Abstract
Stable isotope analysis (SIA) measurements from long-term captivity studies provide required parameters for interpretation of consumer SIA data. We raised young-of-the-year (14–19 cm) California yellowtail (Seriola dorsalis) on a low δ15N and δ13C diet (pellet aquaculture feed) for 525 days, then switched to a high δ15N and δ13C diet (mackerel and squid) for 753 days. Yellowtail muscle was sequentially sampled from each individual after the diet switch (0 to 753 days) and analyzed for δ15N and δ13C, allowing for calculation of diet-tissue discrimination factors (DTDFs) from two isotopically different diets (low δ15N and δ13C: pellets; high δ15N and δ13C: fish/squid) and turnover rates of 15N and 13C. DTDFs were diet dependent: Δ15N = 5.1‰, Δ13C = 3.6‰ for pellets and Δ15N = 2.6‰, Δ13C = 1.3‰ for fish/squid. Half-life estimates from 15N and 13C turnover rates for pooled yellowtail were 181 days and 341 days, respectively, but varied considerably by individual (15N: 99–239 d; 13C: 158–899 d). Quantifying DTDFs supports isotopic approaches to field data that assume isotopic steady-state conditions (e.g., mixing models for diet reconstruction). Characterizing and quantifying turnover rates allow for estimates of diet/habitat shifts and “isotopic clock” approaches, and observed inter-individual variability suggests the need for large datasets in field studies. We provide diet-dependent DTDFs and growth effects on turnover rates, and associated error around these parameters, for application to field-collected SIA data from other large teleosts.
Highlights
Fundamental understanding of fish biology, feeding behavior, population dynamics, and movement patterns has expanded in recent years due to technological advances in tools such as electronic tags for animal tracking[1,2], chemical tracer analyses[3], and ‘big data’ analysis[4,5]
By modifying the constants in Eqs. 6 and 7 (Caut et al 2009) to fit results here, we provide predictive equations for diet-tissue discrimination factors (DTDFs) of yellowtail based on diet δ15N and δ13C values:
We reared a large teleost in semi-controlled conditions to provide DTDFs and isotopic turnover estimates, which are relatively rare due to the difficulty of large fish husbandry and the timeframes required for such experiments
Summary
Fundamental understanding of fish biology, feeding behavior, population dynamics, and movement patterns has expanded in recent years due to technological advances in tools such as electronic tags for animal tracking[1,2], chemical tracer analyses[3], and ‘big data’ analysis[4,5]. Captive studies in fish have shown muscle isotopic turnover rates as low as several days (young-of-the-year [YOY] winter flounder Pseudopleuronectes americanus20) to months (summer flounder Paralichthys dentatus, arctic sculpin Myoxocephalus scorpioides21,22) to > 1 year (mado Atypichthys latus, Pacific bluefin tuna Thunnus orientalis[23,24]) These differences are largely driven by fish size and life-stage; since relative growth (proportion of new mass to initial mass over time) is a primary driver of isotopic turnover dynamics, turnover rates will vary with relative growth rates ontogenetically (faster turnover in younger fish) and inter- (faster turnover in fish with high growth rates). Measured SIA values in fish that recently migrated allow retrospective reconstructions of large-scale movements, such as entire river migrations by lake sturgeon (Acipenser fulvescens)[33] and transPacific migrations by Pacific bluefin tuna[34] Accuracy of these migratory timeframes is maximized with accurate species-specific isotopic turnover rates, which are best calculated from laboratory experiments
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
