Idk do you all do your own writeups on the animals? I'll summarise

Found in the NE Pacific ocean. It's a type of blenny that lives in shallow ocea (up to _75m/210ft deep) but also apparently tolerates brackish and freshwater. They grow roughly 30cm/1ft long. They look kinda froggy n cute when their huge mouth is closed.

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The whole umbrella mouth thing is a display of territorial aggression. Often seen when the fish fight over favourable nooks and crannies on the ocean/riverbed to settle into.

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Not sure how reliable this site is but it appears to cite some sources, it also explains that the name 'sarcastic' comes 'from the Greek word sarkázein, which means ‘to tear flesh’ – referring to their aggressive behaviour'