Multiple threats leave Hauraki Gulf in uncharted waters, report finds

One of New Zealand's greatest taonga, the Hauraki Gulf, is in trouble due in part to overfishing, excessive sediment and the impact of climate change, a new report says.

The Hauraki Gulf Marine Park, Tīkapa Moana, Te Moananui-ō-Toi, spans some 14,000 square kilometres from Te Arai to Waihi.

It is the seabird capital of the world, home to resident tohorā, and around 2 million people live by its shores.

A State of the Environment Report , released on Thursday, shows the marine park is experiencing continued ecological collapse.

It was facing multiple threats such as overfishing, excessive sediment and nutrient runoff and catastrophic climate changes.

The report also found marine heat waves, invasive seaweeds, more frequent storms and acidifying waters all posed serious new threats to the health of the gulf.

This comes just days after the government announced a fisheries plan for the gulf and a new set of marine protection areas.

Hauraki Gulf Forum co-chair Toby Adams said the latest report painted a grim picture of the current health of the Hauraki Gulf.

He said seabirds were struggling to feed their chicks, scallop beds were dwindling, and rising kina numbers were some of the problems to have arisen since the last report in 2020.

Adams said the best defence was to restore and protect the Hauraki Gulf at a community and government level.

This is the seventh report, following a succession of previous reports expressing concerns about environmental loss, degradation and inadequate responses to many of the issues impacting the gulf.

The 2023 findings also suggested Aotearoa was on the cusp of delivering important changes to improve biodiversity and environmental outcomes.

It found the gulf's resilience could be improved, as long as policymakers acted quickly and at scale.

It said creating new marine protected areas would be an important part of the solution and would cost comparatively little.

Dealing with land-based contaminants was arguably much harder, particularly for the sediment generated during extreme weather events, the report said.

Fishing

The total reported commercial catch of fish in the most recent three-year period was around 21,000.

Blue mackerel and snapper continued to be the two main species caught. Snapper landings were similar, but blue mackerel landings have decreased by 22 percent over the past three years.

The use of commercial methods that disturb the seabed have declined, with 27 percent fewer bottom trawls and 21 percent fewer Danish seines (a type of fishing used to catch species on the ocean floor) conducted.

Mass mortalities

Mass mortalities of fish, shellfish and seabirds were likely to become increasingly common due to the impacts of climate change, the report noted.

Mass mortalities of sponges have occurred already due to prolonged marine heatwaves.

Algae

Aotearoa's first recorded cases of shellfish poisoning caused by harmful algae occurred in 1992.

Since then, 19 harmful algal blooms have occurred in the marine park that resulted in closures or public warnings.

Auckland Museum's head of natural sciences, Tom Trnksi, said the gulf has been on a downward trajectory for years.

He said it was frustrating how long it was taking to establish any new marine protected areas.

''The increase of any useful marine protection is going from .3 percent to 6 percent which is well below what is considered best practice of what is considered a 30 percent target of marine protection."

Trnksi said over-fishing was not the only stress on the area, with factors like climate change also playing a part.

''We have to stop considering the gulf as an extraction basket solely; it is actually an eco-system and there are multiple stresses coming from land, human use and the sea."

Over-fishing, extreme weather events and excessive sediment made the area less resilient, meaning it could not recover from major events.