Big "Transsexual" Fish in Peril

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July 13, 2009—A favorite of divers in Australia, the blue groper grows to about three feet (one meter) long and can change its own sex. But its numbers are diving, and researchers are trying to throw the groper a lifeline.

© 2009 National Geographic (AP)

Unedited Transcript

One of the Australian state of New South Wales favorite ocean-living icons is Bluey, the blue groper.

Their friendly nature makes them a favorite of divers.

SOUNDBITE (English), Diver: "Well it's magical, like any type of marine species, if you can scuba dive or snorkel along the trail and you see these magnificent fish, it's breathtaking it really is, it's true magic."

The groper can grow about 3 feet in length, and live up to 50 years. And it has a clever trick to maintain its numbers it can change its sex.

SOUNDBITE (English), Bob Harcourt, Associate Professor Macquarie University: "The blue groper is a large fish, but the really sexy thing about Blue Groper is they start off as females. We've got lots of blue groper that are small green groper and as an old male dies then the largest most dominant females turns blue and becomes male. And so one of the really cool things about these fish, is the sex ratio doesn't really vary, but it is a function of how well protected they are. If you take a lot of males out, then the females have to spend a lot of their time turning into males, which means they can't breed and they can't lay eggs."

The eastern blue groper is inquisitive and possibly too trusting for its own good.

Although New South Wales has effectively banned commercial fishing of the blue groper since 1980, and reserves have been set aside to protect the official state fish, there are concerns that sport fishing outside of these zones is putting undue pressure on the groper.

Soon, we may know much more about 'Bluey's' secret underwater world.

30 gropers inside and outside the zone are being tagged in a study to determine the reserve's effectiveness.

SOUNDBITE (English), Kate Lee, Researcher: "How much time they spend in the different zones. Obviously we've come along and put down these are boundaries and put it on as a human boundary but animals don't listen to the boundaries we put. So we are looking at how much movement there is between the fished zones and the un-fished zones and if there spending a lot of time moving between the two, then obviously the reserve is going to be less effective than if they were staying in those particular zones."

The study of the blue groper will last a year. Its hoped it will help guarantee a safe future for bluey.

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