Exposure of zebrafish to brominated environmental chemicals

Fish reproduction and embryonic development may be sensitive to environmental chemicals. This thesis investigated effects of brominated flame retardants (BFRs) and polybrominated dibenzo-p-dioxins (PBDDs) on reproduction and early life-stage development in zebrafish (Danio rerio). Most of these compounds are highly hydrophobic, hence it was hypothesized that important routes of exposure are dietary uptake and maternal transfer. Adult zebrafish were exposed to feed spiked with a mixture of structurally diverse BFRs to investigate accumulation from feed, maternal transfer, and effects on reproduction and early life-stage development. One of the compounds in the BFR mixture, i.e. 2,4,6-tribromophenol, was tested separately. The BFRs were also tested individually in an embryo toxicity test, to screen for effects of waterborne BFRs on early life stages. To investigate effects of PBDDs on reproduction, early life-stage development, and on the aryl hydrocarbon receptor (AHR) pathway, adult zebrafish were exposed to feed spiked with 2,3,7,8-tetraBDD (TBDD), or a mixture of PBDDs that was designed to reflect relative concentrations found in Baltic Sea biota. Most brominated chemicals exposed via feed were detected in females and in their offspring. Ovarian morphology was altered in all studies, and the PBDDs induced AHR-regulated genes and ethoxyresorufin-O-deethylase activity. Effects on early life-stage development were seen after parental and water exposure, although at concentrations generally higher than in the environment. However, compared to several other fish species, zebrafish have a relatively low sensitivity to AHR agonists regarding effects on early life stages. To be able to evaluate the risk of PBDDs for fish in the Baltic Sea, future studies should focus on fish species native in the Baltic Sea. Overall, the results suggest that maternal transfer is an important exposure route for several brominated environmental chemicals, and that these compounds may interfere with reproduction and early life-stage development in fish

Securing sustainable access to aquatic foods

Global nutrition needs are increasing and aquatic foods have recently been identified as crucial in addressing many of the world’s urgent challenges, including hunger and malnutrition. This synthesis highlights the importance of aquatic foods as a source of protein, micronutrients and income, its potential to meet increasing food demands, as well as the challenges in aquatic food production and harvesting.Most importantly, it provides an overview of management initiatives and innovative solutions for secured sustainable access to aquatic foods in the future. Aquatic foods provide micronutrient-rich foods for 3.3 billion people and support the livelihoods of more than 800 million people. Small-scale fisheries, in particular, play a key role in supporting the diversity and nutritional benefits of aquatic foods. However, the capture and production of aquatic foods is not always sustainable, and access to these foods may be unequal. At the water-land nexus, new ways of producing aquatic foods hold the potential to reduce the climate footprint in the food system.The governance of, and investment in, aquatic food systems needs to aim to preserve, support and improve aquatic species diversity and to improve access to this highly nutritious food. These efforts need to include multiple stakeholders, such as fishers, community agencies, policy makers and researchers, and be firmly established in both the latest research and in a local/regional context - ecologically and socially. By incorporating different aspects of aquatic foods, this synthesis aims to inspire and inform the reader about the importance of these systems, and means for a sustainable way forward

Aquaculture and aquafeed in Rwanda: current status and perspectives

A survey was conducted to obtain up-to-date information and create a knowledge base on pond fish farming, local feed ingredients, and their nutritive properties in Rwanda. Sixty-seven pond-farms were randomly sampled from a population of 112 countrywide. Semi-intensive was the dominant (81%) farming-system and three fish species were cultured: Nile tilapia (Oreochromis niloticus), common carp (Cyprinus carpio), and North African catfish (Clarias gariepinus). Tilapia was the most commonly farmed species, and >50% of pond-farms were located in Northern and Southern provinces. There were 1–3 hatcheries per province, all producing tilapia. In total, 31 feed ingredients were identified, with rice, wheat, and maize bran being most commonly used. Feed analysis revealed high protein content (>350 g kg−1 CP) in local fishmeal, chicken viscera, and spent brewer’s yeast. Local ingredients and potential novel-feeds need further investigation prior to their confident use in fish diets to improve aquaculture at a low-cost in Rwanda

The Need of a Structured Tilapia Breeding Program in Tanzania to Enhance Aquaculture Production: A Review

