Marine Farms Research Articles

A 2-stage hierarchical interrupted time-series analysis to quantify the long-term effect of subclinical bacterial kidney disease on performance of farmed Atlantic salmon (Salmo salar L.)

Bacterial Kidney Disease (BKD) is an economically significant disease in salmonid aquaculture and commonly requires antibiotic treatments to reduce its impact. Once a pen of fish is diagnosed with BKD, fish are considered chronically infected, potentially until harvest. Although there appears to be little or no evidence to support it, it is often assumed that subclinical infections affect productivity over the long term. We used a 2-stage hierarchical interrupted time series (ITS) analysis in an attempt to quantify the effect of subclinical BKD on mortality, growth, and food conversion ratio (FCR) of Atlantic salmon cultured in marine farms in Atlantic Canada. For all three outcomes, BKD had for some site cycles a positive effect, and for others a negative effect. Overall, the effect of BKD on mortality and growth could not be detected (effect -0.08 ((95% ci: -0.51, 0.35) and 0.00 (-0.02, 0.02)), while a very small effect showing an increase in FCR was detected (0.07 (-0.01, 0.15)). We hypothesized that minimal interference with fish performance may be compatible with the ecology of Renibacterium salmoninarum, the causative agent of BKD. For this organism, vertical transmission is a primary mode of propagation in low-density host populations as found in the wild. Since farms are always adapting and optimizing their farm management of BKD, these constant adjustments may also have negated our ability to detect the effect of many factors contributing to BKD productivity impacts. Hierarchical ITS analysis is considered an appropriate methodology to investigate the complex relationships with productivity measures over time under farming conditions. In the highly innovative salmon aquaculture industry, health records generating data available for time-series analysis is expected to become more accurate and abundant in the future, providing more opportunities for time-series regression studies.

Co-culture in marine farms: macroalgae can act as chemical refuge for shell-forming molluscs under an ocean acidification scenario

ABSTRACTWith ongoing climate change, aquaculture faces environmental challenges similar to those of natural ecosystems. These include increasing stress for calcifying species, e.g. macroalgae and shellfish. In this context, ocean acidification (OA) has the potential to affect important socioeconomic activities, including shellfish aquaculture, due to changes in the seawater carbonate system. However, coastal environments are characterised by strong diurnal pH fluctuations associated with the metabolic activity of macroalgae; that is, photosynthesis and respiration. This suggests that calcifying organisms that inhabit these ecosystems are adapted to this fluctuating pH environment. Macrophyte-dominated environments may have the potential to act as an OA buffering system in the form of a photosynthetic footprint, by reducing excess of CO2 and increasing the seawater pH and Ωarg. This can support calcification and other threatened physiological processes of calcifying organisms under a reduced pH environment. Because this footprint is supportive beyond the macroalgal canopy spatial area, this chemical refuge mechanism can be applied to support shellfish aquaculture, e.g. mussels. However, this approach should be tested in commercial shellfish farms to determine critical aspects of implementation. This includes critical factors such as target species and productivity rates. The degree of OA buffering capacity caused by the metabolic activity of macroalgae might depend on community structure and hydrodynamic conditions, creating site-specific responses. This concept might aid the development of future adaptive strategies, supporting marine ecological planning for the mussel aquaculture industry in Chile.

Presença de Mytilus cf. edulis platensis em fazendas marinhas de Bombinhas, Santa Catarina, Brasil

A espécie de molusco bivalve Mytilus cf. edulis platensis (d´Orbigny, 1846) está se estabelecendo nas fazendas marinhas catarinenses de mexilhões Perna perna e a sua prevalência, no município de Bombinhas, é calculada e discutida neste estudo. A dominância de M. cf. edulis platensis sobre o P. perna foi constatada em 14 das 20 fazendas marinhas amostradas, numa proporção de ocorrência de 69% do mitilídeo e de 31% do nativo Perna perna. O aumento populacional pode estar relacionado à sua capacidade de adaptação e às alterações ambientais da biosfera causadas pelo aquecimento global. Termos para indexação: mexilhão; Perna perna; molusco; maricultura; ecologia.

