Marine Fish Culture Research Articles

Effects of different temperatures on the embryonic development of the Lebranche mullet Mugil liza.

We herein investigated the influence of temperature on theembryonic development (from fertilisation to hatching) of Mugil liza larvae. For this purpose, oocytes (>600 μm) and sperm were obtained from breeding stock at the laboratory of marine fish culture (LAPMAR). After fertilisation, 1200 eggs were distributed in 12 cylindrical experimental units of 400 mL under four different temperatures 18, 22, 26 and 30 ºC, all in triplicate. Every 15 min until hatching, about 10 eggs were randomly sampled in each treatment. The eggs were visualized and photographed, and the classification of embryonic stages was performed. Temperature influenced the main events of the embryonic development of M. liza. More accelerated development was observed according to the increase in temperature until the gastrula phase. At temperatures of 22 and 26 °C, embryonic development occurred from fertilisation to hatching of the larvae. In the 18 °C treatment, it was verified that most of the embryos ceased development during the final phase of cleavage and the beginning of blastula formation, while in the 30 °C treatment patterns of embryo malformation were also verified, with erratic divisions of the blastomeres, resulting in irregular cells. Unlike what was observed at a temperature of 18 °C, none of the embryos incubated at 30 °C reached the blastopore closure phase, stopping in the gastrula. The larvae hatched in the treatments at 22 and 26 °C were viable and exhibited intense swimming, with a large amount of reserve material (yolk) and an evident drop of oil.

Development of a Technological System of Floating Cages in the Sea for the Farming of Marine Fish Within the Coastline of ILO

The objective of the research work is to develop a technological system of floating cages in the sea for the culture of marine fish within the coast of Ilo. The research method is experimental, applied approach, the process is constituted by a marine cage system which includes the analysis of climatic conditions, oceanographic conditions, legislation, adequate environment and conditions suitable for the development of the project; to then design the prototype to operate the floating sea cage. The preliminary results through the study "Development of technical capacities for the cultivation of Corvina "Cilus gilberti" in the province of Ilo, Moquegua Region" through which the culture cages were installed approximately 1.2 km from the coast in front of the beach "Piedras Negras" north of Ilo in which juvenile corvina were planted. The design and construction of the marine cage for fish culture was appropriate because the materials used are in the optimal quality range, after submitting them in the simulations; you have fish in preliminary growth in the marine cages designed and built for fish culture; and finally, the maintenance of the cages was technically manageable, because it allows periodically its evaluation and maintenance.

Evaluation of the green development efficiency of marine fish culture in China

Green development efficiency (GDE) is an important criterion for measuring the level of green development. GDE considers not only economic development efficiency but also environmental costs. In China, marine fish culture, as one of the pillar industries of mariculture, promotes green development and industrial transformation and upgradation. Based on data from the field surveys of marine fish farmers (2017–2019) and the China Fishery Statistical Yearbook (2018–2020), this study establishes an evaluation index system and uses the super-slack-based measure model (Super-SBM) to evaluate the GDE of marine fish culture. The results show that the average GDE of marine fish culture in China was 0.9529, which was in an inefficient state. As for culture species, golden pompano (Trachinotus ovatus) and cobia (Rachycentron canadum) were the two species farmed in an efficient state, with a GDE of 1.2107 and 1.0659, respectively. Regarding culture modes, green modes (offshore cage aquaculture, industrial recirculating aquaculture, and engineering pond aquaculture) were in an efficient state, with a GDE of 1.2310, 1.0827, and 1.0401, respectively. Traditional modes (industrial flow-through aquaculture, ordinary cage aquaculture, and ordinary pond aquaculture) were in an inefficient state, with their GDE being 0.9884, 0.8746, and 0.8248, respectively. Green modes have higher GDE than traditional modes. In contrast, the production and culture areas of green modes were less than those of traditional modes because the profits of the same species in green modes were lower than those in traditional modes. The results of this study present an objective assessment of the GDE of marine fish culture in China and provide valuable insights for analyzing the mechanisms to improve the GDE of marine fish culture.

