Validation and assessment of Potential Fishing Zone (PFZ) dynamics along the southwest coast of India through environmental proxies and trophic guild analysis

Abstract

Potential Fishing Zone (PFZ) advisories exemplify scientific information with direct societal application, particularly for fishing communities. PFZs are identified using satellite-derived Sea Surface Temperature (SST) and chlorophyll (Chl-a), representing productive ocean fronts that are expected to aggregate fish. This study aims to validate the impact of PFZ advisories on daily village fish landings and to investigate environmental conditions driving PFZ formation and their influence on trophic guild structure of catch, a grouping based on the feeding ecology of the species. To achieve this, the daily PFZ advisories issued by the Indian National Centre for Ocean Information Services (INCOIS) and daily fish landing data of 117 villages across the state of Kerala, southwest coast of India during 2022–23, were used. Using a lag period approach, which accounts for the delayed responses of the environmental variables on PFZ occurrences, we analysed the effects of remotely-sensed and modelled physical and biogeochemical factors on PFZ formation. Our findings revealed significantly higher fish landings on PFZ days and the immediate next day, validating PFZ advisories over a broad spatial range. Trophic guild analysis showed a shift in dominance of planktivores on PFZ days to carnivores in subsequent days, reflecting productivity transfer through the food web. Lag period analysis indicated that environmental precursors within a two-week window before PFZ formation significantly differed from other days of analysis, identifying optimal lag day for each variable to have maximum influence on the PFZ formation. These findings highlight the need for in-situ experiments and time-series observations at evolving ocean fronts to validate PFZ dynamics and trophic succession. While adoption rates during the study period were unavailable, the higher catches associated with PFZ occurrences affirm the reliability of these advisories. Signs of food web progression and lagged environmental responses also offer valuable insights to refine models to support sustainable marine fisheries forecasts.