Many populations of brown trout are managed by hatchery breeding and supportive release. Using a limited number of individuals as founders creates a bottleneck, which can lead to loss of genetic diversity in a population. In this study 17 populations of hatchery-reared brown trout were examined genetically using microsatellite markers. Genetic variation measured as gene diversity and allelic richness were analysed and the effects of effective population size of founders and time since founding on these parameters were explored. Allelic richness and gene diversity decreased with increasing time since founding of the stock, and there was a negative relationship between current effective population size and time since founding. Allelic richness was positively correlated with effective population size at founding. The results indicate that considerations concerning effective population size in hatcheries must be taken seriously to promote high levels of genetic variation among individuals and minimise loss of genetic diversity.
This study provides an overview of the multi-sectoral coastal aquaculture development in Zanzibar (Tanzania) over the last thirty years based on empirical evidence from interviews, field observations, policy reports and literature reviews. Despite the immense potential of aquaculture for food and livelihoods, only seaweed farming has so far established into commercial-scale production. This activity is dominated by women and became widespread in the early 1990s as a small but regular source of income. However, seaweed farming constraints such as frequent seaweed die-offs, as well as economic and institutional constraints inhibit its development. Other types of aquaculture activities such as fish farming, mud crab fattening, half-pearl farming, sea cucumber farming and sponge and coral cultures are under development with limited production or in experimental stages. Common constraints among these activities are economic limitations, lack of technical infrastructure and skills, small and irregular production, and limited trade and market availabilities. At the same time, there is a lack of sufficient management and monitoring systems, while there are no formal regulations or clear strategies to boost aquaculture at the national level. In addition, new aquaculture initiatives are often dominated by donor-driven projects instead of local entrepreneurships. This situation does not encourage engagement in aquaculture and thus such activities are outcompeted by other already established sectors (e.g. agriculture and fisheries). We conclude that aquaculture has great potential to evolve due to high environmental capacity. Nevertheless, achieving profitable production and a stronger commitment within local communities, as well as developing effective mariculture governance through support mechanisms and clear strategies to boost the sector at the national level, are essential for sustainable mariculture development in Zanzibar.
Seaweed mariculture has been promoted as a development project in tropical countries and Zanzibar, Tanzania, is commonly presented as a successful story. However, the results of the present research provide a nuanced picture of the activity identifying serious health problems among farmers. Semi-structured interviews were conducted with female seaweed farmers (n=140) and non-seaweed farmers (n=140) in Zanzibar to evaluate health and working conditions. In-depth interviews with additional 28 female seaweed farmers were performed to deepen the understanding of the working conditions and related problems. The research was undertaken at seven different locations to cover areas where seaweed is extensively executed during August to September 2009 and May to June 2010. Seaweed farmers considered their health significantly poorer than non-seaweed farmers with fatigue, musculoskeletal pain, hunger, respiratory problems, eye related problems, injuries from hazardous animals and sharp shells in the water and allergies as the most serious issues (p<0.05). Income was further reported below the extreme poverty line. Since seaweed farming affects thousands of households in the tropics these results should encourage changes towards better working conditions and sustainability.
In the South China and Java Seas, cage farming is a recent regional activity, which since the year 2000 has experienced an annual growth of 29%. The region holds the highest diversity of marine life, which is partly or completely dependent on coral reefs. The increasingly growing coastal human population in the area relies on ecosystem goods and services provided by the reefs that are threatened by anthropogenic activities. Sea cage farming is one of the stressors negatively impacting coral reefs by being point sources of nutrients and other effluents. To date no systematic information is available on the physical location of marine farms in relation to the coral reefs. Little is known about the distance where impact from the farms can be detected on nearby coral reefs. The present survey aimed to fill this gap by assessing to what extent marine cage farms in South East Asia are placed in the vicinity of the reefs and at which distance stress indicators from the farms are observed. We used Google Earth satellite images to investigate the extension and spatial distribution of sea cage aquaculture in relation to the presence of coral reefs. The stress indicators were locally assessed in Central Vietnam by recording turf algal overgrowth, coral mortality, live coral and branching coral cover at increasing distances from the farms. We found that 90% of sea cage farms throughout the region clustered closer than 5 km from coral reefs and 50% of them closer than 1 km from reefs. In Taiwan, 71% of the cages were located within 100m from a reef. This pattern is nonrandom and could not be explained by the natural distribution of coral reefs; only 5% of the Vietnamese coast harbors coral reefs, and sea cage farms are present in these areas only. This indicates that the farms require similar conditions as the reefs including clear and shallow waters and protection against storms and wave action. We found that turf algal overgrowth decreased at 287 m +/- 54 m, dead coral at 1446m +/- 154 m, live coral cover increased at 566 +/- 221 m and branching corals increased at 867 m +/- 140 m from the cage farms. We conclude that proximity to coral reefs should be considered when planning future developments of sea cage aquaculture, and recommend that distances of at least 1.5 km should be kept. Statement of relevance: Consider coral reefs when planning sea cage aquaculture site.
