Thursday 13th November

Environmental Investigators

White Baiting – Inanga

Kirsty came to see us. She is an environmental scientist. She spoke to us about our Inanga and we found out some very interesting facts.

Inanga is one of 5 different types of white bait. This one is mainly found in Christchurch rivers. It is the smallest of the whitebait species and they are not very good swimmers or climbers. They live from 1-3 years. When they turn 1 they become an adult

Whitebait is eaten by humans and also other animals.

Live in the sea and salt water.

Spring high tide happens once a month. Ignunga use these tides to lay their eggs.

LIFE CYCLE

Eggs are tiny and are laid on the river bank in the grasses on the roots. Keeps them safe from eels and other fish that like to eat fish eggs. The eggs are laid by the adult ingnanga there on that spring high tide. At 3-4 weeks the larvae hatch from eggs and are swept out to sea on the tides.

Larvae at sea feed on small crustaceans and grow into juveniles called whitebait. They use their sense of smell to find fresh water and swim up stream to a river.

They grow into adults in autumn. They return to salt water wedge where they meet and lay their eggs. Each adult can lay 3000 eggs. Eggs stick to grasses. Males fertilise those eggs called spawning.

So Eggs –Larvae –Whitebait – Inanga.

WHERE INANGA LIVE

As eggs they are in the salt water wedge ( love zone )

They need gentle sloping banks, grasses and shade

As larvae they live in the sea

As adults they return to the fresh water part of the river.

To lay eggs they need right mix of salt and freshwater, right tide levels, right time of year,

Inanga numbers are declining

Because if you want them around in the future they need to be looked after now.

They are the bottom of the food chain. So very important

Why They are Declining

Fish ( trout ) slugs and mice are eating them.

Their spawning habitat is changing.

Stock is damaging the river banks

Man-made changes have been happening to the banks

Lawns are getting mowed right down to the river banks affecting spawning

Excessive sediment is occurring on banks and in the rivers

Man has put in tide gates which don’t allow fish through.

 The whitebait lining up to swim up the river.

The predators chasing the whitebait