Comment: David Haynes, co-leader of the NZ Outdoors Party, responds to Tiwana Tibble from the Lake Rotoaira Forest Trust about pushing for a legislation change to remove the prohibition on trout farming in New Zealand.

Tiwana Tibble's article "Why farmers should be allowed to dive into aquaculture" is founded on the notion that the answer to the depletion of our wild sea fisheries by voracious commercial practices is farming fish, specifically trout.

Here are 10 reasons why it's not a good idea:

Feedstock

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Wild sea fish are processed into pellets for feeding farmed fish. So, rather than reducing pressure on our depleted marine ecosystem, it actually increases it. The alternative feedstock is equally unappetising, as you will read below.

Marginal economics

The high capital of establishing infrastructure - pipes, pumps, filters, tanks, refrigeration, treatment, monitoring and control systems, pushes return on investment out decades. Ongoing costs of food, energy and wages tend towards a marginal business where only the mega-aquaculture operations survive. Do we want mega-fish factories?

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Plague and disease

Intensively rearing fish creates three adverse effects: a homogeneous gene pool, fish stress and reduced water quality. The Ministry for Primary Industries has identified 36 different pathogens in fish farms across eleven countries. There is no disease-free fish farming country in the world. Animal welfare and consumer trust are unfortunate casualties in fish farming.

Gene dilution

Fish farms use a few breeding fish (broodstock) to provide milt and eggs from which the fish farm stock is generated. Thus genetic variation in the fish is reduced. As broodstock grow old, they are replaced by young farmed fish, hence genetic diversity (and resilience) is further weakened. If these fish escape this gene weakness is then introduced into our wild fish stocks, reducing their resilience and sustainability.

Commoditisation

Once trout have a saleable value there is the risk, exactly as for recreationally gathered seafood and whitebait, that scumbags will poach trout and establish a black market for personal gain. Trout are most vulnerable to poaching when they gather to spawn, hence both fish stocks and fragile spawning grounds can be severely damaged.

Tongariro River - the anglers' mecca. Photo / David Haynes
Tongariro River - the anglers' mecca. Photo / David Haynes

Poor quality product

Garbage in, garbage out - the old computing maxim - is equally applicable to fish farms. Farmed fish is nutritionally inferior to wild fish - bland, flabby and lower in Omega-3. More so when farmers use cheaper feed comprising ground-up feathers, abattoir waste, bean meal, canola oil, chicken fat and xanthins (to provide that orange flesh colour).

Environmental pollution

Intensively reared fish in tanks produce an equally intensive amount of faecal waste, ammonia, nitrites and carbon dioxide. This combines with mortalities (up to 30 per cent in salmon farms) and uneaten food and, unless micro-filtered, will end up in our waterways. Commercial fish farms here and worldwide add chemicals, such as growth hormones including testosterone, as well as antibiotics and fungicides which also end up in our rivers and seas.

Terrible trade-offs

Some pollution can be mitigated using recirculatory fish farming systems, where the same water is filtered and recirculated back into fish holding tanks, but only solids can be filtered out and so high concentrations of ammonia, nitrites, carbon dioxide and other solubles will still enter the freshwater system. But, these systems also increase the risk of diseases such as whirling disease, fin rot, gill rot, furunculosis, parasites and viruses – and yes, they also end up in our river and lake.

If it ain't broken ...

The Taupō trout fishery, for example, generates $93M per annum and fishing licence income for DOC and Ngāti Tūwharetoa. It provides social, recreational, health benefits for 6000 anglers every year and kai for locals and visitors alike. The wild Taupō trout is a free range, organic, healthy and nutrient dense food source for all New Zealand trout anglers, their friends and whanau. This cultural heritage has afforded New Zealand a wonderful resource since trout were first introduced into the Taupō system in 1887.

The many or the few?

Do we really want to risk our pristine environment, the enjoyment and rewards gained by thousands of New Zealanders?