mes·o·pe·lag·ic 
(mĕz′ə-pə-lăjĭk, mĕs′-)
(mĕz′ə-pə-lăjĭk, mĕs′-)adj.
Relating to or inhabiting the layer of the water column in the open ocean that lies between the epipelagic and bathypelagic layers at depths of about 200 to 1,000 meters (656-3,280 feet).