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Fine-scale spatiotemporal variation in juvenile Chinook Salmon distribution, diet and growth in an oceanographically heterogeneous region
Progress in Oceanography ( IF 4.1 ) Pub Date : 2021-01-30 , DOI: 10.1016/j.pocean.2021.102512
William D.P. Duguid , Thomas W. Iwanicki , Jessica Qualley , Francis Juanes

The existence of fine-scale structure in the abiotic and biotic characteristics of pelagic habitats is widely recognized, but the ecological significance of that structure is understudied. Logistical considerations have meant that research on the ecology of commercially and ecologically important marine species generally occurs at relatively coarse spatial and temporal scales. Many populations of Chinook Salmon (Oncorhynchus tshawytscha) in the Northeast Pacific are currently experiencing low productivity. The hypothesis that survival, and hence recruitment, of Chinook Salmon is related to growth early in marine residence has led to intensive research on the trophic ecology of this species during the first year at sea. We employed a small vessel-based methodology to simultaneously characterize fine-scale spatial and temporal variation in physical and biological oceanography, and juvenile Chinook Salmon distribution, size, diet, temperature exposure, and growth from July through October at five sites within the Southern Gulf Islands of the Salish Sea. Densities of zooplankton prey of Chinook Salmon declined to very low levels by the end of the study period. Juvenile Chinook Salmon stomach fullness and growth also declined by early fall while frequency of empty stomachs and importance of fish in diets increased. We found that both oceanographic conditions and trophic ecology of juvenile Chinook Salmon varied among sites only a few (2–23) kilometers apart. Juvenile Chinook Salmon were larger and faster growing at sites where fish (generally Pacific Herring Clupea pallasii) constituted a larger proportion of the diet. Overall, the most important prey of juvenile Chinook Salmon by mass proportion (25.6%) was Pacific Herring; however, only 8.4% of individuals contained C. pallasii. Analysis of co-occurrence of diet items suggested alternate foraging strategies, with some individuals specializing on Pacific Herring while others targeted a variety of small crustacean zooplankton. Juvenile Chinook Salmon which had consumed Pacific Herring had greater mean stomach fullness than those which had not. Predation on Pacific Herring was strongly related to juvenile salmon length, suggesting that age-0 Pacific Herring may have been too large to be consumed by smaller Chinook Salmon. Our results reinforce the importance of the transition to piscivory in the trophic ecology of juvenile Chinook Salmon. Further research is necessary to determine if fine-scale distribution of larger, piscivorous juvenile salmon is linked to the distribution of their forage fish prey and to understand the role of prey to predator size ratios in limiting the ability of juvenile salmon to transition to piscivory.



中文翻译:

海洋异质性地区奇努克鲑鱼分布,饮食和生长的精细时空变化

远洋生境的非生物和生物特征中存在细微尺度结构已得到广泛认可,但对该结构的生态学意义进行了研究。后勤方面的考虑意味着对商业和生态上重要的海洋物种生态学的研究通常发生在相对粗糙的空间和时间尺度上。奇努克鲑鱼(Oncorhynchus tshawytscha)的许多种群)目前在东北太平洋地区正处于生产力低下的状态。奇努克鲑鱼的存活以及因此的募集与海洋居住早期的生长有关的假说导致人们在海上第一年对该物种的营养生态进行了深入研究。我们采用了一种基于小型容器的方法,同时表征了南洋湾内五个地点在7月到10月期间在物理和生物海洋学上的细小时空变化以及七巧鱼鲑鱼的分布,大小,饮食,温度和生长情况萨利什海的岛屿。在研究期结束时,奇努克鲑鱼的浮游动物捕食密度降低到非常低的水平。奇努克鲑鱼的胃部饱满度和生长率也因早期下降而下降,而空腹的频率和鱼类在饮食中的重要性则有所增加。我们发现,相距仅几(2-23)公里的站点,幼稚的奇努克鲑鱼的海洋环境和营养生态都各不相同。奇努克鲑鱼幼鱼在有鱼类(通常是太平洋鲱鱼)的地方生长较大且生长速度更快。日粮中的Clupea pallasii占较大比例。总体而言,按质量比例(25.6%)计,幼年的奇努克鲑鱼最重要的猎物是太平洋鲱鱼。但是,只有8.4%的人含有帕氏梭菌。对饮食项目共现的分析建议了其他觅食策略,其中有些人专门研究太平洋鲱鱼,而另一些人则针对各种小型甲壳类浮游动物。食用太平洋鲱鱼的奇努克鲑鱼比没有食用太平洋鲱鱼的平均胃饱胀度高。对太平洋鲱鱼的捕食与幼鲑的长度密切相关,这表明0岁太平洋鲱鱼可能太大了,无法被较小的奇努克鲑鱼食用。我们的结果强调了在幼稚的奇努克鲑鱼的营养生态学中过渡到食肉动物的重要性。有必要进行进一步的研究以确定是否较大的,

更新日期:2021-03-15
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