Fishing Regulations - Learning The Rules
In order to fish in Argentina a personal fishing license is required by law in continental Patagonia, however in some providences in Argentina the rivers and Atlantic Ocean are still widely unregulated much like the salt water is in the United States. In Patagonia one can purchase a license at the airport in Bariloche, or at many local fly shops. They vary in price depending on whether you are resident or non-resident. There is no fishing after dark which is one important rule to remember also specific additional licenses are required for well knowm access spots such as the mouth of the Correntoso river and the mouth of the ChimehuĂn river and all access to Rio Grande to name a few. It is also important to pay close attention to the fly fishing only zones which are marked with big blue signs throughout the zone. It is also a good idea to clean and disinfect your waders and wading boots before coming overseas to not introduce exotic species which could harm the ecological balance and biodiversity to the stream systems. For all regulations and local restrictions be sure to consult your local fly shop, or go to this website www.aapm.org.ar and Patagonia will reward you.

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Alex - is only 1 license required for most regions? for example .. only 1 license allows me to fish for dorado outside of buenos aires and also down south in public access patagonia rivers? ..
Great question and extremely difficult to explain the short answer is no from what I understand as they are totally two different jurisdictions. Here is a great link will help explain some of the reason why.
http://www.fish.wa.gov.au/docs/events/ShareFish/papers/pdf/presentations/Present-PabloVigliano.pdf