Net-pen Aquaculture Research Articles

Phasing out open net-pen salmon farming in British Columbia.

Canada has committed to banning salmon open net-pen aquaculture in British Columbia by 2029 and is transitioning the industry to closed containment technologies for salmon farming.

Pathogens from salmon aquaculture in relation to conservation of wild Pacific salmon in Canada.

The spread of pathogens from farmed salmon is a conservation concern for wild Pacific salmon in British Columbia (BC), Canada. Three pathogens are prevalent in farmed Atlantic salmon in BC, spill over to wild Pacific salmon, and are linked to negative impacts on wild salmon: Piscine orthoreovirus, Tenacibaculum spp., and sea lice (Lepeophtheirus salmonis). Molecular screening of infectious agents in farmed and wild salmon and environmental DNA highlights a further 4 agents that are likely elevated near salmon farms and 37 that co-occur in wild and farmed salmon. Pathogens likely affect wild salmon indirectly by mediating migration, competition, and predation. Current net-pen aquaculture practices pose these risks to numerous populations of all species of wild salmon in BC, most of which are not covered in Government of Canada science and advisory reports. Climate change, pathogen evolution, and changes to disease management and aquaculture regulations will influence future risks.

Monitoring Monthly Net-Pen Aquaculture Dynamics of Shallow Lakes Using Sentinel-1 Data: Case Study of Shallow Lakes in Jiangsu Province, China

Net-pen aquaculture, one of the primary forms of aquaculture in shallow lakes, has generated substantial economic benefits but has also triggered eutrophication and ecological degradation. Therefore, the accurate and scientific dynamic monitoring of aquaculture areas is of the utmost importance. However, existing studies have predominantly employed annual monitoring, failing to fully exploit the unique advantage of synthetic aperture radar (SAR) imagery for seasonal, monthly or more frequent time scale monitoring. This study aimed to develop an approach for monitoring the monthly dynamics of net-pen aquaculture using Sentinel-1 time series images. We integrated threshold segmentation and temporal consistency checking to extract spatial data on the net-pen aquaculture from eight typical shallow lakes in Jiangsu Province, one of the eastern coastal provinces of China, from 2016 to 2021. This study yielded the following results: (1) The VV polarization image offers a particularly noticeable contrast between net-pen aquaculture structures and their surroundings and checking for temporal consistency can help alleviate the problem of distinguishing between changes in error caused by misclassification and actual changes that occurred. The overall accuracy of the net-pen aquaculture extraction results was over 85%. (2) This approach not only enables the analysis of changes in the aquaculture area and fence length but can also identify key time points. For instance, the net-pen aquaculture area in Gehu Lake experienced a rapid decline from May to November 2018, the decrease in while Eastern Taihu Lake occurred from September 2018 to June 2019. (3) The removal of net-pen aquaculture in lakes within the Jiangsu Province is primarily attributed to policy responses. In response to the ecological river and lake action plan implemented in Jiangsu Province, a decrease was observed in both the aquaculture areas and fence lengths across most lakes from 2016 to 2021. These results can provide a reference for lake management and ensuring the effective implementation of related policies.

Intrinsic and extrinsic factors associated with the spatio-temporal distribution of infectious agents in early marine Chinook and coho salmon

Understanding the factors driving the spatial distribution of infectious agents in populations is key to predicting infectious agent distributions under future ecological and anthropogenic scenarios. We applied a geostatistical analysis to a data set of 59 infectious agents assayed in thousands of Chinook and coho salmon in their first marine year to identify intrinsic and extrinsic factors associated with the probability and density (infectious agent load) of infection. Meta-analysis of the pathogen-specific geostatistical models indicated that sea surface salinity was the extrinsic factor most frequently associated with infection probability and density for a majority of infectious agents. In addition, agents that were categorized as having a moderate risk of transmission from aquaculture to wild salmon were more likely to occur, and at higher infection densities, in fish collected closer to active aquaculture facilities. Although hypotheses pertaining to other intrinsic and extrinsic factors, including age at ocean entry, known hatchery origin, and sea surface temperature deviation, were not supported by the meta-analysis results, some individual agents demonstrated strong associations with these factors. Our results suggest that climate-change-driven shifts in coastal seawater salinity (and to a lesser extent, temperature) may result in changes to the infection dynamics of several infectious agents. In addition, our results contribute to existing evidence characterizing the risk of infectious agent transmission from netpen aquaculture to free-ranging salmon.

