Phase 2: On-going Research

MultiTip ER - Enhancing Resilience

MultiTip ER will focus on enhancing the resilience of Lake Victoria fisheries and therefore, avoid adverse tipping points. This work reflects an evolution in focus, co-designed with our local partners, that concentrates on the methods (the ‘how’) of exploitation, and therefore focus on the fishers’ choice of gear. 

Lake Victoria shoreline at a landing site close to Entebbe, Uganda.

 The main research is separated into three work-packages. In WP1, our bioeconomic models will evolve towards a size-structured analysis of LV as a multi-species system, reflecting stakeholder interest in size-based regulations of gear, new modeling insights on the role of size specificity in the fishery, and the critical linkage between size and markets for fishing inputs (nets, bait) and outputs (catch). In WP2, our field interventions will evolve towards size-specific interventions that incentivize changes in how fishers choose their gear. Specifically, we will conduct field trials of subsidies for fishing nets of legal mesh size to enhance compliance with existing regulations; and study changing access of long-lining fishers to high-quality bait to explore the potential for new regulations that reconcile fisher profitability and resource system sustainability. Our governance work, in WP3, will evolve towards perceptions and acceptability of different governance strategies among fishers and regulators, with a special emphasis on size- based policies. This will expand and complement recommendations on specific fisheries regulations, taking into account acceptance and responses. Our experiments on behavioral responses will also provide evidence on the drivers of differences in responses to tipping points.

Together, the consistent co-design of WPs and clear action-orientation ensure applicable and actionable new knowledge about the SES of LV. management.  We will synthesize the multi-methods outputs of WP1, 2, and 3 and integrate them into communicable products that relate to partners’ missions and stakeholder interests. These products will be disseminated using an updated website, workshops / seminars and policy briefs. 


WP 1       

Below the surface – Resilience of the resource system in a size-based multi-species model

WP 2 

Interactions – Leveraging Input Choice as Focal Action Situation

WP 3

Above the surface – Surveys and experiments for mental models and acceptance of resilience-enhancing governance




Below the surface – Resilience of the resource system in a size-based multi-species model

WP1 studies the stability of the fisheries and explores regime shifts and tipping points with a size-based multi-species model of the LV resource system. This is a natural extension from Phase 1 with its size-based single-species model of the Nile perch fishery. Building on the experiences from the first phase of MultiTip, we take this step towards a food web model including Nile perch, dagaa, and haplochromines. The comeback of haplochromines, together with sustained fishing pressure, could mean that the tipping of the resource system in the 1980s could be reversed soon, implying a collapse of the Nile perch stock. However, the food web today is different from the 1980s, especially due to the dagaa population. This might result in different interaction patterns between Nile perch and haplochromines with ecological niches that mitigate the instability.

Task 1.1 - Food web stability. The size ratio between predator and prey can play as much a role as the species affiliation in determining the predation rates between individuals (Hartvig, 2011; Andersen, 2019). Thus, in order to assess the relevance of the fish populations’ size structures, we compare the simulations results of a size-structured model with an age-structured ecosystem model, namely Atlantis (Fulton et al., 2011). The size-structured model will be a multi-species model containing Nile perch, dagaa, and a (generalized) haplochromine species. Analogously to phase 1, the model parameters will be calibrated and validated against ecological data from the literature and against empirical survey data (Kammerer, Gómez-Cardona and Nyamweya, 2022). The simulations of the two model types are compared by analyzing the change in steady-state outcomes with respect to variations in the species composition. The comparison between the ecosystem model with dagaa and the counter-factual scenario without dagaa allows to test the hypothesis that the dagaa population plays a stabilizing role in the interaction between the Nile perch and the haplochromines stocks. 

Researchers: Johannes Kammerer (Ph.D. Candidate), Prof. Dr. Anna Marciniak-Czochra.

Partners: Dr. Chrisphine Nyamweya (KMFRI), Dr. Robert Jeremiah Kayanda (LVFO) , Hillary Mrosso (TAFIRI).

