| 1. |
- Norman Haldén, Anna, et al.
(author)
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Retention and maternal transfer of brominated dioxins in zebrafish (Danio rerio) and effects on reproduction, aryl hydrocarbon receptor-regulated genes, and ethoxyresorufin-O-deethylase (EROD) activity
- 2011
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In: Aquatic Toxicology. - Oxford : Elsevier. - 0166-445X .- 1879-1514. ; 102:3-4, s. 150-161
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Journal article (peer-reviewed)abstract
- Brominated dioxins have recently been detected in Baltic Sea biota. Due to their similarities to the highly toxic chlorinated dioxins, concern has been raised about their potential biological effects. The present study investigated retention and effects of brominated dioxins in adult zebrafish, as well as maternal transfer and effects on offspring. We exposed adult zebrafish for nine weeks via feed to 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) or to a mixture of brominated dioxins (Baltic Sea mixture), which was designed to reflect relative concentrations found in Baltic Sea biota. We studied spawning success, gonad morphology, hepatic vitellogenin gene expression, and offspring early life-stage development to investigate effects on zebrafish reproduction. Hepatic ethoxyresorufin-O-deethylase (EROD) activity and hepatic expression of a number of aryl hydrocarbon receptor (AHR)-regulated genes were studied to investigate if the brominated dioxins can activate gene transcription through the AHR pathway in zebrafish. In addition, glutathione reductase activity and expression of genes involved in adaptive responses to intracellular stress were studied to investigate potential stress effects of brominated dioxins. After nine weeks of exposure, all brominated dioxins spiked to the feed were detected in female fish and transferred to eggs. Exposure to the Baltic Sea mixture and TBDD clearly induced AHR-regulated genes and EROD activity. Exposure to TBDD reduced spawning success, altered ovarian morphology and reduced hepatic vitellogenin gene expression, which implies that TBDD has a similar effect pattern as the chlorinated analogue. Overall, our results show that dietary exposure to sublethal concentrations of brominated dioxins may impair reproductive physiology in fish and induce AHR-regulated genes. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Arnoldsson, Kristina, 1961-, et al.
(author)
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Retention and maternal transfer of environmentally relevant polybrominated dibenzo-p-dioxins and dibenzofurans, polychlorinated dibenzo-p-dioxins and dibenzofurans, and polychlorinated biphenyls in zebrafish (Danio rerio) after dietary exposure
- 2012
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In: Environmental Toxicology and Chemistry. - : John Wiley & Sons. - 0730-7268 .- 1552-8618. ; 31:4, s. 804-812
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Journal article (peer-reviewed)abstract
- High levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), mono- and non-ortho polychlorinated biphenyls (PCBs), and polybrominated dibenzo-p-dioxins (PBDDs) are found in fish from coastal areas in the Baltic Sea, which may cause ecotoxicological effects. To increase our understanding of the persistency of the emerging pollutants polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), fish feed was spiked with 21 PBDD/Fs, 17 PCDD/Fs, and 30 PCBs and fed to zebrafish. Concentrations in fish and eggs were examined during a six- or twelve-week uptake period, and a six-week elimination period. Steady-state was reached for 2, 3, 7, and/or 8-substituted tri- and tetra-BDD/Fs, with 2,3,7,8-tetra-BDD (2,3,7,8-TeBDD) being the most strongly retained. Steady-state was not reached for tetra- to hexa-CDDs. Non-2,3,7,8-congeners showed little of or no retention. Most PCBs had high retention and did not reach steady-state. Half-lives decreased in the order: PCBs > PCDD/Fs > PBDD/Fs. Concentrations of 2,3,7,8-penta- to octa-CDD/Fs decreased with their degree of chlorination suggesting that the rate-limiting factor for uptake is low bioavailability. Maternal transfer was observed for all retained compounds, with most transfer factors < 1, indicating that transfer rates are affected by the poor water solubility of the compounds. The limited retention of the major PBDD congeners found in Baltic Sea fish suggests that they are exposed to high or very high concentrations via either food or water.
