High dissolved organic carbon and low pH are often associated with elevated mercury content of fish in boreal lakes, but less is known about the fish mercury dynamics in lakes recovering from acidification stress. We measured total mercury concentration (THg) in muscle of European perch (Perca fluviatilis) and evaluated the overall correlation with environmental and growth variables in 24 boreal headwater lakes in the 2010s. We found negative correlations of length-corrected perch THg with lake pH and perch growth, but no correlation with dissolved organic carbon. The main emphasis in the present study was focused to a subset of ten lakes in southern Finland with known perch THg during severe acidification in the 1980–1990s. The comparison of perch THg concentrations in the 2010s with values determined in the 1980–1990s showed a sharp increase in most acidic lakes where the perch populations suffered from severe acid stress in the 1980s. This increase was attributed to growth condensation caused by sharp decrease in perch growth during recovery of reproduction capacity and the consequent increases in population densities of perch. Our results highlight the importance of perch growth rate and population density for understanding the variability of fish Hg in boreal headwater lakes, where recovery from acidification can lead to higher mercury concentration of fish in certain cases.

高溶解有机碳和低 pH 值通常与北方湖泊中鱼类的汞含量升高有关，但对从酸化压力中恢复的湖泊中的鱼类汞动态知之甚少。我们在欧洲鲈肌肉测得的总汞浓度（THG）（河鲈fluviatilis) 并评估了 2010 年代 24 个北方源头湖泊与环境和增长变量的整体相关性。我们发现长度校正的鲈鱼 THg 与湖泊 pH 值和鲈鱼生长呈负相关，但与溶解有机碳没有相关性。本研究的主要重点是在 1980-1990 年代的严重酸化期间，芬兰南部的 10 个湖泊的子集具有已知的鲈鱼 THg。2010 年代的鲈鱼 THg 浓度与 1980-1990 年代确定的值的比较显示，大多数酸性湖泊在 1980 年代遭受严重酸胁迫的鲈鱼种群急剧增加。这种增加归因于繁殖能力恢复期间鲈鱼生长急剧下降以及随之而来的鲈鱼种群密度增加引起的生长凝结。