The moral worth of an animal is not just a question of whether its species is endangered though. Dolphins seem much more likely to be conscious than the other species you list.
We can't be absolutely sure that anyone except for ourselves suffer (not even other humans) because of the other minds problem, but essentially all the scientific evidence we have suggests that humans and other creatures are sentient if they have basic nervous systems and begin to display behaviors consistent with suffering.
Some of my sources: Studied neuro and cog sci myself, just chatted last night with a PhD candidate in neuro who agrees with me, have taken classes with the former longstanding editor of Brain and Behavioral Science who I believe would also agree. There are cog sci journals out there dedicated to this stuff.
I subscribe to a train of thought that says it's wrong to kill a person; it's okay to kill a cow, but wrong to torture one; and I'm not sure if anything done to a mosquito could count as torture. I think dolphins are around the same level as humans. I think tuna and many other fish are probably between cows and mosquitos, closer to cows, but I haven't read or thought about that one very hard.
Whatever it is that separates cows from humans, also seems to separate cows from dolphins. It's not sentience, according to your definition of the word, but it's what lmm was talking about.
Consciousness is poorly defined, so I don't know exactly what you're getting at there, but one definition is sentience. At any rate, I believe it's fair to say that a sentient being can be described as conscious due to their ability to feel and subjectively process experiences.
Why does consciousness matter if you believe they are sentient? Are you perhaps conflating intelligence with consciousness? Do you believe that it matters more when an intelligent animal suffers than it does when a less intelligent animal suffers? Why? Do they not both suffer? Can the same be said for people with low IQs? Their suffering matters less than mine?
How do you reconcile that slaughterhouse conditions are torturous, even the ones that "ethical farmers" use? That we have video footage that indicate the animals know they are going to die and evidence to suggest the entire process is distressing and painful? That the process by which they are "humanely" anaesthetized/killed (e.g., bolt gun) is still by far not the most humane way to kill animals?
How about the fact we have every reason to believe pigs are incredibly intelligent despite the way we treat them (I'm talking Chimpanzee-level intelligence here — http://animalstudiesrepository.org/cgi/viewcontent.cgi?artic...)? What is this "thing" you believe separates them from dolphins?
Are you sure you are not simply working off of your own unchallenged beliefs that you were raised with by your parents and taking those as ground truth?
As such, I'm going to reply, but then I'm done. You're irritating, and I'm not interested in having a prolonged discussion with you.
I'm not conflating consciousness with the ability to suffer, or with intelligence. I don't know exactly what it is. But far as I understand, humans and dolphins and some other species seem to be aware of their own existence, in a way that cows aren't. (The mirror test is one tool we use to try to judge this.) Humans and dolphins are capable of wanting not to die, in a way that cows aren't. That's what makes it wrong to kill humans and dolphins. Meanwhile, humans and dolphins and cows are capable of suffering, in a way that rocks and (I assume) mosquitos aren't. That's what makes it wrong to torture a human or dolphin or cow, and impossible to torture a rock or mosquito.
> How do you reconcile that slaughterhouse conditions are torturous
Reconcile with what? I specifically said it's wrong to torture a cow. I don't like slaughterhouses. I'm mostly vegetarian.
I didn't say anything about pigs, because I don't know where I'd place them. My understanding is that they seem to be somewhere between cows and dolphins, probably closer to cows.
Moral worth is the function you run inside your head that says you prefer to let a thousand earthworms die to save one dolphin.
Hope this helps.