I've got a vintage Catcherman. It's ideal for filleting fish -- that's what is was designed for -- BUT I don't think that it would be very good as a general EDC knife, which is what the OP also wants.
If you want a corrosion resistant blade suitable for fishing and as an EDC, the Pacific Salt in plain or serrated would probably be best but it costs more than $80 which is the OP's limit.
In the sub-$80 price range, I'd simply suggest a Spyderco Byrd LW FRN Cara Cara 2 w/a plain or combo 3.75" blade. The OP can buy 3 for about $78 -- 1 for the tackle box, 1 to carry and 1 for a spare. Should be fine for cutting/filleting fish and any normal EDC task.
The 8cr13mov steel is stainless and easy to resharpen w/a pocket stone as needed (if you get the plain edged blade). We could argue endlessly about whether or not this steel is any "good" but, fact is, it's been around for decades and works fine if you treat it right. It's supposedly comparable to AUS8 and there's nothing "wrong" w/AUS8 IMO either.
FRN has a great grip (even when wet) and is easy to clean; simply rinse in running water. Just make sure it's completely dry (using an airgun would be best) and coat the blade w/a suitable corrosion resistant lubricant (like Break-free) b4 putting it away and I don't think you'll have to worry much (if at all) about corrosion.
BTW, b4 anyone thumbs their nose at the notion of buying a Spyderco Byrd, I own over 100 Spydercos, including a Byrd Cara Cara 2 and a Meadowlark 2. They are the cheapest knives in my Spyderco collection but they can perform as well as other knives costing 4-8x's more. Nothing wrong w/them if you can't afford (or don't want) to spend more.