Identifying migratorySalmo trutta using carbon and nitrogen stable isotope ratios

Abstract

Many Salmo trutta populations consist of non‐anadromous (freshwater‐resident) brown trout and anadromous (sea‐run migratory) sea trout. Although adult brown trout and sea trout can usually be identified using differences in size and body colouration, it is not possible to easily identify eggs/alevins as the progeny of brown trout or sea trout. In this study we show that δ13C and δ15N, measured using a continuous flow isotope ratio mass spectrometer (CF‐IRMS), can accurately identify fish eggs as the progeny of freshwater‐resident (δ13C(egg) = −25.7 ± 1.9‰,δ15N(egg) = 9.2 ± 1.8‰) or migratory (δ13C(egg) = −19.9 ± 1.1‰, δ15N(egg) = 14.3 ± 1.5‰) adult female Salmo trutta. Case studies show that stable isotope analysis is a more reliable technique for distinguishing anadromous adult fish than differentiation using morphological characteristics. For example, stable isotope analysis of brown trout from Loch Eck, Scotland, revealed that some individuals possessed δ13C and δ15N signatures indicative of marine feeding despite visual identification as freshwater‐resident fish. It is most likely that these fish are misidentified sea trout although it possible that these fish may be brown trout that have adopted an estuarine feeding strategy to avoid interspecific competition for food within Loch Eck with salmon, powan and Arctic charr. Most stable isotope studies of fish ecology use terminal tissue sampling to provide sufficient biological material for isotopic analysis; however, our study suggests that adipose fin tissue could provide a comparable measure of δ13C and δ15N. Such a strategy would be invaluable when studying the trophic ecology or migration patterns of fish of high conservation value. Copyright © 2000 John Wiley & Sons, Ltd.

Use of Isotope Ratio Mass Spectrometry (IRMS) Determination (18O/16O) to Assess the Local Origin of Fish and Asparagus in Western Switzerland

“…This distribution is due to different factors such as multiple distillation/dilution due to evaporation and rainfall; this effect was first reported in 1935 by Dole, [1] who provided the early analytical evidence of heavy isotopes in Lake Michigan water. Since this discovery, analytical methods have been proposed to perform the measurement of 18 O/ 16 O ratio of water at different positions on Earth. One of the methods is to use the capacity of CO 2 to dissolve in water.…”

“…Besides climate and rainfall studies, this method has also been applied to characterise isotopic water composition in living organisms. For example the isotopic water composition of plants grown under different growth conditions has been studied; Dunbar and Wilson [5] showed that 18 O/ 16 O isotopic distribution analysis in water extracted from plants revealed a higher concentration of heavy isotopes ( 18 O) than the groundwater: " 18 O/ 16 O measurements performed on water extracted from vari ous sections of grown plants, showed that the enrichment was found to occur in the following order: leaves > fruit > stem ≥ ground water." The authors indicate "that the physical process causing this enrich ment was probably evaporation, i.e.…”

Neolithic farmers or Neolithic foragers? Organic residue analysis of early pottery from Rakushechny Yar on the Lower Don (Russia)

“…Anadromous fish spend most of their lives in the sea and ocean and migrate into riverine habitats to spawn (Zydlewski and Wilkie 2012 ). Therefore adult anadromous fish, having fed mainly in the marine environment, maintains a relatively enriched δ 13 C signature even when caught up-river (McCarthy and Waldron 2000 ). Sturgeons are the third most represented species in the fishbone assemblage (Zabilska-Kunek 2019 ).…”

Effects of Tissue Preservation on Carbon and Nitrogen Stable Isotope Signatures in Syngnathid Fishes and Prey

“…The disadvantage of sampling fish muscle is that small specimens must be sacrificed [50]. However, there are alternative tissues that do not entail fish killing, providing isotopic signatures highly correlated to those in muscle [15,45,51]. Compared to many teleost, syngnathids are small fishes and their fins are difficult to sample, especially in small specimens.…”