Culture of Seriola dumerili in a marine ecosystem: Insights from genetic and morphometric fish traits and implications of escape events

Commercial net-pen mariculture of Seriola dumerili recently started in Mediterranean countries. While the introduction of new species allows for product diversification and strengthens the European seafood market, net-pen farming and escape events can lead to a number of socio-economic and ecological interactions in the coastal zone. To assist in the genetic management of broodstocks and mitigate the effects of escape events, the potential of morphological and genetic traits of wild, farmed and escaped S. dumerili from the Balearic and the Adriatic Sea were examined as a proxy of wild and farmed origin. Body shape, head profile and mouth position allowed correct classification between fish groups (82%). The global FST of 0.053 across all loci showed significant subdivision between wild and farmed fish, and allowed correct assignment of escapees. Integration of both genetic and morphometric data using the R package assignPOP improved the assignment results of the escaped group with unknown origin. Potential ecological and socioeconomic implications of escape events are discussed, along with guidelines promoting sustainable development of coastal net-pen aquaculture in a future to come.

Инновационный вектор развития морской промышленности Норвегии

According to the updated Norwegian maritime strategy, its further economic growth will be closely linked with the maritime industry development, which is focused on satisfying the world economy's growing demand for food, energy, and transportation services. Along with supporting the traditional sectors of its maritime industry (offshore hydrocarbon production, fishing, coastal aquaculture, shipping, etc.), Oslo plans to develop some innovative areas of the industry, such as offshore aquaculture, offshore renewable energy and “green” shipping, which are the main research objects of this work. The author presents an analysis of the main innovative projects implemented by Norway in various sectors of its maritime economy. Amid the international community's concern over the global environmental situation, Oslo is actively developing and implementing advanced technological solutions in its maritime industry, which can not only reduce the level of negative impact on the environment, but also significantly improve its economic performance. A key feature of Norway's maritime industry development is the deepening of intersectoral collaboration, which enabled it to implement oil and gas technologies into offshore aquaculture and offshore wind energy, as well as traditional net-pen aquaculture technologies into offshore solar energy projects. Particular attention in the article is paid to the digitalization of Norway's maritime industry, aimed at ensuring automation or, in some projects, complete autonomy of the utilization of different floating and fixed maritime constructions (vessels, offshore fish farms and power plants).Moreover, the author assesses the Norwegian government's efforts in facilitating further maritime industry development, which includes educating specialists in information and communication technologies, expanding international cooperation, implementing public-private partnership programs, searching for new sales markets and revising the state investment system. In conclusion, the author suggests that in the future the global demand for environmentally friendly innovative technologies produced by Norway will increase, thereby providing for new employment opportunities, development of the national maritime industry and, as a result, the country's sustainable economic growth.

Changes in aquatic vegetation communities based on satellite images before and after pen aquaculture removal in East Lake Taihu

