Why do fish that live in the ocean not retain salt?

Answer 1

The osmotic balance of fish in salt water is easier than fish living in fresh water. The osmotic pressure on cellular salinity is virtually zero in sea water. Salinity does vary throughout the oceans though, so fish need a mechanism to excrete urea and regulate salts and water. This is achieved using kidneys in the same way that humans regulate their osmotic balance. When fish like Salmon smolt, they move from a salt water to fresh water, which would mean that they kidneys have to work very hard to maintain the correct osmotic balance, in effect, water would be constantly moving into the fish via the gills and digestive system. Some species cannot tolerate lowered salinity, whilst some can manage brackish water. Some sharks like bull sharks can tolerate low salinity for some time and survive.

Answer 2

Ocean fish have tissues that are less salty than the ocean water around them so they tend to lose fluids due to osmosis, yet they must get water from the environment they live in. What kind of adaptations could they have to maintain osmotic balance?

Answer 3

Freshwater Fish maintain a higher osmolarity vs their surroundings by excreting very dilute urine. This evacuates as much water as possible while conserving solutes such as salt in the body.

Answer 4

creation fish have different adaptations to make sure they don't get dehydrated plus, they live in water