PECA: An Integrated Real-Time Biosensing Platform for Detecting Thermal Stress in Aquatic Environments

Thermal stress poses escalating threats to aquatic ecosystems, yet current biomonitoring tools lack real-time integration of multidimensional physiological responses. To address this gap, we developed the Physiological and Ecological Comprehensive Analyzer (PECA), an integrated platform combining non-contact impedance sensors for behavior analysis, dissolved gas probes for metabolic monitoring, and wearable devices for cardiac signal acquisition in freely swimming fish. Using koi carp (Cyprinus carpio var. koi) under controlled thermal regimes (22 °C, 26 °C, 32 °C) with ethical compliance, the PECA calculated a novel Physiological Stress Index (PSI) integrating behavioral strength, the respiratory quotient, and electrocardiographic parameters. The results demonstrated significant PSI reductions under acute thermal stress, correlating with suppressed metabolism and altered cardiac function. This system provides a real-time solution for detecting thermal anomalies in aquatic environments, enabling proactive water resource management in climate-vulnerable ecosystems.