Estimating of the maximum life expectancy and natural mortality of the red king crab on the example of the Barents Sea population

Abstract

The purpose of the study is to establish the maximum life span (tmax) and natural mortality (M) in commercial Lithodidae using the example of the red king crab Paralithodes camtschaticus.Material and methods — after the introduction of P. camtschaticus into the Barents Sea in 1969, the dynamics of the maximum carapace width (CWmax) from the first crab catches in 1974 to 2022 was considered. The data of the authors’ own observations and the results of studies from the open press were used.Results. The retrospective dynamics of the maximum size of crabs for older ages for 1974–2022 is presented. The maximum sizes were established: in males CWmax 280–312 and 298 mm was in 2002 and 2003, and in females CWmax 210–220 mm in 1995, 1998 and in a later period.New data. Based on the fifty-year dynamics of CWmax, it was suggested that after the end of the acclimatization of P. camtschaticus in 1969, the first generation of local juveniles appeared in the area of introduction in the early 1970s; in the absence of fishing, these juveniles were able to freely reach the maximum historical size and maximum age. Males caught in 2002–2003 with CWmax 280–312 mm, could have been 30–33 years old (mean 31 years), and the age of females in 1995 with CWmax 210 mm was 20–25 years (mean 23 years). This age limit of crabs allows us to establish a natural mortality according to the formula М=3/tmax for crabs with CW ≥70–90 mm, when their natural elimination is minimal. In this case, the decrease in M in males will be 10% per year, and in females 13%.Practical significance. To estimate the commercial stock of P. camtschaticus, the values of natural mortality used today are 1.8–2.3 times higher than M established by tmax for this species in the Barents Sea. The use of a double overestimated value of M in model calculations leads to a decrease in the commercial stock of crab and, as a consequence, to a decrease in its total allowable catch.