Reflections

Research by Avondale College lecturer Jason Morton may bring more stability to the social life of a sex-changing fish in waters off the Central Coast.

Morton, a PhD student at the University of Newcastle, has studied crimson-banded and Maori wrasses at Catherine Hill Bay and Norah Head for the past four years. He found the fish begin life as females but become males at the age of four or five. They then live in a harem of up to 10 socially ranked females with the largest, highest ranking female likely to be the one to change sex after the male dies.

Promiscuity is popular, with females making excursions into other harems to determine whether joining a new harem will improve their social rank, reducing the waiting time to become a male.

Enter the zealous fisher who can eliminate all males, which are larger than females and will more readily take bait, in a typical territory (ranging from 600 to 2500 square metres). "The bag limit is 20 fish, but if you bring a mate, that's 40, which could include all the males," said Morton during a recent colloquium address. If so, the highest ranked female in a harem changes sex and the remaining females re-contest their rank. The process takes three weeks, "but in that time, the territory might be fished again," said Morton. He described wrasse at Norah Head as more "skittish" than those at Catherine Hill Bay, which is less regularly fished.

Crimson-banded wrasse can live at least 10 years and Maori wrasse at least 13, partly because they have no natural predators and prolong life by wisely using resources--each species eats similar food but in different proportions and spawns in different seasons.

The 300 hours Morton spent under water with the fish has helped him identify individuals by using unique facial and body markings. He has even named some of the fish--Golf swing, Small circle, V-head. "You can't survey fish," he said, "so you've got to go down and find them."

Mention the word "sex," and the media are interested. Metropolitan and regional newspapers (Daily Telegraph, The Herald) published articles about Morton and his findings, and Morton appeared live on regional radio (810 ABC South East New South Wales, 1233 ABC Newcastle, 2NUR) and television (NBN).