Sea Cage Culture Research Articles

Mapping of potential sea-cage farming sites throughspatial modelling: Preliminary operative suggestionsto aid sustainable mariculture expansion in India

Sea cage farming in marine open waters is considered as the most viable technique in Indianmariculture to enhance production. Owing to the support of the government in researchand development, and policy initiatives, marine cage farming is progressing steadily in thecountry. Technological guidance from research institutions and financing under the ambitious“Pradhan Mantri Matsya Sampada Yojana (PMMSY)” and blue growth mission objectives haveinspired stakeholders and fisheries administrators in maritime states to explore open seacage culture. Site selection is a key parameter affecting the success of cage culture systemsand, technically analysed geo-referenced demarcation of spatial information is necessaryfor minimising the risks. Thus, in the light of rising demand for spatial allocation of coastalareas, the present study identifies and aggregates locations within 3 km of the coastline,that have the potential for sea cage farming operations in the country. The site suitabilitywas examined based on optimal standards required for the prospective candidate speciesselected for mariculture in India. The locations were vectorised in a GIS platform, and thepotential areas available for sea cage installations were demarcated. An optimised sitesuitability schema was developed for the spatial demarcation of potential site selection.The preliminary results identified 134 sites covering a total area of 46,823.2 ha suitablefor marine cage culture along Indian territorial waters. Among the coastal states, the topthree states holding the maximum area suitable for sea cage farming are Andhra Pradesh(11,792 ha), Gujarat (11,572.2 ha) and Tamil Nadu (7,673 ha). It is envisaged that spatialsuitability demarcation even on this pilot scale will accelerate the expansion of sea cagefarming in the country. Keywords:GIS Mapping, Mariculture, PMMSY, Sea cage farming, Site suitability, Spatial planning

Nighttime Lighting Influences on the Plankton Feeding and Growth of Juvenile Pacific Bluefin Tuna, Thunnus orientalis.

During fingerling production of Pacific bluefin tuna (PBF) Thunnus orientalis, heavy mortality can occur immediately after juveniles are transferred from nursery tanks to sea cages; however, nighttime lighting can moderate this mortality. Additionally, various live prey aggregate due to nighttime lighting in practical sea cage culture of PBF. Here, we investigated whether the growth and viability of PBF juveniles could be improved through promoting feeding on live prey that aggregate under nighttime lighting. Two treatment groups were established using land-based tanks under constant environmental conditions, one in which the juveniles were fed live prey at night (night-feed in four replicate tanks) and the other in which juveniles were not fed during the night (control in four replicate tanks). Although the survival rate did not differ significantly between the two groups, growth was significantly improved in the night-feed group, in which 69-78% of the juveniles showed evidence of feeding during the night. Thus, nighttime lighting plays a vital role in the aggregation of various live prey. PBF juveniles consume these prey in sea cages, which promotes their growth. This may partially serve as a countermeasure against the heavy mortality observed in sea cages.

Growth at molt of sub-adult scalloped spiny lobster Panulirus homarus reared in tanks

Grow-out of lobster performed in a tank culture system offers several advantages over floating sea cage culture, particularly in the control of environmental factors. However, the growth of lobster reared in tanks need to be evaluated to determine the rearing period of lobster to achieve market size. Growth in lobster is defined as the change in size through the molting process. Therefore, this study was performed to assess differences in weight and length increment at molt of male and female sub-adult scalloped spiny lobster Panulirus homarus, as well as to determine the annual weight increment of the lobster reared in tanks. Sub-adult lobsters with an initial average weight of 226.18±20.30 g were stocked in twenty 4000-L fiber tanks at 20 lobsters/tank. Each lobster was tagged by a photographic method of the carapace to enable the identification of individual molt, as well as growth increment. Observation of molt and growth of lobster was carried out for 42 days of rearing. Growth observation for 42 days showed that the length increment between male and female lobsters was significantly different. The average length increment of the male was significantly higher (10.00 mm) than those of the female (7.93 mm) (p<0.05). However, the weight increment was not different between the sexes. The average weight increment of males and females was 18.53 g and 20.71 g, respectively (p>0.05). In terms of the annual weight increment, both sexes also had fairly similar growth, achieving 168.38 g.yr-1, on average. This study found that there was increased growth, zero growth, and declined growth at molt in lobster P. homarus.

