I can't answer your question but I will provide my experience.
I have a large drainage ditch which is my north boundary. The area that it drains is the top of a salt dome which was once the site of a large sulfur mine. The site is now used for underground storage and brine production. The salinity in the ditch usually stays between 500 and 800 ppm. I have seen it peak around 3000 ppm when they had a leak on one of the brine lines. There are large pools along the gully that hold water all year. I have caught LMB and BG (many different variety and mixes), There is also an abundance of needle nose and alligator gar. I even caught a small blue crab in a minnow trap once which tells me it is salty enough for their reproduction since this ditch is well over 5 miles from even a brackish body of water.