Offshore Cage Research Articles

Raising the Performance of Gilthead Seabream (Sparus aurata) Juvenile in Offshore Cage Culture

The growth parameters of gilthead seabream (Sparus aurata) fry supplied from three different hatcheries stocked in nine HDPE offshore cages (30 m diameter and 22 m depth) were investigated for 450 days. It was determined that the fish obtained from Firm A on the 450th day gained more weight by consuming less feed. Fishes belonging to Firm A consumed an average of 1.8 kg of feed for one kg body weight gain, while fishes belonging to Firm B consumed an average of 2.29 kg and fishes of Firm C consumed an average of 2.18 kg. However, feed conversion rates were not significant between firms. Also, the highest survival rate was determined in fish from Firm B with 96.11%. As a result, the success of fish culture should be guaranteed by the supply of high standard juvenile fish. Otherwise, production costs and fish quality will be adversely affected.

Analysis of probabilistic fatigue damage of mooring system for offshore fish cage considering long-term stochastic wave conditions

ABSTRACT This study deals with the probability distribution of fatigue damage of the mooring system for offshore fish cage considering the uncertainty of long-term wave conditions. A set of numerical simulations for offshore fish cage are performed to predict the fatigue damage of the mooring system. Through a virtual stochastic process model, the probability density function of the long-term fatigue damage of the mooring system is achieved by the generalized probability density evolution method, and the failure probability of the mooring system is predicted. The results demonstrate that the generalized probability density evolution method can effectively provide the fatigue damage distribution from the stochastic point of view. And the calibration of the engineering-based fatigue design factor of the current regulation can be conducted through the fatigue reliability analysis considering the uncertainty of the long-term wave conditions. This study provides a new understanding of the long-term fatigue damage distribution.

Monthly variation of growth, biochemical composition, fatty and amino acids patterns of gilthead sea bream (Sparus aurata) in offshore cage systems under brackish water conditions in the Black Sea

The aim of this study was to investigate seasonal variations of growth performance and biochemical composition, fatty and amino acids profiles of cage-cultured gilthead sea bream (Sparus aurata) in the Black Sea. The research was carried out on a yearly basis in the offshore cage systems of a commercial fish farm located on the coast of Samsun province, Turkey. Fish with an initial average weight of 2.44 ± 0.03 g reached a harvest weight of 474.60 ± 8.64 g with a survival rate of 94.26 ± 0.60% in 14 months. The average specific growth rate and feed conversion rate were 0.92 ± 0.30% and 1.45 ± 0.05 respectively. Seasonal variation of total essential and total non-essential amino acids and EAA/NEAA ratios ranged between 7.80 ± 0.00–11.22 ± 0.02 g/100 g, 8.19 ± 0.00–9.94 ± 0.01 g/100 g and 1.01 ± 0.00–1.18 ± 0.01 respectively (p < 0.05). The average of total ɷ-3, ɷ-6 and ɷ-9 values were 11.63 ± 0.68%, 24.29 ± 0.84% and 28.78 ± 0.17% respectively. It was determined that gilthead sea bream showed a remarkable growth performance over the 14 months period under offshore marine conditions in the Black Sea. Growth performance, biochemical composition, fatty and amino acids profiles in fish were influenced by seasonal changes of water temperature and nutritional value of the used diets. Findings of the present study provide remarkable information in terms of the year-round growth performance and meat quality of cage-cultured gilthead seabream based on a long-term evaluation throughout the full-cycle of 14-month production period of a commercial cage farm operating in offshore conditions in the Black Sea area.

