Halibut are a popular type of fish, leading many to wonder about their natural habitat. Understanding where these large flatfish live helps clarify their biological classification.
Halibut’s Ocean Home
Halibut are exclusively saltwater fish, thriving in the cold, deep waters of the world’s oceans. Two main species are recognized: the Pacific halibut (Hippoglossus stenolepis) and the Atlantic halibut (Hippoglossus hippoglossus).
Pacific halibut inhabit the northern Pacific Ocean, ranging from California northward to the Bering Sea and westward to Japan. They are found on sandy or muddy seafloors of continental shelves, at depths between 90 and 1,000 feet, though they can exist much deeper, up to 3,600 feet.
Atlantic halibut, the largest flatfish globally, are found across the North Atlantic. Their distribution extends from Labrador and Greenland to Iceland, and from the Barents Sea south to the Bay of Biscay and Virginia. These demersal fish live on or near the ocean bottom, preferring sand, gravel, or clay substrates at depths between 160 and 6,560 feet. Both species are strong swimmers capable of long migrations, moving seasonally between shallower feeding grounds and deeper spawning areas.
Understanding Freshwater and Saltwater Fish
The difference between freshwater and saltwater environments lies in their salinity, dictating the physiological adaptations fish need to survive. Freshwater, found in rivers and lakes, contains low salt concentrations, around 0.5 parts per thousand (ppt). Fish living in these hypotonic conditions are saltier than their surroundings, causing water to constantly enter their bodies through osmosis and salts to diffuse out. To manage this, freshwater fish possess specialized kidneys that excrete large amounts of dilute urine and gills with cells that actively absorb salts from the water.
Conversely, saltwater environments have high salt concentrations, around 35 ppt. Saltwater fish face the opposite challenge; their internal salt concentration is lower than the surrounding water, leading to a constant loss of water from their bodies and a gain of salt. To counteract dehydration, marine fish drink large quantities of seawater and excrete excess salt through specialized chloride cells in their gills. Their kidneys produce very little concentrated urine. This process, known as osmoregulation, maintains the balance of water and salts within their bodies, allowing them to thrive in their specific aquatic habitats.