FIRST EXPERIENCE OF CAGE CULTIVATION OF HATCHERY-PRODUCED JUVENILE SCALLOP MIZUHOPECTEN YESSOENSIS AT EASTERN COAST OF PRIMORYE

Yesso scallop Mizuhopecten yessoensis is the main object of aquaculture in Primorye with annual yield measured in hundreds ton. However, further development of its farming could be restricted by lack of the spat. Availability of the spat imported from China using for the scallop cultivation at the coast of Primorye is explored. The spat from Chinese hatchery located in Shandong province was supplied for one aquaculture company in Primorye in the volume of 660 . 106 ind. in 2018 and settled to hanging collectors (1000 ind. per bag), then to cages in the marine farm located north-eastward from the Moryak-Rybolov Bay. Survival and growth rate of the scallop juveniles were examined in early November 2018, when the water temperature was from 10.3–10.4 оС at the sea surface to 9.7–9.9 оС at the bottom, salinity was about 33.60 psu in the whole water column, chlorophyll a concentration varied in the range 0.4–0.8 mg/L with the maximum in the layer 8–24 m. The spat mortality during transportation was estimated as 15 %, but it increased to 56–90 % during its growing up in cages. This level of mortality is much higher than mortality of the spat collected from the coastal waters at southern Primorye. The highest mortality of artificial spat was observed for large-sized mollusks, whereas it was satisfactory for the small-sized ones. Possible reason of high mortality is too high density of juveniles and damaging of their soft tissues by other shells. The spat shells height did not exceed 5–10 mm in the collectors but increased during their growing in cages to 20–25 mm. This size is similar to the size of scallop growing from natural spat in southern Primorye. However, growth rate of the scallop growing at the Moryak-Rybolov Bay (2.0–2.7 mm/month) is lower than in Peter the Great Bay (3.0–3.5 mm/month) though higher than in the Vladimir Bay and Aniva Bay. Mean body weight of the cultivated scallop in November was 1.5 ± 0.1 g.

Internet of Fish: Integration of acoustic telemetry with LPWAN for efficient real-time monitoring of fish in marine farms

The aim of this study was to develop and test the feasibility of a concept called Internet of Fish (IoF). State-of-the-art acoustic telemetry systems could enable farmers to acquire behavioural data of fish in fish farms, however, the existing systems provide limited real-time access to the telemetry data. Low Power Wide Area Networks (LPWANs) are instrumental in the proliferation of the Internet of Things and enables spatially dispersed devices to communicate over long distances for months using dedicated modulations schemes. The IoF concept exploits the harmony in the performance characteristics of acoustic fish telemetry and LoRa (Long Range wireless data protocol with low power modulation) based LPWAN to provide real-time access to the telemetry data. This was achieved by developing a device designated as the LoRa Add-on Module (LAM), which provides LoRa radio support to underwater acoustic receivers. In this study, feasibility of the IoF concept was tested by conducting an experiment in a commercial marine fish farm in Norway. Four LAM and acoustic receiver pairs with a link-length to a centralized gateway of 150 m to 2.5 km were used in the field experiment. The Quality of Service (QoS) of the proposed LoRa LPWAN was determined to evaluate the effect of link-length. The QoS of more than 90% was achieved for all nodes, affirming the feasibility of real-time monitoring in marine fish farms and exposed aquaculture sites based on the IoF concept.

Environmental issues in Chilean salmon farming: a review

AbstractThe growth of Chilean salmon production has not been free of important sanitary and environmental shortcomings. To ensure sustainability, it is necessary to understand the environmental impacts of salmon production on the Patagonian ecosystems. Currently, there is limited regulation or monitoring of impacts in the freshwater phase compared to the marine fattening stage, and there is some evidence of local eutrophication impact and diversity changes downstream the farms. Eutrophication of Patagonian channels and fjords from marine farms has been recognized as crucial environmental risk, although most scientific evidence comes from local effects below and around farms. So far, there are no regulations based on carrying capacity estimates to limit maximum fish biomass per area or water body. There is controversy regarding the potential role of nutrients derived from farming in triggering harmful algal blooms, yet current environmental monitoring and available information does not allow establishing or rejecting a cause–effect relationship. Pesticides used to control sea lice infestation have been shown to be deleterious to some non‐target species. There is evidence that the use of high quantities of antibiotics has allowed the development of antibiotic‐resistant bacteria in sediments and there is concern that salmon aquaculture has the potential to increase the proportion of antimicrobial‐resistant bacteria to antibiotics that are used in human medicine. There is an urgent need for more comprehensive ecosystem (beyond farm) studies on the impacts of antibiotics. Escapes of salmon (exotic species) from farms are a relevant environmental risk, although the most farmed species, Salmo salar, has shown little success in establishing wild populations. The review identifies critical knowledge gaps whose fulfilment is essential to advance towards an ecosystem approach to aquaculture and to protect Patagonian ecosystems.

