It sounds like you are using a standard camera, not a digital? If so, the best thing you can do is take the pictures up as close as possible. The person taking the pics will think they are too close, but try it and you'll see they come out better.

On digital, you can crop out the sides of the picture to make the subject (you and the fish) appear closer up. That's why a lot of digital pictures online look good, because they are cropped to focus on the subject.

If you have a digital but you want printed copies, try cropping them them like above, then printing them either on your own computer or through Costco or whoever. They'll look a lot better that way than printing the full picture.