It's old line, time tested, and not close to high tech, but:


http://www.amazon.com/Rapala-Fillet-...sh+filet+knife

Incredible extra thin blade allows the greatest flexibility and control
ever.
PTFE non-stick coating lets fillets effortlessly fall away.
Razor-sharp handground stainless steel blade features through tang
construction.
Polished brass ferrule.
Tooled leather sheath.
11 new from $16.99

Shoot, mine don't have the non-stick, oh well...it's OLD.

I do wonder how these would do:

http://www.amazon.com/Rapala-Lithium...sh+filet+knife

List Price: $89.99
Price: $60.12

Nothing you could afford to drop overboard for sure.