engleski

Recent Invasion of the Karstic River Systems in Croatia Through Illegal Introductions of the Signal Crayfish

The signal crayfish, Pacifastacus leniusculus (Dana), is one of the most successful crayfish invaders in Europe. In this study, we report the first evidence of its range expansion into a karstic river in Croatia (Korana River) through deliberate introduction. In order to estimate the extent of this recent invasion and its potential threat to existing native crayfish populations, we examined distributional and population characteristics of signal crayfish in the Korana River. Research showed that the current distribution of signal crayfish in the Korana River is localized within 10 km of its lower reach. The point of introduction was probably at the centre of the invaded area, where the highest catch per unit effort was recorded. Due to the proximity to the confluence with other rivers, the downstream invasion edge represents the most important corridor for further signal crayfish expansion throughout the Sava River Basin. In the invaded area, P. leniusculus is gradually displacing the native Astacus leptodactylus, which was absent from sites with high P. leniusculus abundance, and showed two to ten times lower abundance in mixed populations at both invasion fronts. Spatial analyses demonstrated that two additional native species present in the Korana catchment are under immediate threat from signal crayfish dispersal.

distribution; illegal introductions; mixed population; signal crayfish

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