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The distinction between demersal species of fish and pelagic species is not always clear cut. The Atlantic cod (Gadus morhua) is a typical demersal fish, but can also be found in the open water column, and the Atlantic herring (Clupea harengus) is predominantly a pelagic species but forms large aggregations near the seabed when it spawns on banks of gravel.
Altogether, the pelagic zone occupies 1,330 million km 3 (320 million mi 3) with a mean depth of 3.68 km (2.29 mi) and maximum depth of 11 km (6.8 mi). [2] [3] [4] Pelagic life decreases as depth increases. The pelagic zone contrasts with the benthic and demersal zones at the bottom of the sea. The benthic zone is the ecological region at the ...
The marine pelagic environment is the largest aquatic habitat on Earth, occupying 1,370 million cubic kilometres (330 million cubic miles), and is the habitat for 11% of known fish species. The oceans have a mean depth of 4,000 metres (2.5 miles). About 98% of the total water volume is below 100 metres (330 ft), and 75% is below 1,000 metres ...
Marine habitats can be broadly divided into pelagic and demersal habitats. Pelagic habitats are the habitats of the open water column, away from the bottom of the ocean. Demersal habitats are the habitats that are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish.
Benthic-pelagic coupling are processes that connect the benthic zone and the pelagic zone through the exchange of energy, mass, or nutrients. These processes play a prominent role in both freshwater and marine ecosystems and are influenced by a number of chemical, biological, and physical forces that are crucial to functions from nutrient cycling to energy transfer in food webs.
As with oceans, the benthic zone is the floor of the lake, composed of accumulated sunken organic matter. The littoral zone is the zone bordering the shore; light penetrates easily and aquatic plants thrive. The pelagic zone represents the broad mass of water, down as far as the depth to which no light penetrates. [9]
It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is towing a net at the very bottom of the ocean and demersal trawling is towing a net just above the benthic zone. Bottom trawling can be contrasted with midwater trawling (also known as pelagic ...
Consequently, these species have short pelagic larval durations and do not disperse long distances. Planktotrophic larvae feed while they are in the water column and can be over a long time pelagic and so disperse over long distances. This disperse ability is a key adaptation of benthic marine invertebrates. [3]