A Method to Accurately Estimate Fish Abundance in Offshore Cages

Due to the lack of reliable methods, manual fish counting is popular on farms. However, this approach is time and labor intensive. Using an echosounder and the echo-integration technique could be a better alternative. The echo-integration method has been widely used in fish abundance estimation in waterbodies because of its simplicity. However, most of the research is concentrated on the open ocean, whereas fish count estimation in farming cages has not been explored much. Using the echo-integration method in a cage offers its own unique sets of problems. Firstly, the echo signal reflected from the cage boundaries should also be taken into account. Secondly, the fish inside a cage behave differently with time, as their mobility pattern is highly dependent on sunlight and water current. In this paper, fish behavior inside an offshore cage over time was extensively studied, and based on that a real-time fish counter system using a commercial echosounder was developed. The experiments demonstrate that our method is simple, user-friendly, and has an estimation error of less than 10%. Since our method accurately estimated fish abundance, the method should be reliable when making fish management decisions.

The Effect Of Wind Turbine On Sea Flow

Indonesia is a maritime country that had quite extensive territorial waters, one of which was located in the East Kalimantan region. Despite having a large enough water area, only 30 percent of new marine products were used. Marine resources, especially fisheries in Indonesia, were very abundant but had not been utilized to the full, so it needs to be made offshore cages with the concept of aquaculture. Pembangkit Listrik Tenaga Bayu (PLTB) was renewable alternative energy for the coastal region. To support the development of this technological innovation, this study discussed the movement of ocean currents under the influence of wind turbines. The governing equation consists of the Shallow Water Equation and the wind turbine model. After the governing equation is formed, the model is solved numerically and the effect of wind turbines on sea flow can be observed. The influence of wind turbines on sea currents is large enough that it needs to be reviewed in the planning of developing wind turbines in the offshore sea area.

Biological, socio-economic, and administrative opportunities and challenges to moving aquaculture offshore for small French oyster-farming companies

Oyster production has historically taken place in intertidal zones, and shellfish farms already occupy large extents of the French intertidal space. The expansion of French shellfish aquaculture within intertidal areas is therefore spatially limited, and moving production to the subtidal offshore environment is considered to be a possible solution to this problem. Finding new sites along the French Atlantic coast was studied here from the perspective of small oyster companies run by young farmers, who are interested in offshore bivalve aquaculture expansion compatible with their investment capacity. In assessing the feasibility of such offshore production, we considered three main issues: (1) bivalve growth potential and (2) technical feasibility and conflicting uses, both within a spatial framework, as well as (3) the steps and barriers of the administrative licensing process. Oyster spat in an experimental offshore cage showed significantly faster growth, in terms of both weight and length, compared to those in an intertidal cage, mainly due to lower turbidity and full-time feeding capacity (i.e., constant immersion in the water). A combination of Earth Observation data and bivalve ecophysiological modelling was then used to obtain spatial distribution maps of growth potential, which confirmed that offshore sites have better potential for oyster growth than the traditionally oyster-farmed intertidal sites overall, but that this is highly spatially variable. Small-scale producers indicated two technical factors constraining where farms could be located: bathymetry must be between 5 and 20 m and the distance from a harbor no more than five nautical miles. These were included along with maps of various environmental and socio-economic constraints in a Spatial Multi-Criteria Evaluation (SMCE). Touristic traffic and bottom trawling by fisherman were found to be the two other most restrictive variables. The GIS-based SMCE developed in this study showed that there is almost 400 km2 of highly- to very highly-suitable area within which to develop offshore aquaculture using simple, low-cost bottom-cage techniques, and can be used to assist the shellfish industry in the Marine Spatial Planning decision-making process, still in progress in this coastal area. However, the complexity of the administrative processes necessary to obtain an offshore license is perceived as a stronger barrier by farmers owning small companies than site selection, technical feasibility, and required investments, and will be crucial to address in order to realistically proceed to offshore cultivation. The process demonstrated here, and the results are relevant to other coastal and offshore locations throughout the world and can be adapted for other species.