Breeding programs are crucial for boosting productivity and increase sustainability of aquaculture. Over years, Tanzania has witnessed fluctuation in its capture fisheries production from 320,900 to 375, 535 and back to 362,595 metric tonnes in the years 2000, 2005 and 2016, respectively (URT 2016). The declining trend in fish production has made fish supply in the country unstable and conversely, increased the demand for fishes to about 730,000 metric tonnes in 2017. However, the local aquaculture production has not increased accordingly. Tanzania is importing fish mainly from Asia to meet its increased demand. In 2017, a total of 2,055,721 kg of frozen tilapia were imported from China and Mozambique (URT 2017). The introduction of exotic fish species in Tanzania should be carefully managed because introduced species have many negative impacts to the indigenous species. Tanzania should have a moderate scale tilapia breeding program that will produce good quality fingerlings at affordable price for smallholder fish farmers. The availability of reliable good quality fingerlings is key to improve aquaculture production in the country. Among 17 existing hatcheries, only 12 hatcheries are active, however these hatcheries are not performing well due to low investment and technology leading to the production of low quantity and quality fingerlings. The need for a structured sustainable Tilapia breeding program with bio secured and reliable hatcheries to enhance aquaculture production in Tanzania is given in this review.Keywords: Aquaculture, Breeding programs, Nile tilapia, Local strains

Biosecurity considerations for the Baltic Sea Region : Focus on transmission of microorganisms from livestock to the aquatic environment

Baltic Compass, Work Package

Digestibility of local feed ingredients in tilapia Oreochromis niloticus Juveniles, determined on faeces collected by siphoning or stripping

Eight locally available protein source ingredients in Tanzania were selected for assessment of apparent digestibility (AD) in tilapia Oreochromis niloticus, using faeces samples collected by siphoning or stripping. The selected protein source ingredients were Lake Victoria sardines (FM), brewers spent yeast (BSY), moringa leaves (ML), freshwater shrimp (FSH), marine shrimp (MSH), cattle blood (CB), duckweed (DW) and fish frames (FF). The AD (%) of dry matter (DM), organic matter (OM) and crude protein (CP) was unaffected (p > 0.782–0.901) by the faeces collection method (i.e., siphoning or stripping), with correlation coefficient (r) of 0.98, 0.99 and 0.93 between AD values for DM, OM and CP, respectively, following siphoning and stripping. The AD (%) of DM, OM, CP and gross energy (GE) in the test ingredients differed (p < 0.0001). The AD (%) of DM and OM was lowest in BSY and DW, followed in increasing order by ML, MSH, FF, FSH and CB. In general, the AD (%) of CP was high (>76%), but with a low value (46%) for DW. The AD (%) of GE was closely correlated (r = 0.96) with the AD of OM. In conclusion, FSH, MSH, CB, FF, BSY and ML have acceptable protein digestibility to be used in tilapia diet formulation

Consequences of future nutrient load scenarios on multiple benefits of agricultural production

Nutrient load rates to the Baltic Sea need to be reduced. Agricultural land is regarded as the most significant contributor to the loads, and measures to reduce losses of nitrogen (N) and phosphorus (P) loads have been proposed, both for the near and far future. Agricultural production was to a large extent considered in these scenarios, whereas effects on other ecosystem services were not evaluated. The question to be answered by this report is whether the measures adopted to reduce N and P losses improve or impair multiple benefits of agriculture. The question is answered for a specific catchment (Svärtaån) located in Sweden, but the method is thoroughly described to provide a potential method to also evaluate other catchments. This work was performed as a part of the Baltic Compass project (2013). The answer to the main question of whether the measures adopted to reduce N and P losses from agricultural fields improved or impaired multiple benefits of agriculture, seems to be that they improved. Most of the BAP measures had a positive influence on most of the MB-categories, the clearest exception being liming in tile drains which only improved the cost effectiveness. Except for water protection, the biosecurity MB-category was positively influenced by the most measures (6 out of 9) and with soil quality the next highest (5 out of 9). It is less clear how the absolute values evaluated for the MB index, can be compared among MB-categories. Among the BAP-measures, structural liming was the most positive measure (summing up the indices of all MB-categories), followed by buffer-zones and spring cultivation the next, although the cost effectiveness of these latter measures was evaluated to decrease. In the “unavoidable” future (Future scenarios) GHG emissions strongly increased. The only measure that mitigated that effect was reduced N fertilisation, providing more arguments for applying reduced fertilisation than only to reduce leaching

Antibiotic Use by Small-Scale Farmers for Freshwater Aquaculture in the Upper Mekong Delta, Vietnam