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| 3. |
- Berkström, Charlotte, et al.
(author)
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Securing sustainable access to aquatic foods
- 2023
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Reports (other academic/artistic)abstract
- 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.
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| 4. |
- Bighiu, Maria, et al.
(author)
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Assessing microbial contamination and antibiotic resistant bacteria using zebra mussels (Dreissena polymorpha)
- 2019
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 650, s. 2141-2149
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Journal article (peer-reviewed)abstract
- Aquatic pollution with faecal bacteria and subsequent consumption of contaminated water or food is a worldwide issue that causes severe health effects (e.g. meningitis, salmonellosis, dysentery). In addition, the excessive use of antibiotics in animal husbandry and human medicine has enhanced the selective pressure on pathogenic bacteria, further increasing human health risks and detrimental effects on natural microbial communities. This urges the need to monitor faecal contamination using a time-integrated approach, as grab water samples can miss pathogen peaks. We tested the ability of zebra mussels (Dreissena polymorpha) to take up and depurate faecal indicator bacteria such as Escherichia coli and intestinal enterococci. Furthermore, we quantified the frequency of antibiotic resistant bacteria in water and mussels both in controlled laboratory tests and under in situ conditions downstream of a sewage treatment plant (STP). Laboratory results show that bacterial indicators in mussels were 132 times higher than their concentration in water, and that mussels retained bacteria up to 2 days after pulse exposure. Field results show decreasing bacterial concentrations in both water and mussels downstream the STP, with maximum E. coli concentrations ranging 173-9 cfu mL(-1) in water and 2970-330 cfu g(-1) in mussels. Similarly, enterococci ranged 59-4 cfu mL(-1) and 1450-240 cfu g(-1) in water and mussels, respectively. High proportions of antibiotic resistant E. coli were found in mussels (72%) and water (65%), and slightly lower proportion of resistant enterococci was found in mussels (47%) and in water (34%). Moreover, 33% of the bacteria isolated from mussels were resistant to multiple antibiotics, which emphasizes that resistance is a common feature in surface waters and highlights the need for safe water management. Our results show that zebra mussels provide an efficient, time-integrating tool for quantifying faecal indicators, including resistant and multidrug resistant bacteria. (C) 2018 The Authors. Published by Elsevier B.V.
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| 5. |
- Collentine, Dennis, et al.
(author)
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Consequences of future nutrient load scenarios on multiple benefits of agricultural production
- 2013
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Reports (other academic/artistic)abstract
- 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.
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| 6. |
- Kajungiro, Redempta Athanas, et al.
(author)
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The Need of a Structured Tilapia Breeding Program in Tanzania to Enhance Aquaculture Production: A Review
- 2019
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In: Tanzania Journal of Science. - 0856-1761 .- 2507-7961. ; 45, s. 355-371
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Journal article (peer-reviewed)abstract
- 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.
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| 7. |
- Lindberg, Jan Erik, et al.
(author)
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Mineral content in local feed ingredients used by fish farmers from four different regions in Tanzania
- 2019
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In: Western Indian Ocean Journal Of Marine Science. - : African Journals Online (AJOL). - 0856-860X. ; 18, s. 1-9
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Journal article (peer-reviewed)abstract
- This study investigated the content of selected minerals (P, Ca, K, Na, Mg, Fe and I) in local feed ingredients used by tilapia fish farmers in Tanzania. Analyses were performed on 26 local feed ingredients collected at four different geographical locations in Tanzania (Dar es Salaam, Morogoro, Mbeya and Mwanza). The samples were taken randomly from fish farmers, fish feed producers, fingerling producers and animal feed shops or centers near fish farms in each region. The results showed a wide range of mineral concentrations. The highest levels of P was found in fish skeletons (17.8 g kg-1), of Ca in limestone (107.3 g kg-1), of K in gallant soldier (51.0 g kg-1), of Na in marine shrimp (Exhippolysmata oplophoroides) (11.7 g kg-1), of Mg in prawn head waste (4.2 g kg-1), of Fe in azolla (2355 mg kg-1) and of I in full fat soybean (447 mg kg-1). The data on mineral content in feed ingredients can be used as a platform for better-targeted feed formulation for tilapia farming systems. In conclusion, the data suggest that if more than two ingredients are used in the diet, this may be sufficient to meet the mineral requirements of all cultured tilapia species and their hybrids, without inclusion of any mineral premix.