Task 1.2 - Size-based fishing policies. Phase 1 developed a toolbox to build, calibrate and validate bioeconomic size-based fish population models with the integration of data from stock surveys (Gómez-Cardona, Kammerer and Mrosso, 2022). We found that size-based policies, if implemented effectively, provide a leverage to improve the health of a fish stock and ensure its reproductive capacity (Kammerer, Gómez-Cardona and Nyamweya, 2022). We continue with the tools developed in phase 1 and use the multi-species model to study the effectiveness of size-based fishing policies. This will lead to a ranking of policies in their impacts on the ecosystem and the prospects to secure food and jobs for the fishers according to established metrics (Blanchard et al., 2014; Law et al., 2012). We will simulate the relevant size-based fishery policies in the model and evaluate the effect on the abundance and health of the fish stocks, and of the fishery yields and the stability of the ecosystem (Andersen, 2020; Law et al., 2012). The robustness of the prediction is assessed from comparison with the simulations of the Atlantis model (Fulton et al., 2011). . 

Researchers: Johannes Kammerer (Ph.D. Candidate), Prof. Dr. Anna Marciniak-Czochra.

Partners: Dr. Chrisphine Nyamweya (KMFRI), Dr. Robert Jeremiah Kayanda (LVFO) , Hillary Mrosso (TAFIRI


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Interactions – Leveraging Input Choice as Focal Action Situation

Phase 1 has provided evidence of the potential to improve or find alternatives to existing input regulations in the LV fisheries. WP2 will apply these lessons to two focal action situations: the use of illegal nets in the dagaa fishery (Task 2.1) and the use of bait in the Nile perch fishery (Task 2.2). Jointly, the tasks will generate outputs that can be readily used to inform current and intended changes in gear regulations.

Task 2.1 - Subsidies for Legal Dagaa Nets. In Tanzania, the legal mesh size of dagaa nets is 8mm, while illegal nets with mesh sizes below 8mm dominate the fishery (LVFO, 2021). The use of illegal nets increases fishers’ revenue by capturing a higher proportion of smaller and immature fish (Wanink, 1999), but jeopardizes the sustainability of the fishery. Due to limited state capacity and corruption, conventional policy mechanisms are ineffective. Despite co-management approaches and drastic punishment of caught offenders (e.g., burning of illegal fishing nets; Nunan et al., 2018; Kolding et al., 2014; Obiero et al., 2015; Cepic and Nunan, 2017), illegal fishing practices remain widespread (Eggert and Lokina, 2010; Etiegni et al., 2017). Phase 1 provided a proof of concept that other approaches can be effective and efficient in managing the fishery, such as subsidies for legal inputs (Diekert et al., 2022). Phase one focused on Tanzania, phase two takes the lessons learned and goes forward to measure the subsidy effects in the fishery outcomes in both Tanzania and Kenya.

Dagaanets Lv2023
MultiTip researchers looking at dagaa seine nets at a landing site near Entebbe, Uganda

We will randomly select landing sites each in Tanzania and Kenya. Baseline, follow-up, and endline surveys, related to gear use, harvesting effort and revenues, bookend a subsidy intervention with a 50:50 split between control and treatment sites. During the baseline intervention, in the treatment sites, legal net panels will be offered at a discount to increase take-up. During the endline intervention, we return to sites and offer the nets in the same way as the baseline. We will evaluate the change in fishing effort (time and frequency of fishing), net use (sizes and number of panels, wear on the nets), fishing outcomes (catch per trip, revenue) and potentially lasting effects (demand for subsidized legal nets). The data collection will be coordinated with local authorities and BMU representatives at each landing site.

Researchers: Sorell de Silva (Ph.D. Candidate), Dr. Tillmann Eymess, Prof. Timo Goeschl Ph.D, Prof. Dr. Florian Diekert

Partners: Joseph Luomba, M.Sc. (TAFIRI), Jonda Jane Awuor, M.Sc. (KMFRI).

