Female fish judge their ideal partner by the design of their nest

​London: Female fish judge males based on their ability to design nests best suited for the conditions of their environment, suggests a study.

According to the study, male fish build nests to suit local environments -- and females judge males on their ability to respond to changing conditions.

In the study, which is published in the journal Evolution, the researchers showed that low oxygen can change the way in which fish build nests and also change the nesting preferences of female fish.

Male three-spined stickleback fish are unusual in that they build nests and provide all the parental care for the eggs, which are spawned by females, and for the developing baby fish.

The research team found that males change the design of their nests depending on the oxygen content of the water -- making looser nests under low-oxygen conditions and more compact nests when oxygen increases.

"Male sticklebacks have to work really hard as dads, using their fins to fan water through the nest to supply the eggs with the oxygen they need to develop," said Iain Barber, Researcher at the University of Leicester.

"If the water is low in oxygen, then having a looser, more open nest allows more oxygen to reach the eggs, but it probably comes at the expense of increasing the risk of them being discovered by predators," Barber added.

Low oxygen can also critically affect important reproductive behaviours, with associated effects on the viability of fish populations and even implications for natural selection and evolution.

The research has shown that it was not just male construction that was affected when water oxygen levels changed. The most interesting finding was that female fish also changed their preferences for the design of nest they went for.

Female choices flipped from preferring tighter nests under high oxygen conditions, to preferring looser nests when conditions deteriorated.