Spatial modelling and decision analysis for sustainable aquaculture: the case of Nigeria

Abstract

Aquaculture sector planning takes two forms: expansion and intensification, both requiring context-specific tools to support decisions. This thesis is focused on expansion planning and aimed to help answer a key question about the future of aquaculture in developing countries like Nigeria: how much and where should aquaculture expand in response to global and local projections of future aquatic food demand? First, Delphi technique was used to prioritize factors influencing the aquaculture sector in Nigeria: availability/cost of aquafeed, land use change, government policy and climate change. Through Scenario Analysis, four alternative but plausible pathways (scenarios) were generated for the sector’s development to 2035, thus providing information to support government interventions. Second, a modelling approach was developed which combined the scenarios with Spatial Multi-Criteria Evaluation (SMCE) and GIS-based tools for aquaculture spatial decision support. The design was based on the low predictability of landscape change where legislations are weak, thus not all areas indicated by suitability models will remain suitable in the long-term. The approach was used to locate specific zones for aquaculture in Nigeria, to demonstrate how these vary with different development goals for aquaculture and to select the best zone respectively. Third, a survey of fish farmers in Nigeria was conducted to understand their perception of the concept, potential benefits, and limitations of aquaculture clusters. The questionnaire was divided into 4 sections: farm characteristics, farming practices, farmers’ attributes and perception based on statements about aquaculture clusters. Majority of farmers have a positive perception. Using Random Forest method, the top 2 of 10 factors that influenced perception were farmers’ source of advice and where they discharge farm effluents. Fourth, spatiotemporal changes in major land use: built-up area, vegetation and water surface were assessed in a previously identified potential zone for aquaculture. To identify possible indicators of sustainability, findings were compared with those at an established aquaculture area within the same region. Overall, this thesis provides evidence and methods to support strategies for the sustainable expansion of aquaculture in Nigeria as well as other countries looking to develop spatial plans for existing or new areas for aquaculture.