The marine fish farming industry is growing at a significant rate, yet a number of concerns still remain with regards to environmental impacts on the surrounding coastal sea and its biota. Here, we assessed the impact of intensive farming on benthic prokaryotic communities at a Mediterranean sea bass and sea bream intensive aquaculture site over a period of 10 months, in relation to the increase in fish biomass within the cage together with the organic matter enrichment in the sediments. We report positive relationships between prokaryotic abundance and both organic matter and fish biomass, and a contextual decrease in prokaryotic diversity below the cages. A significant shift in microbial community composition occurred in fish farm sediments (FF) over time, indicating a likely impact of ongoing aquaculture activity on prokaryotic communities. Among the dominant taxa at the impacted site, we found Epsilonproteobacteria and Bacteroidetes, which showed a general increase with fish biomass. Analyses on specialist taxa underlined significant contributions of Clostridiales and Bacteroidales in the farmed sediments. Finally, sea bream and sea bass gut microbiome-related taxa were detected during the sampling period. Our results indicate that prokaryotic community composition underneath the cages is related to fish biomass and organic enrichment over the course of production, and confirms that the study of benthic microbial communities at aquaculture sites represents a useful tool to assess the impact of intensive mariculture on the surrounding environment.
Aquaculture, Seafood, and Food Security
Multi-use in ocean space, and seas, entails the co-location of different industries or technologies and their corresponding activities that take place at the same time in a specific location. This concept focuses on finding solutions to tackle global challenges in food security. However, the effects that seaweed cultivation at offshore wind farms may have on food and feed safety are less readily addressed. This study examined whether currently available food and feed safety standards for seaweed can be applied to multi-use activities at sea. The focus was on the combined use of seaweed cultivation at an offshore wind farm in the North Sea. Literature regarding hazards in seaweed was screened, and standards were evaluated. Expert elicitation on seaweed cultivation was retrieved via in-depth interviews and a workshop. Results showed that although some food safety hazards may be more apparent for seaweed cultivation such as toxic metals (e.g., arsenic, cadmium) and iodine, others may become relevant when considering multi-use (e.g., allergens, polycyclic aromatic hydrocarbons, toxic metabolites). Key factors for food safety include the location of seaweed cultivation, handling and processing of seaweed, and seaweed testing. Public standards, the Food Safety System Certification 22000 standard, and the Marine Stewardship Council/Aquaculture Stewardship Council standard are recommended for the food and marine sectors to consider when determining standards to implement. This case study provides an example of how to address seaweed food and feed safety in a multi-use scenario in the North Sea. We recommend additional case studies for other multi-use at sea scenarios.
In fish-farming areas, copious amounts of organic matter are released into the surrounding environment. Although it is well-known that bacterial community structures and activities are tightly coupled with organic conditions in the environment, actively growing bacteria (AGB) species that are responsible are still largely unknown. Here, we determined seasonal variations in the community structures of free-living and particle-attached AGB in surface and bottom seawater, and also in the easily resuspendable sediment boundary layer. Accordingly, we used bromodeoxyuridine (BrdU) magnetic bead immunocapture and PCR-denaturing gradient gel electrophoresis (BUMP-DGGE) analysis. Whereas overall bacterial communities in the resuspendable sediment were quite different from those of the free-living and particle-attached bacteria, the AGB community structures were similar among them. This result suggests that sediment resuspension in aquaculture environments functions as an organic source for bacteria in the water column, and that bacterial species contributing to the environmental capacity and carbon cycle are limited. We identified 25 AGB phylotypes, belonging to Alphaproteobacteria (Roseobacter clade, nine phylotypes), Gammaproteobacteria (five phylotypes), Deltaproteobacteria (one phylotype), Bacteroidetes (seven phylotypes), and Actinobacteria (three phylotypes). Among them, some AGB phylotypes appeared throughout the year with high frequency and were also identified in other coastal environments. This result suggests that these species are responsible for the environmental capacity and carbon cycle, and are key species in this fish-farming area, as well as other coastal environments.