Addressing viral and bacterial threats to salmon farming in Chile: historical contexts and perspectives for management and control

AbstractThe rapid growth of the salmon farming industry in Chile has led to the appearance of various viral, bacterial, parasitic, and fungal pathogens affecting farmed fish. The Chilean salmon industry has suffered several health crises associated with high fish mortalities, such as caused by the infectious salmon anaemia virus (2007) and harmful algal blooms (2016). In addition to these events, marine farms are continuously affected by outbreaks of harmful pathogens, including the bacteria Piscirickettsia salmonis and, most recently, a reappearance of Renibacterium salmoninarum, and the infectious pancreatic necrosis virus. These outbreaks have led to stricter regulations, but the salmon farming industry continues to struggle despite reforms. In addition to the aforementioned pathogens, which are a continuous threat, other apparently under control pathogens have also reappeared in recent years. In this review, we analyse the current state of knowledge on four of the main pathogens affecting salmon farming in Chile. The infectious pancreatic necrosis virus is relevant as it affects freshwater‐stage fish, with survivors then acting as carriers. The infectious salmon anaemia virus currently appears to be under control; however, P. salmonis and R. salmoninarum continue to be the cause for high mortalities in the Chilean aquaculture industry.

Effects of stock origin and environment on growth and reproduction of the green-lipped mussel Perna canaliculus

The effect of stock origin and growing environment on growth and reproduction of the green-lipped mussel Perna canaliculus was investigated on the marine farms in the Marlborough Sounds, New Zealand. Following the normal commercial practice, mussel stocks from three widely separated origins in New Zealand were transplanted to six sites in Marlborough Sounds and grown on ropes hung from commercial longlines for eleven months. Stock origin had significant effects on growth rates as measured by shell length and flesh weight. Growing sites also showed a significant effect on flesh growth rate but only a small effect on shell length growth, with considerable variation among sites. Two sites (Beatrix Bay and Hallam Cove) had the fastest growth in flesh weight. One stock (Golden Bay) showed the fastest growth and lowest mid-winter reproductive rates, while the Kaitaia stock (the most commonly used one in industry) showed highest winter reproductive rate. Spawning was responsible for mid-winter declines in flesh weight among all stocks, but the Golden Bay stock recovered flesh weight more rapidly than other stocks after spawning. The stock differences in growth suggest that genetic traits of stock origin remained after mussels were grown in different environments (sites). In addition, we speculate that there would be a large variation of physiological rates between stocks including filtration, ingestion and respiration rates. The variation in growth and reproduction suggests that there would be a significant difference in energy allocation for reproduction, flesh and shell growth among stocks. The study has obvious application to the mussel industry for planning and selective seeding of stocks to maximise economic benefits. The use of fast-growing stocks and timing of harvesting in mid-winter can dramatically improve quality and quantity of production.

Characteristics of intestinal microbiota in the Pacific white shrimp Litopenaeus vannamei differing growth performances in the marine cultured environment

