SalmonJellyfish that caused mass farmed salmon deaths making a troubling return to NorwayThis particular jellyfish species led to mass deaths in 1997 and 2001."During the last 20 years, we have only seen these many sightings in 2021 and 2022," the Norwegian Institute of Marine Research jellyfish scientist Tone Falkenhaug said.Foto: Erling Svensen / HavforskningsinstituttetTorhild M. MartinussenHanna Gezelius