A majority of the sea cage farms in South East Asia are located close to coral reefs. This causes a conflict between conservation and food production since sea cage aquaculture has a number of negative impacts on coral reefs. The aim of this investigation was to assess the drivers causing the sea cage farmers to place their farms close to reefs and to examine some potential farming effects in detail i.e. usage of coral reef fish for grow out farming and feed. For some 3500 Vietnamese fish and lobster farms, we measured; the distance to the closest coastal city (proxy for infrastructure access), satellite derived Chl a (proxy for water quality), wind fetch, and the adjacent coastal slope and elevation. We also performed 159 semi-structured interviews with fish and lobster cage farmers from three regions in Vietnam. The interviews revealed that the choice of farming site is mainly determined by access to infrastructure, wind and wave shelter, and water quality. Although the farmers used coral reef services, e.g. coral reef derived seedlings, they were in general not aware of coral reef presence or did not find it important for selection of site. Both coral reefs and sea cage farms were found close to steep rocky coasts, which are favorable for corals, and provide sufficient depth for sea cages. Sea cages were always found on the leeward side of the coast where the wind fetch is low enough for the floating farms and their inhabitants. Most of the farms were located within 20 km from a coastal city confirming the importance of access to infrastructure. With few exceptions, sea cage farms were located in areas with good water quality, where also coral reefs are present. The study showed that several of the coral associated species groups farmed were dependent on wild caught seedlings and that 22% of the feed used at farms was trashfish of coral reef associated species. We consider the spatial correlation between sea cage farms and coral reefs as circumstantial and suggest that shared environmental preferences explain the farm distribution pattern, rather than access to ecosystem services provided by the nearby reef itself. We found no evidence that it is necessary for sea cage farms to be located near coral reefs and strongly recommend that sea cages are moved further away from coral reefs, but to areas still providing clear water, shelter and access to infrastructure.
Several papers have reported on the development of antibiotic resistance and implications for human medicine but fewer deal with environmental impacts of antibiotic use. Marine sea cage aquaculture in SE Asia is often established close to coral reef ecosystems. Large amounts of antibiotics are used in the cultivation of fish and lobster and hence released directly into the environment. This study investigates the antibiotic practices in sea cage farms producing fish and spiny lobster in Vietnam, mainly for the domestic market. There are approximately 3500 sea cage farms in Vietnam and we performed semi-structured interviews with 109 sea cage farmers asking them if they use antibiotics and if so; what sort/when/how often/how much. We found that the Vietnamese cage farmers are using antibiotics in an unstructured way, which seems to have little or no effect on the survival of the stock, or profit of the farm. The fact that the farmers live at their farm and use the sea next to the cages both for fishing and collecting filter-feeding bivalves for direct consumption, as well as a toilet, poses an additional risk for the spreading of human antibiotic resistant pathogens. Thirteen different antibiotics were found in the study. Eighty-two percentage of the lobster farmers and 28% of the fishfarmers used antibiotics. The average amounts used were over 5 kg per produced ton of lobster and about 0.6 kg per ton of fish, which is much higher than in other studies. Several antibiotic substances listed as critical and highly important for human medicine by WHO were used prophylactically and routinely with little control and enforcement of regulations. We tested and detected antibiotic resistance to Tetracycline, Vancomycin and Rifampicin in the coral associated bacteria Bacillus niabensis as far as 660m from fish farms with resistance decreasing with distance from the cage farms. The antibiotics are likely to have negative effects on the coral-symbiont relationship adding further risks to an already stressed environment.
