Question

Describe and the osmoregulatory challenges faced by freshwater fish, and how they differ from oceanic (saltwater) fish.

Answer 1

Osmoregulation is the process to maintain an internal balance of salt and water in the body of fish.

Fresh water fishes have higher concentration of salt inside than the external surroundings. Hence, fishes loose salt and absorb water. These fishes have very efficient kidneys to excrete water quickly. They also reabsorb salt from their urine before it is ejected to minimize losses and actively take salt from their surroundings using special cells in the gills.

In contrast in oceanic surroundings, fishes have relatively more salt and less water outside their bodies than the freshwater fishes. This leads to the intake of salt and lose water. To solve this, oceanic fishes drink huge amount of water and urinate little. These fishes have special cells in the gills which actively excrete salt and do not absorb any salt from the water.