Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
Glenora Fisheries Station, Ontario Ministry of Natural Resources and Forestry, R.R. #4, Picton, Ontario, K0K 2T0, Canada.
Rapid Commun Mass Spectrom. 2021 Jun 30;35(12):e9093. doi: 10.1002/rcm.9093.
Chemical lipid extraction or using alternative tissues such as fish fin as opposed to muscle may alter isotopic ratios and influence interpretations of δ C, δ N, and previously unassessed δ S values in stable isotope analyses (SIA). Our objectives were to determine if lipid extraction alters these isotope ratios in muscle, if lipid normalization models can be used for lipid-rich salmonids, and if fin isotope ratios are comparable with those of muscle in adult salmonids.
In six adult salmonid species (n = 106) collected from Lake Ontario, we compared three isotope ratios in lipid-extracted (LE) muscle with bulk muscle, and LE muscle with fin tissue, with paired t-tests and linear regressions. We compared differences between δ C values in LE and bulk muscle with predicted values from lipid normalization models and the log-linear model of best fit and determined model efficiency.
The δ N values in LE muscle increased (<1‰) relative to bulk muscle for most salmonids, with relationships nearing 1:1. There were either no differences or strong 1:1 relationships in δ S values between species-specific bulk and LE muscle. One lipid normalization model had greater model efficiency (97%) than the model of best fit (94%). Fin had higher δ C values than LE muscle while δ N trends varied (<1‰); however, both isotope ratios had either no or weak linear relationships with fin and LE muscle within species. The δ S values in fin were similar to those in LE muscle and had strong 1:1 relationships across species.
We recommend using the lipid normalization model to adjust for δ C values in lipid-rich muscle (C:N >3.4). LE muscle could be used without δ N or δ S adjustments, but the minimal increase in δ N values may affect SIA interpretation. With high unexplained variability among adult species in fin-muscle δ C and δ N relationships, species-specific fin-muscle adjustments are warranted. No fin-muscle tissue adjustment would be required for δ S values.
与肌肉相比，化学脂质提取或使用替代组织（如鱼鳍）可能会改变同位素比值，并影响稳定同位素分析（SIA）中 δ C、δ N 和以前未评估的 δ S 值的解释。我们的目标是确定脂质提取是否会改变肌肉中的这些同位素比值，脂质归一化模型是否可用于富含脂质的鲑鱼，以及鱼鳍的同位素比值是否与成年鲑鱼肌肉中的同位素比值相当。
在从安大略湖采集的六个成年鲑鱼物种（n = 106）中，我们比较了三种脂质提取（LE）肌肉与大块肌肉、LE 肌肉与鳍组织的同位素比值，使用配对 t 检验和线性回归。我们比较了 LE 和大块肌肉中 δ C 值与脂质归一化模型和最佳拟合的对数线性模型的预测值之间的差异，并确定了模型效率。
对于大多数鲑鱼来说，LE 肌肉中的 δ N 值相对于大块肌肉增加（<1‰），且关系接近 1:1。特定物种的大块和 LE 肌肉之间的 δ S 值要么没有差异，要么存在很强的 1:1 关系。一个脂质归一化模型的模型效率（97%）高于最佳拟合模型（94%）。鱼鳍的 δ C 值高于 LE 肌肉，而 δ N 趋势不同（<1‰）；然而，在同种内，两种同位素比值与鱼鳍和 LE 肌肉之间要么没有或线性关系较弱。鱼鳍的 δ S 值与 LE 肌肉相似，且在不同物种之间具有很强的 1:1 关系。
我们建议使用脂质归一化模型来调整富含脂质的肌肉（C:N >3.4）中的 δ C 值。LE 肌肉可以在不进行 δ N 或 δ S 调整的情况下使用，但 δ N 值的微小增加可能会影响 SIA 解释。由于成年物种之间鱼鳍-肌肉 δ C 和 δ N 关系的高度不可解释变异性，需要进行特定物种的鱼鳍-肌肉调整。对于 δ S 值，不需要进行鱼鳍-肌肉组织调整。