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| 8. |
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| 9. |
- Mmanda, Francis Pius, et al.
(author)
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Fish farming in Tanzania : the availability and nutritive value of local feed ingredients
- 2020
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In: Journal of Applied Aquaculture. - : Informa UK Limited. - 1045-4438 .- 1545-0805. ; 32:4, s. 341-360
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Journal article (peer-reviewed)abstract
- An investigative field survey was performed to gather baseline data on locally available feed ingredients and fish farming practices in different regions of Tanzania. More than 80% of respondents relied on locally available feed ingredients as a major feed supplement for their cultured fish, with maize bran being the most commonly used feed ingredient in all regions. Crude protein content in most analyzed local feed ingredients was medium-high, while crude fat content was high in some animal and agricultural by-products, and medium-low in other ingredients. Most respondents were males and the majority of fish farms were owned by individuals. Earthen pond was the most common fish farming system in all regions except Dar es Salaam. Semi-intensively mixed-sex tilapia monoculture was the dominating fish farming practice. The results of the survey presented provide a good platform for future development of culture systems and feeding strategies for tilapia in Tanzania.
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| 10. |
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| 11. |
- Norman Haldén, Anna
(author)
-
Exposure of zebrafish to brominated environmental chemicals : studies on reproduction, maternal transfer and early life-stage development
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- 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.
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| 12. |
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| 13. |
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| 14. |
- Norman Haldén, Anna, et al.
(author)
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Oral exposure of adult zebrafish (Danio rerio) to 2,4,6-tribromophenol affects reproduction
- 2010
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In: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 100, s. 30-37
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Journal article (peer-reviewed)abstract
- The bromophenol 2,4,6-tribromophenol (TBP) is widely used as an industrial chemical, formed by degradation of tetrabromobisphenol-A, and it occurs naturally in marine organisms. Concentrations of TBP in fish have been related to intake via feed, but little is known about effects on fish health after oral exposure. In this study, we exposed adult male and female zebrafish (Danio rerio) to TBP via feed in nominal concentrations of 33, 330, and 3300??g/g feed (or control feed) for 6 weeks to assess the effects of TBP on reproductive output, gonad morphology, circulatory vitellogenin levels, and early embryo development. The aim was also to investigate the extent to which TBP was metabolised to 2,4,6-tribromoanisole (TBA) in dietary exposed zebrafish, and the amounts of TBP and TBA found in offspring. After 6 weeks of exposure, we found about 3% of the daily dose of TBP in adult fish and the mean concentration of TBA was 25–30% of the TBP concentration. TBP and TBA were detected in offspring with wet weight-based egg/fish concentration ratios well below one. Exposure to TBP significantly reduced the fertilization success and disturbed the gonad morphology, i.e. fewer spermatid cysts in males and increased presence of atretic follicles and oocytes with decreased vitellogenesis in females. In females, the disturbed gonad morphology was accompanied by increased levels of circulating vitellogenin. Significant effects were observed at 3300??g/g feed. Offspring early development was not significantly affected, but yolk-sac oedema tended to increase in frequency in exposed groups with time. Our results show that dietary exposure to TBP, at concentrations found in marine organisms that are part of the natural diet of wild fish, can interfere with reproduction in zebrafish. We also observed low accumulation from feed of TBP in zebrafish and biotransformation of TBP to TBA. This is the first paper showing gonadal histopathological changes and effects on fertility in TBP exposed fish
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| 15. |
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| 16. |
- Pius Mmanda, Francis, et al.