Substitution effect of fish meal with meat meal in diet on growth performance, feed consumption, feed utilization, chemical composition, hematology, and innate immune responses of rockfish (Sebastes schlegeli)

Fish meal (FM) is widely used as a main protein source in formulated feed for marine fish culture. However, the production of FM has shrunk or plateaued due to the overfishing and climate change in the wild. Meat meal (MM) is known as a good replacer for FM in fish feeds. Dietary replacement effect of MM for FM on the growth, feed consumption, feed utilization, body composition, hematology, and innate immune responses of rockfish was determined. A total of 630 fish (initial weight of 2.3 g) was randomly distributed into 21, 50 L flow-through tanks (30 fish/tank). Seven experimental diets were formulated. The control (MM0) diet contained 55% FM. Then, 10, 20, 40, 60, 80, and 100% FM in the MM0 diet were replaced with MM, referred to as the MM10, MM20, MM40, MM60, MM80, and MM100 diets, respectively. All experimental diets were allocated to triplicate groups of fish. Fish were hand-fed to visual satiation twice a day for 8 weeks. Increased substitution of FM with MM in diets resulted in decreased essential amino acids (EAA), such as lysine and threonine and the sum n-3 highly unsaturated fatty acids, but increased EAA, such as arginine and methionine, and the sums of saturated and monoene FA. Weight gain (9.8 g/fish) of fish fed the MM10 diet was significantly (P < .003) greater than that (8.8, 8.9, 8.2, and 7.9 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Specific growth rate (SGR) (2.93%/day) of fish fed the MM10 diet was significantly (P < .004) higher than that (2.79, 2.69, and 2.64%/day, respectively) of fish fed the MM0, MM80, and MM100 diets. Weight gain and SGR of fish fed the MM100 diet were (P < .05) significantly lower than those of fish fed the MM0 diet. Feed consumption (9.34 g/fish) of fish fed the MM10 diet was significantly (P < .002) higher than that (8.72, 8.59, 8.32, and 8.10 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Feed efficiency (1.04%) of fish fed the MM10, MM40, and MM60 diets was significantly (P < .009) higher than that (0.99, and 0.98%, respectively) of fish fed the MM80, and MM100 diets. Condition factor, protein efficiency ratio, protein retention, hematological parameters, and innate immune responses (lysozyme and superoxide dismutase activities) of fish was not significantly (P > .05) different among the experimental diets. The chemical composition, and AA and FA profiles of the whole-body fish were not influenced by the experimental diets. In conclusion, dietary substitution FM up to 80% with MM can be made without deteriorating growth performance of rockfish. However, the optimum substitution level of FM with MM in diets were estimated to be 18.5, and 18.2% based on regression analysis of weight gain and SGR of rockfish, respectively.

Title: Effects of Using Different Diets in the Growth Performance of Mangrove Red Snapper Lutjanus argentimaculatus

The mangrove red Snapper (Lutjanus argentimaculatus) is a high-value marine fish and ideal culture species. The study was conducted to evaluate the growth and survival rate of mangrove red snapper fed with different diet types. The study was laid out in a randomized setup using three (3) treatments: Treatment 1- Trash fish, Treatment 2- Golden apple snail, and Treatment 3- Fiddler Crab using One- way ANOVA as a statistical tool. Based on the result of the study, mangrove red snappers fed with Trash fish gained the highest growth rate in terms of length, width, and weight of 8.89 cm, 2.19 cm, and 63.46 g. However, samples fed with fiddler crab (T3) obtained the lowest growth rate in terms of length, width, and weight of 3.72 cm, 1.06 cm, and 43.86 g. This study demonstrates that the samples got a 100% survival rate regardless of the treatment used. Furthermore, the result showed a significant difference in the growth rate of Mangrove Red Snapper in terms of length F=2100.544, width F=175.280, and weight F=319.770 with P<0.0001. Therefore, it was concluded that the use of trash fish (halfbeak and scalloped perchlet) is effective as a feed for the growth and survival of the Mangrove Red Snapper

A remotely controlled automated field measurement system for light extinction in coastal waters

The Secchi disk depth (SD) is an important parameter in aquatic ecosystem monitoring. As algal growth depends on solar irradiation, the SD - a measure of light extinction - gives an indirect indication of the chlorophyll concentration. However, most SD measurements are manually based and too sparse to resolve water quality variations during algal blooms.A remotely controlled automatic system for field measurement of light extinction has been developed and installed in three marine fish culture zones in Hong Kong. The visual images of the disk at different prescribed depths and the surrounding water are taken. Based on the contrast theory and image analysis, the recorded light intensity distributions can be analyzed to give the SD and the light extinction coefficient. The method has been extensively verified by field data over a wide range of water quality and hydro-meteorological conditions. The proposed system enables high frequency SD measurements on demand for environmental management and emergency response.

