They are protected here now and the population is booming. Protection may have been lifted though, not sure. A diver I know kills them with a bangstick every chance he gets since they eat all the slipper lobster. No, I don't approve of what he does.
... It may not come directly from Judaism or Jews, but it does come from their cultural/religious practices. We first encounter the word in English in 1679: "The Jew fish crowds to be one of the first three of our most worthy Fish," wrote T. Trapham in his Discourse on the State of Health of Jamaica. It was only 18 years later that W. Dampier wrote "The Jew-fish is a very good Fish, and I judge so called by the English, because it hath Scales and Fins, therefore a clean Fish, according to the Levitical Law."
So based on Jewish dietary laws, Epinephelus itjara (and others), also known as the grouper, was fit for human consumption. The name jewfish was applied to several different species of fish, most belonging to the family Serranidae. These include Promicops guasa, Epinephelus nigritus, Megalops atlanticus, Aralichthys dentalus (all from the U.S. Atlantic coast), Stereolepis gigas (from the California coast), Polyprion americanus and Polyprion couchii (from the waters around Madeira), and Sciaena antarcitca and Glaucosoma hebraicum (from Australia).
Note that the last one, Glaucosoma hebraicum, contains the Latin adjective for "Hebrew".