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 Mt Albert Aftermath

Personality politics – Jacinda is great! Jacinda is not so great! – have dominated the coverage of the Labour Party’s fortunes this week...

Still, this is a relatively new and welcome problem for the centre-left. Labour has seemed so bereft of crossover talent for so long that it seems almost embarrassed by this latest development. More>>

 

Conservation: Central Govt Takes Over 1080 Regulation

“This new approach standardises the rules for using such poisons rather than the current system of different rules in different regions. This change will reduce costs and delays for operators, ensure consistent conditions throughout the country, reduce mistakes from misunderstanding rule differences and allow best practice approaches to be used." More>>

ALSO:

Election Entertainments: ACT Has Prison Plan, Greens Have Water Bill

Green Party launches Member’s Bill to protect our freshwater The Green Party has today launched a member’s bill that will keep water from underground sources, called aquifers, safe from pollution and contamination. More>>

ALSO:

2040 Target And Lower Standards: “Swimmable” Rivers Five Times More Likely To Make You Sick

Forest & Bird has condemned the government’s new water quality standards, warning New Zealanders that they lock in current levels of water pollution and allow for a 5-fold increase in the chance of getting sick from swimming in a river. More>>

ALSO:

Immigration: Clampdown On Rogue Employers Good First Step

The Human Trafficking Research Coalition is pleased at the new clampdown on rouge employers who exploit migrants announced by Minister Woodhouse this morning, and believes this is a step in the right direction. More>>

ALSO:

Mayor: 750 New Social And Affordable Homes For Wellington (Over A Decade)

The next stage of Wellington’s Housing Upgrade Programme will see at least 750 new units of social and affordable housing built over the next decade, Mayor Justin Lester has announced. More>>

ALSO:

22/2: Christchurch Quake Memorial Unveiled

A city, a region, a nation and an international community impacted by the Canterbury Earthquakes will come together to mark the sixth anniversary of the deadly quake and dedicate Oi Manawa Canterbury Earthquake National Memorial. More>>

ALSO:


November Quakes:

Gordon Campbell: On The Mana-Maori Party Deal

If the self-interest involved wasn’t so blatant, the electorate deal between the Maori Party and Hone Harawira would be kind of poignant. It’s a bit like seeing the remaining members of Guns’n’Roses or the Eagles back on the road touring the nostalgia circuit… playing all the old hits of Maori unity and kaupapa Maori politics. More>>

ALSO:

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news