Report of a Fish Kill Due to a Dinoflagellate Bloom in Perak and Penang, Malaysia

A fish kill incident was reported at the marine fish culture areas north of Perak and south of Penang, Malaysia, on 26 May 2020. An investigation was carried out at 10 stations in Kerian, Perak and Seberang Perai Selatan, Penang. Seawater samples were collected to identify microalgae species and determination of dissolved inorganic nutrients. The physical parameters of water such as salinity, pH, temperature and dissolved oxygen were measured in situ while the dissolved inorganic nutrients were analysed spectrophotometrically. The dominant microalga was identified as Margalefidinium fulvescens (Iwataki, Kawami &amp; Matsuoka) Gómez, Richlen &amp; Anderson, 2017, based on the morphological and molecular characterisation of the large subunit ribosomal gene. Long rounded and ellipsoidal cells, 30-43 µm in length, appeared in chains of single, two, four or eight cells. The sulcus was slightly narrow surrounding the cell about one turn, but the cingulum was rather deep, encircling the cell approximately twice, and the chloroplasts were brownish, granular and scattered peripherally. The highest M. fulvescens cell counts were recorded at 6.22 × 105 cells L-1 and 4.61 × 105 cells L−1 in Kerian, Perak and Seberang Perai Selatan, Penang, respectively. The physical parameters of the seawater from the affected sites were within the Malaysian Marine Water Quality Standard (MMWQS) for aquaculture. However, slightly higher levels of nitrate, phosphate and ammonia were noted at several stations. Although the exact cause of the bloom was undecided, it could be due to nutrient discharge along the coasts, which also concurred with the transition phase of the northeast to the southwest monsoon.

PH Regulates the Formation and Hatching of Cryptocaryon irritans Tomonts, Which Affects Cryptocaryoniasis Occurrence in Larimichthys crocea Aquaculture.

Cryptocaryon irritans are the main pathogens of white spot disease in marine teleost. However, the occurrence of cryptocaryoniasis is influenced by several abiotic factors including the pH. To explore the effect of pH on the life cycle of C. irritans (encystment, cleavage, and hatchability), protomonts and tomonts of C. irritans were incubated in seawater of 10 different pH levels (2-11). pH 8 was used as the control. The change in morphology and infectivity of theronts that hatched from tomonts against Larimichthys crocea were then recorded. We found that pH 6-9 had no significant effect on the encystment, cleavage, and hatching of the parasites. However, pH beyond this limit decreased the cleavage and hatching of the tomonts. Furthermore, extreme pH decreased the number of theronts hatched by each tomont and the pathogenicity of the theronts, but increased the aspect ratio of the theronts. Infectivity experiments further revealed that extreme pH significantly decreased the infectivity of C. irritans against L. crocea. In conclusion, the C. irritans can survive in pH of 5 to 10, but pH 6-9 is the optimal range for the reproduction and infectivity of C. irritans. However, extreme pH negatively affects these aspects. IMPORTANCECryptocaryon irritans is a ciliate parasite that causes "white spot disease" in marine teleosts. The disease outbreak is influenced by hosts and a range of abiotic factors, such as temperature, salinity, and pH. Studies have shown that change in pH of seawater affects the structure (diversity and abundance of marine organisms) of marine ecosystem. However, how pH affects the life cycle and survival of C. irritans, and how future ocean acidification will affect the occurrence of cryptocaryoniasis, are not well understood. In this study, we explored the effect of pH on the formation and hatching of C. irritans tomonts. The findings of this study provide the foundation of the environmental adaptation of C. irritans, the occurrence of cryptocaryoniasis, and better management of marine fish culture.

