Beaudoin Catherine P, Tonn William M, Prepas Ellie E, Wassenaar Leonard I
Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada e-mail:
Environment Canada, National Water Research Institute, 11 Innovation Blvd, Saskatoon, SK, S7N 3H5, Canada, , , , , , CA.
Oecologia. 1999 Aug;120(3):386-396. doi: 10.1007/s004420050871.
Northern pike (Esox lucius) are often considered to be specialist piscivores, but under some circumstances will continue to eat invertebrates as adults. To examine effects of fish assemblage composition on the trophic ecology of pike, we combined stable isotope analysis (SIA) of carbon and nitrogen and stomach content analysis (SCA) on pike from five lakes in northern Alberta, three of which contain only pike ("pike-only") and two that also contain yellow perch (Perca flavescens) or white sucker (Catostomus commersoni) ("pike-other"). Fish were more important as prey and empty stomachs, which often characterize piscivores, were significantly more frequent in pike-other than in pike-only lakes. However, even though invertebrates were more important for pike in pike-only lakes, SIA and SCA indicated that invertebrates were also an important component of pike diets in pike-other lakes. SIA and SCA also revealed considerable intrapopulation variation in trophic ecology, with individuals in some populations differing by as much as two trophic levels. Comparisons of stomach contents and isotope signatures of the same fish suggested that within these variable populations, specialization on invertebrates or fish was a long-term trait of some individuals. SIA indicated that trophic position increased and diets shifted to a greater importance of littoral prey as pike grew in pike-only lakes, but not in lakes with other fish present. Trophic adaptability in northern pike is expressed at both the population level, where the trophic ecology is sensitive to differences in prey regimes, and at the organismal level, in the form of intrapopulation variation and individual specialization.
白斑狗鱼（Esox lucius）通常被认为是专性食鱼动物，但在某些情况下，成年后也会继续食用无脊椎动物。为了研究鱼类群落组成对白斑狗鱼营养生态学的影响，我们结合了对阿尔伯塔省北部五个湖泊中白斑狗鱼的碳和氮稳定同位素分析（SIA）以及胃内容物分析（SCA），其中三个湖泊只包含白斑狗鱼（“仅白斑狗鱼”），另外两个湖泊还包含黄鲈（Perca flavescens）或白吸盘鱼（Catostomus commersoni）（“白斑狗鱼-其他鱼类”）。鱼类作为猎物更为重要，而空腹（这通常是食鱼动物的特征）在有其他鱼类的白斑狗鱼湖泊中比仅白斑狗鱼的湖泊中更为常见。然而，尽管在仅白斑狗鱼的湖泊中无脊椎动物对白斑狗鱼更为重要，但SIA和SCA表明，在有其他鱼类的白斑狗鱼湖泊中，无脊椎动物也是白斑狗鱼饮食的重要组成部分。SIA和SCA还揭示了营养生态学中相当大的种群内变异，一些种群中的个体在营养级上相差多达两个营养级。对同一条鱼的胃内容物和同位素特征的比较表明，在这些可变种群中，对无脊椎动物或鱼类的专化是一些个体的长期特征。SIA表明，在仅白斑狗鱼的湖泊中，随着白斑狗鱼的生长，营养级升高，饮食转向沿岸猎物更为重要，但在有其他鱼类的湖泊中并非如此。白斑狗鱼的营养适应性在种群水平上表现为营养生态学对猎物模式差异敏感，在个体水平上则表现为种群内变异和个体专化。
