Saturday, December 4

Abundant kina damages reefs as fish numbers decline


For Saturday

Reduced numbers of snappers, blue cod and crayfish have resulted in rocky and arid reefs off parts of New Zealand’s coastline.

A barren kina on Tonga Island Marine Rerserve - The reserve is one of two marine reserves in Tasman Bay at the top of the South Island, offering protection to less than one percent of the bay.

A barren kina on Tonga Island Marine Rerserve – The reserve is one of two marine reserves in Tasman Bay at the top of the South Island, offering protection to less than one percent of the bay.
Photo: Supplied / Stew Robertson

The New Zealand common sea urchin, or kina, is one of the main herbivores in our coastal marine environment and historically, their numbers were controlled by predators, but overfishing, warmer sea temperatures, and human activity have seen their boom.

The result is a sterile kina, where the urchins graze among the algae and seaweed and leaving behind a bare or low-productivity reef.

Some marine scientists say that stopping fishing alone is not enough and that it is time to intervene.

Auckland University Associate Professor of Marine Sciences Dr Nick Shears said that in certain parts of the country, the Hauraki Gulf, along the country’s northeast coast and in the upper part of the South Island, the wastelands of kina are prolific.

In the Horoirangi Marine Reserve, near Nelson in Tasman Bay, parts of the reserve are still dominated by kina barren even though the area has been protected for 15 years.

The 904-hectare reserve was created in 2006 and Shears said it could take decades to see algae and seaweed regenerate.

“We live in a system that has been heavily fished for 70 years, so the current abundance of predators is a small fraction of what it would have been naturally and has been for a long time. So, in some In some cases, in a reserve, over time, you can protect those predators and restore that balance, but it takes a long time. “

Horoirangi Marine Reserve in Glenduan, near Nelson.  The reserve was formed in 2005 and covers an area of ​​904 hectares.

Horoirangi Marine Reserve in Glenduan, near Nelson. The reserve was formed in 2005 and covers an area of ​​904 hectares.
Photo: RNZ / Samantha Gee

The first marine reserve to be established in New Zealand was the Cape Rodney-Okakari Point Marine Reserve, known as Goat Island near Leigh, in 1975.

It was through the recovery of that coastal environment that scientists learned that the kina barren did not occur naturally, but were the result of overfishing.

Shears, who is based at the Leigh Marine Laboratory, said the numbers of snapper and crayfish increased on Goat Island in the first five to 10 years, but it took another 10 to 15 years for those predators to reduce the number. of hedgehogs.

In places like Long Island – Kokomohua Marine Reserve in Queen Charlotte Sound, Shears said kina densities were so high that it could take several more decades for wastelands to recover.

In the Hauraki Gulf, a project is underway with iwi to reduce kina numbers in order to establish whether removal of sea urchins can be used as a tool to aid the recovery of kelp forests.

“If you just go in and remove the kina and do nothing else, the kina will come back … so you have to do it in conjunction with other forms of handling, protecting predators but also using other common measures like rahui.”

It was a great effort to remove the kina by hand, but the results showed that in one year there were high recovery rates of several species of seaweed.

Similar experimental work was planned for parts of the Queen Charlotte Sound, but could not continue due to the Auckland blockade.

“A very small fraction of our coastline is actually protected from fishing and it’s not one or the other, we don’t need marine protection or we need better fisheries management, we need both and you can’t do one without the other.”

Shears said that kina is a kind of taonga and an important food resource that was not a problem in many parts of the country.

A crayfish in the Tonga Island Marine Reserve, the reserve was formed in 1993 and covers an area of ​​1835 hectares.

A crayfish in the Tonga Island Marine Reserve, the reserve was formed in 1993 and covers an area of ​​1835 hectares.
Photo: Supplied / Stew Robertson

Across Tasman Bay from the Horoirangi Marine Reserve off the Abel Tasman coast is the Tonga Island Marine Reserve.

Established in 1993 with a size of 1835 hectares, it is twice the size and almost twice the age of Horoirangi.

The two marine reserves offer protection to less than one percent of Tasman Bay.

Less than 10 percent of Aotearoa’s coastal waters are protected by marine reserves.

The Kina fells were documented along the Abel Tasman coastline as early as the 1960s.

Marine Reserves Conservation Department Ranger Stew Robertson said after nearly 30 years of protection: the recovery of the marine environment on the island of Tonga it was clear.

“Legal blue cod is 40 times more abundant inside the reserve than outside, we monitor the reefs on the outskirts of the reserve and up to a few kilometers away and we hardly see legal blue cod, while inside the reserve they are everywhere, they are like rats and crayfish are the same. “

He said there is now more algae and young algae, especially in the deeper parts of the reserve.

Tonga Island Marine Reserve, off the coast of Abel Tasman National Park in Tasman Bay.  The reserve was formed in 1993 and covers an area of ​​1,835 hectares.

A comparison of a reef in and out of the Tonga Island Marine Reserve, off the coast of Abel Tasman National Park in Tasman Bay.
Photo: Supplied / Stew Robertson

Massey University Senior Lecturer in Marine Evolutionary Ecology, Dr. Libby Liggins, said it had reached the point where protecting marine environments was not enough.

“I think we are at a point where we need to take a more active approach and think about restoration as we do in the landscape, we really do not do it in our marine environments, as such, I think we are at the point now where we have to. lend a hand to those algae to overcome those wastes. “

Massey University associate professor of marine science, Dr. David Aguirre, said that kina itself was not the problem, it was simply the answer to it.

Globally, most temperate rocky reefs harboring urchins and kelps struggled with the same problem, often due to overfishing.

“Suddenly they become what we all point to when, in fact, it is our own actions that have allowed them to reach those numbers by eliminating the predators.”

The restoration of the coastal marine environment required a two-pronged strategy.

“A combined approach, whereby removing kina for translocation or moving them into the aquaculture setting, as well as adding recruits to the system from laboratory-grown algal spores, is one way that you can start that restoration process and It would be a much more active approach than the passive approach to marine reserves. “

He said that Aotearoa had the opportunity to be a world leader by using kina ethically, respecting the taonga species, which is found nowhere else in the world.


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