Sieglind Wallner Hahn


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Works at Department of Ecology, Environment and Plant Sciences
Telephone 08-16 42 43
Visiting address Svante Arrhenius väg 20 A
Room N 320
Postal address Institutionen för ekologi miljö och botanik 106 91 Stockholm

About me

The title of my PhD project is "Towards transformation in seagrass-associated small-scale fisheries: problems and potential solutions."

The aim of this thesis is to analyze empirically how social-ecological elements of seagrass-associated small-scale fisheries can practically be addressed to transform them from the current degraded state to healthier social-ecological systems.  My study area is the Western Indian Ocean region (East Africa) with a context of tropical developing countries, where coastal populations are to a high extent depending on the resources the marine environment has to offer.

With the results of my research, I aim to highlight perceptions of local fishers which often are overlooked in fisheries management. The findings of my work will contribute to a basis towards a more sustainable management of small-scale fisheries by investigating how to break activities like destructive gear use. The findings will deliver pieces of knowledge to be able to propose practical management approaches and institutional arrangements contributing to improved governance and sustainability of small-scale fisheries to secure local livelihoods in the long-run.

Data for my PhD work is collected in coastal areas of Kenya, Zanzibar, Mozambique, Mayotte and Madagascar mainly through the conduction of interviews with fishers, managers and scientists.


I will defend my thesis publicly on May 5th 2017 09:00 at the Department of Ecology, Environment and Plant Sciences.



A selection from Stockholm University publication database
  • 2016. Sieglind Wallner-Hahn (et al.). Marine Policy 72, 199-210

    The aim of this study was to empirically assess institutional aspects shaping fishers' behavior leading to unsustainable resource use, by using the example of destructive drag-net fishing in Zanzibar, Tanzania. A broad institutional approach was used to specifically assess institutional factors influencing the fishers' reasons for the current use of destructive drag-nets as well as their willingness- and economic capacity to change to less destructive gears. Different regulative, normative, cultural-cognitive and economic factors (tradition, group-belonging, social acceptance, common practice, identity of drag-net users and weak economic capacity) were identified as critical elements influencing the current use of destructive gears, as well as obstructing changes to other gears. Hence, the importance of addressing all of these factors, matching to the different contexts, rather than focusing on fast-moving regulative measures, is emphasized to increase chances of management success. More promising approaches would be resource allocations to more sustainable fishing gears, well-managed gear exchange programs, as well as alterations of slow-moving normative and cultural factors, e.g. awareness raising on the advantages of more sustainable fishing gears, their traditional and cultural values, information on the actual income they generate, as well as education and an exchange of traditional knowledge on how to use them.

  • 2015. Sieglind Wallner-Hahn (et al.). Ocean and Coastal Management 107, 16-27

    Marine ecosystems generate a wide variety of goods and services, but are globally deteriorating due to multiple drivers associated with anthropogenic activities. Intense fishing pressure can lead to changes in structure and function of marine food webs. Particularly overfishing of predatory species at high trophic levels can cause cascading effects leading to ecosystem degradation, affecting both marine organisms and people dependent on them. In the Western Indian Ocean region, intensive fishing takes place and degradation of coral reefs and seagrass beds has been documented. One reason behind this degradation is overgrazing by increasing numbers of sea urchins. An essential step towards better management is to thoroughly understand the drivers leading to such changes in ecosystems. Against this background, the general aim of this study was to gain understanding about whether sea urchin predators in the WIO region are fished, and to identify the drivers behind the fishing of these species. The study had four objectives: Cl) to document if and how predatory fish eating sea urchins are caught in smallscale fisheries, (ii) to assess if, and if so why, sea urchin predators are targeted species, (iii) to assess if and to what degree local ecological knowledge (LEK) on ecological complexity involving sea urchins and their predators (e.g. trophic cascades) is present among local fishers, and (iv) to identify fishers' suggestions for management that can reduce problems linked to sea urchin overgrazing. The results show that all investigated species of sea urchin predators are fished by local small-scale fishers. Most sea urchin predators are not actively targeted, are not popular local food fish, and have minor use and economic importance for fishers. This stands in sharp contrast to their ecological keystone role by controlling sea urchin populations. The fishers' awareness and LEK were weak and partly lacking. Management suggestions targeted mostly the symptoms of food web changes rather than the drivers behind them. Based on the results we suggest that management of degraded ecosystems, as a result of food web changes, should encompass a wide variety of strategies and scales. Specific suggestions for sea urchin predator management are education of local stakeholders on destructive gear effects and food web complexity, further investigations of catch- and release fishing as well as the use of selective gears.

Show all publications by Sieglind Wallner Hahn at Stockholm University

Last updated: November 30, 2018

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