Fish findings prove reserve is a swimming success

Posted at 12:15pm Monday 29 Jun, 2020

Harry Allard went diving for data over a three-year period.Harry Allard went diving for data over a three-year period.

Despite common complaints that there are fewer fish at Goat Island Marine Reserve, a researcher has found that the ecosystem is in fact a thriving success story.

Harry Allard, from the Leigh Marine Laboratory, says that although the actual number of individual snapper is down, the biomass (total quantity of organisms) has doubled.

“There were high populations of juvenile snapper. But now there are big ancient adult snapper, which are strong breeding fish,” Harry says.

“The average snapper size has increased by six centimetres, which makes a big difference.”

Harry completed a three-year research paper this month, comparing numbers of fish with baselines collected in the 1970s, when the reserve was established.

He has been diving and counting fish in the same spots as the original study.

The largest snapper in the reserve may have been there since 1978, including the famously named “monkey face” fish.

“They are good at keeping within a few hundred metres of the reserve because there is food around.”

A healthy balance between kelp and sea urchins in the forest has allowed the snapper to thrive.

Harry believes that the perception that fish are less abundant at Goat Island comes because of a ban on feeding fish within the reserve. They are not as visible, as they no longer swarm for a feeding frenzy of frozen food.

“Feeding them peas and bread set an unrealistic expectation. It's a more natural habitat now.

“But snapper can live to 90 years old and there are 50-year-old fish who still remember and follow people around expecting food.”

Similarly, long-term residents would remember when blue maomao fish were a common sight at Goat Island.

“They are still in the reserve further offshore, but no longer come in close to shore for food.”

As part of his research, Harry also monitored reserves at Tawharanui and Hahei, and found that the biomass of snapper was increasing at each location.

“The common effect is an overall increase in snapper. Their babies also leave the reserve and seed the waters around them.

“It shows what a success a reserve can be and how restoring a small area can have benefits that spread.”


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