| 1. |
- Persson, Lo, et al.
(författare)
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The effect of physiological and environmental conditions on smolt migration in Atlantic salmon Salmo salar
- 2019
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Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 28, s. 190-199
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Tidskriftsartikel (refereegranskat)abstract
- Hydropower development has negatively influenced Atlantic salmon (Salmo salar) populations. Compensatory hatchery-rearing programmes exist, but released fish suffer from high mortality that may be related to the lack of experience from natural environments in hatchery-reared smolts and their large body size and high energetic state. Here, we used acoustic telemetry to test how body size, energetic state, and the environmental conditions of the river affect migration in hatchery-reared smolts. The study was conducted in three consecutive years between 2011 and 2013 in the lower part of the River Umealven, Sweden. For individual fish, there was no effect of body size but the energetic state of the fish had a negative effect on sea entry. The most important factor affecting sea entry rate was the water discharge in the old river bed that differed among years. Smolts were more likely to enter the sea in years when the discharge was high or when the discharge increased substantially shortly after release. Hatchery-reared fish had higher migration speed at a slower flowing section compared with a faster flowing section, which was likely a result of large hesitation to enter the rapid section. The increase in water discharge led to an increase in fish migration speed disproportional to the increase in water velocity. Our results highlight the importance of water discharge for the smolts during smolt migration, and we argue that concern should be given to migrating fish when managing regulated rivers.
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| 2. |
- Waldo, Staffan, et al.
(författare)
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Swedish coastal herring fisheries in the wake of an ITQ system
- 2013
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Ingår i: Marine Policy. - : Elsevier. - 0308-597X .- 1872-9460. ; 38, s. 321-324
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Tidskriftsartikel (refereegranskat)abstract
- The European common fisheries policy (CFP) advocates measures to sustain small-scale fisheries; hence, in the European Commission's proposal for a reformed CFP, these are exempted from a mandatory system with tradable fishing concessions. This opens up for management actions designed for small-scale fisheries, but also implies new management issues. This article provides insights into the topic based on a Swedish small-scale herring fishery in the western Baltic Sea that was exempted from an ITQ-system. The fishery has been profitable since the system was introduced, and the increasing effort of both incumbent fishermen and new entrants implies a situation where fishermen compete for a limited quota. The migratory pattern of the herring implies high densities in the southern parts of the fishing areas during spring and in the northern parts during autumn. This forms the basis for two different fisheries in the area, as well as for the current management proposal to divide the quota into a spring and an autumn part. This and other management proposals are discussed in the paper. The main conclusion from the case study is that, when exempting a fishery from tradable fishing concessions, it is important to build other institutions dealing with the fundamental problem of access to the quota. Failure to do so might result in an over-capacity issue and threaten the long-run development of an otherwise successful small-scale fishery.
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| 3. |
- Ericsson, Philip, et al.
(författare)
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Personality-dependent inter- and intraspecific foraging competition in the invasive round goby, Neogobius melanostomus
- 2021
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Ingår i: Journal of Fish Biology. - : Wiley-Blackwell. - 0022-1112 .- 1095-8649. ; 98:5, s. 1234-1241
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Tidskriftsartikel (refereegranskat)abstract
- This study examines the impact of boldness on foraging competition of the highly invasive round goby Neogobius melanostomus Pallas 1815. Individual risk tolerance, or boldness, was measured as the time to resume movement after a simulated predation strike. Fish that resumed movement faster were categorized as "bold," fish that took more time to resume movement were categorized as "shy" and those that fell in between these two categories were determined to have "intermediate" boldness. Competitive impacts of boldness in N. melanostomus were determined in a laboratory foraging experiment in which interspecific (juvenile Atlantic cod Gadus morhua Linnaeus 1758) and intraspecific (intermediate N. melanostomus) individuals were exposed to either bold or shy N. melanostomus competitors. G. morhua consumed fewer prey when competing with bold N. melanostomus than when competing with shy N. melanostomus, whereas intermediately bold N. melanostomus foraging was not affected by competitor boldness. Bold and shy N. melanostomus consumed similar amounts of prey, and the number of interactions between paired fish did not vary depending on the personality of N. melanostomus individuals. Therefore, intraspecific foraging competition was not found to be personality dependent. This study provides evidence that individual differences in boldness can mediate competitive interactions in N. melanostomus; nonetheless, results also show that competition is also governed by other mechanisms that require further study.
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| 4. |
- Tieva, Åse, et al.
