Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, R3T 2N6, Canada.
Integrative Biology, University of Windsor, Windsor, ON, N9B 3P4, Canada.
Oecologia. 2023 Jul;202(3):601-616. doi: 10.1007/s00442-023-05423-9. Epub 2023 Jul 24.
Within and among species variation in trophic and habitat shifts with body size can indicate the potential adaptive capacity of species to ecosystem change. In Arctic coastal ecosystems, which experience dramatic seasonal shifts and are undergoing rapid change, quantifying the trophic flexibility of coastal fishes with different migratory tactics has received limited attention. We examined the relationships among body length and condition (Fulton's K, phase angle from Bioelectrical Impedance Analysis) with trophic and habitat shifts (differences in δN and δC between blood tissues with different turnover rates) of two abundant and culturally important species, anadromous Arctic char (Salvelinus alpinus, n = 38) and sedentary Greenland cod (Gadus ogac, n = 65) during summer in coastal marine waters near Ulukhaktok, Northwest Territories, Canada. Habitat shifts (δC) increased with length (i.e., pelagic to benthic-littoral) and crossed-equilibrium (zero) at mid-sizes for both species. Seasonal trophic shifts (δN) were generally positive (i.e., increasing trophic level) for Arctic char and negative for Greenland cod. As hypothesised, intra-individual variation in size-based trophic shifts (δN-length residuals) increased with length for Arctic char. However, there were no trends with length in Greenland cod. Our findings highlight the importance of flexibility through ontogeny and mobility for Arctic char, whereas Greenland cod were generalist to localized prey and habitat across all sizes. The significant effect of body condition (phase angle) on size-based trophic shifts in Arctic char, and size-based habitat shifts in Greenland cod, highlight the potential trade-offs of contrasting life history strategies and capacity for ontogenetic niche plasticity.
种内和种间的营养级和生境转变随体型变化，可以表明物种对生态系统变化的潜在适应能力。在北极沿海生态系统中，季节性变化剧烈，且正经历快速变化，量化具有不同洄游策略的沿海鱼类的营养级灵活性受到了有限的关注。我们研究了体型（体长和肥满度，用费氏 K 值和生物电阻抗分析的相位角表示）与营养级和生境转变（血液组织中不同周转率的 δN 和 δC 之间的差异）之间的关系，这两个变量分别代表两种丰富且具有文化重要性的物种，即溯河洄游的北极红点鲑（Salvelinus alpinus，n = 38）和定居性格陵兰鳕鱼（Gadus ogac，n = 65）在加拿大西北地区的乌卢卢克托克（Ulukhaktok）附近沿海海域的夏季。生境转变（δC）随体长（即从洄游到底栖-沿岸）而增加，并在两个物种的中等体型处穿过平衡（零）。季节性营养级转变（δN）对于北极红点鲑通常为正值（即营养级增加），而对于格陵兰鳕鱼则为负值。正如假设的那样，基于个体的体型营养级转变（δN-体长残差）的个体内变异随体长增加而增加。然而，格陵兰鳕鱼的体长没有趋势。我们的研究结果强调了通过个体发育和移动性实现灵活性对于北极红点鲑的重要性，而格陵兰鳕鱼则是所有体型的通用型到局部性猎物和生境。身体状况（相位角）对北极红点鲑基于体型的营养级转变以及格陵兰鳕鱼基于体型的生境转变的显著影响，突显了对比鲜明的生活史策略和个体发育生态位可塑性的潜在权衡。
