Farmer cleaning up with fishy venture

MILKING FISH: Ben Smith says the fish farming venture is not a quick fix, and needs time and resources. PHOTOS/JOHN STONE

A Spanish biologist is testing vials of water in a makeshift lab in an old milking shed.

Large tanks, placed on what was the cowshed yard, hold thousands of tiny fish of three freshwater varieties. Nineteen species of native grasses and freshwater plants poke through mud in pots sitting in vats of water piped from nearby farm drains.

Dairy farmer Ben Smith holds a 25cm fish which, had it not been dead for a couple of days, would have squirted out 50,000 eggs in the next week or two.

Those eggs would have become a mass of whitebait that could be fritter-ready in a few short months.

Never mind, there's plenty more fish in the tank. Gazillions more eggs.

We are on the drained-and-canalled Hikurangi Swamp which supports one of Northland's most productive dairying districts.

And we are on a whitebait farm, where not cows but the tiny transparent young of the native freshwater kokopu are about to be milked for all they are worth.

They are New Zealand whitebait, and at the top of a food chain in which freshwater fish live on aquatic plants grown in farm effluent and help cleanse that water in the process.

In turn, those little fish become another kind of white gold - commercially valuable fish products; food, fertiliser or fish oil for local and export markets.

Before the whitebait can thrive, two other fish species do the dirty work.

Silver and grass carp, which are unable to breed in Northland waters, eat the heavy effluent solids and excrete nutrients in water from farm drains and ponds.

That water is next pumped into a tank where young mullet munch on the leftovers (eventually they will live below plants growing hydroponically).

The water is then recirculated to where whitebait do their thing, each female capable of laying 50,000 eggs in tanks or in the great outdoors.

"If I could get rid of my effluent ponds out of this, we'd have clean discharge into our waterways," Mr Smith says.

The tank water can also be reused on the land. "Fish sweat ammonia and poo phosphate. You couldn't ask for more," Mr Smith enthuses.

The back-to-the-future system is called aquaponics and is based on 2000 years of Asian fish-farming practices, he says.

Local spin-offs could include cleaner waterways, food and fish-based fertiliser production and, Mr Smith and others hope, a barrier to proposed upstream gold mining.

He is putting his mettle where his mouth is after promising cleaner waterways, economic development and local jobs during a hui at nearby Whakapara Marae, where iwi, residents and farmers, politicians and environmentalists gathered late in 2013 to discuss an Australian company's hopes to mine Puhipuhi Mountain's mercury-laden rocks for gold and silver.

A year later, backed by the weight of 20 years of New Zealand research, the entrepreneurial Mr Smith had Ministry of Primary Industries' Sustainable Farming Fund money for a three-year trial and set-up.

Plans are under way to build a 2500sq m fish farm shed containing 60 tanks on his farm.

Freshwater shellfish specialist Maria Mugica, fresh from Spain, is contracted to the project for three years, first assessing the performance of different plants.

At this stage, it is mainly grasses and wetland plants but the system could also be used for commercial vegetable or stockfood crops, Mr Smith said.

"This is not a quick fix, it needs time, it needs resources, but this has been done on a cocky's shoe string.

"Any cocky could do it, all they need is two pumps and an aerator."