Nutrient compositional differentiation in the muscle of wild, inshore and offshore cage-cultured large yellow croaker (Pseudosciaena crocea)

The proximate composition, amino acid and fatty acid composition in the muscle of wild, inshore and offshore cage-cultured large yellow croaker (Pseudosciaena crocea) were determined to identify nutritional differences. Wild fish groups showed highest content of moisture and crude protein, but lowest lipid content. Offshore cage-cultured fish showed significantly higher content of moisture and crude protein content, but lower crude lipid content than inshore cage-cultured fish. The content of aspartic acid, glutamic acid, and alanine was higher in wild large yellow croaker than that of in inshore cage-cultured groups, but similar to offshore cage-cultured fish. Significant lower contents of total amino acids, essential amino acids, non-essential amino acids and flavor-enhancing amino acids content were recorded in two cultured fish groups than those in wild group. While no major differences in fatty acids composition were found between wild and cage-cultured groups except for linoleic acid. The fish from offshore cages has much better nutrient profile than inshore cage-cultured fish, but is still inferior compared to wild fish.

Paracentrotus lividus roe enhancement by a short-time rearing in offshore cages using two agar-based experimental feed

In this study, we tested the effect of two agar-based biocomposites (differing for the fish meal source), on the Paracentrotus lividus gonad cycle progression and biochemical composition, in an offshore pilot scale trial. The purpose of this study was to identify a feeding regime for P. lividus that would allow adequate gonadal growth without accelerating the gamete maturation, in order to extend the market period. The purpose was pursued through the use of agar as a binding agent in the manufacturing of biocomposites to be used as feed for P. lividus and the realization of special offshore cages. The gonad index, histology, biochemical composition of fatty acids (FA) and free amino acids (FAA) and volatile molecule fingerprint were evaluated. Both the gonad index and the histological analysis showed a slower gametogenesis progression in the gonads of caged sea urchins with respect to the field collected ones, consistent with our previous results obtained testing a similar feed composition in a recirculating system. The amount and the relative proportions of FA and FAA in the gonads of wild and cultured gonads were similar, while the analysis of the volatile substances of the gonads of the sea urchin conducted using the electronic nose, shows that they vary as a result of the different feeding treatments. These results show that P. lividus sea urchins can be housed, under this feeding regime during the recovery phase of the gonads, without acceleration of the maturation of the gametes and thus in conditions to allow the extension of the market period. Moreover, the here tested agar-based biocomposites make it possible to reduce the management costs of the rearing system as they need to be replaced only once a week, and its environmental impact as they guarantee a limited nutrient dispersion in the water.

Feasibility study of Ulva sp. (Chlorophyta) intensive cultivation in a coastal area of the Eastern Mediterranean Sea

AbstractIncreasing biomass production yields is a critical challenge for macroalgae biorefineries. The continuous tumbling and mixing of free‐floating algae through water or airflow has been shown to increase the productivity of algae in land‐based cultivation systems. This approach has not been tested thoroughly in offshore cultivation. We report, here, a field feasibility study on the increase in green macroalga Ulva sp. growth rates in offshore cages, achieved by the combined effect of tumbling and mixing of the algae using influxes of water and air. The experimental system was tested in a shallow coastal area in central Israel, in the eastern Mediterranean Sea. A maximum daily growth rate of 19.2%, areal productivity of 33.72 g dry weight (DW) day−1 m−2, and volumetric yields of 37.78 g DW day−1 m−3, together with 38.47 ± 0.01% ash and 5.28% protein content on a dry matter basis were achieved in the cages with intensified cultivation in the first week of May 2017. Our study shows that cultivation with tumbling and mixing of biomass with air, and water exchange with the environment is a feasible method to increase Ulva sp. biomass productivity offshore. © 2019 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Genome sequence of the barred knifejaw Oplegnathus fasciatus (Temminck & Schlegel, 1844): the first chromosome-level draft genome in the family Oplegnathidae.

