefficients based on First Order Variance Analysis reveals the relative importance of fish stock (loading), physical size (volume), tidal flushing rate and boundary conditions in the prediction of key water quality variables.

Tracing the organic matter source of cage culture sediments based on stable carbon and nitrogen isotopes in Poyang Lake, China.

Collected sediment samples from the cage fish farm were measured to determine carbon and nitrogen stable isotope compositions and to understand the influence of the aquaculture waste on the sediment. The average δ13C of the sediment organic matter was -27.2 ‰ and -26.5 ‰, and the average δ15N value was 5.6 ‰ and 6.2 ‰ in October 2017 and November 2018, respectively. A linear mixing model was used to calculate the contribution ratios of the aquaculture waste in sediment organic matter. The contribution ratio of fish feces was 53.9 % and 25.5 %, and the contribution ratio of waste feed was 18.4 % and 52.6 % in October 2017 and November 2018, respectively. The sediment in the "cage fish area" was characterized by high waste feed ratio in sediment organic matter. The sediment organic matter was affected by the aquaculture waste even at sites 1500 m away from the cage fish farm.

Feed types affect the growth, nutrient utilization, digestive capabilities, and endocrine functions of Megalobrama amblycephala: a comparative study between pelleted and extruded feed.

Nowadays, both pelleted feed (PF) and extruded feed (EF) have been widely adopted in the aquaculture industry. However, limited information is available comparing their utilization efficiencies and meanwhile interpreting the underlying mechanisms. This study aimed to compare the utilization efficiencies of both PF and EF by blunt snout bream (Megalobrama amblycephala) based on growth performance, digestive capacities, and endocrine functions. Two feeds with identical formulas were prepared and named PF and EF. Fish were randomly distributed into two groups, including one that fed the PF continuously, and one that offered the EF continuously. The whole feeding trail lasted 8 weeks. The results showed that the protein efficiency (PER), retention of nitrogen and energy (NRE and ERE), viscera index (VSI), apparent digestibility of dry matter, protein, carbohydrate, and gross energy, whole-body crude protein and energy contents, intestinal enzymatic activities of protease, amylase, and Na+,K+-ATPase, intestinal villi length, crypt depth, muscular layer thickness, and the transcriptions of leptin (LEP) and cholecystokinin (CCK) of the EF group were all significantly higher than those of the PF group, while the opposite was true for feed intake and feed conversion ratio. These findings suggested that compared with PF, EF could improve the feed utilization and nutrient retention of blunt snout bream by enhancing the intestinal digestive and absorptive functions but reduce the feed intake through the stimulation of both LEP and CCK.

Does Fish Farming Improve Household Nutritional Status? Evidence from Bangladesh.

In the present study, nutritional status was assessed using dietary diversity of fish and non-fish farming households in Mymensingh district of Bangladesh. It has determined the incidence of poverty in fish and non-fish farm households through a comparative analysis of family profile, food consumption, calories, and protein intake. A total of 420 farms were selected for data collection using structured questionnaires with 210 fish and 210 non-fish farm families. The study using both descriptive and functional analysis revealed that the respondent age of both farms was 45.10 years, family size was 5.70, average education was 4.64 schooling years, and average farm size was 0.514 hectares. As a result, due to the increase in household income, fish farm families improved their food consumption, calories, and protein intake in comparison with non-fish farms. On a direct calorie intake (DCI) basis, the overall absolute and hardcore poverty levels of fish farm households were 32 percent and 18 percent, respectively, while those of non-fish farm households were 22 percent and 10 percent, respectively. Therefore, the incidence of poverty was higher in non-fish farming families than in fish farming families. In principle, provision of various forms of government assistance through the Department of Fisheries (DOF) will further intensify and strengthen fish farming, which will easily bring fallow and uncultivated lands of the area under fish farming. Moreover, it is possible to inspire the younger generation through this research that will help them to become a fish farm-based entrepreneur. The main conclusion of the present study is that fish farming is more positively related to household income, family food intake, and nutritional status than any other type of farming.

Interactions between dietary carbohydrate and thiamine: implications on the growth performance and intestinal mitochondrial biogenesis and function of Megalobrama amblycephala.

