Abstract:

Submerged macrophytes such as Elodea nuttallii and Vallisneria natans are essential for ecological stability and stable production in ponds used for the culture of the Chinese mitten crab (Eriocheir sinensis). Under increasingly frequent summer heat events, the decline of aquatic plants has become a major constraint on pond aquaculture. This study aimed to clarify the effects of high-temperature stress on the growth condition of dominant aquatic plants in crab ponds and on production performance, and to construct a response model linking climatic stress, aquatic plant condition, and production outcome. Based on meteorological data, industrial information, sales records of aquatic-plant protection products from three representative aquatic drugstores, and survey data from 36 representative crab ponds in Taizhou for three consecutive years during 2023-2025, eight heat-related indicators, including mean air temperature in July-August, extreme maximum temperature, number of days with temperature≥35℃, maximum consecutive high-temperature days, number of hot nights, precipitation anomaly, sunshine duration, and mean wind speed, were selected. The analytic hierarchy process was used to construct a high-temperature hazard index (HMI). An aquatic plant condition index (WCI) was established using June aquatic plant coverage and the August aquatic plant decline score. Correlation analysis and multiple linear regression were applied to develop a chain-response model of “HMI-WCI-production outcome”. High-temperature stress in Taizhou showed a clear interannual pattern, being lowest in 2023, highest in 2024, and second highest in 2025. The most severe heat damage occurred in 2024, when prolonged heat, frequent hot nights, and reduced precipitation occurred simultaneously. Aquatic plant condition showed the opposite trend, being best in 2023, worst in 2024, and partially recovering in 2025. Changes in yield, mean body size, and proportion of high-quality crabs were generally consistent with the variation in aquatic plant condition. Monthly sales of aquatic-plant protection products and the number of consulting ponds were both significantly positively correlated with the number of days with temperature≥35℃, maximum consecutive high-temperature days, and hot nights. The August aquatic plant decline score and the maximum crab mortality during the high-temperature period were significantly negatively correlated with yield, mean body size, and the proportion of high-quality crabs, with the decline score showing a stronger effect than mortality. The yield-estimation model established using the August aquatic plant decline score and maximum mortality rate showed good performance (R²=0.580, P<0.001). The chain-response model demonstrated that increasing high-temperature hazard reduced the aquatic plant condition index, which in turn led to declines in yield and body size. Aquatic plant decline was the key intermediate link through which heat stress affected production outcome. The effects of high-temperature stress on crab pond production in Taizhou showed a clear chain-response pattern. Maximum consecutive high-temperature days were the key meteorological hazard factors, and the August aquatic plant decline score was the core biological indicator restricting aquaculture benefit. These results provide a scientific basis for heat-disaster warning, pond management optimization, and yield prediction in Eriocheir sinensis culture.

Key words: Taizhou, Eriocheir sinensis, high temperature stress, aquatic plant condition, chain response model