BackgroundThe barred knifejaw (Oplegnathus fasciatus), a member of the Oplegnathidae family of the Centrarchiformes, is a commercially important rocky reef fish native to East Asia. Oplegnathus fasciatus has become an important fishery resource for offshore cage aquaculture and fish stocking of marine ranching in China, Japan, and Korea. Recently, sexual dimorphism in growth with neo-sex chromosome and widespread biotic diseases in O. fasciatus have been increasing concern in the industry. However, adequate genome resources for gaining insight into sex-determining mechanisms and establishing genetically resistant breeding systems for O. fasciatus are lacking. Here, we analyzed the entire genome of a female O. fasciatus fish using long-read sequencing and Hi-C data to generate chromosome-length scaffolds and a highly contiguous genome assembly.FindingsWe assembled the O. fasciatus genome with a total of 245.0 Gb of raw reads that were generated using both Pacific Bioscience (PacBio) Sequel and Illumina HiSeq 2000 platforms. The final draft genome assembly was approximately 778.7 Mb, which reached a high level of continuity with a contig N50 of 2.1 Mb. The genome size was consistent with the estimated genome size (777.5 Mb) based on k-mer analysis. We combined Hi-C data with a draft genome assembly to generate chromosome-length scaffolds. Twenty-four scaffolds corresponding to the 24 chromosomes were assembled to a final size of 768.8 Mb with a contig N50 of 2.1 Mb and a scaffold N50 of 33.5 Mb using 1,372 contigs. The identified repeat sequences accounted for 33.9% of the entire genome, and 24 003 protein-coding genes with an average of 10.1 exons per gene were annotated using de novo methods, with RNA sequencing data and homologies to other teleosts. According to phylogenetic analysis using protein-coding genes, O. fasciatus is closely related to Larimichthys crocea, with O. fasciatus diverging from their common ancestor approximately 70.5–88.5 million years ago.ConclusionsWe generated a high-quality draft genome for O. fasciatus using long-read PacBio sequencing technology, which represents the first chromosome-level reference genome for Oplegnathidae species. Assembly of this genome assists research into fish sex-determining mechanisms and can serve as a resource for accelerating genome-assisted improvements in resistant breeding systems.

Successful rearing of common octopus (Octopus vulgaris ) fed a formulated feed in an offshore cage

Aquaculture ResearchVolume 50, Issue 3 p. 968-972 SHORT COMMUNICATION Successful rearing of common octopus (Octopus vulgaris) fed a formulated feed in an offshore cage Jesús Cerezo Valverde, Corresponding Author Jesús Cerezo Valverde jesuscerval@gmail.com orcid.org/0000-0003-3989-6740 Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, Spain Correspondence Jesús Cerezo Valverde, IMIDA-Acuicultura, Puerto de San Pedro del Pinatar, Murcia, Spain. Email: jesuscerval@gmail.comSearch for more papers by this authorTania Rodríguez-González, Tania Rodríguez-González orcid.org/0000-0001-5755-8716 Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this authorMaría Dolores Granero-Fernández, María Dolores Granero-Fernández Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this authorFelipe Aguado-Giménez, Felipe Aguado-Giménez Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this authorBenjamín García García, Benjamín García García Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this author Jesús Cerezo Valverde, Corresponding Author Jesús Cerezo Valverde jesuscerval@gmail.com orcid.org/0000-0003-3989-6740 Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, Spain Correspondence Jesús Cerezo Valverde, IMIDA-Acuicultura, Puerto de San Pedro del Pinatar, Murcia, Spain. Email: jesuscerval@gmail.comSearch for more papers by this authorTania Rodríguez-González, Tania Rodríguez-González orcid.org/0000-0001-5755-8716 Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this authorMaría Dolores Granero-Fernández, María Dolores Granero-Fernández Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this authorFelipe Aguado-Giménez, Felipe Aguado-Giménez Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this authorBenjamín García García, Benjamín García García Marine Aquaculture Station, Murcia Institute of Agri-Food Research and Development (IMIDA), Puerto de San Pedro del Pinatar, Murcia, SpainSearch for more papers by this author First published: 07 January 2019 https://doi.org/10.1111/are.13955Citations: 4Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume50, Issue3March 2019Pages 968-972 RelatedInformation