The Pacific white shrimp Litopenaeus vannamei is the most widely cultivated shrimp in the world, particularly in Asia. The growth performance is a vital factor in shrimp farming. In the present study, comparisons were made among the bacterial communities in shrimp intestines and the related marine farm sediments that supported different growth performances, based on Miseq sequencing data of the V3-V4 region of 16S rRNA gene. Fifty three phyla were identified with the classifiable sequence. Sequencing data demonstrated a statistically significant diversity in microbiota compositions at the phylum and genus levels. The dominant phyla were Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Verrucomicrobia, and Saccharibacteria. Of which, Actinobacteria and Saccharibacteria were more abundant in the shrimp intestines with a normal growth performance, these phyla may be related with shrimp immunity and digestion. Proteobacteria were more abundant in shrimp intestines with slow growth performance, an increased abundance of Proteobacteria was a potential risk of disease. At the genus level, norank_f__Propionibacteriaceae, Ruegeria, Robiginitalea, unclassified_c__Actinobacteria and norank_f__TM146 exhibited extremely statistically significant differences at 0.001 < P ≤ 0.01 while norank_c__Cyanobacteria exhibited statistically significant differences at 0.01 < P ≤ 0.05 among the four groups. The relative abundances of the intestinal bacterial communities in the normal growth shrimps differed significantly from those in the slow growth shrimps. The Firmicutes/Bacteroidetes ratio in the normal growth shrimp intestines was 3.08/3.31 in comparison with 0.34/6.04 in the slow growth shrimp intestines, which suggests that the normal growth shrimp can absorb the nutrient better than the slow growth shrimp. Overall, this study provides valuable findings on the shrimp intestinal microbiota and helps guide the healthy aquaculture practices.

Prevalence of nervous necrosis virus (NNV) and Streptococcus species in wild marine fish and crustaceans from the Levantine Basin, Mediterranean Sea.

Infectious diseases in marine animals have ecological, socio-economic and environmental impacts. Nervous necrosis virus (NNV) and Streptococcus iniae have become major threats to marine aquaculture and have been detected in morbid marine organisms worldwide. However, despite their importance, there is a lack of knowledge regarding the prevalence of these pathogens in wild fish species. Here we sampled indigenous and Lessepsian species from different trophic levels and different biological niches in the eastern Mediterranean. A total of 174 fish and 32 crustaceans were tested for S. iniae and a total of 195 fish and 33 crustaceans were tested for NNV. We found an overall prevalence of 9.71% Streptococcus spp. and 21.49% NNV in selected marine fish and crustaceans by PCR and qPCR. In fish, the zoonotic agent S. iniae was detected at a higher prevalence in kidney compared to liver tissue. Co-infection by both pathogens was detected only in 5 specimens. We also examined gilthead sea bream Sparus aurata from an Israeli offshore marine farm during the grow-out period, in order to assess the possibility of horizontal pathogen transmission from wild to maricultured fish. Three out of 15 (20%) fish were found to be NNV positive after 120 d in the sea, suggesting spontaneous transmission from wild to farmed fish. Our findings suggest that more surveys should be conducted, especially in areas were mariculture farms are planned to be established.

Detection of Visual Signatures of Marine Mammals and Fish within Marine Renewable Energy Farms using Multibeam Imaging Sonar

Techniques for marine monitoring have been greatly evolved over the past decades, making the acquisition of environmental data safer, more reliable and more efficient. On the other hand, the marine renewable energy sector has introduced dissimilar ways of exploring the oceans. Marine energy is mostly harvested in murky and high energetic places where conventional data acquisition techniques are impractical. This new frontier on marine operations brings the need for finding new techniques for environmental data acquisition, processing and analysis. Modern sonar systems, operating at high frequencies, can acquire detailed images of the underwater environment. Variables such as occurrence, size, class and behavior of a variety of aquatic species of fish, birds, and mammals that coexist within marine energy sites can be monitored using imaging sonar systems. Although sonar images can provide high levels of detail, in most of the cases they are still difficult to decipher. In order to facilitate the classification of targets using sonar images, this study introduces a framework of extracting visual features of marine animals that would serve as unique signatures. The acoustic visibility measure (AVM) is here introduced as technique of identification and classification of targets by comparing the observed size with a standard value. This information can be used to instruct algorithms and protocols in order to automate the identification and classification of underwater targets using imaging sonar systems. Using image processing algorithms embedded in Proviwer4 and FIJI software, this study found that acoustic images can be effectively used to classify cod, harbour and grey seals, and orcas through their size, shape and swimming behavior. The sonar images showed that cod occurred as bright, 0.9 m long, ellipsoidal targets shoaling in groups. Harbour seals occurred as bright torpedo-like fast moving targets, whereas grey seals occurred as bulky-ellipsoidal targets with serpentine movements. Orca or larger marine mammals occurred with relatively low visibility on the acoustic images compared to their body size, which measured between 4 m and 7 m. This framework provide a new window of performing qualitative and quantitative observations of underwater targets, and with further improvements, this method can be useful for environmental studies within marine renewable energy farms and for other purposes.

