A PRELIMINARY STUDY ON ECOLOGICAL SUITABILITY EVALUATION BENCHMARKS FOR DISSOLVED OXYGEN (DO) IN GRASS CARP AQUACULTURE PONDS

Dissolved oxygen (DO) is a critical environmental factor determining the survival, health, and growth efficiency of grass carp (Ctenopharyngodon idella), which is the most productive freshwater aquaculture species in China.However, the lack of standardized, practical benchmarks for DO suitability has hindered effective water quality management in grass carp ponds.This study aims to establish a set of ecologically relevant DO benchmarks for grass carp through a systematic synthesis of published physiological and ecological research.We conducted a comprehensive, literature-based synthesis by retrieving studies from major databases including Web of Science, Scopus, and the China National Knowledge Infrastructure (CNKI).Data on DO concentrations and corresponding physiological or ecological responses of grass carp were extracted, compared, and analyzed to define distinct suitability levels.The analysis resulted in five ecological suitability levels with the following DO benchmarks (ranges): death period (≤0.60 mg/L), danger period (0.60-1.60 mg/L), impact period (1.60-4.70 mg/L), normal period (4.70-7.50mg/L), and optimal period (≥7.50 mg/L).For reliable monitoring, it is recommended that water samples be collected at dawn from near the pond bottom in both upwind and downwind areas, with the lowest measured DO value used for assessment.The proposed benchmarks offer a scientifically grounded and practical tool for aquaculture practitioners to diagnose DO status and implement timely interventions, thereby promoting healthy cultivation and sustainable production of grass carp.