Lake Tana, Ethiopia's largest lake, has a remarkable and conservation-worthy assemblage of fish species, requiring fisheries management for sustainable exploitation. However, due to anthropogenic impacts, many of these fish species are threatened. Hence, an improved management of these resources is recommended. To allow a more sustainable exploitation of natural resources, a better understanding of the cause-effect relationships between anthropogenic impacts and environmental components is fundamental. The Drivers-Pressure-State-Impact-Responses (DPSIR) framework is a useful tool to describe these links in a meaningful way to managers and policy makers. Despite its potential, application of DPSIR is virtually lacking in developing countries. This paper assessed the potential of the DPSIR framework and used it to comprehensively describe the available knowledge and management needs in the lake catchment. Rapid population growth and the economic transformation are the main driving forces leading to various pressures such as water quality and wetlands degradation as well as declining fish community, which is detrimental to the socio-economic state and health of the local inhabitants. As feedback to the driving forces, pressures, state changes and impacts, optimal multi-level responses are developed. This study aims at providing policy makers a better understanding of the lake catchment in order to bridge the gap between science and decision-making.
Abstract. The Amazon and Congo basins are the two largest continuous blocks of tropical forest with a central role for global biogeochemical cycles and ecology. However, both biomes differ in structure and species richness and composition. Understanding future directions of the response of both biomes to environmental change is paramount. We used one elevational gradient on both continents to investigate functional and stoichiometric trait shifts of tropical forest in South America and Africa. We measured communityweighted functional canopy traits and canopy and topsoil δ 15 N signatures. We found that the functional forest composition response along both transects was parallel, with a shift towards more nitrogen-conservative species at higher elevations. Moreover, canopy and topsoil δ 15 N signals decreased with increasing altitude, suggesting a more conservative N cycle at higher elevations. This cross-continental study provides empirical indications that both South American and African tropical forest show a parallel response with altitude, driven by nitrogen availability along the elevational gradients, which in turn induces a shift in the functional forest composition. More standardized research, and more research on other elevational gradients is needed to confirm our observations.
Fisheries play a significant role in the livelihoods of the world population, while the dependence on fisheries is acute in developing countries. Fisheries are consequently a critical element for meeting the sustainable development (SDG) and FAO goals to reduce poverty, hunger and improve health and well-being. However, 90% of global marine fish stocks are fully or over-exploited. The amount of biologically unsustainable stocks increased from 10% in 1975 to 33% in 2015. Freshwater ecosystems are the most endangered ecosystems and freshwater fish stocks are worldwide in a state of crisis. The continuous fish stock decline indicates that the world is still far from achieving SDG 14 (Life Below Water), FAO’s Blue Growth Initiative goal and SDG 15 (Life on Land, including freshwater systems). Failure to effectively manage world fish stocks can have disastrous effects on biodiversity and the livelihoods and socio-economic conditions of millions of people. Therefore, management strategies that successfully conserve the stocks and provide optimal sustainable yields are urgently needed. However, successful management is only possible when the necessary data are obtained and decision-makers are well informed. The main problem for the management of fisheries, particularly in developing countries, is the lack of information on the past and current status of the fish stocks. Sound data collection and validation methods are, therefore, important. Stock assessment models, which support sustainable fisheries, require life history traits as input parameters. In order to provide accurate estimates of these life history traits, standardized methods for otolith preparation and validation of the rate of growth zone deposition are essential. This review aims to assist researchers and fisheries managers, working on marine and freshwater fish species, in understanding concepts and processes related to stock assessment and population dynamics. Although most examples and case studies originate from developing countries in the African continent, the review remains of great value to many other countries.
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