Морские ландшафты и использование различных якорных систем на морских фермах Крыма

Seascape complexes are decisive in choosing of technologies for growing different species of fish and mollusks, as well as in designing and installing farms on the Black Sea shelf. Marine farms, as hydrotechnical installations, play the role of artificial underwater seascapes and have a mutual influence on natural local systems. This article describes the main elements of mussel-oyster farms, the criteria for choosing a location for them, technological solutions of anchor systems, taking into account the peculiarities of the marine seascapes of the Crimean peninsula. In the Black Sea, it is advisable to install farms of the long-line type, which satisfy almost all the requirements for growing mollusks: they are quite stable during strong storms and wind impacts, allow changing the depth of mollusk placement if necessary, and are easy to install and maintain. The depths at the site which was selected for the installation of the marine farm should be in confines 10...30 m, and 15...20 m is the optimal depth for it. The permissible depth must be at least 10 m under the marine farm in consequence. The choice of optimal depths is associated with the need to save materials also. The characteristics, applicability and installation features of several types of anchors (concrete, screw and plow) for grounds of different composition and density are proposed. Promising areas for the development of the Black Sea mariculture are the western and eastern coasts of the Crimean peninsula.

Genotyping of Vibrio Parahemolyticus Isolated from Some Marine Fish

A total 180 marine fish samples, 60 of each mullet (Mugil cephalus), seabream (Sparus aurata) and seabass (Dicentrarchus labrax),were randomly collected from different fish farms in Port-Said Governorate. Some of collected fishes displayed hemorrhages on the external body surface, base of fins and operculum (gill cover) with congested gills, pale liver and corneal opacity were noticed. Bacteriological examination of samples was collected from fish surface, liver, kidney, spleen, muscle and gills revealed that the highest level of the isolates was recorded in liver followed by kidney, spleen, muscle and gill. Biochemical identification results of the isolated Vibrio species were revealed that 38 samples (21.11%) from the total collected samples were positive for the prevalence of Vibrio species at a percentage of (28.33%), (18.33%) and (16.67%) for mullet, seabream and seabass respectively. Molecular identification of Vibrio species isolated from some marine fishes using 16S rRNA and toxR revealed that 32 strains of the isolated Vibrio were belong to V. parahaemolyticus with a prevalence of 15, 8 and 9 from mullet, seabream and seabass respectively. Meanwhile molecular characterization of the identified V. parahaemolyticus by using PCR showed that all 32 isolates were harbored recA gene and only 25 isolates were harbored tlh gene. The public health hazards of this microorganism, as well as improve quality status of marine farms fishes were discussed. Keywords: Vibrio parahaemolytius, virulence, mullet, seabream, seabass fish, PCR, Public health.

Results of economic activity and problems of aquaculture development in the Possiet Bay (Japan Sea) in 2000–2015

The Possiet Bay in the western Japan Sea is crucially important for marine aquaculture of Primorye because of the environments favorable for cultivation of many aquatic species. The local marine farms cultivate sea cucumber and several bivalve species, including the most valuable yesso scallop, which output production is counted in hundreds of tons. The number of farms in the Possiet Bay increases recently, as well as their production of seeding materials and marketable output of seafood. Cultivation of 3 bivalve species (yesso scallop, pacifc blue mussel, and pacifc oyster) and 1 holothurian species (japanese spiky sea cucumber) is considered. The seeding material is collected by the farms located in the Possiet Bay, which prefer to collect more valuable spat of the scallop and sea cucumber, while the mussel and oyster are collected in smaller amounts. In total, more than 640 million of the scallop juveniles and about 1.2 million of the sea cucumber juveniles were collected by local farms in the period from 2000 to 2015, including both the spat collected on their own collectors or bought from other vendors. Dynamics of the output is presented for these species. The greatest harvest of the marketable scallop (over 1800 t) was produced in 2006–2010, with the highest annual output over 510 t. The summary production of all marine farms in the Possiet Bay within the 15-year period (2001–2015) is estimated as 4,300 t, that exceeds the registered catch of scallop in this area in the whole history of its fshery (that was banned in the middle of 1980s). Even before the fshery opening in the early XX century, the yeaso scallop biomass in this area did not exceed 1,000 t. Dynamics of anthropogenic pressure to the Possiet Bay waters is analyzed, as well. There is concluded that yesso scallop has natural ability to considerable growth of its biomass because of high fecundity, though this potential is limited by lack of substrate for the spat settling that is successfully compensated with artifcial substrata provided by marine farms. However, the growth of scallop biomass and production causes higher phytoplankton consumption, increasing of water pollution by dissolved and particulate organic matter, and accumulation of metabolic by-products in marine organisms. Rapid development of aquaculture causes some social and ecological risks, as well, as territorial disputes, legislative problems (with harvesting permits, etc.), starfsh expansion, grazing of farmed mollusks by marine birds, destruction of aquaculture facilities in new areas located in the insuffciently closed bights by typhoons, and epizootics (most dangerous for the sea cucumbers).