为削减东太湖养殖污染，改善湖泊水质，苏州市于2018年底基本完成东太湖养殖围网拆除工作.围网拆除后，湖泊生态环境对此如何响应，已成为学者及相关管理部门关注的重点.水生植被在维持湖泊生态系统平衡、物质循环和净化水质方面发挥着重要的作用，是诊断湖泊生态系统健康状态的关键指标.本研究基于Sentinel-2卫星数据，利用分类决策树模型和基于生活史的沉水植被优势种群提取方法，监测了东太湖2017年（围网拆除前）和2019年（围网拆除后）的水生植被类群和沉水植被优势种群的空间分布.经验证，水生植被类群监测精度为82.66%，Kappa系数为0.77；沉水植被优势种群的监测精度为62.08%，Kappa系数为0.56.结果表明：围网拆除后，东太湖水生植被优势类群由围网拆除前的沉水植被转变为浮叶植被；沉水植被分布面积减少，且种群由优势度相差不大的七大优势种群逐步向菹草和伊乐藻占据绝对优势发展，逐渐趋于单一化.;To improve water quality and enhance ecological management, all the net-pen aquaculture facilities in the East Lake Taihu have been removed by the end of 2018. Understanding the impact of this activity on lake ecosystem health is critical to promote efficient ecological management. Aquatic vegetation, especially submerged aquatic vegetation is an essential component of healthy lake ecosystem, as they provide food and shelter, help to secure and stabilize shorelines and modulate nutrient circulation. Additionally, submerged aquatic vegetation can improve water clarity by competing for nutrient with algae. Monitoring submerged aquatic vegetation is fundamental to lake ecosystem health evaluation. In this study, we leverage Sentinel-2 data to map the temporal change of different types of aquatic vegetation types (i.e., emergent vegetation, floating-leaved vegetation and submerged aquatic vegetation), as well as the dominant submerged aquatic vegetation species. We found that the dominant vegetation shifted from submerged to floating-leaved vegetation after the pen aquaculture removal in East Lake Taihu. Meanwhile, the total coverage of submerged aquatic vegetation and its diversity significantly decreased, suggesting environmental degradation in this area. Our research indicated that removing net-pen culture has negative effect on lake ecosystem health. Efficient ecological management of this critical lake system requires comprehensive evaluation before they implement any management activities.

Рыбопромышленный комплекс Норвегии

Received 24.07.2020. Over the half of a century, the oil and gas industry remained a key sector of Norway’s economy, which had been receiving the highest governmental support. However, the situation has changed dramatically, since Oslo decided to reduce the volume of government investments in the petroleum industry, redirecting them to the assets of “green” companies. That decision initiated modernization of Norway’s seafood industry, which starts occupying a more prominent place in the country’s economy. In this paper, the author intends to study the current state of the Norwegian seafood industry and prospects for its development. Seafood makes up the country’s third export commodity by the value, sales volume of which increases annually. The government seeks to ensure further development of the industry avoiding the growth of negative environmental impacts. In order to achieve this goal Norway established a rigid system of state regulation, in both fishing and aquaculture, which bases on the principles of the ecosystem approach. Moreover, Oslo initiated several programs to find new technological solutions for seafood production. In fishing sector, it was decided to replace the old coastal vessels with high-tech ocean-going ones that ensure residue-free processing of extracted biological resources. Norway also started a new technological trend in the world aquaculture – construction of offshore fish farms – that will increase production volumes while reducing environmental risks related to the traditional net-pen aquaculture. The overall purpose of the Norwegian government is to increase profitability of its seafood industry, so in the future it could compensate for the shortfall in income of its oil and gas industry. Apart from that, particular attention in this paper paid to considering the Norwegian approach to fisheries regulation in maritime areas around Svalbard, where national interests of the parties to the Treaty of Paris collide. The author also analyses the role of a competition and cooperation in further development of Norway’s seafood industry.

A novel histozoic myxosporean, Enteromyxum caesio n. sp., infecting the redbelly yellowtail fusilier, Caesio cuning, with the creation of the Enteromyxidae n. fam., to formally accommodate this commercially important genus.

Gastrointestinal myxosporean parasites from the genus Enteromyxum are known to cause severe disease, resulting in high mortalities in numerous species of cultured marine fishes globally. Originally described as Myxidium spp., they were transferred to a new genus, Enteromyxum, to emphasize their novel characteristics. Their retention in the family Myxidiidae at the time was warranted, but more comprehensive phylogenetic analyses have since demonstrated the need for a new family for these parasites. We discovered a novel Enteromyxum in wild fish from Malaysia and herein describe the fourth species in the genus and erect a new family, the Enteromyxidae n. fam., to accommodate them. Enteromyxum caesio n. sp. is described infecting the tissues of the stomach in the redbelly yellowtail fusilier, Caesio cuning, from Malaysia. The new species is distinct from all others in the genus, as the myxospores although morphologically similar, are significantly smaller in size. Furthermore, small subunit ribosomal DNA sequence data reveal that E. caesio is <84% similar to others in the genus, but collectively they form a robust and discrete clade, the Enteromyxidae n. fam., which is placed as a sister taxon to other histozoic marine myxosporeans. In addition, we describe, using transmission electron microscopy, the epicellular stages of Enteromyxum fugu and show a scanning electron micrograph of a mature myxospore of E. caesio detailing the otherwise indistinct sutural line, features of the polar capsules and spore valve ridges. The Enteromyxidae n. fam. is a commercially important group of parasites infecting the gastrointestinal tract of marine fishes and the histozoic species can cause the disease enteromyxosis in intensive finfish aquaculture facilities. Epicellular and sloughed histozoic stages are responsible for fish-to-fish transmission in net pen aquaculture systems but actinospores from an annelid host are thought to be necessary for transmission to fish in the wild.