Design of water surface collection robot based on deep sea cage culture

At present, the collection of floating garbage such as dead fish in deep and far sea cage culture waters mainly depends on manpower, which is not only difficult and inefficient, but also has great potential safety hazards. In order to solve the above problems, a water surface collection robot based on marine cage culture is designed and developed. The dead fish on the water surface are collected through the joint action of propeller and forearm drainage and retraction device. At the same time, the relevant performance indexes of the designed water surface collection robot are verified by making the prototype and water surface collection experiments, which meets the needs of simple and efficient collection and cleaning of dead fish in deep and open sea cage culture, so as to provide a reference basis for the practical application of the collection robot.

Socio-economic elevation through open sea cage farming-Evidence from Mandapam region of Tamil Nadu, India

Cage culture guarantees the multiplication of seafood output and revenue generation from a small unit area when compared to significant capital investment oriented onshore farming technologies. The Mandapam Centre for Sustainable Aquaculture (MCeSA) of Tamil Nadu Dr. J. Jayalalithaa Fisheries University (TNJFU) through the cage culture demonstration as part of the NFDB-funded project ‘Open Sea Cage Culture of Marine Finfishes along the Coast of Ramanathapuram District in Tamil Nadu’ is continuously involved in disseminating this valuable technology which provides higher yield and income to meet the alternative livelihood needs and to uplift the socioeconomic conditions of the coastal fisherfolk in Ramanathapuram District, Tamil Nadu. Case studies were undertaken in the region to assess the impact of MCeSA and a success story of Mr. V. Nagadas, one of the NFDB scheme beneficiaries is shared here who has implemented the cage culture of lobster and earned a total profit of 280000 INR. The farmer's success and the MCeSA's technical guidance and support are now inspiring other fishermen to adopt the farming.

Community-Based Cobia, Rachycentron canadum (Linnaeus, 1766) Culture in Open Sea Cages at Olaikuda, Pamban Island, India: An Economic Analysis of Technology Transfer Initiative

The Olaikuda Village of Pamban Island was chosen to demonstrate and transfer the open sea cage culture technology of cobia by the National Institute of Ocean Technology (NIOT). Olaikuda is a fishing hamlet with 1,000 traditional fishers who are primarily involved in trap fishing. An attempt was made to supplement their income under the societal development initiative of the NIOT. With the active participation of the local fishers of Olaikuda, 3,000 hatcheryproduced cobia, Rachycentron canadum (Linnaeus, 1766) fingerlings were stocked equally in two cages with a stocking density of 4.7 fingerlings.m-3 . The cobia stocked in sea cages were reared with the locally available low-value fishes for 8 months. The sea farmed cobia attained an average weight of 3.3 kg resulting in an average daily growth rate of 13.5 g with a survival rate of 75 %. The fish were harvested on the 245th day of culture, which yielded 7,000 kg of marketable size cobia fish (1st cage 3,687 kg and 2nd cage 3,313 kg with an FCR of 1:5.5). The harvested fish were sold at the farm gate price of USD4.42 kg-1 , fetched USD30911.84. The economic analysis revealed a profit margin of USD1.26 kg-1 . The parameters such as cost of production, productivity, profitability, socio-economic impacts of native fishers were analysed during the study. The result of this farmer-driven attempt is encouraging the farmers across the coastal states to do cage culture farming in a big way. Similar efforts in more organised massive programs will create new jobs and reduce the fishing pressure on the natural sea stocks and considered a viable alternative livelihood for the fishers’ community affected by the declining natural fishery resources and international border issues.

