The densities of existing fish populations in streams may affect salmonid stocking programs. Non-native brown trout (Salmo trutta) now occur in rivers in Japan that are managed via stocking programs to restore recreational fisheries for native white-spotted charr (Salvelinus leucomaenis), but how they affect charr stocking programs needs to be better understood. We investigate how suppressing populations of brown trout affects the density and biomass of stocked charr population sizes and biomasses. We report no significant change in charr abundance or biomass after stocking into areas in which brown trout are abundant. However, following suppression of brown trout, charr significantly increased in numbers and biomass, and their settlement rates rose in excess of 10 times. We suggest that brown trout outcompete charr for habitat and food resources, and that stocking charr in streams in which brown trout populations exist is unlikely to be effective in the management and restoration of recreational fisheries, but that stocking them into streams in which brown trout have been suppressed is more likely to be effective.

溪流中现有鱼类种群的密度可能会影响鲑鱼放养计划。非本地褐鳟（Salmo trutta）现在出现在日本的河流中，这些河流通过放养计划进行管理，以恢复本地白点红点鲑（Salvelinus leucomaenis）的休闲渔业，但需要更好地了解它们如何影响红点鲑放养计划。我们研究了抑制褐鳟鱼种群如何影响放养的红点鲑鱼种群规模和生物量的密度和生物量。我们报告称，在褐鳟鱼丰富的地区放养后，红点鲑丰度或生物量没有显着变化。然而，在褐鳟受到抑制后，红点鲑的数量和生物量显着增加，其沉降率增加了10倍以上。我们认为，褐鳟在栖息地和食物资源方面胜过红鲑，在存在褐鳟种群的溪流中放养红鲑不太可能对休闲渔业的管理和恢复有效，但将它们放养到存在褐鳟的溪流中不太可能有效。被压制的可能性更大。