Task 2.2. - Bait Policies in the Nile Perch Fishery. Type and quality of hooked bait determine the overall success or failure of longline fishing methods (Løkkeborget al., 2014). Nile perch fishers preferentially use hooks with live bait, set in reasonably deep water (Chitamwebwa et al., 2009). The growing importance of this method has led to the creation of a subsector, the live bait fishery, which captures and supplies bait to Nile perch fishers from wild catch in the lake and from ecologically vulnerable wetlands in the LV (Mkumbo, et al 2007). There is a diversity of sizes and species used with this purpose. Judged by the available evidence on fishing decisions (Peter & van Zweiten, 2022), most likely availability and efficiency of different bait types drives their use. Unfortunately, scientifically validated information regarding these patterns is scarce. There is a general understanding among researchers that a local catfish species Clarias gariepinus, locally known as ‘clarias’, could be a good species for this purpose. This due to it being more robust to handling, and being able to be grown in using aquaculture methods. This is not the case for other species and currently, most clarias used as bait seem to be captured and not grown. Current regulation at LV focuses on restricting fish target size with the aim of sparing immature fish. This regulation relies on a minimal hook size and it does not consider bait characteristics; this leads to hook regulation not being enforced in practice, leaving an important proportion of the Nile perch fishing fleet unregulated (Gómez, Kammerer & Mrosso, 2022). The more promising regulatory target of bait choice has yet to be explored. Bait regulation has the potential to improve outcomes in community welfare (increase fishers’ income) and sustainability (improve fish stock’s management).

To inform these possibilities, a field intervention facilitating high-quality aquaculture bait will measure fisher’s willingness to use this type of bait and derive potential benefits of overall bait access improvement. If aquaculture bait can be provided to fishers, there is a potential for a policy based on it to reduce the deleterious environmental effects of bait caught in ecologically vulnerable areas and regulate catches by reducing the proportion of immature Nile Perch captured using hook-and-line methods.

Task 2.2 consists of two activities that will be implemented in Uganda. First, we will collect data on the use of bait in the Nile perch fishery and the associated catches. This involves obtaining detailed information regarding bait (species, sizes, number of units, source and price), basic information on the fishing trip (boat, propulsion, crew experience and time in the water) and detailed information on the catch (number of fish head, sizes (length/weight) and selling price per unit). Only longline hook fishers will be targeted. This will provide valuable baseline information regarding the use, availability and relative efficiency of different bait. The second activity aims to convey the desirability of aquaculture bait for local producers. A selection of longline users will be identified with this purpose. We will implement the selling of aquaculture bait through a randomized mechanism that will allow us to determine the willingness to pay for this type of bait (at what prices fishers are willing to buy the bait) and the potential of it to displace the use of other bait types (examine the differences in willingness to pay due to the usual bait used). Detailed descriptions of their fishing activities during these days will be recorded for those participating in the survey. This includes inputs, time and location, catch amount, income, etc. Contact with local/regional bait producers will be established to provide the bait; this will also allow getting a detailed overview of the costs and effort required to implement aquaculture bait.


Researchers: Sorell de Silva (Ph.D. Candidate), Dr. Santiago Gomez-Cardona, Prof. Timo Goeschl Ph.D.

Partners: Bwambale Mbilingi, M.Sc. (NaFIRRI)


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Above the surface – Surveys and experiments for mental models and acceptance of resilience-enhancing governance


WP3 explores how people perceive the governance system and how they behave with respect to different outcomes and in different organizational structures (for example, Beach Management Units (BMU) versus Fisheries Protection Units (FPU) in Uganda). Phase 1 focused on the fishers’ system understanding of the ecological system and factors that influence their fishing behavior (e.g. Klein et al. 2021, Dannenberg et al. 2022). Phase 2 will both refine existing results as well as shift the focus to the governance system. Tools developed in Phase 1 will help identify the role of causality in behavioral response and help map mental models of conservation strategies of the ecosystem. Experimental studies will examine different information scenarios for causal attribution of tipping points and study the interaction of different governance strategies and the willingness of fishers to comply with regulations, esp. size-related regulations. LV is a common pool resource, with different user groups and different interests and views. This is a situation found all over the world in different contexts. A better understanding of the problems and possible solutions will also be helpful for other regions and contexts. There are three tasks in this WP.

