Demersal fish is obtained from

The correct option is sea bottom.

To understand why this is correct, we can break down the definition and habitat of demersal fish:
1. Definition of Demersal Fish: The term "demersal" comes from the Latin word demergere, which means "to sink" or "to plunge". In marine biology, demersal fish refer to species that live and feed on or near the bottom of seas, oceans, or deep lakes.
2. Habitat Zones: Aquatic environments are divided into different zones. The open waters are known as the pelagic zone (where pelagic fish like tuna or mackerel swim), whereas the lowermost column of water and the seabed itself constitute the demersal or benthic zone.
3. Examples and Adaptations: Common demersal fish include cod, flatfish (like flounder, sole, and halibut), rays, and haddock. These fish have adapted specifically to search for food, camouflage, or rest on the sea floor.
Therefore, demersal fish are obtained primarily from the sea bottom.