An approach to the assessment of risk from chronic radiation to populations of European lobster, Homarus gammarus (L.)

The basic principles underlying a four-discrete age group, logistic, growth model for the European lobster Homarus gammarus are presented and discussed at proof-of-concept level. The model considers reproduction, removal by predation, natural death, fishing, radiation and migration. Non-stochastic effects of chronic low linear energy transfer (LET) radiation are modelled with emphasis on 99Tc, using three endpoints: repairable radiation damage, impairment of reproductive ability and, at higher dose rates, mortality. An allometric approach for the calculation of LD50/30 as a function of the mass of each life stage is used in model calibration. The model predicts that at a dose rate of 1 Gy day−1, lobster population reproduction and survival become severely compromised, leading eventually to population extinction. At 0.01 Gy day−1, the survival rate of an isolated population is reduced by 10%, mainly through loss of fecundity, comparable to natural migration losses. Fishing is the main ecological stress and only dose rates in the range 0.03–0.1 Gy day−1 can achieve discernible effects above it. On the balance of radiation and other ecological stresses, a benchmark value of 0.01 Gy day−1 is proposed for the protection of lobster populations. This value appears consistent with available information on radiation effects in wildlife.