Down on the farm

Clean and green? Or a noxious blight on our coasts? A sustainable way to feed the world? Or just another example of fishing down the food chain? Opprobrium towards fish farms, finds Marieke Hilhorst, is sometimes based on perceptions either outdated or just plain wrong.

Fish farming excites conflict whenever – wherever – it’s mooted. Last year, a bid by King Salmon to add nine more salmon farms to the five it already runs in the Marlborough Sounds saw protest flotillas put to sea (in early March this year, the Environmental Protection Agency approved five of the nine applied for. The Environmental Defence Society has mounted a High Court appeal.), and science wielded like a club in trenchant submissions, both community and corporate.

Expect to see more such arguments: aquaculture is one of New Zealand’s fastest-growing primary industries, and means to be a billion-dollar business by 2025. That ambition is backed by the Government’s 2012 aquaculture strategy and a five-year action plan, along with revamped resource management planning to expedite new applications.

Presently, more than 70 per cent of marine farms are raising green-lipped mussels, but molluscs won’t be delivering those billion-dollar earnings alone, says Andrew Forsythe, NIWA’s Chief Scientist, Aquaculture. He points out that a hectare of mussels returns about $50,000 – a typical one-hectare fish farm, however, could gross $25 million.

“Growing aquaculture through mussels would need thousands of hectares of space, which would be politically and socially difficult,” says Forsythe. “Far less is needed for finfish farming – the scale and the value are worlds apart.”

But with the returns comes the strife. Unlike mussels, which simply eat whatever the sea wafts past them, fish need feeding. Opponents say that leaves the environment vulnerable to excess nitrogen loads, algal blooms, pollution and smothering by uneaten feed or faeces. They also question the ecological wisdom of catching wild fish simply to feed farmed fish.

That criticism, says Forsythe, is 20 years out of date: “People think it’s all fish meal and oil from reduction fisheries – Peruvian anchovies dried, ground up and turned into fish pellets. That hasn’t happened since the early 1990s.”

Today’s standard commercial salmon diet is probably 10 per cent marine protein at most, he says, and that would be sourced from certified sustainable reduction fisheries and fish waste (see sidebar: 'You are what your fish eats').

NIWA’s General Manager, Strategy, Dr Bryce Cooper, says public antipathy stands in the way of the industry’s aspirations. Aquaculture, he says, will always be a challenging environment: “It’s a complex, dynamic, changing environment, with many influences. Aquaculture uses public space for private gain, and that coastal space is highly treasured by New Zealanders.”

But, he insists, many negative perceptions are based on less-than-enlightened aquaculture practices elsewhere. “There have been past examples from overseas,” says Cooper, “where extreme stocking densities, poor feed and disease management and inappropriate siting of farms have led to fish kills and significant damage to the environment. But New Zealand has learnt from those. Our record is far better than that. “We need to remove the misinformation that’s out there,” says Cooper, “and get some balance and trust back into the debate. At one extreme you have people saying any fish farming will be an environmental disaster, and on the other you have some in the industry saying there are no real problems and they should be allowed to get on with it unimpeded. Somewhere in between is the truth.”

NIWA’s job is to find it. New Zealand’s largest team of aquaculture specialists is delving into how fish farms affect the vitality of the environment, and vice versa. Two main research threads are environmental performance – how to monitor and manage the environment to minimise any adverse effects – and fish husbandry – how to grow good animals well.

To that end, NIWA’s been looking beyond the fish-farming staple of salmon, towards new species – kingfish and groper, or hāpuku. From those species, it’s selected and bred the healthiest, fastest-growing stock. The programme also develops and tests fish diets based on nutritious, environmentally-responsible ingredients – often from unlikely sources such as leaf and twig meal from the wine industry and oil from mussel industry waste.

Forsythe says the lab work on kingfish is “done and dusted,” while hāpuku is “nearly there". The next step is to test the species’ commercial viability in sea pens, and to ensure the broodstock can reliably produce the young for ongrowing.

Monitoring the environment

The environmental component of NIWA’s research programme is looking at what happens to fish farm waste: where it goes, what effects it has and whether those consequences are socially and ecologically acceptable. That means measuring any effects on the seabed directly under a fish farm, as well as the water column.

“We all recognise that immediately under a fish farm there will be environmental damage – changes to the flora and fauna on the bottom,” says Forsythe. “So the questions are: do they affect wild fish or the farmed stock? How far do those effects spread? Are they reversible? Are there rare species that could be lost?”

When fish farms are consented, reasons Forsythe, regulators have effectively accepted measurable impacts on the benthic communities beneath them. And because fish are very sensitive to water quality, he says, it’s in fish farmers’ own interests to minimise those impacts because consequences like depleted oxygen and hydrogen sulphide loadings can affect the fish in the pens above.

