Census (N-C) and effective population size (N-e) were estimated for a lake-resident population of brown trout Salmo trutta as 576 and 63, respectively. The point estimate of the ratio of effective to census population size (N-e:N-C) for this population is 0.11 with a range of 0.06-0.26, suggesting that N-e:N-C ratio for lake-resident populations agree more w(i)th estimates for fishes with anadromous life histories than the small ratios observed in many marine fishes. (C) 2011 The Authors Journal of Fish Biology (C) 2011 The Fisheries Society of the British Isles