Some ecological parameters of Artemia parthenogenetica Gahai and their use in resource exploitation

The effects of temperature on population characteristics of Artemia parthenogenetica Gahai from the Gahai Salt Lake, Qinghai Province, China, were studied in the laboratory at a salinity of 60‰. The major conclusions are as follows: (1) it was found that the adaptive temperature for the development of brine shrimp ranged from 10℃ to 39℃. The threshold temperature of development (TD) and the effective accumulative tem-perature (TA) for hatching were 9.94℃·d and (22.91±2.08)℃·d, respectively. The TD and TA for the larva were 10.33℃·d and (261.26±24.1)℃·d, respec-tively, and for the whole generation were 10.28℃ and (458.68±57.60)℃·d, respectively. (2) It showed that the population's net reproduction rate (Ro), the intrinsic rate of natural increase (rm), the mean generation time (T), the finite rate of increase (λ), and the days for population to double (t) of the brine shrimp were determined over temperatures ranging from 19℃ to 34℃ by analyzing the life table and numerical model. In the temperature range of 14.3℃ to 37.3℃ for Ro> 1, the optimum temperature (℃) for Ro, rm,λ, and t were 25.8℃, 29.8℃, 30.5℃, and 29.02℃, respectively. The maximum values of Ro, rm and λ were 54.86 ind., 0.106138/d, and 1.1070/d, respectively. The minimum value oft was 4.73 d. The value of T was in a range of 96.77 to 16.10d. (3) Based on the 1993-1994 and 1997 data of the water temperature in the Gahai Salt Lake, Qinghai Province, it was estimated that the number of generation of A. parthenogenetica Gahai and the number of the reproductive peak value were 2.67±0.34 and 4.69±0.43 in a year, respectively. The peak of nauplii of the first generation was on April 20 to 28. The last whole generation began on August 10. The first reproductive peak was on June 18 to 25. The last reproductive peak was on September 12 to 17. The nauplii that hatched after September 1 cannot complete the development from nauplii to adults because of insufficient habitat effective accumulative temperature. During the period from July 11 to September 20, there was a relatively high productivity of the population. In this case, doubling the population would take less than 30 d, and the intrinsic rate of natural increase was over 0.02/d. Therefore, the value of resource exploitation would be maximal during that period annually.