POTENTIAL ENVIRONMENTAL IMPACTS OF TUNA CAGE FARMING IN THE AEGEAN SEA

The present study aimed to investigate the potential impacts of Atlantic Bluefin Tuna ( Thunnus thynnus ) farming in offshore cage systems in the Aegean Sea (Sigacik Bay-Izmir, Turkey), in respect to physico-chemical water quality parameters, nutrient loads, chlorophyll- a , total suspended solids, zooplankton groups, and TRIX index calculations for the potentially affected cage farm area and an unaffected reference site. Concentrations of physico-chemical variables (temperature, salinity, dissolved oxygen, pH) in the study carried out in May and August 2018, were within the acceptable limits for marine aquaculture in terms of water quality characteristics. The concentrations of PO 4 -P, NH 4 -N, and NO 2 -N showed no temporal or spatial changes, and were recorded below 0.01 mg/L (<0.01) for PO 4 -P and NH 4 -N, whereas lower than 0.005 mg/L (<0.005) for NO 2 -N values in both cage and reference stations in May and August 2018 periods. Results showed low levels of TSS (0.33-11.87 mg/L), both in the cage farm area and the reference site, remaining below the general quality criteria of 30 mg/L for marine environment. No eutrophication risk (TRIX index, T<4 ) was observed around the Tuna Cage Farm Site in Sigacik Bay, according to the legislations enacted for “Sensitive Areas of Enclosed Bays where fish farms are not allowed”. Based on these findings, demonstrating highly interactive trophic level variability, it can be concluded that the impacts of the Tuna Cage Farm were not significant, possibly due to the consistent movement of the water in currents in the study area.

Comparison of Fatty Acid and Biochemical Composition of Cultured Meagre (Argyrosomus regius Asso 1801) in Two Different Regions of Turkey

This study was designed for comparison of biochemical and fatty acid composition of cultured meagre (Argyrosomus regius) in off-shore cage system in two different regions of Turkey. For this purpose, meagre with an average weights of 513.80±52.40 g and 726.52±116.19 g were obtained from commercial fish farms in South (Mediterranean) and North (Black Sea) of Turkey, respectively. No significant differences were detected among the fish originated from the Mediterranean (MSO) and the Blacksea (BSO) in terms of body compositions (p 0.05). The fatty acid compositions of MSO and BSO fish showed significantly differences (p>0.05). The fatty acids such as SFA, PUFA, C16:0 (PA), C23:0 (MT), C20:3n-3 (ETA), C22:6n-3 (DHA), n-3 and n3/n6 were higher in MSO than BSO. Whereas, the fatty acids such as MUFA, n-6, C18:1n-9 (OLA), C20:1n-9 (EA), C22:1n-9 (ESA), C18:2n-6 (LA) and C18:3n-6 ( -ALA) were higher in BSO fish than MSO fish. However, no difference was detected in the C20:5n-3 (EPA) of fish from both regions. EPA was identified as 3.30±0.05% for MSO and 3.38±0.05% for BSO. No differences were detected in the other fatty acids between two regions (p<0.05). In conclusion, despite the differences in fatty acid compositions of the cultured fish in both regions, high levels of EPA and DHA as well as favorable proportions of n-3 and n-6 fatty acids showed that meagre was valuable food for human nutrition.

Perfuorooctane Sulfonate (PFOS), Perfluorooctanoic Acid (PFOA), Brominated Dioxins (PBDDs) and Furans (PBDFs) in Wild and Farmed Organisms at Different Trophic Levels in the Mediterranean Sea.

