I heard my name mentioned...
I do fishing photography for a living (I work for DHP Ltd - Total Carp, Advanced Carp Fishing etc) and TBH, a lens like the 17-70mm (I use a Nikon 17-55mm) is my staple lens, especially when it comes to catch shots.
I know the guys on the carp mags who shoot their own stuff opt for 35mm and 50mm primes on crop bodies because they keep things looking 'real'. Go too wise, say 12mm, and you run the risk of the fish distorting and looking like a 80lb barrel!!!
It all depends though on what you want to achieve; think of normal trophy shots like portraiture in that you want minimal distortion so the fish looks accurate.
I love shooting on a 14mm and a 10.5mm fisheye, getting right up to the fish, but that's for impact shots that are meant to grab the reader's attention and nothing more. I also shoot a lot on a 70-200mm because I can use DoF to create lots of background blur that the designers can lay text over, especially when it comes to covers. I think background separation is massively important anyway because it just makes a trophy shot look better.
Have a gander at my Flickr page and you should see plenty of varying shots with exif info. Might help
If you want any info, my work e-mail (public) is
patrick@dhpub.co.uk 