A12-week experiment was conducted to evaluate the influences of thiamine ongrowth performance, and intestinal mitochondrial biogenesis and function of Megalobramaamblycephala fed a high-carbohydrate (HC) diet. Fish (24·73 (sem 0·45) g) were randomly assigned to one of four diets: two carbohydrate (CHO) levels (30 and 45 %) and two thiamine levels (0 and 1·5 mg/kg). HC diets significantly decreased DGC, GRMBW, FIMBW, intestinal activities of amylase, lipase, Na+, K+-ATPase, CK, complexes I, III and IV, intestinal ML, number of mitochondrial per field, ΔΨm, the P-AMPK: T-AMPK ratio, PGC-1ß protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1ß, mitochondrial transcription factor A, Opa-1, ND-1 and COX-1 and 2, while the opposite was true for ATP, AMP and reactive oxygen species, and the transcriptions of dynamin-related protein-1, fission-1 and mitochondrial fission factor. Dietarythiamine concentrations significantly increased DGC, GRMBW, intestinal activities of amylase, Na+, K+-ATPase, CK, complexes I and IV, intestinal ML, number of mitochondrial per field, ΔΨm, the P-AMPK:T-AMPK ratio, PGC-1ß protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1ß, Opa-1, ND-1, COX-1 and 2, SGLT-1 and GLUT-2. Furthermore, a significant interaction between dietary CHO and thiamine was observed in DGC, GRMBW, intestinal activities of amylase, CK, complexes I and IV, ΔΨm, the AMP:ATP ratio, the P-AMPK:T-AMPK ratio, PGC-1ß protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1ß, Opa-1, COX-1 and 2, SGLT-1 and GLUT-2. Overall, thiamine supplementation improved growth performance, and intestinal mitochondrial biogenesis and function of M. amblycephala fed HC diets.

Strategies for Prevention and Control of Vibriosis in Asian Fish Culture.

It is estimated that vibriosis account for about half of the economic losses in Asian fish culture. Consequently, the prevention and control of vibriosis is one of the priority research topics in the field of Asian fish culture disease. Relevant measures have been proposed to control some Vibrios that pose a threat to Asian fish culture, but there are currently only a few effective vaccines available to combat these Vibrios. The purpose of our review is to sum up the main prevention methods and the latest control strategies of seven Vibrio species that cause great harm to Asian aquaculture, including Vibrio harveyi, Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio mimicus, Vibrio anguillarum, Vibrio alginolyticus and Vibrio cholerae. Strategies such as antibiotics, probiotics, bacteriophages, antimicrobials from plants and other natural sources, as well as vaccines, are compared and discussed here. We expect this review will provide some new views and recommendations for the future better prevention and control of vibriosis in Asian fish culture.

Growth and health status of Pangasionodon hypophthalmus reared under manipulated photoperiod conditions.

Background: In general, the length of photoperiod affects the physiology of Pangasionodon hypophthalmus. This study aimed to understand the growth and health status of this fish reared under manipulated photoperiods. Methods: The study was conducted between May and August 2020. Three treatments were applied: control (natural photoperiod); 18 hours of darkness (18D6L; tanks were placed under a dark tarp tent for 18 hours); and 24 hours of darkness (24D0L; tanks were placed under a dark tarp tent continuously). Three replications were performed per treatment. At baseline, fish were approx. 3 inch total length (TL) and 4 g body weight (BW), and were reared in circular plastic tanks (100 L; 30 fish/tank) with aerators and filters, and fed with commercial fish feed pellet (2 times/day to satiation). Fish growth and survival were studied once/week, and blood and tissue samples were taken at the end of the experiment (8 th week). Tissue was formalin fixed and HE stained. Results: The survival of fish in all treatment was 100%. The fish reared in 24D0L and 18D6L grew better than control, achieving a mean TL of 23 cm and BW of 98 g (control = 19 cm TL and 72 g BW). There was no difference in hematology condition or tissue structure between the three groups. Tissue structure of gill, kidney and liver were normal, but light abnormality due to parasites was present in the gill of fish reared in 24D0L. Blood samples for all three groups showed mean red blood cell count of 1,800,000 cells/ml and white blood cell (WBC) count of 55,200 cells/ml. WBC consisted of lymphocyte 65%, monocyte 24%, thrombocyte 6%, neutrophil 3%, eosinophil 1% and basophile 1%. Conclusion: Data obtained indicate that a short photoperiod improves the growth of P. hypophthalmus fish and does not negatively affects their health.

Utilization of pelleted and extruded feed by blunt snout bream Megalobrama amblycephala: Insights from growth performance, health status and feed cost.

The present study was conducted to evaluate the utilization of both pelleted feed (PF) and extruded feed (EF) by blunt snout bream Megalobrama amblycephala based on growth performance, stress responses, innate immunity and disease resistance. Both the PF and EF were prepared with the same formula. Fish were divided randomly into 2 groups, including one fed the PF continuously and one offered the EF continuously. The whole feeding trial lasted 8 weeks, after which fish were subjected to Aeromonas hydrophila infection. The results showed that the feed intake, feed conversion ratio, hepatic total superoxide dismutase activity and glutathione content, plasma complement 3 and complement 4 levels as well as myeloperoxidase activity of the EF group were all significantly lower than those of the PF group, while the opposite was true for the condition factor, the viscera index, the abdominal fat percentage, nitrogen and energy retention, hepatic malondialdehyde content, plasma levels of cortisol, glucose, lactate, total protein and globulin as well as the activities of plasma alanine aminotransferase and aspartate aminotransferase. In addition, the EF group also obtained relatively low activities of hepatic glutathione peroxidase and plasma acid phosphatase as well as high cumulative mortality rates at 24-96 h after Aeromonas hydrophila challenge. Furthermore, the feed cost of culturing this species with EF is lower than that with PF. These findings indicated that compared with PF, EF could increase the feed utilization and economic benefits of blunt snout bream, but reduce its anti-stress ability, non-specific immunity, A. hydrophila resistance and feed cost.

