BACKGROUND AND OBJECTIVES:
Small-scale fisheries in tropical multi-gear systems are influenced by marine environmental variability and biological pressure on target resources. Within the Timor Sea, seasonal fluctuations in oceanographic variables—specifically
sea surface temperature and chlorophyll-a concentrations—exhibit the potential to shift the spatio-temporal dynamics of fishing opportunities, while demersal snapper stocks continue to face pronounced vulnerability to anthropogenic to exploitation. The study objectives were to evaluate whether
oceanographic variability and demersal stock pressure were associated with fishing-effort reallocation, while distinguishing fleet-level restructuring from vessel-level gear switching.METHODS: Vessel-level landing records from ۲۰۱۴ to ۲۰۲۰ were analyzed for vessels of ۳۰ gross tonnage or less, comprising ۳,۴۴۱ records from ۶۱۹ vessels. Sea surface temperature and chlorophyll-a data were obtained from satellite products, spatially averaged over the fishing domain, aggregated into monthly means, transformed into anomalies, and matched to landing records. To comprehensively evaluate gear dynamics, a multi-tiered analytical framework comprising compositional testing, multinomial logistic regression models, functional gear groupings, and vessel-level Markovian transition matrices were established. Demersal stock status for Lutjanus malabaricus, Lutjanus sebae, and Pristipomoides multidens was determined via length-based spawning potential ratio estimates.FINDINGS: Sea surface temperature and chlorophyll-a showed strong seasonal and interannual variability but no significant long-term trends. Gear composition shifted significantly over the study period;
purse seine effort increased sharply, whereas bottom longline deployment declined relative to handlines. The environmental multinomial model showed that
purse seine became increasingly likely over time after controlling for month, vessel size, trip intensity,
sea surface temperature anomaly, and chlorophyll-a anomaly. Purse seine use was significantly associated with lagged
sea surface temperature and chlorophyll-a anomalies, indicating that pelagic-oriented gear use was linked to environmentally mediated fishing opportunities rather than productivity alone. Vessel-level transition analysis revealed a high degree of operational inertia; out of ۳۵۵ paired vessel-year empirical observations, only ۳۲ instances of gear switching were detected, yielding a nominal transition rate of ۹.۰ percent. Spawning potential ratio values were below the ۴۰ percent management target for all assessed species, with Lutjanus sebae and Pristipomoides multidens below the ۲۰ percent limit reference point.CONCLUSION: The Timor Sea small-scale fishery is undergoing partial
fishing-effort reallocation rather than complete gear migration. The expansion of
purse seine operations reflects a structural reconfiguration of the fleet, signaling selective adaptation strategies in response to spatio-temporal environmental heterogeneity and pronounced depletion trajectories among demersal stocks. Management should integrate snapper stock rebuilding, pelagic effort monitoring, vessel-level gear tracking, and satellite-based environmental indicators.
