Question

Coastal rainbow trout (Oncorhynchus mykiss) move between marine and freshwater systems yet are homoiosmotic organisms. What physiological challenges do these fish have to meet in each environment (marine and freshwater) affect of temperature, ect? How does their physiology change to overcome these challenges?

Answer 1

Coastal rainbow trout is a species of salmonid native. There life cycle is in between fresh and marine water .They migrate to the fresh water for spawn   in early or late spring when the water temperature is in between 40 to 44 F ,to release sperm and egg .They live in well oxygenated and good vegetation fresh water body as this is breeding time for them .once these fish grows as juvenile they migrate to ocean again .

These Juvenile fish shows physiological change to adapt themselves from living in fresh water to marine water ,this physiological change is called smoltification. Physiological changes during smoltification include altered body shape, increased skin reflectance and increased Na+/k+ ATPase in gills .The mechanism which regulate it is called Osmoregulation. Rainbow trout have osmoreceptors which is found in hypothalamus, it detect the change in osmotic pressure to maintain homeostasis of the fish water content. With this Rainbow trout maintain fluid and electrolyte balance and save its body fluid from getting too diluted or concentrated .