<P> As jellyfish are not true fish, which are vertebrates, the word jellyfish is considered by some to be a misnomer . Public aquaria often use the terms jellies or sea jellies instead . The term "jellies" may have become more popular than "jellyfish". In scientific literature, "jelly" and "jellyfish" are often used interchangeably . Some sources may use the term "jelly" to refer to organisms in this taxon, as "jellyfish" may be considered inappropriate . </P> <P> Many textbooks and sources refer to only scyphozoans as "true jellyfish". </P> <P> A group of jellyfish is sometimes called a bloom or a swarm . "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to seasonal increases, or numbers beyond what was expected . Other collective names for a group of jellyfish are "fluther" and "smack," though neither term is commonly used by scientists who study jellyfish . Jellyfish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large numbers, even when an ecosystem is in balance . Using "swarm" usually implies some kind of active ability to stay together, which a few species such as Aurelia, the moon jelly, demonstrate . </P> <P> Medusa jellyfish may be classified as scyphomedusae ("true" jellyfish), stauromedusae (stalked jellyfish), cubomedusae (box jellyfish), or hydromedusae, according to which clade their species belongs . </P>

What do you call a group of jelly fish