Jellyfish attacks leave a harmful legacy, study finds

An article published recently in the scientific journal Aquaculture Environment Interactions show that the economic consequences of a jellyfish incident can be quite long lasting.

 

The past year has seen an increase in jellyfish zooplankton incidents (jellyfish and related organisms) causing fish kills and economic losses to aquaculture companies, particularly in Norway.

 

The report says the stingers in their tentacles can injure and even kill fish in pens. Although precautions against jellyfish blooms are increasingly used, the effects of jellyfish tentacles, which can easily break off and float around, have not been taken into account.

 

These floating tentacles with active stingers can injure fish even after the jellyfish swarm has left the area, but for how long was unknown. In this study, it was indirectly assessed how long these tentacles of a lion’s mane jellyfish (l. Cyanea capillata), can continue to injure fish in pens after they are released from the jellyfish themselves.

 

The experiments were carried out at the Icelandic University of Science and Technology’s experimental station in Sandgerði in breeding tanks, with tentacles that were cut from fin whales that were collected in Eyjafjörður in late summer.

 

The tentacles and thus the sting cells remained fully capable of trapping the brine shrimp Artemia salina for 24 days, and are therefore capable of injuring fish in pens during that time. The tentacles then stopped being able to catch prey from the 26th day onwards.

 

This is thought to be the first scientific evidence showing how long the sting cells in the jellyfish tentacles are active after they are torn from the main body.

 

It is important to keep this information in mind when assessing risks and designing preparedness for jellyfish around aquaculture, say the authors.

 

Detached tentacles of lion’s mane jellyfish Cyanea capillata can injure aquaculture fish (Sigurdsson, Lüskow, Gislason and Svavarsson, Aquaculture Environment Interactions, October 2024).