I'd also maybe grab a bottle of the water you catch them in, and if you do not have the test kits, take it to your nearest good aquarium store where you live- preferrably an aquarium dealer that has brackish and marines and get them to test the water for the usuals like:pH, hardness, S.G, salinity etc. If yu have a cannister- set it up and if you are experienced then you know you need to cycle the tank for a week or two at least ( if just using shellgrit/sand etc). Take the temp of the water where you catch them too. Biggest issue is stress, and feeding. Not unworkable, but other than the "cool" factor- any reason why you can't just set traps or net the day you go fishing?....
Love aquariums, almost more than fishing!