I think you can read that part of the statute two ways; 1. That only need to have the fishing license or be a salt water fisherman... 2. That you need to have the fishing license and be carrying the knife for lawful fishing activities.
However, I think it's pretty clear that the intent of the Legislature was that you be engaged in lawful hunting or fishing activities, and it's probably not a good idea to become a test case to see if they worded the statute properly.
I think the words "for" and "purposes" are actually relatively ingenious verbiage. They seem very useful for indirect hunting, trapping fishing activities- say hanging a legally killed deer behind your home for butchering or something like that.
Now, what I wonder, is to what exact extent it would cover somebody. Would they be covered if they had a 4''+ knife and some tackle in their trunk, with a real intent to go fishing (or hunting, or trapping) after work (fore example)?
The only other snafu with CT law, is that is does not specify how length should be measured- whether the portion would be measured along the curve of the blade or linearly. Presumably, this vaguity could allow an officer to measure the edge either way.
On the plus side, though, is that Connecticut is concerened with length of the edged portion, unlike most other states.
Also, you always want to have the license on you when your fishing. Not carrying it while engaged is a (IIRC) $70 fine or something like that.
The other good thing is that Connecticut courts have held (and the legislature has incorporated) that a knife not so defined as a dangerous weapon in 53-206 is not a dangerous weapon when peacibly carried.
I had one very positiveinterraction with a Farmington cop while fishing at Batterson once. It went real well, and they didn't so much as ask a single quiestion about the sheathed knife hanging off my neck (it was a small knife, but I would have expected a much different reaction from an LEO confronting somebody he didn't know). They simply wanted to check fishing licenses (as I produced mine from my wallet, they were satisfied- they didn't even review the info)- they were trying to scare off miscreants IMO- it seemed like there's a bit of drug activity going on up there until the rolled through. Was glad to see them up there- a little scum can make a good day really miserable.
BTW- the Gerber is a good knife. I have a similar model with the teflon coated 3" partially serrated blade.