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The bull shark is a euryhaline species that moves at will from fresh to salt water, and many marine fish make a diel vertical migration, rising to the surface to feed at night and sinking to lower layers of the ocean by day. Some fish such as tuna move to the north and south at different times of year following temperature gradients. The ...
This is the most common form of vertical migration. Organisms migrate on a daily basis through different depths in the water column. Migration usually occurs between shallow surface waters of the epipelagic zone and deeper mesopelagic zone of the ocean or hypolimnion zone of lakes. [2] There are three recognized types of diel vertical migration:
Swordfish feed daily, most often at night, when they rise to surface and near-surface waters in search of smaller fish. During the day, they commonly occur to depths of 550 m (1,800 ft; 300 fathoms) and have exceptionally been recorded as deep as 2,878 m (9,442 ft; 1,574 fathoms). [ 3 ]
Anadromous – fish that live their adult lives in the ocean but migrate up fresh water rivers to spawn. Examples are Pacific salmon. Fish that migrate in the opposite direction are called catadromous. Anoxic sea water – sea water depleted of oxygen. See hypoxia. Anoxic sediments – sediments depleted of oxygen.
The species of benthic invertebrates are those which arise greater interest since they are enriched by a great variety of forms and colours due to the abundance of Cnidaria (sea anemones, madrepore and corals). A clear example is the "forest" of yellow and red Paramuricea clavata. These, adding to the substrate, create an ideal benthic ...
Eels in this so-called "recruitment" developmental stage are known as glass eels because of the transparency of their bodies. The term typically refers to a transparent eel of the family Anguillidae. It is applied to an intermediary stage in the eel's complex life history between the leptocephalus stage and the juvenile (elver) stage.
Billfish have a long, bony, spear-shaped bill, sometimes called a snout, beak or rostrum. The swordfish has the longest bill, about one-third its body length. Like a true sword, it is smooth, flat, pointed and sharp. The bills of other billfish are shorter and rounder, more like spears. [40] Billfish normally use their bills to slash at ...
A thermocline (also known as the thermal layer or the metalimnion in lakes) is a distinct layer based on temperature within a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) with a high gradient of distinct temperature differences associated with depth.