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

 


Looking for the ‘X factor’ in fish

IMMEDIATE RELEASE 18/6/2014

Trout are spawning and its ‘talent time’ – looking for the ‘X factor’ in fish

It’s spawning time on the Rotorua lakes – when a few trout heading upstream find themselves hauled off into a fishy talent show!

Fish & Game staff know exactly what they’re looking for as they trap fish and screen out the biggest and best trout for their Big Fish Breeding Programme. These hand-picked (literally) specimens are the breeding stock used to raise more than 100,000 fish to keep North Island lakes stocked up for anglers.

The fish are trapped as they swim upstream to spawn – in a stream that flows into Lake Tarawera, known for its hard-fighting trophy trout. They are carted off to holdings pens in a stream which flows through Fish & Game’s Ngongotaha hatchery grounds.

A set of selection criteria are used to pick only the best fish as parents – a female to supply the eggs and “cross” with a male that’s used to fertilise them. The aim is to produce fish which are healthy and grow rapidly to a large size for anglers to catch.

Most of the fish used for breeding are three year-olds, along with a smaller number of four year-olds which are breeding for the first time. Trout stop growing once they reach maturity and spawn, so by selecting older maiden trout for breeding the hatchery improves the chance of their offspring growing bigger.

Previous spawners are often rejected because they have poorer quality eggs and these, Fish & Game officer Lloyd Gledhill explains, can be picked by signs such as the ragged edges on their fins where they’ve been digging redds (nests) in the gravel.

This year the largest fish appear to be around the 65cm to 68cm mark, so fish which are over 62cm fit the selection category for the time being. “Later in the season we might change the selection size depending on how the run is going. You never quite know how many fish might come in, and once they have been through the trap it’s too late to get more.

“If we don’t get eggs now, there’ll be no fish to release next year so the pressure in on” says Mr Gledhill.

After selecting for size, it comes down to a “judgement call” on the look of the fish. Mr Gledhill says you get fish that are different shapes including those which are “all head and shoulders” and tail off to the back. “I like a fish that’s a much more even shape all the way through. We look for robust, healthy fit fish.”

Fish & Game staff aim to end up with 135,000 viable fish, which means stripping an estimated 250 thousand eggs from the “ripe” hens. Every spawning season they “cross” a total of about 90 males with the same number of females, 180 fish in total.

“That gives us a good margin – some eggs die and others die at hatching so that gives a good number of viable fry at the end. It also ensures we get good genetic variety in the fish being released to the lakes.”

How are the eggs extracted? The fish are firstly sedated in a fish bin with a synthetic clove oil added, then a small gauge tube is inserted into the fishes belly cavity, and compressed air used to gently push the eggs out.

“The sperm activates as soon as it hits the water – so you’ve got about 20 seconds for the sperm to get to the egg and fertilise it.”

The eggs are taken inside the hatchery and placed into trays with running water piped over them, to begin the process of growing first into first “eye ova,” and then into fry.

When they’re big enough, the young fish are loaded into the ‘live trout truck’ and carted off for one of the many releases into North Island lakes.


© Scoop Media

 
 
 
 
 
Parliament Headlines | Politics Headlines | Regional Headlines

Gordon Campbell: On The Labour/Greens Deal (And The NZDF)

If Labour and the Greens were hoping their Budget Responsibility Rules (BRR) agreement would foster an unlikely alliance then hey… mission accomplished! Because it isn’t every day that Sue Bradford, the CTU and Matthew Hooton speak with one voice, as happened yesterday.

Unfortunately though, it’s hard to see how the BRR agreement will work to the advantage of Labour and the Greens in the context of the 2017 election campaign. More>>

 

Little Heading For Court: Apology Over Donation/Hotel Contract Claims Not Accepted

Today I want to publicly apologise unreservedly to Mr Hagaman for any hurt, embarrassment or adverse reflection on his reputation which may have resulted from my various media statements. I have offered that apology to the Hagamans. More>>

ALSO:

Biscuit Tin Of Democracy: World Heritage Site Protection, Ombudsman and Equal Pay Bills Drawn

On Thursday, 23 March 2017 three places are available on the Order Paper for the first reading of a Member’s bill. The ballot was held, and resulted in the following bills being drawn... More>>

ALSO:

Emissions Plan: NZ Needs More Science, More Trees, Fewer Beasts

A combination of technology breakthroughs, much more plantation forestry, and a big switch away from pastoral, particularly dairy farming, are identified as the key elements of any approach New Zealand takes to reducing its carbon emissions to a net zero level, according to a new report sponsored by the New Zealand chapter of GLOBE, a multi-party, global parliamentary grouping. More>>

ALSO:

"Backed To Win Seats": Labour Māori Seat MPs Won't Stand On List

The Labour Party is backing a request from its Māori seat MPs to stand as electorate MPs only, says Labour Leader Andrew Little. More>>

OutsKey: John Key's Valedictory Speech

I rise to address this House for the very last time. It has been a huge privilege to have served the people of Helensville as their member of Parliament, and, of course, the people of New Zealand as their Prime Minister. More>>

ALSO:

Productivity Commission: New Models Of Tertiary Education Are Coming

The report is a broad-ranging inquiry into how well New Zealand’s tertiary education system is set up to respond to emerging trends in technology and the internationalisation of education, and changes in the structure of the population, and the skills needed in the economy and society... More>>

ALSO:

PM's Press Conference: Water Everywhere

Monday's Post-Cabinet press conference focused on water, with the Prime Minister fielding questions about the possibility pricing water taken for export. Mr English said the government was directing their water allocation technical advisory group to include export water in considerations. More>>

ALSO:

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news