Everyone is entitled to their own sense of ethics and conduct. Keep in mind that "Shoot what you and eat what you shoot" originated in the ocean where life is in a "natural" state, and the existing balances and species need to be kept intact for our benefit as well as their own. Just like ANY moral code, it is there for a highly logical, biological reason, and not because of some unwavering, divine proclamation that blindly decrees "because I say so". The fragile ocean and its reefs are where I learned to spearfish, so that philosophy resonates strongly with me as well.
Freshwater, however, is a completely different ballgame - we're dealing with the legacy of past generations of humans building dams, diverting rivers, introducing different species for food and for catch and release fisheries. The damage has been done, unfortunately. The native species which the Mojave indian tribes depended on for food (example: Colorado pikeminnow) are nearly extinct, so the ethical implications are very different.
Perhaps Daniel should have answered "I shoot them for fun AND to help control their numbers, and to refine my shooting skills so that when I shoot more sensitive species in the ocean I have a higher chance of landing them".
My own sense of ethics views life as a continuum, not as scattered individual dots that are isolated from one another. Hence, nothing ever truly goes to waste. The carp get recycled within the lake, or their biomass just gets plain removed from the system and becomes part of another when a coyote eats them.
As far as their eating quality goes, I've tried it and personally find it to be really foul even when cooked right. Another issue that is often encountered is that their lateral line runs very high on their bodies, so anything other than a perfect head shot either hits the gut, hits the meat, or hits the kidneys, or all three. So the meat often gets spoiled as a result of getting speared.
Edit: maybe Dan should move this to another thread so it doesn't distract too much from the records discussion.