Monday, 21 July 2025 How Does the Invasive Goldfish Affect Native Dragonfly Species?

A new study from the Department of Biodiversity, led by Assoc. Prof. Jure Jugovic in collaboration with Assist. Prof. Martina Lužnik reveals how the presence of the invasive goldfish (Carassius auratus) impacts dragonflies in sub-Mediterranean ponds.

Researchers compared ponds with and without goldfish and found that their presence in karst ponds threatens both the diversity and abundance of damselflies! In addition to reduced species richness and numbers, dragonflies in goldfish-inhabited ponds show changes in body shapes and defensive structures of their nymphs (e.g., longer spines); a higher resistance of large predatory species (e.g., Anax imperator) that can successfully withstand the presence of fish; and a complete absence of some sensitive dragonfly species, such as the willow emerald damselfly (Chalcolestes viridis) and the white-legged damselfly (Platycnemis pennipes).

Since ponds in karst areas are crucial habitats for many aquatic organisms, the widespread presence of goldfish, confirmed in as many as 33% of ponds (Lužnik et al. 2022), poses a serious threat to biodiversity. 
These findings highlight the significant ecological consequences of introducing non-native species and the importance of preserving natural, fish-free habitats.

The full article is available in the journal Hydrobiologia: https://doi.org/10.1007/s10750-025-05926-x