Egyptian aquaculture is gaining importance as an affordable and nutritious source of animal protein among Egyptians. Nile tilapia dominates production (77% of total production), followed by carps (17%) and mullets (11%). Egyptian tilapia farmers are, however, facing challenges with regards to financial viability and poor water quality. Fish farms are also contributing towards water pollution and other environmental impacts. In order to improve the situation, WorldFish launched the IEIDEAS project in 2011 with the ambition to train farmers in best management practices (BMP) and distribute the 9th generation of the Abbassa strain (G9). The present study aimed at evaluating any relative environmental gains that BMP and G9 offers compared to conventional farming using life cycle assessment (LCA). Inventory data representing 137 farmers and four groups (control, BMP, G9 and BMP + G9) were evaluated. Life cycle impact assessment results including quantitative uncertainties were then calculated and statistically tested, using Monte Carlo analysis and Wilcoxon paired significance test. Five impact categories were explored: global warming, eutrophication, acidification, freshwater consumption and land use. The G9 stain offered the greatest improvements across the evaluated impact categories, significantly reducing environmental impacts with between 12% and 36%. BMP, in the meantime, only offered significant improvements compared to the control with regards to eutrophication, acidification, freshwater consumption and land use. Meanwhile, BMP + G9 performed comparably to only G9 except for eutrophication where it had a significantly larger environmental footprint. More efficient feed utilization and higher productivity were the main reasons for the environmental improvements. Additional improvements that should be explored include improved feeds made of sustainably sourced raw materials, and better pond water management, including probiotics and paddle-wheels.
Statement of relevance: BMP and improved stains help reduce environmental impacts
Interactions between aquaculture and the environment remain a debated issue, especially in areas where the aquaculture sector is still expanding, such as in the Mekong delta in Vietnam. In response to environmental concerns, various eco-certification schemes have been introduced for seafood, aiming to improve production practices. In order to reflect upon the criteria of these certification schemes, life cycle assessment (LCA) was applied to conventional and certified extensive organic mangrove-shrimp farms in the lower Mekong. In total, 21 organic and 20 non-organic farms were included in the study for evaluation of effects on global warming (including emissions from land transformation and occupation), eutrophication and acidification. Monte Carlo simulations and random sampling were applied to aggregate contributing processes into results. The emissions of greenhouse gasses per ton of shrimp produced were substantial for both groups, and almost solely caused by the release of carbon during mangrove land transformation. Differences in the land area needed to support shrimp production explain the discrepancy. Organic farms emitted less CO2-equivalents (eq.) than the non-organic farms in 75% of the Monte Carlo iterations. Acidification impacts were similar for the two groups, with higher emissions from the non-organic farms in 67% of the iterations. Meanwhile, most mangrove-integrated farms showed a net uptake of eutrophying substances, indicating that both types of mangrove-shrimp production systems are nutrient limited. In order to put the results into perspective, a comparison with intensive and semi-intensive shrimp farms was made. While the extensive mangrove-shrimp farms showed higher emissions of CO2-eq. per ton shrimp produced (20 tons in average for organic and non-organic farms compared to 10 tons from intensive/semi-intensive production), results indicated lower impacts in terms of both acidification and eutrophication. We recommend LCA to be used as a central tool for identifying practices relevant for eco-certification audits, including considerations for land use. However, a better understanding of the consequences of land quality change and linkages to impacts at the ecosystem level e.g. effects on ecosystem services, is needed.
Failure of the blue revolutionis a global risk. The international problem is that there is a gap in knowledge exchange between the aquaculture industry, policy makers trying to support aquaculture development and people who depend on aquaculture for a job and/or food source. Thus, governments and international organizations promoting aquaculture as the solution to improving food security, nutrition and income are failing to optimise production of natural aquatic resources. We identify a people-policy gap, and suggest that this is an understudied constraint, which needs to be overcome before worldwide food security can be achieved from aquatic environments. We argue that this gap leads to uneven distribution of benefits, a disconnection between benefits and local needs, and detrimental effects on human health and food security, all of which can have negative repercussions on human communities and ecosystems. In order to address this need, we present an analytical framework to guide context specific, policy-relevant assessments of the social, economic and ecological dimensions of aquaculture on a case-by-case basis. The framework is designed to make best use of existing data and scientific tools for decision-making. In conclusion, we argue for: equal consideration of ecological, social and economic issues in aquaculture policy-making; pre-emptive identification of likely social impacts; integration of people-and context-specific social framing conditions into planning and policy review; addressing the social disconnection between global consumption and production; and, encouragement of creative combinations of theories and methods to assess and interpret the social dimensions of aquaculture in multiple contexts.