Three-dimensional path following control system for net cage inspection using bionic robotic fish

With the increasing impacts of overfishing and environmental pollution, the deep-sea cage culture of marine fishes has become an important direction of mariculture. In this paper, a tuna-like robotic fish with a three-dimensional helix path-following control system is designed for deep-sea net cage inspection. To mimic the flexibility of the fish’s movement, the kinematic model of the robotic fish adopts a tuna-like double-joint design with an additional thruster device at the tail. Since the descending interval control plays a critical role in deep-sea net cage inspection, the control system utilizes the proportion integration differentiation (PID) based fuzzy logic control method to control the descending interval and yaw angle during the helix path movement. A polar coordinate path definition method is also proposed to simplify the reference path definition during net cage inspection. The experimental results demonstrates that the proposed three-dimensional path-following model can conduct net inspection task in an interferential environment and move along predefined reference path.

Integration of metabolomic and transcriptomic analyses to characterize the influence of the gill metabolism of Nibea albiflora on the response to Cryptocaryon irritans infection

The parasite Cryptocaryon irritans causes massive losses in the marine fish culture industry and is one of the most threatening pathogens affecting teleost species. The acute death of infected fish is primarily caused by the destruction of gill cells, resulting in osmotic imbalance and respiratory stress. C. irritans has wide host specificity; however, the yellow drum Nibea albiflora is highly resistant to this parasite. Metabolomic approaches in combination with transcriptomic analysis were used to characterize the host immune reaction and metabolic changes in yellow drum in response to C. irritans infection and to identify the key genes and compounds in the gills that have the strongest contribution to disease resistance. The yellow drum was challenged with theronts at a median death rate (2050 theronts per gram fish). The samples were collected from the gills 24 h and 72 h after the infection (hpi). The results of metabolomic analysis indicated that metabolites involved in energy metabolism were predominantly downregulated. In contrast, a compensatory increase in the expression of the genes involved in the citric acid cycle and glycolysis was detected 24 hpi. The suppression of metabolites was alleviated after feed intake recovery 72 hpi. The levels of amino acids were decreased, and the expression of aminoacyl-tRNA was increased. Additionally, elevated levels of arachidonic acid derivatives, primarily prostaglandins, were responsible for anti-inflammatory, osmotic, and hypoxia regulations. Purine metabolism was also involved in the immune response via generation of reactive oxygen species catalyzed by xanthine oxidase. A significant increase in the generation of retinoic acid, which could enhance mucosal adaptive immunity by stimulating the synthesis of antibodies and accelerating the restoration of epithelial integrity, was observed at 72 hpi. This result was consistent with high expression of the genes related to secreted immunoglobulin T 72 hpi. In conclusion, the present study comprehensively described the key compounds and genes related to C. irritans infection in yellow drum gills. Biomarkers that were significantly changed during the infection may represent future targets for nutritional intervention to enhance host immunity against C. irritans infection and to accelerate disease recovery.

The Application of Duckweed Liquid Organic Fertilizer to Cell Populations in the Culture of Nannochloropsis oculata

Nannochloropsis oculata is one of the single-celled microalgae that has been commonly cultured in the marine fish culture sector as zooplankton feed which has high nutritional content. To support growth and reproduction, the availability of nutrients in N. oculata culture media needs to be considered. This study aims to determine the effect of the best liquid organic fertilizer (POC) duckweed (L. minor) on cell population growth in N. oculata culture. The method used in this research is an experimental method using Completely Randomized Design (CRD) with 5 treatments, namely P0 (TSP 10 mg + ZA 40 mg + urea 45 mg) as a control treatment, P1 (POC duckweed 5%), P2 (POC duckweed 10%), P3 (POC duckweed 15%), and P4 (POC duckweed 20%) were repeated 3 times in each treatment. The initial density of N.oculata cells was 2 x 106 cells/ml in a culture media volume of 1000 ml. Growth was observed every day for 14 days. The results showed that the POC concentration of 10% duckweed can be used as an alternative to inorganic fertilizers (TSP, ZA, and urea) because it can increase cell population growth by 30.92 ± 1.84 cells/ml at the peak of the exponential phase, as well as the value of the growth rate. cells 0.38 ± 0.03 cells / ml / day and cell generation time of 43.88 ± 3.24 hours were not significantly different (p&gt; 0.05) with P0 treatment (TSP, ZA, and urea). The range of water quality parameters in the culture media during the study were temperature 25-33oC, pH 4.89-8.40, salinity 25-38.33 ppt, and DO 4.07-7.27 ml / l. The measured value of water quality in culture media was still within the tolerance limits of N. oculata cells so that cells could still grow and divide.