(författare)
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Effect on energy and macronutrient intake with partial replacement of external food supply by in-house cooking at a nursing home for older people in Sweden
- 2015
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Ingår i: International Journal of Consumer Studies. - : Wiley. - 1470-6423 .- 1470-6431. ; 39:4, s. 369-379
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Tidskriftsartikel (refereegranskat)abstract
- An increased awareness of the importance of nutrition for older people's health and quality of life has underpinned projects and quality improvements for the meal situation in care establishments. The present study took place in a nursing home in a village outside an average-sized town situated in mid-Sweden. Care staff had initiated a change from external catered meals to purchase the food and cook the main meals themselves. The intention was to increase flexibility in accommodating the requests and needs of the elderly and, in doing so, to achieve increased professional pride and satisfaction. To ensure that no negative effects resulted for the residents in the nursing home, outcomes were evaluated through the present intervention study. The objective was to investigate whether and, if so, how their energy and nutrient intake and weight were affected. At the start, only one main hot meal was exchanged for home cooking to avoid work load problems as no increased costs were allowed and no extra staff were to be recruited. The study population consisted of 21 residents, aged 69-97 years. Weight, energy and nutrient intake were recorded before and during the intervention by 3-day food records validated by Goldberg's cutoff method. The same 3 days of the weekSunday to Tuesdayand the same menus were used for both measurement periods. At group level, the energy intake corresponded to the estimated energy requirements, both at baseline and at follow-up, although the intervention resulted in a significantly higher energy intake from the meals cooked in the ward kitchens. Two-thirds of the residents (n=13) slightly increased in weight from baseline to follow-up, while two participants (with body mass index 27.5 kg/m(2) and 33.5 kg/m(2), respectively) lost 5.0 kg and 6.9 kg, respectively. The total protein intake was insufficient both at baseline and follow-up and only met the participants' needs to 8122% and 83 +/- 26%, respectively. In conclusion, the intervention resulted in no adverse consequences for participants in terms of energy and nutrient intake. Most participants were weight stable or had small increases in weight, and the greatest weight gain was observed in the lighter clients. The low protein intake at both time points causes concern and suggests the need for further nutritional interventions to optimize older people's protein intake.
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| 5. |
- Bryngelsson, David, 1981, et al.
(författare)
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The effect of food-price movements on African households - An investigation of food production and consumption patterns in four African countries
- 2009
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The recent spike in world food prices has intensified the debate regarding the impact of food prices on poverty. In this paper we aim to assess households’ vulnerability to food-price increases in four countries in Sub-Saharan Africa. Using household data from the World Bank’s Living Standard Measurement Surveys in Ghana (2005–2006), Kagera region, Tanzania (2004), Malawi (2004–2005) and South Africa (1993) we analyze food production and consumption patterns in rural and urban populations. We use two established indicators of sensitivity to food price changes—one measuring the share of income spent on food, the other measuring net sales of food compared to total expenditures. We find that the shares of the populations spending more than half of their income on food ranges from 62–81% in rural areas and from 26–67% in urban areas. Further we find that in all regions studied, most households (74–99%) in rural areas are net buyers of food and stand to lose in the short term from higher food prices. As expected, for urban households this is true to an even higher extent. In contrast to earlier studies we look at all food items and not just one or a few staple foods, giving a better understanding of vulnerability to general food price changes. We find that the exclusion of non-staple foods has a significant impact on theresults.
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| 6. |
- Hyvonen, R., et al.
(författare)
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The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review
- 2007
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Ingår i: New Phytologist. - Cambridge : Wiley. - 0028-646X .- 1469-8137. ; 173:3, s. 463-480
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Forskningsöversikt (refereegranskat)abstract
- Temperate and boreal forest ecosystems contain a large part of the carbon stored on land, in the form of both biomass and soil organic matter. Increasing atmospheric [CO2], increasing temperature, elevated nitrogen deposition and intensified management will change this C store. Well documented single-factor responses of net primary production are: higher photosynthetic rate (the main [CO2] response); increasing length of growing season (the main temperature response); and higher leaf-area index (the main N deposition and partly [CO2] response). Soil organic matter will increase with increasing litter input, although priming may decrease the soil C stock initially, but litter quality effects should be minimal (response to [CO2], N deposition, and temperature); will decrease because of increasing temperature; and will increase because of retardation of decomposition with N deposition, although the rate of decomposition of high-quality litter can be increased and that of low-quality litter decreased. Single-factor responses can be misleading because of interactions between factors, in particular those between N and other factors, and indirect effects such as increased N availability from temperature-induced decomposition. In the long term the strength of feedbacks, for example the increasing demand for N from increased growth, will dominate over short-term responses to single factors. However, management has considerable potential for controlling the C store.
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| 7. |
- Juma, Ibrahim, et al.
(författare)
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Characterization of Tanzanian Avocado Using Morphological Traits
- 2020
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Ingår i: Diversity. - : MDPI AG. - 1424-2818. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Two-hundred and twenty-six old avocado trees (Persea americana Mill) derived from seeds were selected from eight districts of the Mbeya, Njombe and Songwe regions in Tanzania. The tree, leaf, fruit and seed characteristics were studied using the descriptors for avocado (Persea spp.) from the International Plant Genetic Resources Institute. Cross tabulation and Chi-square tests were conducted in order to assess the distribution of traits between districts and altitude ranges. Principle coordinate analysis (PCoA) and hierarchical cluster analysis (HCA) were used to assess variation of traits within and among districts. Various morphological features were observed among the samples which point to the existence of the Mexican, Guatemalan and West Indian avocado races in Tanzania. The biplot from PCoA revealed extensive variation between the sampled trees at the district level but no clear groupings of the samples based on geographic location. Likewise, dendrograms ensuing from the neighbor-joining and Wards methods displayed that the avocado samples from the same district and even region differed considerably. This morphological trait variation suggests high diversity that may help in planning germplasm management and conservation, as well as breeding strategies in the future.
