RESUMO
Cassiopea jellyfish have successfully invaded several marine ecosystems worldwide. We investigated if Cassiopea andromeda grows larger (umbrella size) and if their populations are more stable in shrimp farms than in mangroves in the Brazilian coast. Our results show that jellyfish abundance is higher in the shrimp farm during the rainy season and in the mangrove during dry season. The population is stable during both seasons in the shrimp farm, but unstable in the mangroves, as jellyfish are absent during rainy season. Shrimp farm-associated jellyfish are three times larger than those in the mangroves, regardless of season. We recorded the largest (49.2 cm of umbrella diameter) ever C. andromeda individual in the shrimp farm. Unlike the mangroves, the shrimp farm provides environmental intra-annual stability that promotes jellyfish growth and population persistence. Therefore, C. andromeda populations can be seasonally dynamic and artificial environments such as aquaculture facilities may facilitate the invasion process.