Real-time automated identification of algal bloom species for fisheries management in subtropical coastal waters

Harmful Algal Blooms (HAB) pose significant challenges to fisheries management and food and water security. The onset of a HAB is notoriously difficult to predict. Traditional methods of algal species identification under a microscope are also laborious and time consuming. A real-time system for identification and concentration measurement of algal bloom species has been developed at a marine fish culture zone (FCZ) in the subtropical coastal waters of Hong Kong. The system is based on analysis of high frequency algal cell images obtained from an underwater Imaging FlowCytobot (IFCB) deployed on the fish farm. An explainable supervised machine learning technique has been successfuly developed. The algal species classifier is trained by presenting a wide range of extracted image features to a random forest algorithm. An optimized set of 25 features is identified by a recursive feature elimination technique. The random forest (RF) classifier can identify 15 target HAB classes with an overall out-of-bag accuracy of 94.2%, with individual F1 score ranging from 0.8 to 1.0. The classifier performs equally well as a Convolution Neural Network (CNN) developed using transfer learning techniques. Based on the classifier, an automated real-time species identification and cell counting protocol has been developed, with a response time of 10 min after data collection. This work represents the first successful attempt of continuous algal species monitoring by IFCB and artificial intelligence (AI) – based detection of HAB in subtropical coastal waters.

Comparison for ecological economic performance of Chinese sea perch (Lateolabrax Maculatus) under different aquaculture systems

Chinese sea perch (Lateolabrax Maculatus) is one of the main marine fish culture species in China, its green development has received increasing attention and its ecological economic study is rare. Based on field survey, this paper takes water pollution tax of China as conversion indicator for aquaculture eutrophication to simulate aquaculture waste fee for further analyzing the ecological impact of Chinese sea perch's aquaculture. For data analysis, data envelopment analysis model has been used. The comparison for Chinese sea perch's economic performance and ecological economic performance under its main aquaculture systems has been done. The results show that: 1. The simulated waste fee has no significant impact for the comparison. 2. Ranking for ecological economic performance's ecological economic, technical and scale efficiency is as follow: pond farming, offshore cage culture and cage culture. 3. Offshore cage culture is the only system presenting positive increase for ecological economic performance, which makes its aquaculture activity more sustainable than other systems. 4. The key point of green development is to maximize the ecological economic efficiency of main aquaculture systems. Thus, offshore cage culture is the most sustainable aquaculture system among China's current marine fish culture systems, and other systems need innovation for achieving the green development of China's aquaculture.

Marine Fish Primary Hepatocyte Isolation and Culture: New Insights to Enzymatic Dissociation Pancreatin Digestion.

Primary cell cultures from wild organisms have been gaining relevance in ecotoxicology as they are considered more sensitive than immortalized cell lines and retain the biochemical pathways found in vivo. In this study, the efficacy of two methods for primary hepatocyte cell isolation was compared using liver from two marine fish (Sparus aurata and Psetta maxima): (i) two-step collagenase perfusion and (ii) pancreatin digestion with modifications. Cell cultures were incubated in L-15 medium at 17 ± 1 °C and monitored for up to six days for cell viability and function using the trypan blue exclusion test, MTT test, lactate dehydrogenase (LDH) activity, and ethoxyresorufin O-deethylase (EROD) activity after Benzo[a]Pyrene exposure. The results showed significant differences between the number of viable cells (p < 0.05), the highest number being obtained for the pancreatin digestion method (average = 4.5 ± 1.9 × 107 cells). Moreover, the hepatocytes showed solid adherence to the culture plate and the rounded shape, changing into a triangular/polygonal shape. The cell viability and function obtained by pancreatin digestion were maintained for five days, and the EROD induction after exposure to the B[a]P showed that cells were metabolically active. This study shows that the optimized pancreatin digestion method is a valid, cost-effective, and simple alternative to the standard perfusion method for the isolation of primary hepatocytes from fish and is suitable for ecotoxicological studies involving marine pollutants, such as PAHs.