This study describes antibiotic use by small-scale freshwater aquaculture farmers in the upper Mekong Delta in southwestern Vietnam and the knowledge and practices surrounding the cause and prevention of aquaculture disease in that region. Forty five farmers were included in the study, of which 19 (42%) cultivated tilapia Oreochromis spp., 13 (29%) Striped Catfish Pangasianodon hypophthalmus and 13 (29%) giant river prawns Macrobrachium rosenbergii. Antibiotics were used by farmers of tilapia and Striped Catfish (84% and 69% of farmers, respectively), but not by any of the prawn farmers. Most farmers (72%) used antibiotics for around 3\ua0d when treating diseases, depending on the farmers' economic means and whether the fish recovered, as judged by the farmer. If farmers perceived that the antibiotic treatment had failed, the most common response was to change to another type of antibiotic. Some farmers also used antibiotics in the absence of clinical symptoms as a preventive measure. In the absence of rapid, cost-effective diagnostics, the likelihood for the incorrect use of antibiotics is high, which has implications for antibiotic resistance. Moreover, the sequential use of different antibiotics following therapeutic failure is a risk factor for the emergence of resistance. All farmers that were surveyed were aware of the risks associated with antibiotic use. This may lead to successful intervention toward reduced antibiotic use in freshwater fish farming in Vietnam

Mapping erosion- and phosphorus-vulnerable areas in the Baltic Sea Region - data availability, methods and biosecurity aspects

Soil erosion and nutrient leaching from terrestrial systems to rivers, lakes and marine environments cause deteriorating water quality and eutrophication. In all the countries of Northern Europe, agriculture is considered to be responsible for the greatest contribution of phosphorus (P) and high contribution of nitrogen (N) to coastal waters. Recently, there has been great pressure from both the environmental and agricultural sector to target the environmental measures at the areas with the highest risk for nutrient leaching and loading. Topographic, hydrologic, geomorphologic and agronomic factors often combine to make erosion and leaching from certain areas higher and more detrimental to the aquaculture than from others. Therefore, methods to identify and prioritise agri-environmental measures on these nutrient-vulnerable areas are desirable. This report examines data availability and methodology to identify the critical source areas in the Baltic Sea Region (BSR) countries. Here critical source areas are comprised mainly of erosion- and phosphorus-vulnerable areas that can often also be related to the biosecurity risk of animal husbandry. Ava ilability, determination methods and quality in basic background data required for the inventories vary widely in the Baltic Sea basin countries. Background data should include spatially detailed information from elevation, river networks, soil (soil type, P status etc.) and agricultural management (plant cover, fertiliser rates, livestock density etc.). Risk assessments are usually made at the municipal or catchment level, depending on which regional level the statistical data are available. The differences in the soil classification systems, soil P analysis and accuracy of the data needed for the mapping prevent uniform assessments and comparisons between the countries. The accuracy of the existing risk maps is difficult to verify with water quality observations, since the observations are scarce, especially from individual risk areas. Erosion risk maps are produced mostly with USLE based methods, which are also suitable for mapping areas at risk of P leaching. In USLE-maps, the risk areas are mainly located on steeply sloped fields. USLE describes the high risk areas by surface processes. Thus, the transport of solids and P through soil matrix and via the macropores is ignored in USLE examinations. If the calculation takes into account the distance to water and if the channel map is accurate, also fields further away from the water bodies can be classified as risk areas. Meanwhile, when topographic mapping is used as the index calculation methodology, flat areas will be classified as risk areas because this method puts weight on gentle slopes with fairly large catchment areas above them. The third option is based on physical GIS-based models, which can model simultaneously hydrology and nutrient transport. In general, these models require a lot of input data and in lack of them the possibility of erroneous results increases. The P-index is often considered to be a cost-effective tool to reduce P leaching. The major challenges are lack of data (mainly on soil P status), and uncertainties and the need for additional validation of the model. Areas with high animal density and high risk of surface runoff or erosion are potential high-risk areas as regards biosecurity. By combining relevant maps, such as animal density and erosion risk areas, potential high-risk biosecurity areas can be identified. It would be important to improve the availability of more accurate, larger-scale data for the use of researchers and designers. The central issues in presenting the risk areas are accuracy, objectivity and clarity. High-risk areas and fields should be shown as objectively as possible and after solving their locations, possible mitigation measures to reduce risks in the problematic areas could be discussed and agreed with the stakeholders.vokKV