These Fish Went From Saltwater To Freshwater In Just Fifty Years

Threespine sticklebacks hatch in fresh water pools near streams. When they mature, they need to make their way back to the ocean to live. So if their way to the ocean is cut off, they’re screwed. Or are they?

The video tells the story of the 1964 earthquake in Alaska, and the fish it left stranded. The earthquake pushed islands up by meters in just a few seconds. this turned streams into pools, and left many threespine sticklebacks’ young stranded away from the sea. But instead of waiting to be rescued, these fish evolved.

They’re not the first of their kind to do so. Stickleback populate certain inland Alaska lakes, due to an event that cut the lake off from the sea 13,000 years ago. These survivors have accumulated genes and physical traits that allowed them to become full freshwater fish, but no one thought that they did so quickly.

A new study shows that some populations stranded in 1964 adapted within ten years. To all outward appearances, these two populations were stranded at the same time — even though they spent over 10,000 years having different life cycles.

Researchers concluded that this is partially possible because the stickleback, while remaining marine fish for most of their lives, had a hidden arsenal of genetic diversity. Two marine sticklebacks might look alike and behave alike, but the entire populations manages to “maintain a large pool of genetic variation that can be redeployed rapidly when oceanic stickleback colonize freshwater environments. “

Researchers stress, however, that this change in the 1964 population isn’t just a temporary one. The stickleback’s genome has changed. It’s just that it had more of a potential for change, and survival, than we had previously imagined.

[Source: Evolution of stickleback in 50 years on earthquake-uplifted islands]