Short term culture of wild caught juvenile rabbit fishes (Siganus javus) in open sea cages at Palk Bay

Objectives: The main objective of the study was to collect and rear the unmarketable, small sized S.javus which is mostly rejected by the traditional fisherman. During fishing activities, under sized S.javus ranging in sizes from 25 to 40 kg (&lt; 30-40 % of total catch/day) is being captured. Due to very low marketable value these small fishes (&lt;250 g) get rejected. Therefore, we utilized this as an economically viable option for utilization as seeds for rearing until they reach the necessary marketable size. Methods: Undersized juveniles (12-16 cm, 40 -55 g) were collected from nearby Olaikuda village,Rameshwaram using traditional traps made using bamboo and odai tree bark (Acacia planifrons). The collected juveniles were stocked in sea cages and fed with locally formulated plant based feed containing 28-32 % crude protein. Findings: Harvesting was successfully done after 140 days with 90 % survival. The average growth rate achieved was 2.5 g /day with FCR of 2.01. This resulted in an average harvest size of 400 g/fish from its initial stoking size of 50 g with an attracted market value of Rs. 150/kg. Novelty: Till date, no attempts were made to commercialize such harvesting techniques for the species Siganus javus in pilot scale in India (Except James, 1984). Keywords: Rabbit fish; Siganus javus; sea cage culture; rabbit fish culture; Siganidae

A Study on Ecological Succession of Macrofouling Communities in Sea Cage Farm in South-West Coast of India

Development of aquaculture facilities like cages has led to rise in submerged structures which provide ample substratum to biofoulers which could greatly interfere with culture operations. An attempt was made to study the biofouling communities and succession of macro foulers on the cage culture net installed in the open sea. The main objective of the present study is to reveal the succession pattern of the biofouling communities on the panels of cage culture sites to find out seasonal settlement pattern, Dominant species and Climax community. A long-term study on the succession pattern of the cage farm experimental-net-panels revealed results as Hydroids-Gastropods-Hydroids-Barnacles-Modiolus-Green mussels. Hydroids were initial communities on the net panels and green mussels (Perna viridis) formed the climax community, also dominating on the cage culture nets. Different succession patterns were observed in two sites as well as in culture nets studied. The net panels of the cage were loaded with hydroids in the initial months and the peak fouling was during May. So frequent net cleaning was required during summer and during the spat settlement period of green mussel (September, October and November). Modiolus settlement during February month on the culture nets can be avoided by net exchange immediately after spat fall in this month. This attempt was made to study the ecological succession on the panels, in cages installed in Karwar, which is the first attempt, since the open sea cage culture was initiated in India. Looking at vast opportunities for further development in biofouling research, the aim of this investigations was to obtain the baseline information about the ecological succession pattern of biofouling organisms in fish cage sites. More research on biofouling in mariculture is essential to ensure the profitability of the aquaculture operations with environmental safety measures as a prime criteria&#x0D;

Health status evaluation of striped bass ( Morone saxatilis ) exposed to low temperature in sea cage culture during the grow‐out

Striped bass (Morone saxatilis) is a species with high production potential for human consumption. However, like any other cultured species, they are prone to be exposed to adverse climate conditions, compromising their health status until a certain degree compromises the success of reaching commercial size. It is proposed that haematological parameters testing during the whole growing out season represents a useful tool to assess the overall fish health status. Information on M. saxatilis haematology is limited. Therefore, the present study aimed was to provide the haematological and blood chemistry values for commercial striped bass grow-out. Fish from three different group sizes and under low sub-optimal temperature (16 to 18°C) were sampled in correlation to copepods (Peniculus sp.) present attached to the fins. Thirty fish from each group (sized 0.17, 0.54 and 1.17 kg, corresponding to different ages and batches) were all sampled (blood and external parasites count) during the spring (5 June, June 12 and June 16, 2019). The results show that differences in blood parameters were only observed according to the weight of striped bass such as the haematocrit (HCT), haemoglobin, mean corpuscular haemoglobin concentration (MCHC), white blood cells (WBC) count, total protein, globulin, ratio A/G, cholesterol, triglycerides and glucose. In contrast, the copepods present showed a preference for the caudal fin of the striped bass, followed by the first dorsal and pectoral fin. The smaller fish (0.179 kg) were the most susceptible to Peniculus sp., compared to the largest fish (1.174 kg). So far, it can be concluded that at this stage, the copepod does not show any adverse effect on the fish health since the condition factor and blood parameters were statistically similar along with the different copepod infestation levels (intensity ranged from 7 to 109). However, this new copepod, here registered for the first time in the Morone saxatilis, was registered during the sunset to increase environmental temperature. Even if no signs of a harmful relationship between parasites between young and old organisms, it will be necessary to be further monitored. The copepod incidence and the blood parameters should be analysed along the year (different temperatures), aiming to detect any correlation to the copepods present or, in any case, the overall health status or another parasite present under the seabass culture conditions.

