Dennis Otieno, Cosmas Munga, Gladys Okemwa, James Mwaluma

Abstract

Background: Mangroves, seagrass beds, and coral reefs form a critical trinity in marine ecosystems, providing essential services like shelter and nursery grounds for diverse fish assemblages. Understanding connectivity across these habitats is crucial for designing effective Marine Protected Areas. This study assessed fish assemblages in this continuum along the south coast of Kenya.

Methods: Juvenile fish specimens were collected monthly every three days by experimental fishing using a beach seine net. Fishing was done across three habitats in a sea area harboring mangrove, sea grass beds, and coral reefs during low tides for 10 months, from November 2021 to August 2022 in south coast Kenya. Fish species were identified by family and species levels using standard fish identification guides. Composition of fish by abundance and species diversity was analyzed using descriptive statistics.

Results:A total of 7,354 individuals representing 52 families and 232 species were identified. Labridae was the most diverse family, while Scombridae, Bothidae, and Acanthuridae were the least. Coral reefs hosted the highest abundance (528 individuals) and diversity (Shannon- Wiener H’ = 3.766), followed by seagrass (432 individuals, H’ = 3.685) and mangroves (321 individuals, H’ = 3.644). Connectivity was evident, with 11 species found in all three habitats and 43 in at least two. Trophic guilds also showed connections, with herbivores dominating mangroves (34%) and carnivores most prevalent in corals (23%). Canonical correspondence analysis revealed associations of environmental variables with specific fish families. Salinity positively influenced the families Mullidae, Scaridae, Lutjanidae, and Carangidae, while Labridae responded negatively. Temperature had positive correlations with Tetraodontidae, Chaetodontidae, and Pomacentridae, and negative ones with Lethrinidae and Apogonidae.

Conclusion:The findings highlight the ecological significance of the mangrove-seagrass-coral reef continuum and its connectivity for fish assemblages. The high abundance and diversity in coral reefs, coupled with prevalent inter-habitat species presence and trophic guild variations, reinforce the need for MPAs encompassing all three habitats for effective fisheries management and ecosystem conservation.