Modeling the growth of the invasive river crayfish species Procambarus virginalis (Decapoda, Astacidea) under different temperature conditions

In the marbled crayfish Procambarus virginalis, the dependence of the duration of inter-larval intervals on body weight and the magnitude of body weight gains for individual inter-larval intervals in the temperature ranges 15.3–17.9 °С, 7.5–18.9, 19.1–20.8, 21.0–22.8, 22.9–25.2 and 25.3–28.9 °С was determined. The growth curves of individuals in these temperature ranges and the sum of effective temperatures (Sef) of individuals during juvenile growth and breeding periods were calculated from these data. The average Sef value for the juvenile period of P. virginalis (until newborn individuals reach a body weight of 1.4 g) in the studied temperature ranges is 4316 degree·days at the biological zero temperature of 7.6 °C. For the breeding period (until reaching the body weight from 1.4 g to the limit weight of 15 g) – respectively 10630 degree·days and 3.0 °C. Based on the annual dynamics of mean monthly temperatures in six continental water bodies within the invasive range of P. virginalis (Sweden, Belarus, Germany, Slovakia, North Macedonia and Malawi), Sef values were calculated for the periods of the year during which juvenile growth and reproduction of sexually mature individuals are possible. In temperate water bodies located in Sweden, Belarus, Germany and Slovakia, Sef values during the juvenile growth period vary between 1083 and 2099 degree·days. In the more southern body of water in Northern Macedonia, this value reaches 2990 degree·days, and in the tropical African body of water in Malawi it reaches 7076 degree·days. Consequently, newborn individuals of P. virginalis, which in water bodies of the temperate zone of Europe hatch in the first half of summer, can reach sexual maturity only in the third summer of life, and in a tropical water body – already in the first summer of life. Sef values for periods of the year favorable for the growth of sexually mature individuals in the studied water bodies of Europe increase from 2031 degree·days (water body in Sweden) to 4657 degree·days (water body in Northern Macedonia). In the tropical water body of Malawi, this figure reaches 8058 degree·days, i.e. the maximum life span of P. virginalis in this water body does not exceed two years. Nevertheless, throughout the entire range, sexually mature individuals of P. virginalis are capable of producing no more than 2–5 clutches of eggs per life cycle.