That leaves the pelagic effect: nutrients that end up in the water column – particularly nitrogen. Cooper says the best mitigation is to limit them in the first place. If feed is well formulated, and applied in quantities just sufficient for fishes’ needs, he says, only a small fraction of nitrogen enters the environment. "High conversion of feed to fish flesh is in the best interests of the farmer and the environment. It’s a win-win. No-one farming fish should want to waste feed – its expensive."

That’s cold comfort to those who cite damage caused by fish farm nutrients overseas (see sidebar: The nuances of nitrogen). Forsythe says there’s a recognised lack of scientifically robust, publicly available information about feed conversion rates in fish farms here and overseas, as aquaculture companies keep commercially sensitive feed conversion rates close to their chests.

Tracking the fate of nutrients

Forsythe says NIWA’s research has already shown us how much a fish eats, how much it excretes, and the difference between them – in other words, how much feed gets converted into fish. NIWA’s hydrodynamic models predict where the waste feed, fish faeces and nitrogen excreted through the gills will end up. “Feed has a certain settling velocity in the water, so if we say up to one per cent might not be consumed by the fish, we can plot where those uneaten chunks of food might land on the seafloor.” Faeces behave differently, but with appropriate analysis, says Forsythe, “we can plot where that falls on the bottom, and where the nitrogen discharged through the fish’s gills goes. Then we can add that nitrogen into a model and say how likely it is to be converted into algae.”

Today’s consumers are informed, says Forsythe. “Their interests go beyond the things that are physically embodied in the product; beyond wholesomeness and taste and appearance – those are all taken as read. They also have an expectation that the product is produced in an environmentally and socially appropriate manner. And that’s where I think it actually becomes quite intriguing – our job isn’t just to figure out how to produce fish in a conventional sense, but how to produce it in a manner that will be acceptable to the consumer.”

Negative perceptions can sometimes resist all manner of evidence to the contrary. What’s more, the protagonists view each other’s information with deep distrust. Says NIWA Assistant Regional Manager, Michael Bruce, some people are blind to the many other sources of nutrients – farms, forests, towns, sewage treatment plants, industry – yet are fixated on fish farming. Ideally, the ecological effects of aquaculture would be considered alongside all those other activities, but too often that holistic view is lacking. “Above all, our position at NIWA is to provide good scientific information,” says Bruce, “upon which sensible and realistic decisions can be made.”

Minding the gaps

So when the  set out to gather the best available information about the ecology of aquaculture in New Zealand, NIWA was on their call list.

Stephanie Hopkins, an MPI Senior Aquaculture Advisor, is overseeing the project. It’s intended to help local government and industry, but she hopes it will be used by anyone with an interest in fish farming. The Internet is brimming with overseas content, but, says Hopkins, much of it is either dubious or has no relevance here. “We identified a lack of quality information, and quite a bit of misinformation, around the ecological effects of different forms of aquaculture in New Zealand.”

After gleaning everything we know about the ecology of marine farming in New Zealand, Hopkins’ project will sift that information, looking for the biggest risks to be managed. Then the findings will be presented in a userfriendly summary that presents an accurate, simple picture of likely issues and effects at future New Zealand aquaculture sites.

It’s hoped the information package, due out in mid-2013, will foster a more informed and balanced debate thanks to input, not just from NIWA, but from other scientists, councils and environmental NGOs. It will address the raft of concerns that surface whenever aquaculture is on the table: pelagic effects; benthic effects; impacts on marine mammals, wild fish and seabirds; biosecurity threats; escapees; genetic modification; additives and impacts on water flows.

Hopkins says the review covered not only existing species – salmon, mussels and oysters – but those likely to be commercialised in the next five years or so, such as kingfish, hāpuku, undaria and sea cucumbers.

“This latest effort builds on earlier work, and identifies some management options and knowledge gaps within each topic,” Hopkins says. “It points us to what we need to look at now with our research.”

MPI scientist Rich Ford says the project’s risk analysis will prove vital to informed debate. Technical information alone would easily mislead discussion, he says, because not all issues and risks are equal – hydrodynamic effects, for example, get less attention than biosecurity, which is a top concern. “So we’ve done a lot of work on getting better context and risk analysis, and it’s very useful in identifying where we believe most of our effort should be,” says Ford.

The literature review made it clear that nitrogen loading is a critical consideration in fish farm applications, determining just where they might be placed and how many should be permitted.

Ford says another useful exercise would be to create good biosecurity management plans and guidance on best practice for adaptive management (see sidebar: 'Learning by doing'). He also wants coasts surveyed for any ecologically sensitive areas that should be considered no-go zones for aquaculture. “We know there are benthic impacts from aquaculture, particularly fish farming, so if there are areas we think shouldn’t be impacted at all … we don’t want to put (farms) on top of them.”