Dynamics of Competition in the Marine Aquaculture Industry: A Research on Turkey

In this study, competition elements of marine fish culture industry in Turkey was investigated. Today, with the development of technology people's access to information has facilitated. People, with access to information, began to give importance to a healthy nutrition. Therefore; as a source of healthy protein, the demand for fish is increasing day by day. Also, this increasing demand motivates growth of fish farming industry intensevely. The production of fishery products are performing almost without any problem. Enterprises which are reaching higher levels in technical knowledge on aquaculture, focus at fierce competition with each other. The aim of this study is to uncover how the elements like; aquaculture enterprises, feed producers, processing enterprises, ministry employees, universities, retail businesses, research institutes and employees working for suppliers determine the competition in the sector. Survey prepared for this purpose was conducted with 344 people. Results were evaluated and interpreted both separately and in total according to business types in the sector. In the industry, selling prices of products, quickly delivering products to the market, and financial power were determined to be important competitive factors.

Geographic Information System as an instrument to determine suitable areas and identify suitable zones to the development of emerging marine finfish farming in Brazil

Worldwide, the availability of suitable areas for aquaculture has become a significant concern. In Brazil, the former Ministry of Fisheries and Aquaculture (MPA) has begun to promote discussions and plan meetings on Local Mariculture Development Plans (PLDMs): a planning tool for the establishment of parks and aquatic areas. However, hundreds of groups and individuals still practice aquaculture awaiting a definitive license. This study aimed to serve as a tool to identify suitable sites for the installation of cobia cage farming and also to contribute to the PLDM zoning process. We created 27 criterion maps for marine fish farming. Their individual weights were assigned based on the best judgment of technicians, researchers and other stakeholders using the pair-wise comparison method. The criteria and their weights were combined using multi-criteria decision rules, and a final map according to suitability was derived by reclassification. Of the total area, 54,663 ha (14%) were composed of restrictions, and 341,083 ha (86%) were found useful; of which <1% is considered top score. Even so, these are more than enough to ensure the growth of activity. In Rio de Janeiro state, two bays have suitable areas to marine fish culture development. To ensure the sustainability of marine fish farming, we suggested the adoption of limited production areas based on assimilation and production capacity. Through this methodological approach, it was possible to identify suitable areas for cobia farming development. Additionally, the results may serve as a useful tool on which the PLDM can be based on.

Review Vibriosis Management in Indonesian Marine Fish Farming

Vibriosis is a bacterial disease that has been reported in Indonesian marine fish culture since the 1990s. The disease was reported mostly in grouper and shrimp (monodon and vanname) farming, although the infections in snapper (Lates calcarifer)and abalone (Haliotis squamata)aquaculture were also occurred. Causative agents of vibriosis in Indonesia marine fish is involving 14 species of vibrio namelyVibrio harveyi, V. anguillarum, V. alginoluticus, V. parahaemolyticus, V. fluvialis, V. furnisii, V. methcnikovii, V. vulnificus, V. ordalii, V. cincinnatiensis, V. carchariae, V. azureus, V. mimicus and V. damsela. Control of vibriosis is conducted with water quality management, applications of vaccines, antibiotics, probiotics and immunostimulants. Most vaccines developed and commercially available in Indonesia are in the form of inactive-whole cell types. The vaccine product is effective enough to protect fish from vibriosis. Probiotics have been widely studied since the 2000s and have been shown to increase fish and shrimp growth and resistances against vibriosis. Immunostimulants began to be developed since 2010 based on the extracts of terrestrial plants, seaweeds and chitosan. It is therefore concluded that the continuous existence of pathogenic strains in aquaculture farm requires further development of the control methods, including periodic updating of the vaccines, probiotics and immunostimulant formulas for more potent efficacies.

Characterization and production of IgY antibodies anti-Photobacterium damselae subsp. piscicida: Therapeutic and prophylactic use in Rachycentron canadum

Pseudotuberculosis is caused by Photobacterium damselae subsp. piscicida (Phdp), an important pathogen in marine fish culture. In this study, Phdp isolated from a Rachycentron canadum farm was used to produce anti-Photobacterium damselae IgY and its protective effect were evaluated in R. canadum challenged with the homologous strain. The IgY was obtained from egg yolks of White Leghorn hens using polyethylene glycol precipitation method. Anti-Phdp IgY showed strongly specific reaction against Phdp proteins. Finally, it was performed the antibody efficacy in vivo to determinate their prophylactic and therapeutic effects during sepsis in R. canadum. For this, fish received anti-Phdp IgY 48 h and 15 days before the challenged with the homologous bacteria of Phdp. In these groups, it was observed less liver and kidney lesions comparing to control group, which was also correlated to the biochemical profile. In this study, it was also developed an immunohistochemistry test that presented highly specificity and affinity to Phdp that could be used as screening method for the diagnosis and analysis of pathogenesis of this disease. It was concluded that the IgY produced effectively inhibited the dissemination of this bacteria that could be helpful for the treatment and prophylaxis of this disease.

