Trends in the Reproductive Phenology of two Great Lakes Fishes

To assess potential effects of climate change on Great Lakes fish populations, we evaluated trends in the reproductive phenology of Yellow Perch Perca flavescens (spring spawner) and Lake Trout Salvelinus namaycush (autumn spawner). For Yellow Perch in Lake Michigan, the estimated reproductive midpoint date (50% of mature females ripe or spent, 50% not yet spawned) took place 6.2 d/decade earlier in the spring near Milwaukee from 1988 to 2012 and 1.8 d/decade earlier in Green Bay from 1980 to 2012. At both locations water temperatures at the spawning sites on the midpoint date showed no trends, but mean water temperatures during the spring at the spawning site and midlake increased over the study period. This suggests that Yellow Perch spawning areas were warming sooner in the spring and that Yellow Perch were spawning earlier to maintain a consistent spawning temperature. Lake Trout phenological patterns were more complex. For Lake Trout in Lake Michigan near Milwaukee, there was a marginally significant trend for spawning to take place 2.1 d/decade later in the autumn from 1983 to 2006. However, water temperatures at the spawning site at the midpoint date did not change and autumn temperatures at the site and at midlake did not show a warming trend. For Lake Trout in Lake Superior near the Apostle Islands, the midpoint date did not change from 1988 to 2012. Water temperatures at the spawning site on the midpoint date and during the autumn also showed no trends, but midlake summer and autumn water temperatures increased significantly. Overall, Yellow Perch in Lake Michigan have shifted reproductive timing in a manner consistent with a warming climate, but the relationship of climate change to reproductive phenology remains unclear for Lake Trout in Lake Michigan and Lake Superior. Received December 15, 2014; accepted August 7, 2015为评估气候变化对五大湖（Great Lakes）鱼类种群的潜在影响，本研究分析了春季产卵的黄鲈（Yellow Perch，Perca flavescens）与秋季产卵的湖鳟（Lake Trout，Salvelinus namaycush）的繁殖物候（reproductive phenology）变化趋势。针对密歇根湖（Lake Michigan）的黄鲈，1988年至2012年期间，密尔沃基近岸区域的繁殖中点日期——即50%成熟雌性个体已处于产卵或产卵后状态，剩余50%尚未产卵——以每十年6.2天的速率提前；1980年至2012年期间，绿湾（Green Bay）区域的繁殖中点日期则以每十年1.8天的速率提前。两处采样点的繁殖中点当日的产卵场水温均无显著变化趋势，但研究期内产卵场春季平均水温及湖心平均水温均呈上升态势。这表明黄鲈的产卵场春季升温提前，黄鲈通过提前产卵以维持稳定的产卵所需水温。 湖鳟的物候模式更为复杂。1983年至2006年期间，密尔沃基近岸的密歇根湖湖鳟秋季产卵时间以每十年2.1天的速率延后，该趋势仅具有边际显著性。然而，其繁殖中点当日的产卵场水温未发生变化，且该区域产卵场及湖心的秋季水温均无升温趋势。针对阿波斯特尔群岛（Apostle Islands）附近苏必利尔湖（Lake Superior）的湖鳟，1988年至2012年期间其繁殖中点日期未发生改变；产卵场中点当日水温及秋季水温均无显著变化趋势，但湖心夏季与秋季水温呈显著上升态势。 总体而言，密歇根湖黄鲈的繁殖时间调整模式与气候变暖的预期相符，但密歇根湖与苏必利尔湖的湖鳟繁殖物候与气候变化的关联仍不明确。本文于2014年12月15日收稿，2015年8月7日录用。