Assessment of potential production for sea cucumber Apostichopus japonicus in a bicultural marine farm in Peter the Great Bay (Japan Sea)

Marine farms in Peter the Great Bay are oriented predominantly to cultivation of bivalve mollusks that causes excessive accumulation of biodeposits in the areas of plantations. To reduce this negative impact on the ecosystem, development of bicultural farms with cultivation of flterfeeders and detritivores is recommended. In the area of mussel (Mytilus trossulus) plantations in the Sukhodol Bay, the sedimentation rate reaches 34.1 g.m–2.day–1, with mean portion of organic carbon in the biodeposits as 20.2 %. Annual biodeposition from 1 hectare of mussel plantations is about 124 t that corresponds to annual consumption of detritus by 1 million of 1-year-old sea cucumberApostichopus japonicus. By the end of the 4-year cycle of cultivation, the sea cucumbers of commercial size consume this amount of biodeposits within a month (60 g of organic carbon per year each). Production of a sea cucumber plantation with 5 million juveniles of sea cucumber settling every year can exceed 700 t in 10 years of operation, if it is mounted within the bicultural marine farm with bivalve cages as additional source of suspended organic matter.

Operational performance in aquaculture: A case study of the manual harvesting of cultivated mussels

Aquaculture is one of the fastest growing food production sectors in recent decades. Such rapid development emphasizes the need to adopt more efficient production strategies while simultaneously increasing productivity and sustainability. Monitoring of production is an important strategy to achieve process efficiency. Therefore, we conducted a time and motion study using operational performance indicators to evaluate mussel harvesting on a commercial marine farm in Southern Brazil. We analyzed the operations of mussel sea withdrawal and disaggregation, which are widely used by local farmers but demanding for workers to perform. Mussel sea withdrawal and disaggregation had standard times of 133.7 and 266.7 s, respectively, for one mussel rope; operational production capacities of 0.16 and 0.08 kg s−1, respectively; operational efficiencies of 100 and 31.6%, respectively; time efficiencies of 56.1 and 34.7%, respectively, rework percentages of 0 and 65%, respectively; and percentages of damaged products of 0 and 3.4%, respectively. These parameters indicate low operational performance. The approach used in this study also allowed us to identify process wastes and propose ways to eliminate or mitigate them, with the aim of adopting more efficient work methods.

Robust H∞ control for stability assessment in grid‐connected offshore wind and marine current hybrid system

The geographic suitability brings the offshore wind farm (OWF) and marine current farm (MCF) together with their aggregated power fed to grid simultaneously in most relevant energy harnessing infrastructures. However, stability assessment of the integrated system is a major concern due to the integration of stochastic and intermittent sources with parametric uncertainty. Bridge-type fault current limiter (BFCL) has consolidated their application for a suitable enhancement of stability margin for most modern supply systems. In this article, a detailed modelling of the integrated system is carried out in the presence of BFCL along with consideration of uncertainty as well. A robust H∞ controller design strategy for stability assessment of grid-connected OWF and MCF in the presence of parametric uncertainties is presented in this article. Linear matrix inequality (LMI) conditions are derived in the context of evaluating the robust controller gain with respect to desired robust stability margin. The efficacy of the controller design is compared with that of H∞ loop shaping and conventional P-I control through different case studies with simulation followed by real-time digital simulator (RTDS) validation.

