Aperture is another great product for image processing (if you have a Mac). Personally I have both Aperture and Lightroom. Another setting you would want to play with is the highlights and shadows. Photoshop is yet another great program to help clean up images.
Note:
-Upping the exposure too much will make the image very grainy.
-Upping the brightness too much will wash out the image.
-Be careful when adjusting an image that you do not accidentally create a color shift that detracts from the original intent of the image. Colors can become "fake" looking (too bright or distorted).
I also noticed that you may wish to increase your shutter speed which will help you better capture the moving fish. In darker situations make sure that if you have to increase the shutter speed that you also decrease the aperture (allow more light in).
Here are a couple of samples of your last image reworked (very quickly).
Notice:
The rocks maintain their natural look.
The false percs maintain their natural orange"ish" color.
The Photoshop image preserved the background black better (not to say that Aperture can not do just as good of a job).
Sample Reworked in Aperture
Sample reworked in Photoshop (only adjusting the highlights and shadows)