In this paper, we critically analyze how sustainability is considered in aquaculture policies and strategies using the Nordic countries as a case. The strong versus weak sustainability concepts are used to define and clarify what sustainability aspects are central to each state. To illustrate these concepts further, we draw on and modify four mainstream environmental discourses defined by John Dryzek and apply them to the strong and weak sustainability dichotomy to help categorize how environmental sustainability is portrayed in Nordic aquaculture policies and strategies. Subsequently we apply the characteristics of the concepts to aquaculture and sustainability in the Nordic countries. This allows us to identify each state's depiction of sustainable aquaculture, compare these to one another and assess where the Nordic states position themselves regarding sustainability and aquaculture. Our findings show that the policies emphasize technological advancements, intensification, and economic growth, which correlates with weak sustainability. Environmental sustainability receives a significant role in the documents too but does not seem to trump increased intensification or profitability. All policies are heavily focused on fed aquaculture and in order to reduce negative impacts from aquaculture there is a need to incorporate key elements of strong sustainability in policies, including measures to reduce impacts from pollution and the spread of pathogens, use of high-grade food resources and energy consumption. This to transform the industry to sustainability rather than just making it less unsustainable.
A Dynamic Energy Budget (DEB) model is used to simulate growth and reproduction of the shellfish Mytilus galloprovincialis and Crassostrea gigas in an integrated multi-trophic aquaculture (IMTA) farm scenario situated in the Southern Mediterranean (the Gulf of Castellammare, Sicily). We modelled the effect of primary production enrichment at fish cages on shellfish growth and life history traits using 4 years-hourly temperature data (01 January 2006–31 December 2009) at a depth of 1 m. Outputs of the DEB simulations were: the maximum theoretical total shell length of shellfish, the potential reproductive outputs and the mean annual von Bertalanffy growth rate. There was a mean increase in empirically measured suspended chlorophyll-a of approximately 45% close (within about 100 m) to fish cages (2.3 ± 1.1 μg l− 1) compared to sites away (about 1.5 km) from the cages (1.3 ± 0.6 μg l− 1). DEB simulations using localised CHL-a measures showed that mussels close to cages could reach greater maximum length at the end of 4th year than those far from cages and in open-sea. Simulations of oyster growth close to cage sites resulted in double growth rate (12 cm in 4 years) compared to oysters at far sites (6.5 cm in 4 years). The present study improves knowledge of the application of DEB models to predict the potential fitness of shellfish starting from First Principles. This is an innovative approach with potential for application at larger scales than those of local facilities.
In decapod crustaceans, the eyestalk represents the pivotal source for several neuropeptides influencing various physiological activities concerned with metabolism, growth and reproduction. Prominent among them is-the crustacean hyperglycaemic hormone (CHH) which regulates the blood glucose level by its 'diabetogenic' action. This paper reports on the first characterisation of a CHH in the commercially important penaeid species Penaeus indicus. Reversed phase HPLC of extracts from eyestalk ganglia on a Waters mu-Bondapak phenyl column combined with an enzyme linked immunosorbent assay revealed that among six immunoreactive peptide fractions in total a late eluting peak fraction,with the retention time of about 50 min shows the strongest immunoreactivity to a polyclonal rabbit antiserum raised against the CHH of the freshwater crayfish Orconectes limosus. The amino acid composition of this peptide, purified by rechromatography was determined according to the orthophthaldialdehyde post column derivatisation method. The most interesting features are the low molar concentration of acidic amino acid residues (e.g. Asx, Glx) but a high molar concentration of lysine residues. The CHH material was localised immunocytochemically in the neurosecretory centres of X-organ sinus gland system using the same antiserum. A large number of perikarya of the medulla terminalis X-organ, the neural tract as well as the sinus gland showed intense immunoreactivity. Though the hyperglycaemic response of this HPLC purified CHH of P. indicus was found to be very poor when injected into eyestalkless as well as eyestalk-intact crayfish, O. limosus, it clearly induced hyperglycaemia in P. indicus.
The maintenance of brood stock in appropriate conditions is an important requirement for the production of high quality offspring. In this study, we investigated fertility of the two life history forms of Atlantic salmon males, precocious parr, brought up in breeding tanks in the hatchery and anadromous, migratory searanched males, caught when returning to the home river. The sperm quality was assessed by experiments between equal amount of sperm from one adult and one parr male in competition to fertilize eggs of a single female. The paternity was determined by a microsatellite analysis. Parr males achieved greater reproductive success than anadromous males under competition, and anadromous adults had greater fertility in controls as compared to the sperm competition situation. In total, parr males achieved 3.6 times greater fertilization success than anadromous males. Sperm ATP content contributed significantly to male fertility. Our results provide evidence that ejaculates of precociously mature Atlantic salmon parr are of increased quality as an adaptation to high sperm competition intensity due to better maintenance in the fish farm than in the wild.