Michele, that is a pretty good definition of osmoregulation. Osmoregulation is essentially the process that fish have to do to control the water/solute balance in their bodies. Their bodies are at different salinities (and other concentration of ions) than their surroundings. Freshwater fish have to constantly pump water out, and saltwater fish have to prevent the loss of water from their bodies.
Because fish respire through their gills (through a barrier only one cell thick), they are at great risk to losing control by water or salts going in and out of their gills. It takes them a lot of energy to osmoregulate. Fish under stress have to divert energy to dealing with stress, and cannot osmoregulate correctly. Thus, stressed fish usually die from a water/salt imbalance.
Because fish respire through their gills (through a barrier only one cell thick), they are at great risk to losing control by water or salts going in and out of their gills. It takes them a lot of energy to osmoregulate. Fish under stress have to divert energy to dealing with stress, and cannot osmoregulate correctly. Thus, stressed fish usually die from a water/salt imbalance.