Environmental characteristics and development prospective of sea cage aquaculture in Morotai Island Regency

Sea cage aquaculture, if well managed, is one of the most successful and profitable marine aquaculture systems and has demonstrated substantial economic benefits. A relatively suitable sea or coastal water quality, as well as availability waters areas, are the major supporting factors that enable successful sea cage culture. This study explores the environmental characteristics and the potential development of sea cage culture in Morotai Island Regency, North Maluku Province. This study employed a survey method by which environmental data were collected following a random stratified technique in geographical information systems (GIS). The results of water quality analysis generally indicated that the study areas are highly suitable for sea cage culture. The suitability of engineering design based on water depth and safety issues relating to extreme weather and highly exposed coastal areas was the only significant factor that directly limits the suitable areas. After the integration of water depth and safety factors variable into the final spatial analysis, only 398 ha of waters were found suitable for sea cage culture. However, previous studies have suggested that for the sake of sustainability, only a maximum 10% of suitable waters can be used for the sea cage culture. Therefore, this study has recommended no more than 15 units of cages per hectare with a dimension of 8 x 8 m2 per cage or only the 597 units to be allocated for the whole identified suitable areas. A lack of marine aquaculture infrastructure and an inadequate as well unreliable supply of quality fish seed (fry) have been the major constraints for the sustainable production and operation of sea cage aquaculture in the study areas. With a better understanding of the existing suitable areas and its maximum production carrying capacity, aquaculture decision-makers can develop effective and efficient strategies to help improve the product for the sustainability sea cage culture activities in this region.

Effects of night-time light intensity and area of illumination in the sea cage culture of Pacific bluefin tuna (Thunnus orientalis) juveniles

The high mortality rates of Pacific bluefin tuna (PBF; Thunnus orientalis) juveniles due to collision death can be alleviated by night-time lighting both in land-based tanks and sea cages; however, the optimal night-time lighting intensity and area of illumination for sea cages have not been systematically investigated. We addressed these issues in the present study using seven different night-time light intensities ranging from 0 as a negative control (NC) to 329.4 μmol m−2 s−1 covering the same area (Experiment 1) and different areas of illumination (0.12%, 1.34%, and 1.78% per cage; Experiment 2). The results of Experiment 1 showed that surface night-light intensity and survival rate were strongly correlated (r = 0.9643, P < .01), and significant differences were found among the three treatment groups, with survival increasing in the rank order of NC–1.2 < 4.5–38.0 < 116.7–329.4 μmol m−2 s−1 (Kaplan-Meier log-rank test, P < .001). The results of Experiment 2 showed no differences in survival when the area of illuminations was altered. There were no differences in growth performances in Experiments 1 and 2. These results indicate that providing night-time light intensity >116.7 μmol m−2 s−1 at the water surface can enhance PBF juvenile survival, and that light intensity rather than area of illumination is an important parameter in PBF sea cage culture.

