Reef Report for Monday, December 18, 2006
Recent Research on Two Shark Species Shows Need for their Continued Protection on the Great Barrier Reef.
A team of scientists has recently released research on two shark species commonly seen by scuba divers on the Great Barrier Reef. The research, by William Robbins and colleagues at James Cook University and its ARC Centre of Excellence for Coral Reef Studies, appears in the December 5th issue of Current Biology.
They were studying populations of white-tip and gray reef sharks.
These sharks are among the top predators of smaller fish on the Great Barrier Reef, where they hunt in groups by probing the nooks and crannies in the reef, searching for hiding fish. These predators are thought to play an important role in maintaining diversity and the balance of reef ecosystems, much like wolves, lions, and other predators do within their ecosystems.
Their research clearly demonstrated that while reef shark populations are stable on those parts of the Great Barrier Reef that are effectively protected from fishing, they are falling in those zones where fishing is permitted. While that means that the two year-old protective scheme setting aside over 30% of the Great Barrier Reef is working in the protective zones, the spillover effect, where growing populations of a species move from protected to unprotected zones, is not occurring for these two species of sharks.
What's also interesting was the difference in shark populations between pink-zone reefs and green-zone reefs. Pink-zoned reefs have the highest level of protection, no visitation of any kind is allowed without a permit, which are rarely granted for other than scientifice purposes. Green-zoned reefs are protected from fishing and similar activities, but access is permitted.
Shark populations at green-zoned reefs were more similar to the reefs where fishing is allowed than the fully protected pink-zoned reefs. The scientists feel that the small amount of accidental or intention fishing in green zones is enough to cause the decline of these popultaions. Sharks take a long time to mature and reproduce slowly, so any taking of sharks could effect the pouplation. The scientist felt that more effect protection of the green zones from fishing was warranted.
It appears that the long term future of these sharks in the unprotected zones of the Great Barrier Reef must rely on some additional protection of these two shark species. While the Great Barrier Reef is widely considered to be one of the worlds least degraded, and best managed, reef systems
We did a quick bit of research on shark fishing in Queensland, and were surprised to learn about the growth of this industry. White-tip and Gray Reef Sharks are not the major species caught by commercial fishers. The shark catch (of all commercially fished shark species) increased by 300% between 1988 and 2003. Sharks are slow growing fish with low reproductive rates, and the collapse of shark fisheries elsewhere in the world has some scientists wondering if there is a potential of that happening in Queensland given the current catch rate.
News coverage of Dr. Robbins and his teamís research.
Information on commercial shark fishing in Queensland.
Information on sharks in Australia.
The weekly reef report is written by Joel Groberg of DiveTheReef.com,
who compiles them from the many conversations he has with dive staff in the area, as well as† many other local sources in the dive
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