If the water is exceptionally deep, the pelagic zone below 4000 m is sometimes called the lower midnight or abyssopelagic zone. |
They are not generally found at abyssopelagic or hadopelagic depths or on the abyssal plain. |
Zones which vary according to their depth include the epipelagic, mesopelagic, bathypelagic, abyssopelagic, and hadopelagic zones. |