Ion-regulation, acid/base-balance, kidney function, and effects of hypoxia in coho salmon, Oncorhynchus kisutch, after long-term acclimation to different salinities

Land-based salmon farming in closed containment recirculation aquaculture systems (RAS) is an emerging industry with the potential for reducing disease prevalence, improving production efficiency, and reducing environmental impacts compared with open net-pen aquaculture. Salinity and oxygen levels are environmental factors that have significant impacts on the physiology of fishes and possibly influence the production efficiency of fishes in aquaculture. These parameters are particularly relevant for fish production in RAS, where most water parameters can be manipulated and tightly controlled. While much is known about the specific mechanisms associated with the acute transfer between FW and SW and the reverse, little is known about the effects of long-term acclimation on ion- and acid/base-regulation, especially at intermediate salinities. We measured gas-exchange, ion-regulation, acid/base balance, and renal function in coho salmon (Oncorhynchus kisutch Walbaum, 1792) acclimated to four salinities (2.5, 5.0, 10, and 30 ppt) for over a year in RAS and investigated how animals prioritize these functions when faced with 24 h exposure to hypoxia (PO2 = 63 mmHg = 8.4 kPa = 3.76–4.48 mg l−1). We show that fish that were long-term acclimated to 30 ppt had substantially higher plasma osmolality and [Na+] than fish acclimated to lower salinities. These changes were associated with a marked reduction in blood pH at 30 ppt relative to 2.5 ppt, and we discuss a possible thermodynamic link between salinity acclimation and acid/base regulation. Further, we show that hypoxia exposure results in changes in plasma osmolality by over 80 mOsm kg−1, but only in 30 ppt water, demonstrating a salinity-dependent trade-off between gas exchange and osmoregulation. This study provides insight into the physiological state and hypoxia sensitivity of market sized salmon reared under industry-relevant conditions in RAS.

Low susceptibility of sockeye salmon Oncorhynchus nerka to viral hemorrhagic septicemia virus genotype IVa.

Viral hemorrhagic septicemia virus (VHSV) genotype IVa is an endemic pathogen to the marine waters of British Columbia, with numerous marine fishes being susceptible to infection and disease, including Atlantic salmon Salmo salar reared in open net-pen aquaculture. The susceptibility of Atlantic salmon and sockeye salmon Oncorhynchus nerka to VHSV-IVa infection was evaluated using exposure routes including injection, static immersion, and cohabitation with diseased Pacific herring Clupea pallasii. Exposed fish were monitored for mortality and external pathology, mortalities were tested by virus isolation assay, and live fish were regularly sampled and screened for infection. Among injected sockeye, VHSV was detected in 1 mortality (n = 195) and 2 sub-sampled fish (n = 30), whereas sockeye exposed by immersion and cohabitation did not experience mortality nor was systemic infection indicated by tissue screening. Injection and cohabitation exposure routes confirmed the susceptibility of Atlantic salmon to VHSV. Neither sockeye nor Atlantic salmon surviving the cohabitation served as a reservoir of VHSV, but Pacific herring did. The results suggest that VHSV-IVa poses low risk to sockeye salmon under natural routes of exposure.

