Mercury (Hg) levels in Ontario top predator fishes have been increasing in recent decades. These increases may be a result of many additive factors, including global climate change. Only recently has research been conducted on how climate change may impact Hg levels in freshwater fishes at large-scales. We examined the relationship between Hg trends and (1) local weather, (2) large-scale climate drivers, and (3) anthropogenic Hg emissions, in native cool water (walleye and northern pike) and warm water (smallmouth bass and largemouth bass) predatory fishes in Ontario, Canada, for historical (1970–1992) and recent (1993–2014) time periods. For each fish species studied, > 25% of Ontario's secondary watersheds shifted from historically declining to recently increasing fish Hg trends, and ≥ 50% of watersheds experienced increasing trends between 1993 and 2014. Recent fish Hg increased at up to 0.20 µg/g/decade; which were significant (p < 0.05) for walleye, northern pike and smallmouth bass. Multiple linear regressions revealed a complex interplay of local weather, large-scale climate drivers, and anthropogenic Hg emissions influencing fish Hg levels. Recent Hg levels for walleye and largemouth bass increased with changes in global climate drivers, while higher precipitation influenced smallmouth bass Hg levels the most. Walleye Hg levels increased during the positive phases of global climate drivers, reflecting the local influence of local temperatures and precipitation indirectly. Differentiating the effects of climate-related parameters and emissions is increasingly crucial to assess how changing multiple environmental stressors may impact health of wildlife and humans consuming fish.

近几十年来，安大略省顶级捕食鱼类的汞（Hg）水平一直在上升。这些增加可能是包括全球气候变化在内的许多附加因素的结果。直到最近才进行了有关气候变化如何大规模影响淡水鱼类中汞含量的研究。我们研究了汞趋势与（1）当地天气，（2）大规模气候驱动因素和（3）人为汞排放之间的关系，这些汞在天然凉水（角膜白斑和北派克）和温水（小嘴鲈和大嘴鲈）中）历史时期（1970-1992年）和最近时期（1993-2014年）加拿大安大略省的掠食性鱼类。对于每种研究的鱼类，安大略省超过25％的次要流域从历史上的下降趋势转向了最近的鱼类汞趋势上升趋势，在1993年至2014年之间，流域的增长趋势达到50％以上。最近的鱼类汞含量增加到0.20 µg / g /十年。对于角膜白斑，北部派克和小嘴鲈鱼来说，这是显着（p <0.05）。多元线性回归揭示了当地天气，大规模气候驱动因素和人为汞排放影响鱼汞水平的复杂相互作用。随着全球气候驱动因素的变化，最近的大眼鲈和大嘴鲈鱼的汞含量增加，而较高的降水量对小嘴鲈鱼的汞含量影响最大。在全球气候驱动因素的积极阶段，角膜白斑中的汞含量增加，间接反映了当地温度和降水的局部影响。