Why are salt water fish not salty to eat?
This week's question comes to us from Donna Kemp in Ottawa. She asks:
Why are salt water fish not salty to eat? They 'breathe' in salt water and drink it too. So why isn't the flesh salty?
Dr. Daniel Pauly, the Principal Investigator of the Sea Around Us Initiative and a Professor in the Institute For The Oceans and Fisheries at the University of British Columbia, has the answer.
Marine fish need to maintain a balance of electrolytes - including salt - in their body, that is lower than the amount of salt in their environment. This is important for the various chemical changes, nerve reactions and other biological processes that take place within their bodies.
Because marine fish take in so much salt, they need to get rid of the excess. This is mainly done through their kidneys and gills in the form of urine. If this process did not occur, salt would build up beyond the healthy levels and the fish would die.