The present study shows the results of perfuorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), brominated dioxins (PBDDs) and furans (PBDFs) measured in several marine fish and seafood of commercial interest at different trophic levels of the food chain. The aims were to investigate the level of the contamination in Mediterranean aquatic wildlife, and in farmed fish, to assess human exposure associated to fishery products consumption. Samples of wild fish were collected during three different sampling campaigns in different Food and Agriculture Organization (FAO) 37 areas of the Mediterranean Sea. In addition, farmed fish (gilthead sea bream and European sea bass) from off-shore cages from different marine aquaculture plants. Results showed contamination values of PFOS and PFOA were lower than those detected in sea basins other than the Mediterranean Sea. Concentration values of PFOS were generally higher than those of PFOA; moreover, levels in farmed fish were lower than in wild samples from the Mediterranean Sea. Intake of PFOS and PFOA through fishery products consumption was estimated to be 2.12 and 0.24 ng/kg·BW·day, respectively, for high consumers (95th percentile). Results of 2,3,7,8-substituted congeners of PBDDs and PBDFs were almost all below the limit of detection (LOD), making it difficult to establish the contribution of these compounds to the total contamination of dioxin-like compounds in fish and fishery products.

Analysis of static structural of ocean FARMITS offshore cage due to environmental load

Consumption of fish in Indonesia continuously increase from 2000 to 2014. Particularly fish farming in Java from 2006-2014 is quite high, so there need to be adequate facilities for fish farming. Responding to these challenges, we developed Offshore Cage Ocean FARMITS technology specifically designed For the southern waters of Java Island. This paper discusses the static structure strength analysis of deformation and maximum yield strength that occurs on the offshore cage structure of Ocean FARMITS. The frame structure made of hollow pipe made from HDPE will be placed at 4,41m Wave Height, with a period of 19s. Numerical simulations are performed to obtain a motion response RAO and structural response due to random waves. This Structure is then analyzed under mooring conditions with the Catenary Mooring configuration. Rope stress that occur due to environmental loads will give tension stress to the structure, resulting in the offshore cage structure to occur maximum stress and deformation. The result of this research is to prove that the structure that is made by HDPE able to restrain the tension force of mooring line stress. This has been validated by the standard of Practical Aspects of Offshore Aquaculture System Design from Aquaculture America, so this structure can be said to be operating safely under Indonesian Irregular Wave.

Analyzing functional diversity to determine the effects of fish cages in insular coastal wild fish assemblages

Fish cages attract a high variety of wild fish, and therefore are similar to fish aggregation devices. Aquaculture cages enhance local fisheries, with a more diverse and abundant fish assemblages compared to control stations, not influenced by fish cages. Previous studies have been mainly focused on taxonomic and ecological indices, such as species richness, individual abundances or Shannon-Weaver index. In the present study, we explore if functional diversity may be feasible to understand the consequences of changes in the composition of fish aggregates around cages. We studied fish aggregates from three cages on the coast of Tenerife (Canary Islands, Atlantic Ocean) over several years. All fishes were identified and counted using rapid visual counts (RVCs) in cage and control stations. An increase of species richness and individual abundance occurred in fish aggregates around the studied cages persisting over time. Functional diversity showed increase on cage stations, with higher values of functional evenness and functional divergence relative to control stations. A slight dissimilarity in the taxonomic composition was only observed in the eastern farm. In terms of functional diversity, the studied aquaculture cages exhibited a slight increase in wild fish aggregates over time. These results are similar to previous studies based on taxonomic and ecologic diversity in which a long lasting effect was observed on wild fish aggregates. Thus, aquaculture cages might be considered as a figure of conservation or fishery interest. Statement of relevanceOur results showed a functionally diverse fish community around offshore cages. Thus, aquaculture leases could work as a “reservoir”, promoting the development of diverse fish assemblages, as marine protected areas (MPAs) are designed for.The development of aquaculture offshore cages might include their positive effects on wild fish aggregates, with a “buffer” fish-ban zone to protect fish stocks from the fishermen.