Assessing environmental carrying capacity of sea cage culture in the Yellow Sea, China, using a coupled diffusion model

The rapid development of offshore mariculture brings the environmental challenges and requests for carrying capacity-based management strategy. A pollutant diffusion model coupled hydrodynamic model and 3-D Lagrangian particle-tracking model was implemented to evaluate the environmental carrying capacity of the sea cage in off-coast farming in the Yellow Sea, China. The water level data on August 1–31, 2018 and concentration of nutrient in surface sediment in May, August, November 2018, and January 2019 were used to verify the model. The results showed that the model is reliable to capture the main characteristics of the environmental variables in the study area. Total annual sea bass output were around 335 t per year (t a−1), the nitrogen and phosphorus emissions of about 30.95 t a−1, 5.90 t a−1, respectively. Total nitrogen in the sediment accumulated to 691.4 mg kg−1 (0.056 kg m−2) on average after a year simulation. The selection of culture sites, especially the current velocity, and settling velocity of the particles play significant roles on the fish output and the diffusion of pollutants. According to the acceptable standards of sediment nitrogenous nutrient, the sea bass culture density can be expanded to 1.46 times the present level to reach the environmental carrying capacity. Feed formulations and feeding regimes are important factors in determining the carrying capacity that need to be strategically improved with developing technology. The model provides a useful tool to sustainable environmental management of sea cage culture.

Numerical assessment of the environmental impacts of deep sea cage culture in the Yellow Sea, China

In light of environmental deterioration in coastal areas, deep sea cage aquaculture is becoming an increasingly attractive mode of mariculture. A key factor in determining the potential of deep sea cage aquaculture is to evaluate the environmental impacts of these practices. Here, a numerical model consisting of coupled hydrodynamic-, tracer-tracking- and 3-D Lagrangian particle-tracking models was set up and applied to evaluate the environmental impacts of deep sea cage cultivation of sea bass (Lateolabrax japonicus) in the Yellow Sea, China. The model was verified using water level data on August 1–31, 2018 and nutrient concentration in water and surface sediments in May, August, and November 2018, and January 2019. Results show that the model successfully captures the characteristics of local tidal currents and the total particulate nitrogen and phosphorus concentrations of the underlying sediments. Water quality simulations indicate that deep sea cages account for 26% of the total dissolved inorganic nitrogen and 19% of the active phosphorus content. Residual feed particles are predicted to fall in an ellipse centered on the cage location, with a long axis of 200 m and a short axis of 50 m. Feces are predicted to fall in an ellipse with a long axis of 1400 m and a short axis of 600 m. The Superposition particles are predicted to settle in an ellipse with a long axis of 320 m and a short axis of 150 m. The model results indicate that installation of all deep sea cages will lead to acceptable levels of water quality, but that sediments may become polluted. The coupled model can be used to predict the environmental impacts of deep sea cage farming and provide a useful tool for designing the layout of integrated multi-trophic aquaculture of organic extractive or inorganic extractive species.

Marine Environmental Suitability Mapping for Lobster Sea-cage Culture in East Lombok Using Remote Sensing Data and GIS Approaches

Lobster, one of the high values sea-cage culture commodities in Indonesia, has some specific requirements of life environment. However, there haven’t been any studies that specifically identify these potential sites. Until today it is only 3.50 ha out of 526.86 Ha of these that have been utilized. This study aims to map the marine suitability environment for lobster cultivation in Ekas Bay, using remote sensing and GIS approaches. The requirement parameters maps for lobster marine suitability, includes oxygen levels (DO), nutrition, salinity, temperature, depthness, pH, and water clearence which are able to be extracted from Landsat 8 imagery. Using GIS, a model was developed to integrate those maps with marine environment secondary maps, water laboratory analysis, and other information from interview result with the local farmer’s. The result shows that lobsters live in the environment which has the temperature between 20 0 to 25 0 C and at the water depth of reaching 100 m. Laboratory analysis result presents the pH value of above 7 in average, DO ranges from 5-8 ppm, and salinity level from 28 to 35 ppt. In summary, the integration of remote sensing and GIS approaches are able to identify the common parameter that support the environment suitability for lobsters which is then formulated as a standard of marine environment suitability mapping.

