compass jellyfish

<em>Chrysaora hysoscella</em>, the compass jellyfish, is a large scyphozoan medusa in the family Pelagiidae widely distributed in the northeastern Atlantic Ocean and North Sea, with documented presence in the coastal waters of Belgium, Denmark, Norway, and Sweden, as well as along the coasts of the British Isles and into the Mediterranean. It is named for the distinctive brown, V-shaped radiating markings on its umbrella that resemble a mariner's compass rose. The bell of an adult compass jellyfish typically reaches 30 to 60 centimetres in diameter, though larger individuals are recorded. It is a voracious predator of zooplankton, fish eggs, larvae, small fish, and other jellyfish, trailing long tentacles armed with stinging nematocysts to capture prey. The compass jellyfish is a pelagic species, drifting with ocean currents through coastal and shelf waters during the summer months before dying back in autumn. Populations can form dense seasonal blooms that may impact local fisheries and aquaculture operations. It is Not Evaluated on the IUCN Red List, consistent with its broad distribution and lack of targeted exploitation. Biological traits including precise lifespan, growth rates, and population trend data remain poorly documented for this species. Water temperature and plankton availability are believed to influence bloom intensity from year to year.