Communicating a risk-controversy: Exploring the public discourse on net-pen aquaculture within the Canadian media

Finfish net-pen aquaculture in Canada is an important economic industry that supports coastal rural livelihoods. However, aquaculture development faces several types of barriers, including technological, environmental, regulatory, and social. Public perceptions linked to the aforementioned barriers have largely influenced aquaculture development in Canada, where maintaining social acceptance and public trust have been an enduring challenge. Since the media is important for spreading information and shaping public opinion, this study explored how media defines aquaculture to better understand the public discourse and implications for policy. Using qualitative and quantitative content analysis to explore the coverage of major Canadian newspapers in 2015 and 2016, we found a complex discourse expressing a range of aquaculture attributes and stakeholders. Our results indicate that media frames finfish net-pen aquaculture in a mostly negative tone, although there are considerable regional variabilities and differences across specific attributes. Risk-oriented frames focused on environmental challenges and management responses, while positive aspects surrounded scientific and technological advances and economic benefits. Complex interactions between environmental, social, economic, and management attributes further emphasizes the multi-faceted nature of the public discourse surrounding finfish aquaculture in Canada. Media relied not only on environmental groups or scientists in their reporting, but also considerably on fish farmers and government to offer expert opinions or as proponents of the industry. This supports a shift away from an ‘elitist’ role of the media, towards a more ‘deliberative’ role of balancing perspectives and democratic dialogue. These findings have implications for private and public responses and highlight the need for interdisciplinary solutions that emphasize transparency, communication, and accountability to improve public trust and guide sector development.

Extensive hybridization following a large escape of domesticated Atlantic salmon in the Northwest Atlantic

Domestication is rife with episodes of interbreeding between cultured and wild populations, potentially challenging adaptive variation in the wild. In Atlantic salmon, Salmo salar, the number of domesticated individuals far exceeds wild individuals, and escape events occur regularly, yet evidence of the magnitude and geographic scale of interbreeding resulting from individual escape events is lacking. We screened juvenile Atlantic salmon using 95 single nucleotide polymorphisms following a single, large aquaculture escape in the Northwest Atlantic and report the landscape-scale detection of hybrid and feral salmon (27.1%, 17/18 rivers). Hybrids were reproductively viable, and observed at higher frequency in smaller wild populations. Repeated annual sampling of this cohort revealed decreases in the presence of hybrid and feral offspring over time. These results link previous observations of escaped salmon in rivers with reports of population genetic change, and demonstrate the potential negative consequences of escapes from net-pen aquaculture on wild populations.

Polyphyletic ancestry of expanding Patagonian Chinook salmon populations

Chinook salmon native to North America are spreading through South America’s Patagonia and have become the most widespread anadromous salmon invasion ever documented. To better understand the colonization history and role that genetic diversity might have played in the founding and radiation of these new populations, we characterized ancestry and genetic diversity across latitude (39–48°S). Samples from four distant basins in Chile were genotyped for 13 microsatellite loci, and allocated, through probabilistic mixture models, to 148 potential donor populations in North America representing 46 distinct genetic lineages. Patagonian Chinook salmon clearly had a diverse and heterogeneous ancestry. Lineages from the Lower Columbia River were introduced for salmon open-ocean ranching in the late 1970s and 1980s, and were prevalent south of 43°S. In the north, however, a diverse assembly of lineages was found, associated with net-pen aquaculture during the 1990s. Finally, we showed that possible lineage admixture in the introduced range can confound allocations inferred from mixture models, a caveat previously overlooked in studies of this kind. While we documented high genetic and lineage diversity in expanding Patagonian populations, the degree to which diversity drives adaptive potential remains unclear. Our new understanding of diversity across latitude will guide future research.

Sediment nitrogen cycling rates and microbial abundance along a submerged vegetation gradient in a eutrophic lake