Assessment of the production and dispersal of faecal waste from the sea-cage aquaculture of spiny lobsters

Despite the rapid expansion of spiny lobster aquaculture, very little is known about its potential environmental impacts. In an effort to understand the potential impacts of sea-cage culture of spiny lobsters, the faecal output and settling velocity of faeces of spiny lobster were quantified. These data were then used in hydrodynamic modelling to assess the dispersal pattern of faecal material from two sizes of hypothetical spiny lobster farms, so that inferences about likely benthic impacts could be made by modelling different scenarios of farm stocking density and food conversion efficiency. The overall mean settling velocity of lobster faecal strands was 0.9 ± 0.05 cm s−1. There was a positive correlation between both the weight and density of faecal strands and their settling velocity. Conversely, neither the length nor the surface area of faecal strands was correlated with the settling velocity. Hydrodynamic modelling showed that faecal material deposition mainly occurred directly beneath the sea-cages. The density of faecal material deposition increased proportionately with higher stocking density and FCR values. Overall, the results indicate that the deposition of faecal waste from sea-cage lobster aquaculture is unlikely to cause widespread benthic impacts when operating to the current highest commercial stocking and feeding levels.

Transcriptional immune response of cage-cultured Pacific bluefin tuna during infection by two Cardicola blood fluke species

Infections by two blood fluke species, Cardicola orientalis and Cardicola opisthorchis, currently present the greatest disease concern for the sea-cage culture of Pacific bluefin tuna (PBT) – a species of high global economic importance and ecological concern. In this study, we aimed to rapidly, quantitatively, and differentially identify infections by these two parasite species in cultured PBT as well as identify potential host immune responses. Using real-time qPCR, we were successful in quantitatively detecting parasite-specific DNA from within host blood, gill, and heart tissues; positively identifying parasitic infections 44 days earlier than microscopy methods previously employed. Both gill and heart became heavily infected by both parasite species in PBT within two months of sea-cage culture, which was only mitigated by the administration of anthelmintic praziquantel. Nevertheless, fish were observed to mount an organ specific transcriptive immune response during infection that mirrored the relative quantity of pathogenic load. In heart, significant (3–6 fold) increases in IgM, MHC2, TCRβ, and IL-8 transcription was observed in infected fish relative to uninfected controls; whereas in the gills only IgM transcription was observed to be induced (11 fold) by infection. Interestingly, the relative quantity of IgM transcription was highly correlated to the relative abundance of C. orientalis but not C. opisthorchis DNA in the gill samples, even though this organ showed high prevalence of DNA from both parasite species. Taken together, these findings indicate that although ineffective at combating infection during primary exposure, a cellular immune response is mounted in PBT as a potential rejoinder to future Cardicola exposure, particularly against C. orientalis. Although future investigation into antibody effectiveness will be needed, this work provides valuable preliminary insight into host responsiveness to Cardicola infection as well as additional support for the need of anthelmintic treatment following primary parasite exposure during PBT culture.

The impact of a moderate chronic temperature increase on spleen immune-relevant gene transcription depends on whether Atlantic cod (Gadus morhua) are stimulated with bacterial versus viral antigens

Exposure to elevated temperature is an inherent feature of Atlantic cod (Gadus morhua) sea-cage culture in some regions (e.g., Newfoundland) and may also become an increasingly prevalent challenge for wild fish populations because of accelerated climate change. Therefore, understanding how elevated temperatures impacts the immune response of this commercially important species may help to reduce the potential negative impacts of such challenges. Previously, we investigated the impacts of moderately elevated temperature on the antiviral responses of Atlantic cod (Hori et al. 2012) and reported that elevated temperature modulated the spleen transcriptome response to polyriboinosinic polyribocytidylic acid (pIC, a viral mimic). Herein, we report a complementary microarray study that investigated the impact of the same elevated temperature regime on the Atlantic cod spleen transcriptome response to intraperitoneal (IP) injection of formalin-killed Aeromonas salmonicida (ASAL). Fish were held at two different temperatures (10 °C and 16 °C) prior to immune stimulation and sampled 6 and 24 h post-injection (HPI). In this experiment, we identified 711 and 666 nonredundant ASAL-responsive genes at 6HPI and 24HPI, respectively. These included several known antibacterial genes, including hepcidin, cathelicidin, ferritin heavy subunit, and interleukin 8. However, we only identified 15 differentially expressed genes at 6HPI and 2 at 24HPI (FDR 1%) when comparing ASAL-injected fish held at 10 °C versus 16 °C. In contrast, the same comparisons with pIC-injected fish yielded 290 and 339 differentially expressed genes (FDR 1%) at 6HPI and 24HPI, respectively. These results suggest that moderately elevated temperature has a lesser effect on the Atlantic cod spleen transcriptome response to ASAL (i.e., the antibacterial response) than to pIC (i.e., antiviral response). Thus, the impacts of high temperatures on the cod's immune response may be pathogen dependent.