Uso de perifiton en un sistema de policultivo en agro acuicultura integrada en la comunidad indígena de Jimaín, Sierra Nevada de Santa Marta (Colombia) / Periphyton-based polyculture in an integrated agri-aquaculture system at the indigenous community of Jimaín, Sierra Nevada de Santa Marta (Colombia)

RESUMEN Los Sistemas de Agro Acuicultura Integrada (SAAI) han sido estudiados como opción para la producción de pescado en comunidades con recursos limitados. Así mismo, el uso de perifiton se ha convertido recientemente en una alternativa viable por el aporte de alimento natural de bajo costo. El objetivo de este estudio fue evaluar el efecto del perifiton sobre el desempeño productivo del policultivo Piaractus sp. (cachama híbrida) y Prochilodus magdalenae (bocachico) en SAAI en la comunidad Indígena de Jimaín, Colombia. Se sembraron 1,5 alevinos de cachama híbrida y 1,5 bocachicos/m2, con peso promedio de 0,49 ± 0,14 g y 1,83 ±1,61 g respectivamente, en seis estaques en tierra de 90 m2 tres de los cuales contaron con varas de madera (3 varas/m2) para la fijación de perifiton. La duración del cultivo fue de 135 días. Los tratamientos (CS: con sustrato y SS: sin sustratos) recibieron una dieta suplementaria dos veces al día, calculada como porcentaje de la biomasa con ajuste quincenal. Se realizaron biometrías quincenales. Los datos productivos por especie y para el policultivo se evaluaron mediante ANOVA con un modelo lineal general (p < 0,05). Los datos de peso (g) y longitud estándar (cm) por especie se evaluaron mediante un modelo mixto de medidas repetidas. No se encontraron efectos del sustrato sobre los parámetros productivos analizados tanto para cada especie, como para el policultivo. Se presentó interacción significativa para el peso del bocachico el día 90 (CS: 74,7 y SS: 47,1). Según los resultados obtenidos, la utilización de perifiton y el manejo en policultivo de especies nativas requiere más estudios.

ABSTRACT Integrated agri-aquaculture systems (IAAS) have been studied as an option for fish production in communities with limited resources. Likewise, the use of periphyton has recently become a viable alternative for its contribution of low-cost natural food. The effect of periphyton use on the productive yield of a hybrid cachama and bocachico polyculture in IAAS, was studied in the Jimaín Indigenous community, Colombia. For this experiment, 1.5 hybrid cachama and 1.5 bocachico fingerlings/m2 were stocked with average weights of 0.49 ± 0.14 g and 1.83 ± 1.61 g, respectively, in six 90 m2 land ponds; three of these ponds had wooden dowels (three dowels/m2) for periphyton fixation. The growth evaluation lasted 135 days. The treatments (WS: with substrate and WOS: without substrates) received a supplementary diet, adjusted as a percentage of the biomass with biweekly adjustment, twice a day. Biometrics were performed every two weeks. The productive data by species and for the polyculture were evaluated using an ANOVA with a general linear model (p <0.05). Weight (g) and standard length (cm) data by species were evaluated using a mixed model of repeated measures. No substrate effects were found on the productive parameters analyzed for each species as well as for the polyculture. A significant interaction was observed for bocachico weight on day 90 (WS: 74.7 and WOS: 47.1). According to the obtained results, optimizing the use of periphyton and the management of native species polyculture requires further studies.

Carbon and Nitrogen Stable Isotopes Evidence for the Environmental Impact of the Cage Fish Farm in Poyang Lake, China.

The carbon and nitrogen stable isotope compositions of the sediment organic matter, fish feed and fish feces were measured to assess the impact of the aquaculture waste from the cage fish farm in Poyang Lake. The results provide evidence of the non-negligible effect of aquaculture waste on the sediment organic matter. The δ13C and δ15N of sediments varied from - 27.62 to - 25.66‰ and 4.83 to 6.92‰, respectively. The sediment organic matter had a mixed source of waste feed, fish feces and plankton. The average contribution ratio of waste feed and fish feces was 53.1% and 24.6%, respectively. The aquaculture derived organic matter ratio was high with ranging from 57.6 to 95.6%. The aquaculture waste seemed to disperse widely enough to influence the study site about 2.5 km distance from the cage. The dispersion and resuspension were the main two factors which can explain the great effect area found in this study.