Biosecurity is trickier: “The best we can do is manage the risks – we’ll never eliminate them because there are things like larvae which can be released. And aquaculture is only one small part of that picture; it’s (also) about port activities and recreational boaties.”

We know plenty about farm-level impacts, says Hopkins, but we don’t know enough about the cumulative impacts of aquaculture at a broader, ecosystem level. “That’s hard to nail down, because it requires a more collaborative approach – it’s not just about aquaculture. You’re looking at the assimilation capacity, the carrying capacity, of the environment on a bay-wide level.”

You are what your fish eats

Some 90 per cent of fish meal protein nowadays comes from terrestrial byproducts or fish offal. Farm salmon dine on such incongruities as soya beans, canola and lupin, even feather meal. “Feathers are quite high in protein,” says Andrew Forsythe, “so, instead of just chucking them away, you can turn them into quite a nice protein source.” So too, chicken skin; the waste from the skinless fillets on supermarket shelves. “Nobody wants to buy a kilo of chicken skin, but it’s all food grade, so that valuable protein gets used in fish pellets.” And energy efficiencies have improved, he says. “Thirty years ago, it wouldn’t have been unreasonable to get three kilograms of feed making one kilogram of fish – the other two kilos went into the environment. But today, if you’re an Atlantic salmon farmer and you couldn’t get 1.2 kilograms of feed making one kilogram of fish flesh, you’d lose your job.” New Zealand’s Chinook salmon is a different beast, but there are still opportunities to improve conversion rates. NIWA estimates a kilogram of Chinook flesh might conservatively take 1.7 kilos of feed to produce.

The nuances of nitrogen

A major criticism of fish farming stems from the fact that captive fish must be fed. Says Ministry of Primary Industry (MPI) scientist Rich Ford: “As opposed to mussel farming, you’re putting food into the system, and that food – and the faeces from that food – releases nitrogen. One of the harmful spinoffs of excess nitrogen is excess algal growth.”

At best that’s merely a nuisance, but when an algal bloom turns toxic, ecosystems suffer. In extreme cases, the water is robbed of dissolved oxygen, killing fish both inside the cages and out, as has happened in shallow Scandinavian bays.

However, proving any link between nitrogen from fish farms and harmful algal blooms, says Ford, is complicated: “It’s not just about the nitrogen. It’s also about stratification, and wind and temperature.”

That means it’s difficult to set limits on fish farms on the basis of nitrogen output alone. “We’re not really sure about … how many farms we can stick in the Hauraki Gulf, or Tasman and Golden Bay, or the Marlborough Sounds, before we get to a level where we’re likely to see harmful impacts from the build-up of nitrogen.”

An MPI review of overseas literature might offer some answers. The temperate environments of Norway, Scotland, Canada or Chile may be similar enough to our own to allow for analogies between stocking densities, nitrogen outputs and harmful effects. If we’re not seeing harmful effects at New Zealand’s lower stocking densities, says Ford, “that may suggest what we should be thinking about it in terms of limiting growth".

Informing the debate

Stephanie Hopkins, an MPI Senior Aquaculture Advisor, hopes the Ministry’s work will go some way to clearing the air around aquaculture, and that people on all sides will see it as neutral, up-to-date and independent. “That’s why, with the literature review, we got the leading New Zealand experts from NIWA and Cawthron to work collaboratively on it." Exhaustive peer review meant “it’s been a very thorough process, and I’m hoping that this will become the ‘bible’ of ecological effects … that people can really trust.”

New Zealanders value their environment, she says, but it’s difficult convincing them of scientific rigour. “We have a very high bar that industry has to pass, so they do have to keep constantly proving their environmental performance. It’s a tough dance.”

Learning by doing

Given the controversy around finfish farms, Dr Bryce Cooper says ‘learning by doing’ is entirely appropriate.

Waikato Regional Council applied adaptive management to a staged expansion of mussel farming in the Firth of Thames, and may follow the same approach in a designated finfish zone west of Coromandel. While the designation allows for 8000 tonnes of fish a year, the first stage, if consented, would likely provide for around half that, with a requirement for environmental monitoring.

“So, you introduce some nets at lower production, then see how it works, and whether everything goes according to our modelling and best estimates. If it does, everyone is more comfortable with expansion.”

One key assumption, Cooper says, is the feed conversion ratio. If Firth finfish farms get the green light, monitoring would deliver actual feed conversion ratios, rather than NIWA’s estimates, improving the accuracy of modelled effects.

“That would show us whether it's financially viable. Even if it is, the environmental consequences may mean you could possibly only go up to 5000 tonnes per annum, instead of 8000. Or maybe 8000 tonnes is easily absorbed.”


Chief Scientist - Aquaculture & Biotechnology