Trout Centre

The Environment


Did you know?

- Trout are not native to New Zealand. Brown trout were introduced from the UK in 1867 and rainbow trout from California in 1888, and are highly valued sports fish.

- The Taupo fishery currently has about 90% rainbow trout and 10% brown trout.

- A rainbow trout is known as a ‘pelagic’ feeder or in other words, it will search for its food in the open water. The brown trout is a ‘littoral’ feeder meaning that it lives and feeds near the bottom and edges of lakes and rivers. Therefore, there is a very low chance of seeing a brown trout in steams.

- From April to November adult trout migrate up streams and rivers to spawn. Using caudal fin (tail) a hen digs a nest (redd) in the river bed gravel in which to lay her eggs. At the same time a jack fertilises these eggs with his sperm (milt) and then they are covered with gravel for protection. They move along a stretch of the gravel bed say 2-3 metres in length, laying a number of these ‘nests’ and as each nest is dug, so the gravel from the next one covers the newly laid and fertilised eggs.

- After about 30 days, the young trout (alevin) start to hatch under the gravel bed. At this stage it remains attached to its yolk sac which it feeds from. After about another 3-4 weeks, the trout will have eaten all of the yolk sac and will burrow up through the gravel and become free swimming.

- The free swimming trout is now called fry and for the rest of its time in the river it feeds on insects, most of which also live in the water.

- As the juvenile trout grows it enters the next stage called parr after the dark bars or parr marks that colour its sides.

- Between 12 and 18 months of age trout are called fingerlings. In human terms this is equivalent to the ‘teenage stage’ of their life cycle. It marks an important transition point when they leave the river environment and go to the lake for the first time. In the lake fingerlings begin feeding on a small native fish called smelt. Smelt were first introduced into Lake Taupo from Rotorua in the 1930’s specifically to be used as a food source for trout. Since their introduction, lake-dwelling trout fed mainly on another small native fish, koaro and a freshwater crayfish, koura. Eventually koaro numbers were greatly reduced. Smelt, which are much better adapted to resist predation, offered a solution to this diminishing food supply. Between Stages 1-5 trout mortality rates are quite high, only about 2 of every 3000 eggs will reach the spawning stage.

- Rainbow trout reach maturity and begin their own spawning journeys at about 3 years of age. The majority of trout return to spawn at the same grounds where they originally hatched.


Didymosphenia Geminata (Didymo)

Keep Didymo out of your river.

If you are moving items between waterways, you could be spreading Didymo which can be spread by a single drop of water on wet fishing gear, in a kayak, swimming togs or on boots to infect YOUR river. So even if you can't see it, you could be spreading it.

It's your job to make sure you, and your mates and visitors know the rules and apply them every time. No Excuses.

CLEAN: Soak or scrub all items for at least one minute with a 5% solution of dishwahing detergent, or a 5% solution of household disinfectant. A 5% solution is 500ml (two large cups) with water added to make 10 liters.

DRY: If cleaning is not practical, dry the item to the touch then leave for at least 48 hours before using in another waterway.

Remember felt soled fishing waders and wading boots are now not allowed.

Pest Fish

A growing problem
In recent years, the distribution of some introduced fish species has increased throughout New Zealand. Fish don’t walk; people are moving them around accidentally and on purpose.

Why worry?
The spread of these fish threatens New Zealand’s freshwater environments, native species and the whitebait, eel and trout fisheries.
• Some species such as Koi carp and catfish can degrade water quality by increasing turbidity, siltation, nutrient loads and algal concentrations.
• Some species such as Gambusia, impact on native fish either by preying on them directly, driving them from habitat or by altering their habitat.
• Fish diseases may be spread by the illegal transfer of pest fish
• Some species can build up to large numbers quickly and dominate communities.
• Introducing fish (or other animals and plants) into new places can dramatically alter the ecosystem and spoil other people’s enjoyment of that environment.

Which Fish?
New Zealand has 21 species of introduced freshwater fish. Some of these fish have become pests, notably:
- Gambusia (formally known as mosquito fish)
- Koi Carp
- Rudd (Outside the Auckland/Waikato Fish & Game Region)

It is important to keep native and introduced fish within their existing range. All fish can cause irreversible change when introduced to new habitats.

Other Threats
It’s not just fish that cause problems. New Zealand has also got invasive aquatic weeds (e.g. Oxygen weed Lagarosiphon and Egeria which choke our lakes and rivers) that have been spread on boats and trailers. Exotic snails and freshwater jellyfish may also have arrived on fishing gear.

You can help!
- Don’t liberate any fish into freshwater without first obtaining the appropriate authority.
- Wash all your gear down at the end of the day and before you go to a new place (including trailers, rods, nets and waders).
- If you see people releasing fish, contact your local Fish & Game New Zealand office or Department of Conservation office as soon as possible. Take details of the person, vehicle registration, etc.
- Encourage friends and gardeners not to spread Gambusia around. Native whitebait, bullies and insects are more effective, environmentally-friendly mosquito controllers.
- Empty your aquariums into the garden, not drains or streams.

The Law
It is illegal to liberate any aquatic life (including native and introduced fish, plants and invertebrates) to a water body where it doesn’t already exist. People caught liberating species without a permit from the Minister of Conservation are liable to a fine of $5,000 under the Conservation Act 1987.

In addition, Koi carp and Gambusia are classified as Unwanted Organisms under the Biosecurity Act 1993. People caught releasing, spreading, selling or breeding them are liable to a fine of $100,000 0o three years imprisonment.

Koi carp and Rudd (Outside the Auckland/Waikato Fish & Game region) are classified as noxious species under the Freshwater Fisheries Regulations 1983. A fine of $5,000 can be given to people who possess, have under control, rear, raise or consign these species.

If you want to introduce any species of fish, plant or invertebrate to freshwater you must receive authorisation from the Minister of Conservation before proceeding. Contact the Department of Conservation for a booklet that outlines the application process.


What is poaching?

Poaching is the illegal taking of trout. Poaching at Taupo usually involves setting gill-nets (up to 50 metres long) around the lake edge at night, or spearing or netting trout in small spawning streams, often by day.

Why is it important to prevent poaching?

The Taupo fishery is a wild fishery and totally sustained by natural spawning. Wading poachers not only kill adult trout yet to lay their eggs but stand on and kill many thousands of eggs already in the gravels.

The penaly for poaching is a maximum fine of up to $10,000 or one year in jail.