Global demand for freshwater and marine foods (i.e., seafood) is rising and an increasing proportion is farmed. Aquaculture encompasses a range of species and cultivation methods, resulting in diverse social, economic, nutritional, and environmental outcomes. As a result, how aquaculture develops will influence human wellbeing and environmental health outcomes. Recognition of this has spurred a push for nutrition-sensitive aquaculture, which aims to benefit public health through the production of diverse, nutrient-rich seafood and enabling equitable access. This article explores plausible aquaculture futures and their role in nutrition security using a qualitative scenario approach. Two dimensions of economic development – the degree of globalization and the predominant economic development philosophy – bound four scenarios representing systems that are either localized or globalized, and orientated toward maximizing sectoral economic growth or to meeting environmental and equity dimensions of sustainability. The potential contribution of aquaculture in improving nutrition security is then evaluated within each scenario. While aquaculture could be “nutrition-sensitive” under any of the scenarios, its contribution to addressing health inequities is more likely in the economic and political context of a more globally harmonized trade environment and where economic policies are oriented toward social equity and environmental sustainability.
It is hard to find a definition of gill health in the literature although there is a lot of information on changes to gill structure as a result of infectious and non-infectious challenge. How these changes relate to overall fish health is sometimes not clear. Interaction between the gill, the fish, and a range of anticipated changes in the environment will have a currently unknown effect on marine health and aquaculture production. To a degree, fish will likely be able to ameliorate certain changes, such as compensating for slightly elevated carbon dioxide; however, these actions may come at the cost of compromising other functions such as osmoregulation. Compensation will also depend on gill epithelial health and other environmental factors like external nitrogen and ammonia sources which can rise depending on the direction future culture and levels of eutrophication take. Fish can also remodel gill structure in response to salinity, hypoxia, or acidification but it appears that increased temperatures may be associated with increased pathology observable in the gill, and certain fishes may be more susceptible to change. There is a need for more targeted research into climate change-specific gill physiology and a need to recognise gill health as being a key component of food security and not just fish health.
Understanding the cultural contributions of ecosystems is essential for recognising how environmental policy impacts on human well-being. We developed an integrated cultural ecosystem services (CES) valuation approach involving non-monetary valuation through a eudaemonic well-being questionnaire and monetary valuation through hedonic pricing. This approach was applied to assess CES values on the west coast of Scotland. The impact of scenic area and marine protected area (MPA) designations on CES values and potential trade-offs with aquaculture, an increasingly important provisioning ecosystem service in the region, were investigated. Results confirmed a eudaemonic well-being value structure of seven factors: engagement and interaction with nature, place identity, therapeutic value, spiritual value, social bonds, memory/transformative value, and challenge and skill. Visibility of, but not proximity to aquaculture negatively influenced housing prices. In contrast, proximity to MPAs and visibility of scenic areas increased property values. All eudaemonic well-being value factors were positively and significantly associated with scenic areas and a subset of these with MPAs. The integration of the two methods can provide decision-makers with a more comprehensive picture of CES values, their relation to conservation policies and interactions and trade-offs with other activities and services.
The expansion of the aquaculture industry in the last several decades has raised concerns about potential ecological impacts of the industry. Bivalve culture, particularly mussel farming, relies on naturally occurring plankton and numerous studies have demonstrated top-down control on phytoplankton, increased nutrients through excretion of metabolic wastes and remineralization of faeces and pseudofaeces, and bottom-up effects on predators and scavengers through mussel fall-off. However, results are inconsistent between studies, and hydrodynamic conditions and nutrient availability are thought to play an important role in the magnitude and the direction of the ecological effects of mussel culture on the surrounding ecosystem. We used qualitative network models (QNMs), to outline a general model that integrates these environmental conditions and (1) evaluated the ability of different model configurations to reproduce known responses to perturbations, (2) analyzed the behaviour of key components to contrasting hydrodynamic and nutrient condition scenarios, and (3) identified the most influential features of the derived scenarios. The model that included uncertain linkages to characterize unknown relationships performed best based on predetermined validation criteria; the addition of semi-quantitative information on the relative strength of certain linkages improved accuracy and sign determinacy of outcomes. The presence of suspended mussel culture negatively affected primary producers, zooplankton and deposit-feeders, and had a positive effect on predators and scavengers, especially in low-energy environments. Hydrodynamic conditions were shown to have a major impact on the response of the community to mussel culture, while nutrient availability had a very minor impact.
