mesopelagic

meso- +‎ pelagic

mesopelagic (not comparable)

1. (oceanography) Describing a pelagic zone of the oceans between the photic epipelagic and the aphotic bathypelagic zones
   • 2001, James Willard Nybakken, Marine Biology: An Ecological Approach, page 153:

     For those animals living in the mesopelagic zone, where some light downwells from the surface, a visual predator looking up at them could see a silhouette.

mesopelagic (plural mesopelagics)

1. A mesopelagic fish