Savvy offshore anglers know when dolphins (and sharks) are thick around rigs and wrecks the snapper hold tight to the structure and will not bite.
I have found the opposite to be true around jetty systems in relation to bull redfish. I have a spot at the Sabine Jetties that my friends and I have caught reds 40 inches or over at all but three times in around 150 trips since 1996. On those three occasions there were no dolphins feeding in the immediate area. The rest of the time we had dolphins working all around us.
I believe it has something to do with a shared food preference (probably large mullet) of the dolphins and bull reds. Dolphins could certainly kill and eat the reds but items that big are not on their list of favorites.
I absolutely love catching big bull redfish and if you want to turn someone on to saltwater fishing letting them catch one of these beasts is a good way to do it. Here are some pics of a trip my neighbor Ronnie Toney ad I took awhile back.