Task 3.1 – Causes of tipping points in resource systems and user response. The first task is to produce additional experimental evidence on the drivers of differences in behavioral responses to tipping points. The required large-scale sample that is representative of a heterogeneous population of resource users will be recruited through an online platform and exposed to different treatments in a modified coordination game in a finite resource context, giving rise to different biographies of experiencing tipping points of either an anthropogenic (miscoordination) or natural type. Treatment variations will introduce subtle differences in the origins of the event (direct action versus strategy method) and the information structure of the interaction. Interactions will be realized in an online setting that allows for fast, large-scale participant matching.

Researchers: Prof. Timo Goeschl, Ph.D.


Task 3.2. – Perceptions and maps of mental models of governance. The second task is taking stock of the perceived consequences, conservation, and adaptation to tipping points in the resource system and mapping mental models of the consequences, conservation, and adaptation strategies to tipping points in this globally connected system. In all three countries, a sample representing key stakeholders of the Nile perch fishery will be assembled. These include fishers, fish processors/traders, Civil Society Organisation staff, Law enforcers, Policymakers, and researchers. Their perceptions will be assessed using a survey approach (Klein et al., 2021) that includes open questions on the consequences of a tipping point in Nile perch stock, possible conservation strategies, and adaptation strategies to a collapse in the Nile perch stock. The survey will be rolled out to stakeholders in the most appropriate or convenient format (paper-based or online). The open responses will be coded to provide a comprehensive overview of the perceptions to be analyzed and will serve as input for the subsequent mapping.

For the mapping, Task 3.2 will employ M-Tool, populating it with the consequence concepts of the previous step. Instructions will be tailored to the task at hand in local languages. Deployment will be through visiting subjects with tablets, or inviting them online, as appropriate. An accompanying survey assesses preferences for conservation and adaptation strategies.

Researchers: Dr. Karlijn van den Broek

Partners: Fonda Jane Awuor, M.Sc. (KMFRI)Joseph Luomba, M.Sc. (TAFIRI)Bwambale Mbilingi, M.Sc. (NaFIRRI)Dorothy Birungi, M.Sc. (NaFIRRI)

Task 3.3 – Acceptance of and cooperation in governance systems. The third task is to study the acceptance of different governance systems and how different governance systems affect compliance behavior. Here, we will use a stated-choice experiment to elicit preferences for governance systems and a lab-in-the-field experiment to identify the impact of different governance and enforcement systems on cooperation. The study will focus on fisherfolk in the Ugandan part of LV, which has seen the most drastic changes in governance in recent years , and the Kenyan part of LV, which experienced the least changes in recent years (Mudilar 2020). The survey and experimental investigations follow a common standardized protocol that builds on our extensive field experience.

The stated-choice experiment will focus on the preferences of different enforcement institutions (e.g. monitoring, conviction, or punishment) as an important part of the governance system. Fishers will choose between enforcement institutions that vary in the involvement of fishers, the potential punishment, and the costs of these institutions. The results will show the value fishers give those different aspects of the enforcement system and allow comparisons. An understanding of these preferences can help in the communication and creation of effective governance structures that consider fishers’ preferences. In the lab-in-the-field experiment, participants play an experimental common pool resource game, which mimics their real-life social dilemma situation. In a series of different treatments, participants will be confronted with enforcement systems that aim to increase fishers’ cooperation within the common pool resource game. The treatments will be designed to mimic endogenous and exogenous punishment systems. The main goal is to identify effective and ineffective enforcement systems in an environment that is subject to dynamic population development. The outcomes of this experiment will reveal which enforcement system will lead to sustainable resource harvesting behavior of fishers and, hence, to a lower risk of resource depletion. Furthermore, the usage of insights from the stated choice experiment is used to understand the relationship between fishers’ stated preference for governance strategies and actual behavior under introduced enforcement systems.

Researchers: Philipp Händel (Ph.D. Candidate),  Pia Pico (Ph.D. Candidate), Prof. Dr. Astrid Dannenberg.

Partners: Fonda Jane Awuor, M.Sc. (KMFRI), Bwambale Mbilingi, M.Sc. (NaFIRRI)Dorothy Birungi, M.Sc. (NaFIRRI)


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Letzte Änderung: 13.10.2023
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