Local Govt | National News Video | Parliament Headlines | Politics Headlines | Search

 


Trout heads give up browns' spawning secrets

Trout heads give up browns' spawning secrets

What clues to the origins of the Waikato’s brown trout can you gather from a fish head…or more precisely, the small bones in a fish’s head?

The answer, according to Fish & Game Auckland-Waikato, is plenty.

Fish & Game officers have completed the first phase of a study aimed at tracing the origins of brown trout in the Waikato fishery.

Auckland-Waikato fisheries manager Dr Adam Daniel explains that researchers can use the ear bones of fish, called an otolith, to estimate age and also track their life history from the geochemical signals preserved in the otolith.

The otolith is formed as consecutive layers of calcium carbonate are laid around a core that forms soon after a fish hatches, so it is possible to cut through an otolith, revealing the layers like growth rings of a tree. Each ring contains a fingerprint of the water chemistry that matches the water the fish swam in when the layer was formed. So if you can extract the information, you come up with a sort of ‘fish's diary,’ from hatching through to when the fish was captured.

Dr Daniel says the first phase of their study involved collecting more than 70 heads from adult brown trout. A local eel fisher Bob Clark, the organisers of the Kilwell Lower Waikato River Trout Contest and a handful of keen anglers donated heads for the project. “We are very grateful to them all for their help in this work,” he says.

The adult brown trout, some over 50cm long, had come from a wide area, stretching from Tuakau to the base of the Karapiro Dam.

The study also involved catching juvenile browns by electrofishing (electric shock).

Dr Daniel says to determine where the brown trout that inhabit the lower Waikato River are spawning, the chemical signatures from the ear bones of the adults, will be matched up with the signatures of otoliths from juvenile brown trout caught in tributaries of the Waipa River – and water samples.

“We won’t be able to get it down to an exact tributary, but we should be able to get it down to at least a catchment or basin.

“For example, fish from Pirongia should have a different signal to those we get out of south Waikato streams, like the upper Waipa sites.”

Dr Daniel says the benefits will come in finding out which streams are actually producing the large numbers of brown trout found in the lower Waikato fishery. “We know we have a pretty healthy fishery there but we don’t know where those fish are coming from.”

Collecting the juvenile trout has involved a huge amount of foot slogging. So far more than 14 different tributaries have been electrofished with little success, but ironically, a dozen juvenile browns were pulled out of a “mud puddle” next to the Mangatutu River which rises in the Pureora Forest.

Dr Daniel says that once their collecting has been completed, and samples have been analysed by Cawthron Institute scientists, the information can be applied “almost immediately.”

What we need to know, he explains, is which are the “priority rivers” for brown trout spawning, which can be applied to fisheries management – for example, decisions on season lengths, enforcement and environmental protection.

This knowledge can be used in Fish & Game submissions on RMA-related issues like water takes or discharges from sewage plants. “The information will be very helpful when prioritising fencing and planting projects.”

Dr Daniel says: “It will help us better utilize our resources because we simply can’t monitor all 20,000-plus kilometres of trout streams we have in the Auckland-Waikato Region every year.”

ENDS

© Scoop Media

 
 
 
 
 
Parliament Headlines | Politics Headlines | Regional Headlines

Gordon Campbell: On Drone Strikes And Judith Collins‘ Last Stand

The news that a New Zealand citizen was killed last November in a US drone attack in Yemen brings the drones controversy closer to home.

To the US, drones are a legitimate response to the threat posed by the al Qaeda organisation and its franchisees... To the US, the drones carry the added advantage of not putting US troops at risk on the ground, and minimises the need for putting them in large numbers in bases in the countries concerned, always a politically sensitive point.

The counter-argument, well articulated by security analyst Paul Buchanan on RNZ this morning, is that this particular drone attack can be said to amount to an extra-judicial execution of a New Zealand citizen by one of our military allies, in circumstances where the person concerned posed no threat to New Zealand’s domestic security. More>>

 

Parliament Today:

Policies: Labour’s Economic Upgrade For Manufacturing

Labour Leader David Cunliffe has today announced his Economic Upgrade for the manufacturing sector – a plan that will create better jobs and higher wages. More>>

ALSO:

Gordon Campbell: On The Life And ACC Work Of Sir Owen Woodhouse

With the death of Sir Owen Woodhouse, the founding father of the Accident Compensation Scheme, New Zealand has lost one of the titans of its post-war social policy. More>>

ALSO:

Bad Transnationals: Rio Tinto Wins 2013 Roger Award

It won the 2011 Roger Award and was runner up in 2012, 2009 and 08. One 2013 nomination said simply and in its entirety: “Blackmailing country”... More>>

ALSO:

Select Committees: Tobacco Plain Packaging Hearings

The Stroke Foundation is today backing the Cancer Society and Smokefree Coalition who are making oral submissions to the Health Select Committee in support of proposed legislation to remove of all branding from tobacco products. More>>

ALSO:

Milk: Oravida Asked For Cabinet Help

New evidence released by New Zealand First today reveals Justice Minister Judith Collins used her position to manipulate the Government to help her husband’s company, Oravida, after the Fonterra botulism scare, says New Zealand First Leader Rt Hon Winston Peters. More>>

ALSO:

With Conditions: Ruataniwha Consents Approved In Draft Decision

The Tukituki Catchment Proposal Board of Inquiry has granted 17 resource consents relating to the $265 million Ruataniwha Water Storage Scheme in a draft decision that would open more of the Hawke’s Bay to irrigation. More>>

ALSO:

Fast Lanes, Campervans: Labour 'Making The Holidays Easier For Kiwi Drivers'

The next Labour Government will make the holidays easier and journeys quicker for Kiwi families driving on the roads, says Labour Leader David Cunliffe. More>>

ALSO:

Gordon Campbell: On Royalty And Its Tourism Spin-Offs

Ultimately the Queen’s longevity has been one of her most significant accomplishments. A transition to Prince Charles while the monarchy was in the pits of public esteem in the mid to late 1990s would have been disastrous for the Royal Firm. Far more congenial representatives have now emerged... More>>

ALSO:

Privacy (Again): ACC Demands Excessive Privacy Waivers

Labour: “This is just another example of ACC under National deliberately acting to deny treatment and compensation... Those who did fill in the form have effectively been victims of yet another ACC privacy breach. This time Judith Collins knew it was happening..." More>>

ALSO:

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news