Thermal accumulation indicator as a dynamic ocean management tool in the Gulf of Ulloa, Mexico

Abstract

This study examines the occurrence of cumulative cold events in the Gulf of Ulloa, Baja California Sur, defined as sea surface temperatures (SST < 18°C) for ≥5 consecutive days, as a basis for developing an operational environmental indicator to support adaptive fisheries management and reduce sea turtle bycatch. High-resolution MUR satellite data (1.1 km2) from 2003-2023 were analyzed to generate climatologies, annual maps, and spatial accumulations that reveal critical areas and temporal patterns of thermal persistence. Results indicate a clear seasonal pattern, with the highest frequency of cold events between March and June, coinciding with intensified coastal upwelling and the residence of juvenile Caretta caretta. Interannual variability was pronounced: cold years (e.g. 2008, 2011, 2022) showed widespread event coverage, while warm ENSO phases (2014-2016) exhibited minimal incidence. The cumulative analysis revealed up to 84 cold events in the northern coastal sectors of the gulf and identified 18 critical polygons of persistent conditions that overlap zones of turtle-fishery interaction. The proposed indicator is both replicable and scalable, consistent with the principles of Dynamic Ocean Management. It provides near-real-time environmental information to anticipate sea turtles' ecological vulnerability and support conservation decisions without impairing local fisheries or relying on static fishery closures.