Nowadays, pond ecosystems face many negative effects – from eutrophication, through biodiversity loss, to biological invasions. Biological invasions have a negative impact on the functioning of ecosystems; additionally, invasions are costly. Topmouth gudgeon (Pseudorasbora parva), a small omnivorous fish introduced from Asia, is one of the invasive species that established stable populations throughout Europe and troubles both conservation authorities and fish farmers. Our study aimed to investigate the adverse ecosystem and production impacts that the presence of topmouth gudgeon in the pond ecosystem may cause.
Our results showed a significant top-down effect of topmouth gudgeon on planktonic crustaceans, especially large Daphnia, and other cladocerans, calanoids, and cyclopoids. Large daphnids are an important transformation link in lentic waters, utilizing the primary production of algae and microbial production of bacteria and protozoans. Therefore, in the absence of large daphnids, the flow of nutrients and energy to farmed fish is significantly reduced. Besides that, another consequence of the decreased filtering activity of planktonic crustaceans might be poor water quality. The low density of daphnids might bring about a reduced growth rate of common carp as well as an increased feeding pressure on food organisms inhabiting the pond bottom (zoobenthos). We assume that topmouth gudgeon has a considerable competitive pressure on commercially reared common carp – after eliminating planktonic crustaceans, the carp "switches" to other food sources, which is reflected in lower biomass and the density of bottom-dwelling invertebrates in ponds where topmouth gudgeon occurred.
More detailed information can be found in the original article: Kajgrová, L., Blabolil, P., Drozd, B., Roy, K., Regenda, J., Šorf, M., & Vrba, J. (2022). Negative effects of undesirable fish on common carp production and overall structure and functioning of fishpond ecosystems. Aquaculture 549, 737811. https://doi.org/10.1016/j.aquaculture.2021.737811
Besides the publication mentioned above, we wrote a popularization article that provides information on topmouth gudgeon to the general public – briefly describes its appearance, distribution, negative impacts on aquatic ecosystems, and possible elimination options and legislative aspects. The article is available online here.
Napsala: Ing. Lenka Kajgrová