Phase V – Fish juvenile recruitment in coastal habitats of western Indian Ocean

This interdisciplinary research project, titled “Fish Juvenile Recruitment in Coastal Habitats of the Western Indian Ocean,” was implemented by the Institut Halieutique et des Sciences Marines (IH.SM) in Madagascar and the Kenya Marine and Fisheries Research Institute (KMFRI) with funding from the MASMA program. The project, which began on March 1, 2021, and concluded on February 28, 2023, focused on understanding the recruitment patterns of the shoemaker spinefoot rabbitfish (Siganus sutor) in critical coastal habitats of the western Indian Ocean and aimed to explore sustainable solutions for enhancing the welfare of coastal communities relying on marine resources.

The project was organized into four work packages (WPs). Work Package 1 (WP1) concentrated on identifying S. sutor recruitment patterns in coastal habitats, as well as the nursery areas and recruitment periods. Research efforts achieved significant outcomes, identifying essential nursery habitats, particularly emphasizing the role of seagrass meadows as primary nurseries in Madagascar. High densities of Tanaidacea and abundant phanerogam cover were critical environmental factors affecting juvenile fish abundance. The findings suggested a clear seasonal recruitment pattern for S. sutor, primarily during the cool season, with peak recruitment periods observed in August and December-January across both Madagascar and Kenya.

In Work Package 2 (WP2), the project investigated the population connectivity of S. sutor, determining the origins of juvenile fish that populate these vital coastal habitats. Although the genetic analysis is still underway, significant progress was made in collecting adult and juvenile samples from multiple sites in both countries and sending them to KU Leuven for genotyping. The data from this work package are expected to underpin future studies on the dynamics and migratory patterns of S. sutor populations.

In the third work package (WP3), ecological modeling was employed to predict the arrival patterns of newly settled juveniles. This work utilized historical data and juvenile recruitment patterns collected during the project to fit predictive models, with the aim of understanding environmental variables influencing the recruitment process. By leveraging satellite-derived oceanographic data, the project sought to elucidate the conditions facilitating the successful arrival and settlement of juvenile rabbitfish in coastal habitats.

The final work package (WP4) focused on exploring the biology and aquaculture of S. sutor. Experiments conducted at the Belaza research station in Madagascar revealed valuable insights into the diet and growth performance of juvenile rabbitfish. By comparing the efficiency of locally produced industrial diets against artisanal options, the project showcased the potential of capture-based aquaculture. Results demonstrated superior growth rates and feed conversion efficiencies for fish fed on industrial diets, although this came with a lower survival rate compared to those fed on cooked rice. These findings highlight the possibility of implementing aquaculture as a means to support local livelihoods while enhancing the sustainability of fish populations.

Throughout the project period, significant challenges were addressed, including logistical hurdles faced during genetic analysis and the collection of field data. Collaboration with various educational and research institutions enriched the project, fostering a trained workforce in coastal and marine sciences. Several Master’s and PhD students participated actively in research activities, contributing to knowledge transfer and capacity building within local communities and research institutions.

As a result of the comprehensive research activities conducted, the project yielded critical scientific results that not only advanced our understanding of S. sutor recruitment but also provided a basis for policy-making and community-level actions regarding marine resource management in the western Indian Ocean. The project team disseminated findings through multiple conferences and workshops, aiming to raise public awareness about the ecological significance of coastal habitats and the importance of sustainable fishing practices. Additionally, community engagement activities were initiated to bolster local buy-in and to communicate research outcomes effectively to stakeholders, enhancing the visibility of the project and its implications for policy and management actions.

In conclusion, this research initiative has made substantial progress toward understanding the recruitment dynamics of S. sutor while simultaneously contributing to the socioeconomic wellbeing of coastal communities in Madagascar and Kenya. The findings are expected to inform future conservation strategies, aquaculture development, and fisheries management aimed at sustainable utilization of marine resources, thus ensuring the resilience of marine ecosystems and the communities that depend on them.