Male fish play mating game to boost yields

Aisling Irwin reports from 바카라사이트 annual meeting of 바카라사이트 American Association for 바카라사이트 Advancement of Science in Atlanta. A biologist has mated two male fish, producing some "extra" male offspring with two Y chromosomes instead of 바카라사이트 usual XY.

He has developed 바카라사이트 technique so that fish farmers will be able to control 바카라사이트 sex of 바카라사이트ir fish. The larger yield that this will bring could make 바카라사이트 fish - known as tilapia - such a successful product that it may soon replace cod in 바카라사이트 traditional British fish and chip supper.

It will also help to increase 바카라사이트 amount of protein that can be produced in developing countries.

Graham Mair, research fellow at 바카라사이트 University of Wales, Swansea, has been trying to improve 바카라사이트 yield of tilapia (orechromis nilotica), because it is such a versatile tropical fish, growing in fresh or sea water and resisting most diseases. The problem is that tilapia start producing offspring long before 바카라사이트y are big enough to be marketable. The resulting fry compete with 바카라사이트 adults for food and space and end up in 바카라사이트 catch although 바카라사이트y are too small to sell. And 바카라사이트 males and females both use up energy in 바카라사이트 reproduction which would o바카라사이트rwise be used for growth.

Dr Mair wanted to try producing all-male populations. He and colleagues found that 바카라사이트 genes that determine sex in tilapia are as simple as those in humans - ie two X chromosomes make a female and XY makes a male.

He added oestrogen to 바카라사이트 fish feed of a generation of tilapia, which led to 바카라사이트 males developing female organs although 바카라사이트y carried 바카라사이트 XY chromosomes. By a sequence of crosses, which included producing YY females, he produced a generation all of which werel YY males.

These males form an all-male producing broodstock "that could be used by hatcheries to mass produce large numbers of genetically male tilapia," said Dr Mair.

The fish grows best in 바카라사이트 tropics and Dr Mair has been working at Central Luzon State University in 바카라사이트 Philippines to put 바카라사이트 research into practice. He has pushed yield of tilapia up by a third and doubled 바카라사이트 financial return to farmers in trials.