Successful propagation in seawater of the guppy Poecilia reticulata with reference to high salinity tolerance at birth

Seawater tolerance of newborn guppies was measured by way of survival rates 24 h after transfer to seawater. The newborn guppies showed high seawater tolerance and some of them survived in 35 ppt seawater. Seawater tolerance significantly decreased within 5 days after birth and then became stable at a level comparable to adults. After a challenge test with 35 ppt seawater at birth, the surviving individuals remained alive more days and grew in 35 ppt seawater. They yielded offspring, and most of their progeny survived in 35 ppt seawater. Therefore, the guppies could propagate in seawater and a seawater-tolerant strain was established.