Decline of submerged vegetation is one of the most serious ecological problems in eutrophic lakes worldwide. Although restoration of submerged vegetation is widely assumed to enhance ecological functions (e.g., nitrogen removal) and aquatic biodiversity, the evidence for this assumption is very limited. Here, we investigated the spatio-temporal patterns of sediment potential nitrification, unamended denitrification and N2O production rates along a vegetation gradient in the Lake Honghu, where submerged vegetation was largely restored by prohibiting net-pen aquaculture. We also used five functional genes as markers to quantify the abundance of sediment nitrifying and denitrifying microorganisms. Results showed that unvegetated sediments supported greater nitrification rates than rhizosphere sediments of perennial or seasonal vegetation. However, the absence of submerged vegetation had no significant effect on denitrification and N2O production rates. Additionally, the abundance of functional microorganisms in sediments was not significantly different among vegetation types. Season had a strong effect on both nitrogen cycling processes and microbial abundances. The highest nitrification rates were observed in September, while the highest denitrification rates occurred in December. The temporal variation of sediment nitrification, denitrification and N2O production rates could be due to changes in water quality and sediment properties rather than submerged vegetation and microbial abundances. Our findings highlight that vegetation restoration in eutrophic lakes improves water quality but does not enhance sediment nitrogen removal rates and microbial abundances. Therefore, for reducing the N level in eutrophic lakes, major efforts should be made to control nutrients export from terrestrial ecosystems.

Forecasting the Genetic Impacts of Net Pen Failures on Gulf of Mexico Cobia Populations Using Individual-based Model Simulations

Offshore net pen fish farming provides a cost-efficient means for production of marine finfish, and there is great interest in development of net pen operations in domestic waters. However, there are concerns over the possible genetic and ecological impacts that escaped fish may have on wild populations. We used individual-based simulations, with parameter values informed by life history and genetic data, to investigate the short-term (50 yr) impacts of net pen failures on the genetic composition of cobia, Rachycentron canadum, stocks in the Gulf of Mexico. Higher net pen failure rates resulted in greater genetic impacts on the wild population. Additionally, the use of more genetically differentiated source populations led to larger influxes of non-native alleles and greater temporal genetic change in the population as a result of net pen failure. Our results highlight the importance of considering the appropriate source population for broodstock collection in net pen aquaculture systems and help to provide a general set of best management practices for broodstock selection and maintenance in net pen aquaculture operations. A thorough understanding of the genetic diversity, stock structure, and population demography of target species is important to determine the impact escapees can have on wild populations.

Disentangling the contributions of ocean ranching and net-pen aquaculture in the successful establishment of Chinook salmon in a Patagonian basin

The presence of Chinook salmon in Patagonia is an example of a successful invasion by a Pacific salmon species. The combination of historical records and genetic data can help to determine the origin of invasive / introduced species and allow the identification of the sources and dispersal process. We analyzed the genetic structure of Chinook salmon in the Futaleufu River (Pacific slope basin of Patagonia) using single nucleotide polymorphism genotypes and a recently described baseline dataset of native North American Chinook salmon populations. Our results revealed that Chinook salmon established in the Futaleufu River have high levels of within-population genetic diversity compared with populations from across the native range. Based on genetic similarity and historical reports, our results indicate that the Futaleufu population was first established by colonizing fish derived from the Lower Columbia River Basin, imported into Chile for ocean ranching purposes during the 1970s and 1980s, and afterward it was strongly supplemented by escaped fish from net pen aquaculture that used broodstock imported during the 1990s from various sources, including the California Central Valley (via New Zealand), the Middle Oregon Coast, and Vancouver Island. The higher incidence of fish derived from the most recent introductions in our sample suggest that the contribution of escaped salmon from these posterior stockings on establishment success must have been particularly strong because included different sources. Subsequent admixture and hybridization among these multiple independent source stocks is likely responsible for the high level of standing genetic variation, which may be facilitating local adaptation and augmenting the opportunity for successful invasion and further colonization.

A game theory based framework for assessing incentives for local area collaboration with an application to Scottish salmon farming

Movements of water that transport pathogens mean that in net-pen aquaculture diseases are often most effectively managed collaboratively among neighbours. Such area management is widely and explicitly applied for pathogen management in marine salmon farms. Effective area management requires the active support of farm managers and a simple game-theory based framework was developed to identify the conditions required under which collaboration is perceived to be in their own best interest. The model applied is based on area management as practiced for Scottish salmon farms, but its simplicity allows it to be generalised to other area-managed net-pen aquaculture systems. In this model managers choose between purchasing tested pathogen-free fish or cheaper, untested fish that might carry pathogens. Perceived pay-off depends on degree of confidence that neighbours will not buy untested fish, risking input of pathogens that spread between farms. For a given level of risk, confidence in neighbours is most important in control of moderate-impact moderate-probability diseases. Common low-impact diseases require high confidence since there is a high probability a neighbour will import, while testing for rare high-impact diseases may be cost-effective regardless of neighbours actions. In some cases testing may be beneficial at an area level, even if all individual farms are better off not testing. Higher confidence is required for areas with many farms and so focusing management on smaller, epidemiologically imperfect, areas may be more effective. The confidence required for collaboration can be enhanced by the development of formal agreements and the involvement of outside disinterested parties such as trade bodies or government.

