Abstract
Biological invasions are crucial issues worldwide and marbled crayfish (Procambarus virginalis, Lyko 2017) is one of the examples of freshwater invaders spreading across Europe and beyond. Marbled crayfish has high growth rate and reproduces via parthenogenesis, making it unique among other decapod species. Even though it is a warm water species, they can resist colder temperatures and are highly adaptable. Furthermore, it is also a vector for Aphanomyces astaci, causing crayfish plague. Due to its high adaptability, fast growth and reproduction, since one individual is enough to start a new population, it is important to understand its invasion ecology in order to implement better management plan in the new invaded ecosystems. In this thesis the main goal was to assess whether the temperature is the main factor of marbled crayfish establishment and distribution in the artificially warm outflow channel of Balti Power Plant in Narva. We hypothesised to find temperature gradient along the channel which reflects marbled crayfish distribution and trophic niche. We analysed marbled crayfish and their potential food sources for stable carbon (13C) and nitrogen (15N) isotopes to assess its trophic niche. Temperature data did not show the gradient in the channel, however the channel was significantly warmer than Narva Reservoir. Stable isotope results showed change in marbled crayfish diets and trophic niche along the channel and between seasons, indicating a shift from enriched carbon to depleted carbon values from head to mouth of the channel and a shift from high to lower trophic level from spring and summer to autumn. Moreover, results showed diets being similar in head and middle of channel where crayfish mostly rely on macroinvertebrates and macrophytes, while in the mouth of the channel diet seems to shift more towards periphyton. Diet also changed from protein-rich in spring to vegetation-based diet in autumn. Based on the results, temperature had important role in the marbled crayfish establishment in the invaded channel, however the distribution of its population might have been affected by ecological aspects rather than temperature, like better food availability in the head of the channel.
Keywords: invasive species • trophic niche • temperature • Procambarus virginalis • stable isotopes
Note: Embargoed until 3 September 2021.
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