Adapting to climate change: Innovative techniques in the smallholder aquaculture sector

Adapted to the country specific contexts, different measures are being used for the GP Fish’s intervention areas. However, the procedure is similar, starting with studying the individual effects of climate change to the region, piloting mitigation strategies to curb them and then implementing the most effective solutions.

In 2022, the GP Fish conducted a vulnerability study for the freshwater aquaculture sector in Madagascar on behalf of the German Federal Ministry for Economic Cooperation and Development (Bundesministerium für wirtschaftliche Zusammenarbeit und Entwicklung, BMZ). Public, private, and society actors of the sector reflected jointly on the impacts of climate change and developed adaptation measures for pond farming and rice-fish culture. 

Moreover, in cooperation with the Lilongwe University of Agriculture and Natural Resources and the former Sectoral Programme for Sustainable Fisheries and Aquaculture, the project researched and implemented measures to protect fish farmers from the total loss of fish stock due to extreme weather events through intermittent harvest.
The aquaculture adaptations were applied and supported through training and consulting services, accompanied by additional activities like the implementation of a mobile phone-based climate information system.

The vulnerability study follows the methodology of the GIZ Vulnerability Sourcebook which uses the vulnerability definition by the AR4 of the IPCC. As a starting point, temperature and precipitation in six focus regions in Madagascar were analysed and climate project maps were created. They served as a basis for the impact analysis. In three interregional workshops, impact chains and adaptation measures were developed by private, public, and civil society actors of the aquaculture sector. In a national workshop these findings were shared and verified. Fish farmers in the Highlands and on the east coast participated in capacity building activities on climate change adaptation.

Overall, the results revealed a high vulnerability of the freshwater aquaculture sector in all six focus regions in Madagascar. The models predict a significant reduction of rainfall, an increase of the number of days without rain and more frequent extreme weather events until 2060. More cyclones (and more intense cyclones) imply flood and erosion and a siltation of rice fields. More frequent and longer droughts lead to a lack of water, shorter production cycles and delays in the fish farming season. Furthermore, extreme weather events can create “panic sales” at low prices which affects the economic performance of fish farmers. 

Through joint efforts the project, Lilongwe University, a method for intermittent harvesting was developed, based on expert discussions and literature research. The size-­selective fish trap was designed for easy and regular harvest of juvenile fish in mixed-sex tilapia cultures, mitigating the risk of a total loss of fish crop due to extreme weather events. Next to the better management of the pond’s carrying capacity, the low-cost fish trap was expected to improve household nutrition and cash flow of small-scale aquaculture farmers. In a series of experiments different fish species, stock densities and time intervals for the use of the trap were tested. On-farm trials were conducted to test the innovation’s use in the field. With the application of the trap for intermittent harvest the total yields under optimal conditions were 25 percent higher than in the control group with single batch harvest. Throughout the three-month trial in the field, the farmers used the trap two to three times a week. An average of 830 g of small but marketable fish was caught each time, adding up to over 20 kg of continuous fish supply for the farmer. 

This additional catch provided a steady source of food for the household or could be sold at favourable prices, especially when local market fish supplies were low during the aquaculture cycle. 

Complex problems require systemic solutions that operate in different dimensions and at different levels.

Based on the vulnerability study results and the piloting intermittent harvest technique, the GP Fish supported various initiatives to enhance the resilience of aquaculture and rice-fish farmers. Through training sessions, farmers learned about the impacts of climate change on aquaculture operations. With support from technical staff, fish farmer cooperatives developed individual adaptation plans, which were then incorporated into their annual planning. Additionally, farmers received training on enhancing watershed functionality and implementing agroforestry practices, including reforestation around ponds to reduce erosion during heavy rains. Due to high community demand, the project also supported the development and management of local tree nurseries to ensure the availability of seedlings.

Other infrastructural adaptations for small-scale aquaculture operations include the use of deeper ponds, which provide thermal refuge and greater dissolved oxygen reserves, thus enhancing fish growth and survival during dry spells. Structural adaptations such as raised pond dikes and strategic timing for stocking and harvesting fish are recommended to prevent losses during seasonal extreme weather events.

Moreover, continuous harvesting of surplus tilapia offspring reduced the risk of total market value loss due to flooding, showcasing an innovative adaptation to increase resilience against climate variability. The cost-­efficient adaptations and techniques were carefully selected to minimize the financial burden on farmers.
These adaptations on an infrastructural level can be complemented by regional activities of the project to mitigate climate change effects. For example, a digital, mobile phone-based climate information system for fish farmers has been introduced in collaboration with mobile network operators and weather stations. The hotline provides early and regular weather updates, which allows farmers to adjust production and harvesting methods to prevent losses from events such as flooding. Additionally, the hotline serves as a marketplace for fish producers and consumers.