Stress tolerance and photoadaptation to solar radiation in Rhodymenia pseudopalmata (Rhodophyta) through mycosporine-like amino acids, phenolic compounds, and pigments in an Integrated Multi-Trophic Aquaculture system

Rhodymenia pseudopalmata lives in the intertidal zone receiving high doses of solar radiation, including the potentially harmful UVR. Previous studies proved it ability to adapt to different artificial light intensities and salinity concentrations. The aim of this study was to describe the differences on the Mycosporine-like amino acids (MAAs), phenolic compounds, and pigments of R. pseudopalmata due to exposure to high solar radiation. Vegetative thalli were exposed to solar radiation using a Solar Exposure Chambers System (SECS) under an Integrated Multi-Trophic Aquaculture (IMTA) approach with marine fish culture. Samples from natural populations in Playa de Carmen, Mexico were included as reference. The biosynthesis of MAAs, and phenolic compounds were stimulated as a response to the stress caused by the exposure to high solar irradiation. Liquid Chromatography-Mass Spectrometry (LC-MS) revealed seven MAAs and their precursor deoxygadusol. Five MAAs were partially characterized through MS2 and fragmentation patterns suggested a common fragmentation pattern pathway. After seven days (D7), the MAAs total content was significant five-fold higher compared to wild populations (0.26 ± 0.1 mg g−1 DW). The Individual composition increased from four MAAs at D0, up to eight at D7, including deoxygadusol, palythene and usujirene, MAAs with high antioxidant activity. At D7, phenolic compounds increased up to 20%, and the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity reduced the IC50 to 4.0 ± 0.6 mg mL−1. The pigment content, Phycoerythrin (PE):Chl-a, and MAAs:Chl-a ratios might confer a unique photoprotection role from PE and MAAs to Chl-a. Similarly, Fv/Fm which was adapted to the variations of Photosynthetic Active Radiation (PAR) indicated a process of dynamic photoinhibition. Overall, our results evidenced the ability of this species to tolerate the stress to high solar irradiance and suggested the photoadaptation of the thalli. Farming possibilities, expected MAAs productivity, potential applications of MAAs and ecological considerations are also discussed.

Common moist diet replacement to promote sustainable Cobia Rachycentron canadum (Linnaeus) near- shore farming in Brazil

ABSTRACT: Cobia is one of the most promising warm water aquaculture species. In Brazil, cobia farming began in 2008 in the state of Rio de Janeiro from experimental scale facilities to regular near-shore farms based on fresh/frozen fish diets composed mostly of Sardinella sp. Despite the encouraging results achieved in the promotion of sustainable cobia farming, we advocate the replacement of fresh/frozen fish by a practical formulated feed. This experiment evaluated the zootechnical performance and environmental efficiency of moist and practical formulated feeds in early grow-out phases in the cycle of cobia nearshore cage culture. Four hundred and twenty juvenile cobia (151 ± 7 g) were fed with moist feed and practical formulated feed for 56 days. Biometrics were taken every two weeks and diets were analyzed for proximate composition, fatty acid composition and pellet quality. Although growth performance was equivalent between treatments, feed consumption and feed conversion ratios (FCR) were different (p < 0.05) and varied according to water temperature. Cobia fed moist feed exhibited an FCR two times higher than those fed formulated feed. Elevated settling speed and low floatability contributed to higher heterogeneity and lower efficiency of fish fed moist diet. Nitrogen excretion rate was reduced (64 %) and protein efficiency ratio elevated (27 %) within formulated diet groups in comparison to those fed moist diet (79 % and 15 %, respectively). The fatty acid profile of cobia muscle was similar across the groups. With no negative effects of diet substitution on production performance and improvement of environmental efficiency, this approach can be applied and advocated globally and contribute to the responsible intensification of sustainable marine fish culture.