Estimating in situ isotopic turnover in Rainbow Trout (Oncorhynchus mykiss) muscle and liver tissue

Abstract

Stable isotope analysis (SIA) is a powerful tool for assessing food webs and diet. However, the underlying assumptions that stable isotope ratios in an organism's tissues reflect that of its present diet may be complicated by isotopic turnover and retention time. Quantification of in situ isotopic turnover of study organisms and different tissues via field studies is essential to inform scientifically sound food web and diet studies utilizing SIA. Rainbow Trout white muscle and liver tissue were collected monthly from North Twin Lake, Washington during the 2013 growing season. Using ANCOVAs, we estimated stable carbon retention time of 154 (95% CI: 106-224) and 292 (95% CI: 257-763) days for Rainbow Trout liver and white muscle, respectively. For nitrogen, we estimated a retention time of 186 (95% CI: 114-329) days for both white muscle and liver. Our analyses suggest longer isotopic retention times (and therefore slower isotope turnover rates) for adult fish in a natural system relative to those commonly reported in the literature. These findings can improve interpretation of SIA in future aquatic food web and diet studies involving adult coldwater fish in freshwater systems.

Seasonality can affect ecological interactions between fishes of different thermal guilds

“…Based on an ectotherm tissue-specific model with body mass as a variable, the isotopic half-life of liver tissue samples from a fish of average weight in our study is 52 days (Vander Zanden et al, 2015). Further, an in situ study of rainbow trout (Oncorhynchus mykiss) found that it takes ∼5-6 months for the liver tissue of a consumer to be at equilibrium with the stable isotope signature of a new diet (Skinner et al, 2017). Stable isotope turnover time may be slower in the winter than in the fall, spring, and summer because cooler water can decrease the turnover time in fish (Maitland et al, 2021).…”

Population niche width is driven by within-individual niche expansion and individual specialization in introduced brook trout in mountain lakes

“…To test the relationship between short-term and longer-term diets, we compared our cross-sectional data from stomach contents to individual stable C and N isotope ratios which provide an integrative measure of diet over weeks to months (Peterson and Fry 1987 ; Bolnick et al 2002 ), with in situ measures of muscle tissue isotopic turnover exceeding 5 months in coldwater rainbow trout (Skinner et al 2017 ). We tested for a relationship between diet and muscle tissue stable isotope ratios using permutational analysis of variance (PERMANOVA) with diet composition as the multivariate response, and δ 13 C and δ 15 N values as explanatory variables using the ‘vegan’ package v2.5–6 in R (Oksanen et al 2019 ).…”

Broad Whitefish (Coregonus nasus) isotopic niches: Stable isotopes reveal diverse foraging strategies and habitat use in Arctic Alaska

“…Differences in δ 13 Cˈ between muscle and liver suggest that most individuals fed on prey with similar δ 13 C (+/-2.5‰) over weeks and months, while a few individuals switched to prey sources or locations with different δ 13 C. Previous research demonstrates differences in isotope turnover rates between liver and muscle tissue in fish [108][109][110] due to the association with metabolism rather than growth in liver tissue [108]. Hesslein et al estimated the half-life of δ 13 C and δ 15 N to be 101 days in juvenile Broad Whitefish muscle tissue, but due to slow growth in adult fish, it is likely that the turnover rate for muscle tissue could be years [27].…”