Oceanographic conditions in the Arctic are changing, with sea ice cover decreasing and sea temperatures increasing. Our understanding of the effects on marine populations in the area is, however, limited. Here, we focus on the Barents Sea stock of polar cod (Boreogadus saida). Polar cod is a key fish species for the transfer of energy from zooplankton to higher trophic levels in the Arctic food web. We analyse the relationships between 30-year data series on the length-at-age of polar cod cohorts (ages 0–4) and sea surface temperature, sea ice concentration, prey biomasses, predator indices, and length-at-age the previous year using multiple linear regression. Results for several ages showed that high length-at-age is significantly associated with low sea ice concentration and high length-at-age the previous year. Only length-at-age for age 1 shows a positive significant relationship with prey biomass. Our results suggest that retreating sea ice has positive effects on the growth of polar cod in the Barents Sea despite previous observations of a stagnating stock biomass and decreasing stock abundance. Our results contribute to identifying mechanisms by which climate variability affects the polar cod population, with implications for our understanding of how future climate change may affect Arctic ecosystems.

中文翻译：

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在巴伦支海中，海冰，温度和猎物对主要北极鱼Boreogadus saida的平均长度的年度变化的影响

北极的海洋条件正在发生变化，海冰覆盖减少，海温升高。但是，我们对该地区海洋人口的影响的了解有限。在这里，我们重点研究极地鳕鱼（Boreogadus saida）。极地鳕鱼是将能量从浮游动物转移到北极食物网中较高营养水平的重要鱼类。我们分析了极性鳕鱼群（0–4岁）的年龄的30年数据系列与海面温度，海冰浓度，猎物生物量，捕食者指数以及先前的年龄长度之间的关系。使用多元线性回归。多个年龄的结果表明，高年龄段与上一年的低海冰浓度和高年龄段显着相关。仅1岁年龄段的长度显示与猎物生物量呈正相关。我们的研究结果表明，尽管先前观察到种群生物量停滞和种群数量减少，但退缩海冰对巴伦支海极地鳕鱼的生长具有积极影响。