Improvement of gonad quality of the sea urchin Mesocentrotus nudus fed the kelp Saccharina japonica during offshore cage culture

In northern Japan, Saccharina kelps are natural diets for sea urchins and are known to enhance sea urchin gonad size. However, little is known about the effects of the kelp diet on gonad quality and consistency among individuals. In the present study, Mesocentrotus nudus adults collected from a barren were cultured in a suspended cage from late February to early June 2014 in Shizugawa Bay, Miyagi Prefecture. They were fed stipes of Undaria pinnatifida for 56 d followed by fresh Saccharina japonica kelp for 42d. At the end of the culture period, gonad indices, gonad hardness, gonad color (L* (lightness), a* (redness), b* (yellowness)), free amino acid (FAA) contents in the gonads, and sensory qualities of the cultured sea urchins (EC) were measured and compared to those of the natural population from the barren (EB) and those from the Eisenia bicyclis kelp bed (EK) in the bay. Gonad index and L* values of EC urchins were higher than those of urchins from the barren at the start of culture (SCB). Total color (L*, a*, b*) of the gonads of EC and EK urchins were similar. Gonad hardness of EC and EK urchins was similar and lower than that of EB urchins, and the coefficients of variation of gonad index, color, and hardness were lower than those from the barren (SCB and EB). Sweet tasting alanine contents of the gonads of EC urchins were markedly higher than those of the gonads from the other urchin specimens. Bitter tasting FAA contents of the EC urchin gonads were higher than those of EK and EB urchins, although arginine and lysine contents were lower than those of EB urchins. Sensory scores of overall taste of EC urchins were higher than those of EB urchins and similar to EK urchins, possibly due to the increased alanine content. These results suggest that gonad size, color, hardness, taste, and consistency among individuals of M. nudus collected from barrens can be improved to reach levels similar to those of urchins from the E. bicyclis kelp bed by cage culture with short-term feeding of Saccharina kelps. Changes in gonad qualities seemed to be mainly due to S. japonica as the food source because hard U. pinnatifida stipes were rarely eaten and had markedly low protein content. Extension of cage culture duration with S. japonica feeding from spring to summer would increase gonad size and further improve gonad quality.

Heavy metals in seabed sediments beneath off-shore fish cages

Heavy metals in seabed sediments beneath off-shore fish cages

외해 가두리 대구 양식업 경제적 타당성 분석

외해 가두리 대구 양식업 경제적 타당성 분석

Antioxidant enzyme activity and lipid peroxidation in gills of fish (Sparus aurata) upon exposure to swarms of Pelagia noctiluca

During the last decade, massive blooms of jellyfish have occurred in the Mediterranean basin, putting great concern on cultured fish in offshore cage. Current studies enter in this task, and they consist on examining the antioxidant responses as well as lipid peroxidation and mucous secretion in gills of the gilthead sea bream (Sparus aurata). This is done upon exposure to the scyphozoan jellyfish Pelagia noctiluca at environmentally realistic densities (3, 7 and 15 individus per tanks). This finding revealed that P. noctiluca was a highly toxic organism to the cultured fish. Morphological examination showed lesions of the secondary gill lamellae in fish exposed to jellyfish. Enzymatic activities were measured after 0, 1, 2, 7, 15 and 30 days after initiating the exposure. The set of analyzed activities included catalase (CAT) and glutathione reductase (GR) activities. Lipid peroxidation was measured by quantifying malondialdehyde (MDA). Estimation of mucus secretion was done by using the phenol sulfuric acid assay protocol. The results showed that jellyfish induced antioxidant enzyme activities (CAT, GR) at different densities. Gills MDA content was significantly increased in all treated groups versus the control groups throughout the exposure periods. Our results show also that fish exposed to jellyfish swarms showed mucus hypersecretion on gills. Based on the results of this study, we consider the scyphozoan jellyfish P. noctiluca to be harmful in aquaculture system. The observed changes in analyzed parameters (especially CAT and GR activities, MDA contents and mucous production) suggest that these parameters could be useful tools in environmental monitoring programs of the aquaculture where jellyfish blooms occur.