School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195, USA.
Department of Ecology, Montana State University, Bozeman, MT, 59717, USA.
Proc Biol Sci. 2023 Feb 8;290(1992):20222248. doi: 10.1098/rspb.2022.2248.
Declining body sizes have been documented for several species of Pacific salmon; however, whether size declines are caused mainly by ocean warming or other ecological factors, and whether they result primarily from trends in age at maturation or changing growth rates remain poorly understood. We quantified changes in mean body size and contributions from shifting size-at-age and age structure of mature sockeye salmon returning to Bristol Bay, Alaska, over the past 60 years. Mean length declined by 3%, corresponding to a 10% decline in mean body mass, since the early 1960s, though much of this decline occurred since the early 2000s. Changes in size-at-age were the dominant cause of body size declines and were more consistent than trends in age structure among the major rivers that flow into Bristol Bay. Annual variation in size-at-age was largely explained by competition among Bristol Bay sockeye salmon and interspecific competition with other salmon in the North Pacific Ocean. Warm winters were associated with better growth of sockeye salmon, whereas warm summers were associated with reduced growth. Our findings point to competition at sea as the main driver of sockeye salmon size declines, and emphasize the trade-off between fish abundance and body size.
已经有文献记录表明,几种太平洋三文鱼的体型正在变小;然而,体型变小主要是由海洋变暖还是其他生态因素造成的,以及这种变化主要是由于成熟年龄的趋势变化还是生长率的变化造成的,这些问题仍然知之甚少。我们量化了过去 60 年来返回阿拉斯加布里斯托尔湾的红大麻哈鱼的平均体型变化以及体型年龄结构变化的贡献。自 20 世纪 60 年代初以来,平均长度下降了 3%,相应的平均体重下降了 10%,尽管大部分下降发生在 21 世纪初以来。体型年龄结构的变化是体型变小的主要原因,而且在流入布里斯托尔湾的主要河流中,其变化比年龄结构趋势更为一致。体型年龄的年际变化在很大程度上归因于布里斯托尔湾红大麻哈鱼之间的竞争以及与北太平洋其他鲑鱼的种间竞争。温暖的冬季有利于红大麻哈鱼的生长,而温暖的夏季则会降低其生长速度。我们的研究结果表明,海洋竞争是红大麻哈鱼体型变小的主要驱动因素,并强调了鱼类数量与体型之间的权衡关系。