Ecological state of Severnaya Bight (Slavianka Bay, Peter the Great Bay, Japan Sea)

Oceanographic and chemical properties, sea currents, bottom topography and sediments in the Severnaya Bight (Slavianka Bay of Peter the Great Bay, Japan Sea) are considered on the base of all available data collected from 1965 to 2018. Mean and extreme values of the water parameters in the bight are determined for the first time. Seasonal and short-term tide-induced variations of the water temperature and salinity at certain depths are described. The environments influence on aquaculture is estimated. The hanging culture equipment can be mounted in the bight at the depth of no less than 10–12 m, whereas the bottom culture is possible in local areas with the depth of 6–10 m located in its northern and northwestern parts and southwestward from the Mininosok Inlet. In the north of the bight, the cultivated scallop is subjected to unfavorable influence of high water temperature and low salinity, but the water regime at the depth of 6–8 m, where the collectors and hatcheries are usually mounted, is relatively stable and favorable for the scallop cultivation, with rather rare and short-term rises of temperature (up to 25 °С), declines of salinity (to 24 ‰), and dissolved oxygen depletion (to 3.17 mL/L, or 58 %). Currents in the Severnaya Bight are strong enough for its waters renewal: 25–30 cm/s. The currents are almost reverse in the top of the bight; the semi-permanent cyclonic circulation develops in its main part that provides the water exchange with the open part of Peter the Great Bay and distribution of suspended solids, contaminants, bacteria, or larvae from marine farms or other sources over the bight. The non-tidal currents are almost twice stronger in winter than in summer.

Deformities in reared cobia, Rachycentron canadum L. and grouper, Epinephelus marginatus, in São Paulo state coast, Brazil: case report

ABSTRACT Skeletal deformities are frequent problems in cultured fish populations due mainly to unfavorable abiotic conditions, inappropriate nutrition, and genetic factors. These may cause erratic swimming, decrease of conversion rate, growth, and market value. The aim of this case report was to present the occurrence of deformities in juvenile cobia and groupers from an offshore marine farm in Ilhabela, São Paulo, Brazil. Nine cobias and seven juvenile groupers, that presented deformities, were euthanized and fixed in 10% formaldehyde. They were tagged, processed, and stained with "Alcian Blue" (AB) and "Alizarin Red-S" (ARS) for visualization of cartilage and bone tissue, respectively. After evisceration, radiographic examination was performed. The deformities observed in cobia were atrophy of the operculum, disorganization of the gill lamellae, deformity of the lower jaw, kyphosis, and scoliosis. Groupers presented lower jaw deformity and saddleback syndrome. The farm studied in this case report had poor management standards, fed commercial feed for freshwater herbivorous fish and cooked sardines, high inbreeding and absence of adequately trained professionals to manage these species. The sum of these factors must have directly influenced the appearance of these deformities. It is necessary to control this situation to minimize the incidence of malformations that have economic impacts to farmers.

Effects of different levels of sweet potato in feeds on body composition and digestive enzymes activities of Apostichopus japonicas Selenka

The aim of this study was to test the effects of including sweet potato tuber and stem powder in feed on the body composition and digestive enzyme activities of the sea cucumber Apostichopus japonicas Selenka. Different proportions of sweet potato tuber and stem powders (from 10% to 50%) were added into compound feeds, which were supplied to A. japonicas during a 60-day experiment. The results showed that the two sweet potato ingredients had different effects on the nutrient contents of the sea cucumber body wall. The group supplied with feed containing 20% sweet potato tuber powder (T2) had the highest level of crude protein in body walls ( P 0.05). In all the groups fed with powdered sweet potato tubers (T groups), the proportions of glutamic acid and lysine in body walls were higher than those in the control, whereas the proportion of methionine decreased slightly. Different proportions of sweet potato ingredients in compound feeds also affected digestive enzyme activities in the sea cucumbers. The activities of protease and lipase first increased and then gradually decreased with increasing proportions of sweet potato materials in the feed. The highest protease activity was in the T2 and the group and the highest lipase activity was in the 10% sweet potato stem (S1) group. These results show that feed components can stimulate digestive enzyme activities in sea cucumber, and that the proportions of tubers and stems of sweet potato in feed can be adjusted to improve the digestion and growth of A. japonicas in marine farms.