Institute of Marine Research, Bergen, Norway.
College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, United States of America.
PLoS One. 2018 Oct 16;13(10):e0205921. doi: 10.1371/journal.pone.0205921. eCollection 2018.
The trophic link between cod (Gadus sp.) and capelin (Mallotus sp.) is important in many panarctic ecosystems. Since the early 2000s, the Northeast Arctic cod stock (G. morhua) in the Barents Sea has increased greatly, and the sea has been exceptionally warm. Such changes have potentially large effects on species distributions and overlap, which in turn could affect the strength of species interactions. Due to its high latitude location, the Barents Sea has strong seasonal variation in physical conditions and interactions. To study drivers of variation in cod-capelin overlap, we use data from two annual surveys run in winter and in autumn of 2004-2015. We first model winter and autumn spatial distributions of mature and immature cod and capelin. We then calculate overlap from model predictions on a grid with similar spatial resolution as the survey data. Our approach allowed us to interpret changes in overlap as species-specific effects of stock size and temperature, while accounting for sampling variation due to sampling time and depth. We found that during winter both species expanded their distribution in response to increased stock sizes, but how strongly and where the expansion occurred varied. The effect of temperature on distributions varied in space, and differed for cod and capelin and for different components of the two species. The results for autumn were clearer and more consistent. Both species expanded their distribution areas as their stock sizes increased. A positive effect of temperature was found in the north-eastern Barents Sea, where temperatures were lowest at the start of the study. Overlap increased and shifted north-eastwards during the study period and remained high despite a decline in the capelin stock. The increased overlap during autumn could mainly be attributed to the shift in cod distribution with increased cod stock biomass.
鳕鱼（Gadus sp.）和毛鳞鱼（Mallotus sp.）之间的营养联系在许多泛北极生态系统中都很重要。自 21 世纪初以来，巴伦支海的东北鳕鱼（G. morhua）种群数量大幅增加，海温异常偏高。这些变化可能对物种分布和重叠产生巨大影响，进而影响物种相互作用的强度。由于所处地理位置较高，巴伦支海的物理条件和相互作用具有很强的季节性变化。为了研究鳕鱼-毛鳞鱼重叠变化的驱动因素，我们使用了 2004 年至 2015 年期间冬季和秋季两次年度调查的数据。我们首先建立了成熟和未成熟鳕鱼和毛鳞鱼的冬季和秋季空间分布模型。然后，我们根据模型预测结果在与调查数据相似的空间分辨率网格上计算重叠度。我们的方法使我们能够将重叠变化解释为种群规模和温度的物种特异性影响，同时考虑到由于采样时间和深度而导致的采样变化。我们发现，冬季两种鱼类的分布都因种群数量的增加而扩大，但扩张的强度和位置因物种而异。温度对分布的影响在空间上存在差异，并且因鱼类和毛鳞鱼以及两种鱼类不同组成部分而异。秋季的结果更为清晰和一致。随着种群数量的增加，两种鱼类的分布区域都扩大了。在巴伦支海东北部发现了温度的正效应，研究开始时那里的温度最低。在研究期间，重叠度增加并向东北方向移动，尽管毛鳞鱼种群数量下降，但重叠度仍保持较高水平。秋季重叠度的增加主要归因于鳕鱼种群生物量增加导致的鳕鱼分布变化。
