Thanks for those questions, spindoctor! I've often wondered many of the same things.
First, about slaughter. rehoot gave a great summary of what fish go through. (rehoot, it's awesome how much hands-on experience you've had with animals: You said previously that you lived near free-range cattle, and now I guess you've also worked with fish packing.)
I wrote most of the "Slaughter methods
" section of the Wikipedia article on fish farming. I assume the same applies for wild fish. The articles cited in the footnotes are quite readable as well. Regarding ice baths:
Farmed fish are sometimes chilled on ice or submerged in near-freezing water. The purpose is to dampen muscle movements by the fish and to delay the onset of post-death decay. However, it does not necessarily reduce sensibility to pain; indeed, the chilling process has been shown to elevate cortisol. In addition, reduced body temperature extends the time before fish lose consciousness.
(Incidentally, contributing to Wikipedia
is an excellent way to raise awareness of utilitarian issues, because those articles have such a wide readership.)
spindoctor wrote:Do they have net positive utility in the wild? Are their deaths by humans more or less painful than their otherwise natural deaths (from predation, starvation, disease)? At an ecosystem level, does the rapid decline in wild fish stocks due to overfishing provide a net gain in utility (fewer wild animals to suffer)? And are the fish we are eating predators of other fish, such that removing them may save prey from being eating?
I tend to assume that it's good to prevent the existence of wild fish (since their lives are short, and they have lots of offspring), but I'm not sure whether fishing (including overfishing) accomplishes that. Indeed, it's plausible that the opposite might be true. Here's an email from a friend:
I wrote to my friend about fishes:
When the population of fish in an area collapses because of overfishing, does the total number of fish decrease? At first, it seems that it would. But since humans catch only the big fish, maybe overfishing would make room for more small fish to live (there would be less competition for resources and fewer predators).
I'm not 100% on your fish question, but I know that happens with sunfish in lakes. You end up having more small fish. Then there's sometimes a population boom which is also no good. The biggest problem with removing the big fish is that you're catching the reproducers. The problem with catching slightly smaller fish is that you're taking things before they even have a chance to reproduce.
In general, I would prefer to eat beef over wild-caught fish. There are lots of unknowns, but given my current knowledge, my expectation for the net effect of wild-caught fish is that it's negative.