http://www.bajainsider.com/article/fishing-limits-mexico-–-hey-gringo-put-fish-back
found that...so maybe this is a loop hole. If i'm reading this correctly, technically i could catch fish with a net from shore (going to keep looking for info about bringing back across). I'm driving, not flying....
Fishing licenses
Before fishing in Mexican waters all anglers must have a valid Mexican Sport Fishing License. This license covers all types of fishing and is valid anywhere in Mexico. These licenses may be purchased by day, week, month or year. Purchasing a license for the vessel is no longer required.
The boat operators normally provide licenses for people fishing on charter sport fishing boats, check before you go. A fishing license is also required for underwater fishing.
A fishing license is not required when fishing from land.
Only one rod or line with hook is permitted in the water, per person,
but there is no restriction regarding the number of replacement items.
The fishing license allows you to capture only fin fish. It does not allow you to capture any mollusks or crustaceans, and their capture by anyone is strictly prohibited. Totuava, turtles and marine mammals are under protection of the Ministry and may not be captured at any time.
The exception to this rule is Marlin, Sailfish and Swordfish and Shark, of which only one (1) of each is allowed, and which counts as five (5) toward the overall ten (10) fish limit.
Additionally Dorado, Roosterfish, Shad, or Tarpon, of which only two (2) of each species are allowed, and which count as five (5) toward the overall 10 fish limit.
Like we said, a little confusing so here are some example of daily limits. Remember you can always come back tomorrow.