Skeletal malformations in Australian marine finfish hatcheries

The Australian finfish aquaculture industry has a target to more than treble production from 2005 to 100,000t p.a. by 2015. Most of the current production is from sea cage culture of Salmo salar and Thunnus maccoyii but new and emerging species are predicted to have a faster increase in production and were the focus of this study. The quantity and quality of hatchery-produced fingerlings is an impediment to achieving growth in the marine finfish sector. A survey of 18 hatcheries revealed that 44% indicated skeletal malformations were a significant issue in hatchery production, and 89% reported variability in malformation rates between production batches. Samples of fish from selected hatcheries were cleared and stained for assessment of abnormal bone development. Two hatcheries that had indicated malformations were not a significant problem submitted samples with >5% severe malformations. Jaw and spinal malformations occurred in Lates calcarifer, Seriola lalandi, Epinephelus fuscoguttatus, E. coioides, and Latris lineata. To the best of our knowledge, causative factors of malformations in Australian hatcheries have only been identified for jaw malformation in Lates calcarifer and Latris lineata, and further research is either needed or underway with other species and malformation types in order to improve culture protocols and increase fingerling quality. Improved monitoring techniques for skeletal malformations would substantially enhance the comparison of production methods at a commercial scale and enhance research efforts.

양식업의 양식방법별 어종별 생산효율성 비교분석에 관한 연구

The purpose of this study is to investigate the production efficiencies of the Korean aquaculture fishery with respect to species and methods using a Data Envelopment Analysis. The study extracted the 8 fishes in each of the sea cage culture, aquarium basin, and enclosed aquaculture for the analytical purposes. First, the study estimated the technical, pure technical, and scale efficiencies of the total of 24 aquaculture fishes based on the traditional DEA under the assumptions of both CRS and VRS. 2 fishes were identified as the efficient DMUs under the CCR-model, and 6 fishes under the BCC-model. Second, we tested to see if there was any difference in production efficiencies regarding those three different methods of aquaculture. we could not find any evidence of the differences in efficiency using a rank sum test based on the traditional DEA. However, we could do find that the pure technical efficiency in the sea cage culture was lower than others at 1% level of significance and the pure technical efficiency in enclosed aquaculture was also lower than others at 5% level of significance using Bilateral-DEA, which could explicitly consider the heterogeneity in the 3 production methods of aquaculture. Finally, the study obtained the 95% confidence intervals of the efficiency scores for the 24 fishes under our study using the smoothed bootstraping method in the process of the re-sampling in cooperation with both a kernel density estimation and a reflection method. At the same time, we could estimate the bias-corrected efficiency scores while the traditionally estimated efficiency scores suffered from the biases in the process of solving a linear programming with the deterministic nature of a production frontier. And hence, we could distinguish the differences in production efficiencies of the 8 fishes with respect to those 3 methods of aquaculture.

Vibrio alginolyticusinfection in Asian seabass (Lates calcarifer, Bloch) reared in open sea floating cages in India

Asian seabass (Lates calcarifer) has been designated as a candidate species for open sea cage culture in India. A case of vibriosis in Asian seabass reared in open sea floating cages is reported. Haemorrhage and ulcer were observed grossly in the diseased fish. The pathogen, identified as Vibrio alginolyticus based on biochemical and molecular characterization, was isolated from liver, gill, kidney, brain and blood. Histological examination of the diseased fish showed congestion, haemorrhage and necrosis in vital organs. The LD50 studies showed that the organism was virulent to Asian seabass, and the LD50 value was 103.2 CFU g−1 fish.