Invasive Fish Species Have Larger Trophic Niches Than Native Fish, According to Study Using IRMS

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A new study analyzed the trophic niches and niche overlap between native and introduced cyprinid fishes in Karacaören I reservoir using IRMS.

A recent study, published in Spectroscopy Letters and conducted by Nehir Kaymak and colleagues at Akdeniz University in Turkey, has revealed that non-native fish species have larger trophic niches than native fish (1). The researchers studied the Karacaören I reservoir, where non-native cyprinid fishes, Carassius gibelio and Cyprinus carpio, have been introduced, along with native species Capoeta antalyensis and Squalius fellowesii. By analyzing stable carbon and nitrogen isotopes using isotope ratio mass spectrometry (IRMS), the researchers evaluated the trophic structure and interspecies trophic interactions of these fish.

IRMS is an analytical technique that measures the isotopic composition of a sample including proteins, nucleic acids, lipids, and carbohydrates. It works by ionizing molecules in the sample and separating them based on their mass-to-charge ratio. The ion beams are then detected and measured, providing information on the isotopic composition of the sample. IRMS can be used to measure a wide range of elements, including carbon, nitrogen, oxygen, sulfur, and hydrogen, and can provide information on a variety of sample types, including organic compounds, minerals, and gases. IRMS is used in a wide range of fields, including environmental science, geochemistry, biology, and forensics.

IRMS is often combined with liquid chromatography (LC) or gas chromatography (GC) to enable the analysis of compound-specific isotope ratios (CSIA). This allows for the identification and quantification of specific compounds and their isotopic composition, which can provide valuable information about sources and processes in various fields such as environmental science, food science, and forensics.


The study found that while all food sources contributed to the biomass of all fish species in the summer, their biomass was supported by more specialized sources in the winter season. In the summer, there was an increased niche breadth with increased niche overlap between C. antalyensis and C. gibelio, and C. carpio, and among C. gibelio and C. carpio, whereas in the winter season, there was a decreased niche breadth with decreased niche overlap. The researchers suggest that interspecific competition has led to trophic niche divergence, which may facilitate the coexistence of native species with introduced fishes.

The results also showed that non-native fish had larger niche widths, which may contribute to their invasion success. This study highlights the importance of understanding the potential effects of non-native species on ecologically similar native species and the significance of revealing their trophic relationships. Further research is needed to understand the potential long-term effects of non-native species on the ecosystem and how to manage their impacts.


(1) Kaymak, N.; Emre, N.; Yanim, F. B.; Toslak, C.; Emre, Y.; Akin, S. Seasonal variation in trophic niches and niche overlap between native and introduced cyprinid fishes. Spectrosc. Lett. 2023. DOI: