Well, there are two kinds of organisms: osmoregulators, that can regulate the level of salt and the salinity does not affect them (an example is salmon: for salmon this sentence is true. Generally, for most fish this sentence is true)
However, for some species, such shark - osmoconformers - this is false: they are affected by the salinity. in general I would conclude that This is false: the marine salinity DOES affect the fish (and other organisms) living there.
