Ecological and economic perspectives of two decades of change in a traditional fishing ground in the Philippines

A time-dynamic ecosystem model of the Visayan Sea, a significant traditional fishing area in the Philippines, was employed to calculate a set of ecological indicators from 1997 to 2018. These indicators were used to analyze the biomass, vital rates, community structure, biodiversity, development, and functioning of the Visayan Sea ecosystem. Attributes of system resilience and the ecosystem effects of fishing form the core of the analysis, providing insights into how structural and functional changes have shaped the ecosystem over time. In addition, monetary values of the trends in fisheries landings and catch composition were estimated to document the direct economic consequence of these changes. Results show that the biomass of predator and upper trophic level fishes declined, while small pelagic fishes, herbivores, and benthic invertebrates increased. Most exploited groups exhibited high fishing mortality, and the biodiversity index fell to nearly half its baseline. These trends suggest a development trajectory toward dominance by lower trophic level species, driven by impaired top-down control and increased bottom-up production. Despite structural simplification, the ecosystem remained stable between 1997 and 2018, supported by high detrital cycling and functional redundancy. The detrital pathways were sustained by underutilized low trophic level group biomass following predator decline, while, high species richness within functional groups conferred resilience against external stressors. However, sustained high fishing pressure increasingly threatens these groups. Decreasing catches of high-value large fishes were offset by increasing contributions from smaller fishes and benthic invertebrates, resulting in increased total landings and value over time. However, the average per capita income from fishing declined throughout the period, falling below the national poverty threshold in 2018. Overall, the use of a suite of indicators was useful in evaluating the status of the Visayan Sea between two decades from both ecological and economic perspectives. The combined application of these indicators to re-evaluate existing fisheries policies and their effects with respect to diverse management objectives is further discussed. • A comparative analysis of the Visayan Sea between two decades was performed using multiple ecological indicators. • Over 20 years, changes led to an overall biodiversity decline and a simpler ecosystem structure. • On the other hand, network analysis revealed stable and resilient features. • Increasing biomass of low-TL, economically important species offsets declining predator fish biomass. • The calculated per capita economic share remains low as the number of fishers, legal or illegal, grows.