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| 8. |
- Juma, Ibrahim, et al.
(författare)
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Comparison of morphological and genetic characteristics of avocados grown in Tanzania
- 2021
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Ingår i: Genes. - : MDPI AG. - 2073-4425. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Tanzania has been growing avocado for decades. A wide variability of the avocado germplasm has been found, and the crop is largely contributing to the earnings of the farmers, traders, and the government, but its genetic diversity is scantly investigated. With the purpose of comparing morphological and genetic characteristics of this germplasm and uncovering the correlation between them and the geographical location, 226 adult seedling avocado trees were sampled in southwestern Tanzania. Their morphological characters were recorded, and their genetic diversity was evaluated based on 10 microsatellite loci. Discriminant analysis of principal components showed that the germplasm studied consisted of four genetic clusters that had an overall average gene diversity of 0.59 and 15.9% molecular variation among them. Most of the phenotypes were common in at least two clusters. The genetic clusters were also portrayed by multivariate analysis and hierarchical clustering for the molecular data but not for the morphology data. Using the Mantel test, a weak significant correlation was found between the genetic, morphological, and geographical distances, which indicates that the genetic variation present in the material is weakly reflected by the observed phenotypic variation and that both measures of variation varied slightly with the geographical sampling locations.
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| 9. |
- Juma, Ibrahim, et al.
(författare)
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Genetic diversity of avocado from the southern highlands of Tanzania as revealed by microsatellite markers
- 2020
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Ingår i: Hereditas. - : Springer Science and Business Media LLC. - 0018-0661 .- 1601-5223. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- Background: Avocado is an important cash crop in Tanzania, however its genetic diversity is not thoroughly investigated. This study was undertaken to explore the genetic diversity of avocado in the southern highlands using microsatellite markers. A total of 226 local avocado trees originating from seeds were sampled in eight districts of the Mbeya, Njombe and Songwe regions. Each district was considered as a population. The diversity at 10 microsatellite loci was investigated. Results: A total of 167 alleles were detected across the 10 loci with an average of 16.7 ± 1.3 alleles per locus. The average expected and observed heterozygosity were 0.84 ± 0.02 and 0.65 ± 0.04, respectively. All but two loci showed a significant deviation from the Hardy-Weinberg principle. Analysis of molecular variance showed that about 6% of the variation was partitioned among the eight geographic populations. Population FST pairwise comparisons revealed lack of genetic differentiation for the seven of 28 population pairs tested. The principal components analysis (PCA) and hierarchical cluster analysis showed a mixing of avocado trees from different districts. The model-based STRUCTURE subdivided the trees samples into four major genetic clusters. Conclusion: High diversity detected in the analysed avocado germplasm implies that this germplasm is a potentially valuable source of variable alleles that might be harnessed for genetic improvement of this crop in Tanzania. The mixing of avocado trees from different districts observed in the PCA and dendrogram points to strong gene flow among the avocado populations, which led to population admixture revealed in the STRUCTURE analysis. However, there is still significant differentiation among the tree populations from different districts that can be utilized in the avocado breeding program.
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| 10. |
- Juma, Ibrahim, et al.
(författare)
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Polyphenolic Content and Radical Scavenging Activities of the Peel, Pulp and Seed of Avocado (Persea americana Mill.) Grown in Tanzania
- 2023
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Ingår i: Tanzania Journal of Science. - 0856-1761 .- 2507-7961. ; 49, s. 230-239
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Tidskriftsartikel (refereegranskat)abstract
- Avocado is a healthy fruit and the consumption is continuously growing worldwide. The fruit contains polyphenolic compounds with antioxidant effects. Globally, research has been devoted to exploring the fruit quality, especially compounds with antioxidant effects, from different avocado-growing sites. However, the fruit quality of the Tanzanian avocado has so far not been investigated. In this study, the contents of polyphenols in peel, pulp and seed of avocados sampled in south-western Tanzania are described. The levels of total polyphenolic and flavonoid contents were measured, and antioxidant activity was evaluated using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The total polyphenolic content was highest in the seed and lowest in the peel (424 and 200 mg GAE/100 g DW, respectively). As for the total flavonoid content, the pulp had the highest value of 36.98 mg RE/100 g DW, while the seed had the lowest value of 32.54 mg RE/100 g DW. The overall average half maximal effective concentration (EC50) values in decreasing order, corresponding to an increasing antiradical activity, were 4.90 (peel), 3.63 (seed) and 3.24 µg/mL (pulp). The seed and peel possessed high levels of total polyphenolic and flavonoid content, thus demonstrating substantial antioxidant capacity. Seed and peel can potentially be processed and included in the diet to provide inexpensive antioxidant ingredients of natural origin. Consumption of the seed will not only improve human health but also reduce the environmental pollution, as many thousand tonnes of avocado seeds are produced in Tanzania per year; a huge amount currently remains as waste.
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