We present revised estimates of the instantaneous natural mortality rate of recruited (legal sized) Foveaux Strait dredge oysters ( Ostrea chilensis , Philippi, 1845) for the years 1974–86. A mark‐return experiment was analysed, assuming constant rate of fishing (and hence sampling) over 6 months of the year (i.e., the period of the fishing season). The natural mortality between 1974 and 1986 of recruited oysters increased fro...