WEST LAFAYETTE, Ind. New insights into the reproductive behaviors of freshwater fish a process more bizarre and interesting than commonly realized have been discovered by scientists who used genetic tools first developed for use in humans.
By using genetic fingerprinting techniques such as those used to identify criminals, Andrew DeWoody, assistant professor of forestry and natural resources at Purdue University, and his colleagues, have been able to glean new knowledge about an underwater world of peculiar liaisons.
The findings were published in three scientific papers during the last four months, the most recent appearing in the Monday (4/16) issue of the Proceedings of the National Academy of Science.
Most freshwater fish familiar to sport fishermen reproduce by building nests and laying eggs in the spring. But unlike birds and reptiles, in many freshwater fish species it is the male that builds and tends the nest.
"They try to build an attractive nest to entice females to come and spawn with them," DeWoody says.
Nearly all freshwater fish are external fertilizers, which means that while the female deposits some or all of her eggs in a nest, the male swims over the nest and fertilizes the eggs. The female leaves often to find another male to spawn with while the guardian male waits, fanning his tail to aerate the eggs, protecting the nest from predators and hoping to entice another female to add more eggs to the nest.
There's also a problem with other males. "Occasionally a second male will join the spawning pair and attempt to 'steal' fertilizations from the primary male," DeWoody says.
It's a long, lonely vigil hovering over the nest, and the males can't leave for any reason, even to forage for food. "As soon as they leave the nest, minnows or some other fish would come in and destroy the nest by eating the eggs," DeWoody says.