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    Interactions of invasive pumpkinseed with a riverine endemic fish indicate trophic overlap but minimal consequences for somatic growth and condition
    (EDP Sciences, 2023) Karakuş, Uğur; Tarkan, Ali Serhan; Yalçın-Özdilek, Şükran; Top-Karakuş, Nildeniz; Partal, Nurbanu; Britton, John Robert
    The North American invasive fish pumpkinseed Lepomis gibbosus has been associated with some detrimental ecological consequences in some parts of its invasive range. Here, we tested the trophic interactions of pumpkinseed with the endemic stream fish Aegean chub Squalius fellowesii ('chub') in a Mediterranean-type water course in SW Anatolia, Turkey, using a bulk stable isotope approach (d13C, d15N). Seven sampling sites were able to be grouped as chub in pumpkinseed presence (n=2) and absence (n=3), and pumpkinseed in chub absence (n=2). Across these groups, stable isotope metrics revealed that chub trophic (isotopic) niche size was similar in pumpkinseed presence/absence, but pumpkinseed had a larger niche in chub presence. In sites where they are co-habited, their niches showed some convergence, but with no apparent consequences for their growth or body condition, suggesting there were minimal ecological consequences of this sharing of food resources. These results suggest that the trophic consequences of this riverine invasion of pumpkinseed on this endemic chub was minimal.
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    Öğe
    Trophic Interactions of Two Ponto-Caspian Gobies in the Turkish Part of Their Native Range
    (Central Fisheries Research Inst, 2018) Tarkan, Ali Serhan; Karakus, Ugur; Tepekoy, Erdi Gokhan; Top, Nildeniz; Ozdilek, Sukran Yalcin; Partal, Nurbanu; Britton, John Robert
    Several Ponto-Caspian gobiids have expanded from their native distribution ranges to Europe and North America. As knowledge on their bio-ecological features in their native range is still limited, the trophic ecology of monkey goby Neogobius fluviatilis and Western tubenose goby Proterorhinus semilunaris was studied in three natural lakes in the Marmara Region of NW Turkey using the stable isotopes of delta C-13 and delta N-15. In two of the lakes, the trophic niches ( as the isotopic niche) of the gobies were highly divergent with co-existing native fishes, with no overlap. Moreover, mixing models suggests considerable inter-specific dietary differences. In all lakes, the trophic niches of gobies were never significantly larger than those of coexisting fishes. These results suggest that when introduced outside of their natural range, the gobies might integrate into new fish communities via exploiting resources that are underexploited by native fishes or will initially share resources with these species before their niches diverge, perhaps through competitive displacement.