Abstract:

Based on the daily air temperature and the water temperature monitoring data at 30cm depth from four crayfish-rice ecological meteorological stations in the primary production areas of crayfish in Hubei province during the period from March to May 2022−2024, a spring water temperature simulation model was established. Combined with daily meteorological data from 76 national basic meteorological stations in Hubei province from 1981 to 2022, using the moving average method to calculate the start seedling period for crayfish in Hubei province, analyzing spatiotemporal distribution characteristics of low-temperature cold damage during the spring seeding period of crayfish in Hubei province, a risk index model of low-temperature cold damage was constructed to evaluate the low-temperature cold damage risk of crayfish in different seedling periods in Hubei province, so as to provide scientific basis for the healthy and sustainable development of crayfish industry. The results indicated that the determination coefficient R² of the spring water temperature simulation model based on the average air temperatures of the current day, the previous day, and two days prior constructed in the study was 0.874. The root mean square error (RMSE) and relative error (RE) of the model validation were 1.14℃ and 5.14%, respectively. The model has high simulation accuracy and is able to predict the daily average water temperature in spring throughout the province. The main occurrence of low-temperature cold damage to crayfish during the seedling period in spring in Hubei province is in late March, with a frequency of 29.3%, 20.5%, and 0.2% for slight, moderate and severe damage respectively. There are differences in the occurrence time of low temperature cold damage in different regions: the occurrence time of low-temperature cold damage in southwestern Hubei was in mid March, while in northeastern Hubei, southeastern Hubei, Jianghan plain and other areas it occurred in late March; Northwest Hubei is slightly later, from late March to early April. Most of southeastern Hubei, eastern part of northeastern Hubei, southern Jianghan plain, and the Three Gorges river valley in southwestern Hubei, are high-risk areas for crayfish low-temperature cold damage, and it is appropriate to delay the start of seedling date to reduce the risk of low-temperature cold damage. The southern part of northwest Hubei, the central northern part of Jianghan plain, and the western part of southwest Hubei are areas with medium risk of crayfish low-temperature damage. The northern part of northwestern Hubei and the high mountains in southwestern Hubei are low−risk areas for crayfish low−temperature cold damage, and areas with sufficient water sources are suitable for expanding the scale of crayfish farming in spring. The risk index of low-temperature cold damage increased to 33.60%, 40.41%, 45.27%, and 53.00% respectively when the start of seedling date was advanced by 5 days, 10 days, 15 days, and 20 days; by contrast, the risk index of low−temperature cold damage reduced to 15.23% when the start of seedling date was delayed by 5 days, and the start of seedling date in the southeast will be from March 25-30, while in the northwest it will be from March 30th to April 15th; the risk index of low-temperature cold damage reduced to 7.80% when the start of seedling date was delayed by 10 days, and the start of seedling date in the southeast will be from March 30th to April 5th, while in the northwest it will be from April 5th to April 20th.

Key words: Spring seeding crayfish, Seeding date, Low?temperature cold damage, Risk assessment