HKU Bulletin October 2003 (Vol. 5 No. 1)

11 R eef fish species that had seemingly disappeared from Hong Kong waters have started returning to a marine reserve at Cape D’Aguilar, giving researchers a snapshot of what the marine eco- system was like 50 years ago. Most of the larger species had been over-fished to meet the insatiable appetite for fleshy fish. But since the 18-hectare reserve opened in 1996 – with a total ban on fishing in its borders – 184 reef fish species have been recorded there by Dr Andrew Cornish of the Department of Ecology and Biodiversity and big fish are common again. “Hong Kong waters have been over-fished for decades. If you dive outside the marine reserve, you would think snappers, garoupas, parrotfish and the like were not important components of the ecosystem here,” he said. “But if you talk to old people, they will tell you the waters used to be teeming with fish, including big fish. There even used to be enough sharks to have dedicated shark fisheries in the 1940s and 1950s.” Dr Cornish recently videotaped a juvenile, 35-centimetre Giant Grouper in the reserve which, at adulthood, grows to more than two metres long. He has also recorded several species of fish there which have never been seen in Hong Kong waters before, the most recent being a male Globehead parrotfish. The situation is much different in other local waters. Dr Cornish studied three coral communities outside the reserve and recorded the biomass – the estimated collective weight of all the fish there. The figure was one of the lowest ever recorded in a coral habitat anywhere in the world. The lack of decent sized reef fish in Hong Kong has sent fish traders to Indonesia, the Philippines, the Maldives and elsewhere in the region, putting pressure on fish stocks there. Hong Kong has the largest market for reef fish, and the Taiwan and Mainland China markets are growing. Garoupas and wrasse are especially vulnerable and a World Conservation Union group has been set up under Dr Yvonne Sadovy also of the same department to assess which species should be put on a ‘red list’ of those in danger of extinction. There are more than 1,000 garoupa and wrasse species and the humphead (or Napoleon) wrasse has already been classified as a threatened species. The humphead is a popular choice on Hong Kong tables. Dr Cornish is helping in the red list assessment and said garoupas and wrasse were never very abundant and took a relatively long time to reach sexual maturity, making them vulnerable to over-fishing. Many were caught and eaten before they could reproduce. “I would like to see more natural reefs in Hong Kong fully protected from fishing. It actually enhances fishing outside the reserve. Not only do you protect biodiversity inside, but these large species have the chance to reproduce and their offspring will repopulate reefs outside,” he said. Rare Fish Return to Hong Kong Waters Andrew Cornish Researchers collecting specimen at Cape D’Aguilar. RESEARCH 10