Estimation of Parameters Influencing Waterborne Transmission of Infectious Hematopoietic Necrosis Virus (IHNV) in Atlantic Salmon (Salmo salar)

Understanding how pathogenic organisms spread in the environment is crucial for the management of disease, yet knowledge of propagule dispersal and transmission in aquatic environments is limited. We conducted empirical studies using the aquatic virus, infectious hematopoietic necrosis virus (IHNV), to quantify infectious dose, shedding capacity, and virus destruction rates in order to better understand the transmission of IHN virus among Atlantic salmon marine net-pen aquaculture. Transmission of virus and subsequent mortality in Atlantic salmon post-smolts was initiated with as low as 10 plaque forming units (pfu) ml−1. Virus shedding from IHNV infected Atlantic salmon was detected before the onset of visible signs of disease with peak shed rates averaging 3.2×107 pfu fish−1 hour−1 one to two days prior to mortality. Once shed into the marine environment, the abundance of free IHNV is modulated by sunlight (UV A and B) and the growth of natural biota present in the seawater. Virus decayed very slowly in sterilized seawater while rates as high as k = 4.37 d−1 were observed in natural seawater. Decay rates were further accelerated when exposed to sunlight with virus infectivity reduced by six orders of magnitude within 3 hours of full sunlight exposure. Coupling the IHNV transmission parameter estimates determined here with physical water circulation models, will increase the understanding of IHNV dispersal and provide accurate geospatial predictions of risk for IHNV transmission from marine salmon sites.

Effect of artificial light on marine invertebrate and fish abundance in an area of salmon farming

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 419:147-156 (2010) - DOI: https://doi.org/10.3354/meps08822 Effect of artificial light on marine invertebrate and fish abundance in an area of salmon farming A. McConnell1,*, R. Routledge2, B. M. Connors3 1Department of Biology, 2Department of Statistics and Actuarial Sciences, and 3Evolutionary and Behavioural Ecology Research Group, Department of Biological Sciences; Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada *Email: ajm6@sfu.ca ABSTRACT: Artificial light can change the behaviour of aquatic organisms, although the direction of response can be species and life-stage specific. Open net-pen salmon farms in British Columbia, Canada, routinely illuminate their net-pens during the winter and spring, with unknown consequences on the abundance and distribution of marine fish and invertebrates. Paired lit and control samples consisting of plankton hauls and purse seines were made around a 400 W underwater light such as those used on salmon farms. On lit nights, invertebrates were marginally more abundant, while fish larvae and juvenile and adult fish were significantly more abundant. In particular, the invertebrate taxa Gastropoda and Bivalvia were significantly more abundant on lit nights, as were the fish species Pacific herring Clupea pallasi, sand lance Ammodytes hexapterus, threespine stickleback Gasterosteus aculeatus, soft sculpin Psychrolutes sigalutes, and great sculpin larvae Myoxocephalus polyacanthocephalus. These results suggest that lights commonly used in open net-pen aquaculture may increase the abundance of some fish species around pens, thereby increasing the probability that farmed fish and wild species directly and indirectly interact in coastal marine environments. KEY WORDS: Aquaculture · Phototaxis · Aggregation · Zooplankton · Chum salmon Full text in pdf format PreviousNextCite this article as: McConnell A, Routledge R, Connors BM (2010) Effect of artificial light on marine invertebrate and fish abundance in an area of salmon farming. Mar Ecol Prog Ser 419:147-156. https://doi.org/10.3354/meps08822 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 419. Online publication date: November 30, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.