Tarpon spawn far offshore, miles and fathoms beyond the reach of the fly fisher, but before and after they are just off the beach and very accessible. Snook and Redfish release their eggs near the passes, probably to guarantee the maximum dispersion on the incoming tides. This migration toward saltier water may also be nature's way of maximizing dispersion due to higher egg buoyancy in salty water. Seatrout on the other hand spawn very close to the grassy flats where they live, probably to ensure that the fry will find cover in those very same grasses. All four of these species are very tolerant of high concentrations of fresh water, but when it's time to spawn they all migrate toward the salt.
Comfort is of paramount importance to all species.
Water temperature is one of the factors because it has a dominant effect on the fish's bodily functions. Each species has different limits however. At the other end of the scale, Snook seem to do well with water temperatures in the high 80's, while Tarpon, Redfish and especially Seatrout are beginning to get uncomfortable. Thus, each species has a comfortable temperature range of about 15-20 degrees and when these limits are exceeded the fish want to move elsewhere. Keep in mind that the Gulf water temperatures posted on the local radio and TV stations are indeed Gulf temperatures, away from the beach and a few feet down.