In Estonia, invasive crayfish species from America, such as the signal crayfish (Pacifastacus leniusculus), spiny-cheek crayfish (Faxonius limosus), marbled crayfish (Procambarus virginalis), and narrow-clawed crayfish (Pontastacus leptodactylus), are spreading rapidly, posing a significant threat to native European crayfish by transmitting a deadly plague. Researchers at the University of Life Sciences are actively exploring methods to control these invasive species, though simple solutions remain elusive.
The Threat of Invasive Crayfish
The primary danger posed by these invasive crayfish is the plague they carry, which is almost always fatal to native European crayfish. According to Katrin Kaldre, a junior professor of aquaculture biology, the situation is worsening annually, with new outbreak sites being discovered frequently. Signal crayfish were first identified in Estonia in 2008 and are now found in twenty different water bodies. The marbled crayfish, first spotted in 2017, and the spiny-cheek crayfish, also found in 2017, are other significant threats. The narrow-clawed crayfish, detected in 2023, does not spread the plague but still competes with native species for resources.
Control Methods Explored
Chemical Control
Initially, researchers considered using chemicals to control the invasive species, drawing on experiences from the Norwegian Veterinary Institute. However, the Environmental Board denied permission due to the potential environmental impact, especially in flowing water bodies where poison could disperse uncontrollably.
Trapping and Electrofishing
Trapping is a common method, but it fails to capture smaller crayfish, allowing them to continue reproducing. Electrofishing was tested but proved ineffective as electric pulses do not reach crayfish hiding under rocks.
Biological Control
One promising method involves stocking water bodies with eels, which are natural predators of crayfish. Eels can reach crayfish in their burrows and are active at night when crayfish are most vulnerable. This method has shown some success in the Ropka Reservoir and Reo Quarry, and long-term monitoring will determine its overall effectiveness.
Ongoing Efforts and Future Outlook
The project, which started in 2021, has focused on intensive trapping and public awareness. While complete eradication of invasive crayfish is unlikely, combining multiple control methods could help manage their populations and protect native species. Continued research and monitoring, especially of biological control methods like eel stocking, are crucial to developing effective strategies.
In conclusion, Estonian researchers are dedicated to combating the invasive crayfish threat through a variety of methods, aiming to safeguard the native crayfish populations and maintain ecological balance in local water bodies.
More: https://news.err.ee/1609331331/estonian-scientists-combating-plague-spreading-invasive-crayfish
