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Well Crumbs,
Without knowing the species involved I can't really invest the time to look this up for you, but I know of some Bathynomus that were collected in tropical waters at 500 meters and 5.5 degrees C., so I would be willing to venture that at 1500 meters, the value is going to be close to the thermal minimum of the ocean - say 2 degrees C.
Decompression becomes a moot point - the fish that are prone to gass bladder expansion are going to not make it no matter what. For animals without gas bladders, the first issue is getting them to the surface fast enough that the rising temps won't kill them. The second issue that I do not have first hand experience with is that some deep water animals will die from oxygen poisoning when exposed to higher saturation levels found in captivity as opposed to their normal habitat. Finally, it has been thought that in *some* cases, extreme pressue may actually drive certain metabolic functions in animals - so they just won't live at surface pressures, even if you can get them there safely.
Now, on the chance that you had a typo when you wrote the fish comes to within 1500 m of the surface at night, and you meant 150 m - I'm guessing that you are thinking of lanternfish and or possibly marine hatchetfish. Good luck with that if you are - they have such delicate skin that their scales literally slough off if they touch anything.
Many years ago, I tried night-lighting in the "tongue of the ocean" in the Bahamas and lots of cool epi-pelagics came to the light, but NONE of them survived the confines of my holding tanks for more than a few hours. I had caught one strange needlefish - looking thing that just hovered in the on-board tank and began twitching, and literally broke itself into pieces as I watched. I was so disgusted, I immediatley turned the light off and never tried it again.
The Japanese are collecting some interesting pseudo-deepwater animals from 200 to 800 meters in Suruga Bay, stalked crinoids, odd crabs, etc.
Jay Hemdal
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