(author)
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Digestibility of local feed ingredients in tilapia Oreochromis niloticus Juveniles, determined on faeces collected by siphoning or stripping
- 2020
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In: Fishes. - : MDPI AG. - 2410-3888. ; 5
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Journal article (peer-reviewed)abstract
- 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.
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| 17. |
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| 18. |
- Pius Mmanda, Francis, et al.
(author)
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Replacing fish meal with locally available feed ingredients to reduce feed costs in cultured Nile tilapia (Oreochromis niloticus)
- 2020
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In: Livestock Research For Rural Development. - 0121-3784. ; 32
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Journal article (peer-reviewed)abstract
- A 60-day growth trial was conducted to evaluate growth performance, nutrient utilisation, carcass traits and feeding costs in Nile tilapia juveniles (1.47± 0.31 g body weight) fed diets in which 50% of fishmeal dry matter (DM) in the reference diet (REFD) was replaced with cattle blood, fish frames, freshwater shrimp or brewery spent yeast on a DM basis. The fish were fed 10% of body weight three times a day for the first 30 days, and then 5% of body weight twice a day for the remaining 30 days of the feeding trial. Due to high feed intake, the highest weight gain, final weight and average daily weight gain were recorded in fish fed REFD. Feed conversion ratio was lower in the diet with cattle blood than in the other diets and the protein efficiency ratio were higher for REFD than for the other diets. There were no differences in survival rate, condition factor, hepatosomatic index and viscerosomatic index between treatments. Initial and final whole body composition differed, but there were no differences in carcass traits between treatments. Feed costs per kg feed and feed costs per weight gain were reduced when fishmeal was replaced with locally available feed ingredients, with the largest reduction in feed costs per kg feed (34%) and per weight gain (27.1%) obtained with brewery spent yeast. The results indicate that the economics of small-scale tilapia production in Tanzania can be improved by replacing fishmeal with good-quality, low-cost, locally available feed ingredients.
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| 19. |
- Rattfelt Nyholm, Jenny, et al.
(author)
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Uptake and biotransformation of structurally-diverse brominated flame retardants in zebrafish (Danio Rerio) after dietary exposure
- 2009
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In: Environmental Toxicology and Chemistry. - Hoboken : John Wiley & Sons. - 0730-7268 .- 1552-8618. ; 28:5, s. 1035-1042
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Journal article (peer-reviewed)abstract
- Zebrafish (Danio rerio) were fed a diet containing a mixture of 11 structurally diverse brominated flame retardants (BFRs) at nominal concentrations of either 1 or 100 nmol/g for up to 42 d, followed by an elimination period of 14 d. Uptake rates and elimination constants for five of the BFRs were calculated from measurements of their concentrations in the male fish during the exposure and elimination phases. Observed uptake efficiencies were highest for 2,4,4′-tribromodiphenyl ether (BDE 28) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) and were lowest for decabromodiphenyl ether (BDE 209). Estimated half-lives for TBECH and 2,4,6-tribromophenol were short (<2 d). Four BFR metabolites were identified in the fish: 2,2′,3,4′,5′,6-Hexabromodiphenyl ether (BDE 149), 2,2′,4,4′,5,6′-hexabromodiphenyl ether (BDE 154), 2,4,6-tribromoanisole, and 1,2,4,5-hexabromobenzene. These metabolites were still present in the zebrafish after the 14-d elimination period. No relationship between the BFR concentrations in the zebrafish and their log octanol-water partition coefficient (KOW) values was found. Generally, low tendencies to bioaccumulate were observed for perbrominated and hydroxylated compounds. The observed accumulation of BFR metabolites in fish, however, shows that low concentration of a BFR does not provide, in isolation, a sound indication that the BFR poses low risks.
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| 20. |
- Ström Hallenberg, Gunilla, et al.
(author)
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Antibiotic Use by Small-Scale Farmers for Freshwater Aquaculture in the Upper Mekong Delta, Vietnam
- 2019
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In: Journal of Aquatic Animal Health. - : Wiley. - 0899-7659 .- 1548-8667. ; 31, s. 290-298
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Journal article (peer-reviewed)abstract
- 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 d 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.
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