Number of attempts have been made to cryopreserve fish and shellfish gametes. Success has been achieved to establish only sperm banks in case of some commercially important fish. In shellfish, also particularly in shrimps, though the sperm cryopreservation was successful, no attempts were made to develop sperm banks. As far as cryopreservation of egg and embryos of fish and shellfish is concerned, less research efforts were made with limited success. Number of reasons have been given for the failure of egg/embryo cryopreservation and the main barriers speculated are low membrane permeability in the eggs, the large yolk mass of the oocyte, and the presence of compartments in early developing embryos. These factors result in ice crystal formation during the freezing process. In addition, the oocytes and embryos are prone to chilling injuries unrelated to ice crystal damage. There are number of other problems reported by several researchers in the egg/embryo cryobanking protocols which are elaborately discussed in the present paper. There is an urgent need to develop a viable cryobanking technology for fish egg/embryos to enhance fish production in captive condition. Attempts to cryopreserve larvae of aquatic animals is another challenge occurring in the recent past. The aim of the present review is to collect comprehensive information on the efforts so far made on fish and shellfish egg and embryo cryobanking; and to assess the challenges in the development of viable technology and plan for future research for making this technology viable and cost effective.
Alongside government driven management initiatives to achieve sustainable fisheries management, there remains a role for market-based mechanisms to improve fisheries outcomes. Market-based mechanisms are intended to create positive economic incentives that improve the status and management of fisheries. Research to understand consumer demand for certified fish is central but needs to be mirrored by supply side understanding including why fisheries decide to gain or retain certification and the impact of certification on them and other stakeholders involved. We apply semi-structured interviews in seven different Marine Stewardship Council (MSC) certified fisheries that operate in (or from) Western Australia with the aim of better understanding fisheries sector participation in certification schemes (the supply side) and the impacts and unintended benefits and costs of certification. We find that any positive economic impacts of certification were only realised in a limited number of MSC fisheries in Western Australia, which may be explained by the fact that only a small proportion of Western Australian state-managed fisheries are sold with the MSC label and ex-vessel or consumer market price premiums are therefore mostly not obtained. Positive impacts of certification in these Western Australian fisheries are more of a social and institutional nature, for example, greater social acceptability and increased efficiency in the governance process respectively. However, opinion is divided on whether the combined non-monetary and monetary benefits outweigh the costs.
The direct and indirect impact of fish farms, shellfish aquaculture, and extensive forms of aquaculture such as seeding of juvenile sea urchins, on macrophytes (seaweeds and seagrasses), is reviewed in Mediterranean benthic ecosystems. Fish farms constitute a source of organic matter and nutrients (food and fecal pellets) that causes the extirpation of Posidonia oceanica seagrass meadows beneath and near to farm facilities. In addition to direct effects, the nitrogen enrichment of macrophytes tissues increases the grazing pressure by herbivorous fishes and sea urchins. In some cases, the impact can continue to increase several years after the cessation of farming activities. Natural restoration of extirpated seagrass meadows is generally unlikely at the human time scale. Shellfish aquaculture is the cause of the main flow of introduced macrophytes in the Mediterranean; the main vector is the importation of oyster spat from Japan and Korea. North-eastern Pacific seaweeds are now the dominant biotic component of some Mediterranean lagoons (e.g., Thau, Mar Piccolo, and Venice lagoons). In addition to direct effects, mussel aquaculture can constitute a source of larvae that flow with currents, the adults of which can overwhelm seaweed forests (e.g., Carpodesmia mediterranea). Shellfish aquaculture is also a source of fecal pellets, resulting in changes in bottom macrophytes, and a vector of diseases of metazoans, the extirpation of which may change the functioning of recipient macrophyte ecosystems. The edible sea urchin Paracentrotus lividus is sometimes erroneously considered as in decline due to over-harvesting. However, its abundance in the second half of the 20th century was probably a consequence of human impact (overfishing of its predatory fish, organic pollution. This man-induced proliferation resulted in the extirpation of seaweed forests (e.g., Carpodesmia spp., Treptacantha spp. – formerly Cystoseira spp. – Sargassum spp.; many species are endemic), which play a key role in Mediterranean coastal ecosystems. Therefore, the attempts to restore sea urchin abundance, via seeding of juveniles from hatcheries, has further artificialized the habitats rather than contributing to the restoration of natural ecosystems. Good practices guidelines are proposed aimed at minimizing the impact of aquaculture on macrophytes.