Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 

Existing Reserves Too Small To Protect Crayfish

Even inside fully-protected marine reserves crayfish numbers have plummeted and numbers outside reserves are likely much lower than official estimates, a new University of Auckland study shows.

Researchers, including Dr Nick Shears from the University’s Institute of Marine Science, say existing marine reserves in the Hauraki Gulf are not large enough to protect crayfish.
“We estimate that inside reserves, crayfish have declined by 59-80 per cent in the past 10-15 years despite being inside a strict ‘no-take’ area,” he says.
“Further, our estimate in the Hauraki Gulf is that the crayfish stock is just 3-12 per cent of unfished levels. That’s significantly lower than official fishery estimates of 20 per cent.”
The study combined long-term crayfish monitoring data from three marine reserves and their surrounding fished coasts from the past five decades. It includes data from Tawharanui collected by the late Dr Roger Grace, and Department of Conservation monitoring data collected at Leigh, Tawharanui and Hahei marine reserves over the last 20-25 years.
While the marine reserves at Leigh, Tawharanui and Hahei continue to support much higher numbers and larger crayfish than surrounding fished waters, monitoring shows declines in crayfish inside the reserves of between 59–80 per cent. 
This decline coincides with a wider decline in the surrounding CRA 2 fishery, thought to be a result of poor recruitment combined with sustained fishing pressure.
However, poor recruitment on its own doesn’t explain the decline. The study indicates it has been exacerbated by the continued capture of lobster on the offshore boundaries of these relatively small reserves.
Tracking research has shown that crayfish undertake seasonal movements whereby they move off the reef and out onto sandy habitats where they feed on bivalves. These movements often take them near to and beyond reserve boundaries where they are likely to be caught.
Dr Shears says extending both the Leigh and Hahei reserves have been proposed as part of the SeaChange process in the Hauraki Gulf Marine Park and these recommendations are currently under consideration by the Minister of Conservation and Minister for Oceans and Fisheries.
Steps have been taken to start rebuilding crayfish stocks in the Hauraki Gulf through cuts to commercial quota and halving the daily bag limit from six to three for recreational fishers.
But it likely won’t be enough, he says.
“It’s unclear whether these measures are sufficient to result in a recovery in cray numbers. Given the growing pressure on the Gulf, it’s unlikely traditional fishery management approaches will be enough to restore populations and the important ecological role crayfish once played.”
Currently, less than 1 per cent of crayfish populations in the Hauraki Gulf are protected in marine reserves and these results highlight the urgent and overdue need to substantially increase the level of marine protection in the Gulf, Dr Shears says.
This can be achieved through expansion of existing reserves and implementation of new marine protected areas that are well-designed and large enough to effectively protect these important species and their associated ecosystems.
 

© Scoop Media

 
 
 
Business Headlines | Sci-Tech Headlines

 

Commerce Commission: Warns Genesis Over Business Billing Errors

The Commerce Commission has issued a warning to Genesis Energy Limited about billing errors concerning electricity line charges to business customers. Genesis reported the errors to the Commission. The Commission considers that Genesis is likely to ... More>>

QV: Tax Changes Yet To Dampen Red-Hot Housing Market

Just over a month has passed since the Government announced measures aimed at dampening the rampant growth of the property market, and yet the latest QV House Price Index data shows the market hit a new high in April. The average value increased 8.9% nationally ... More>>

Stats NZ: Consents For New Homes At All-Time High

A record 41,028 new homes have been consented in the year ended March 2021, Stats NZ said today. The previous record for the annual number of new homes consented was 40,025 in the year ended February 1974. “Within 10 years the number of new homes ... More>>

The Conversation: The Outlook For Coral Reefs Remains Grim Unless We Cut Emissions Fast — New Research

A study of 183 coral reefs worldwide quantified the impacts of ocean warming and acidification on reef growth rates. Even under the lowest emissions scenarios, the future of reefs is not bright. More>>

The Conversation: Why Now Would Be A Good Time For The Reserve Bank Of New Zealand To Publish Stress Test Results For Individual Banks

Set against the backdrop of an economy healing from 2020’s annus horribilis , this week’s Financial Stability Report (FSR) from the Reserve Bank (RBNZ) was cautiously reassuring: the country’s financial system is sound, though vulnerabilities remain. More>>

Reserve Bank: Concerned About New Zealand's Rising House Prices

New Zealand house prices have risen significantly in the past 12 months. This has raised concerns at the Reserve Bank of New Zealand – Te Putea Matua about the risk this poses to financial stability. Central banks responded swiftly to the global ... More>>