Salmon Farming at the End of the World

Stewart Island is not technically at the end of the world, but it certainly feels like it. From the South Island it can only be reached by small ferry (cancelled when the Foveaux Strait is too rough) or 8-seater airplane that arrives in a small clearing of trees on a single strip of paved concrete.


To the south, save a small uninhabited archipelago, the next landmass is Antarctica. Despite (or rather because of) its remote, southern location it presents an ideal environment for salmon farming and is home to one of the largest farms in New Zealand. In the Island’s Big Glory Bay, Sanford ltd./Stewart Island Salmon produces almost one-third of all New Zealand-farmed Chinook Salmon. Although the same species is farmed here and at Mt. Cook Alpine Salmon, both farms have vastly different approaches to aquaculture driven by environmental context, scale of operation, and governmental restrictions. This was a chance for me to build off my experiences on a small, freshwater salmon farm and understand how they might differ from those on a large, marine farm.


Two of the most prominent factors of my Watson year have been species and environmental context. I spend a fair amount of me time noticing how these two factors inform and interact with each other. Salmon are somewhat high maintenance when you compare them to other species like tilapia or shrimp. These fish need consistently cool water (ideally sitting at or below 14o C) and a strong water flow to bring in richly oxygenated water and flush out waste. Stewart Island has a slight advantage over Mt. Cook in this respect since the pens are situated in a large, deep bay rather than in comparatively narrow, shallow canals. Since water flow and temperature at Stewart Island Salmon are informed by the physical oceanography of the bay and larger oceanic currents that flow past New Zealand, this farm can be understood as part of a larger, more open system than at Mt. Cook. where the water in the man-made hydropower canals is controlled by a series of locks and dams.


At Mt. Cook, salmon are farmed in a series of man-made canals that connect the Canterbury region’s lakes; producing hydropower for much of the country. Consequently, the water flow in the canals is controlled by energy companies that manage the hydroelectric dams and must maintain certain water levels in the lakes. In the canals, water flow can be variable throughout the day and on one occasion stopped completely because of water levels in the tributary lake. Although Mt. Cook has ways to handle this high variability of flow, it represents a large challenge to salmon farming not found on Stewart Island. Interestingly, the salmon pens at Mt. Cook also “push back”, reducing the flow rate of water in the canals by limiting the free space for water to flow through. This has led to firm limits on the number of salmon rafts that are allowed in the canals and, consequently, the maximum amount of salmon that Mt. Cook can produce. The site-specific interactions between environment, corporations, fish biology, and cage construction at Mt. Cook Alpine Salmon produce a unique set of challenges unlike those I encountered at Stewart Island.

Having a more open system comes with other challenges, such as greater fish predation. The operations manager at Stewart Island said that the smell morts (dead fish) in the pens will attract dolphins and sharks that will make their way into the nets, causing damage and loss of product. To reduce predation threats, commercial divers must regularly enter the water to manually remove dead fish. A larger operation also requires higher levels of monitoring for water quality and environmental degradation. The salmon farm is required to move their entire operation to a new site in the bay every three years to avoid the collection of waste matter beneath the pens. They also carry out weekly water quality tests on the farm and monthly tests throughout the bay to ensure that they maintain low Nitrogen (a key element in animal waste and contributor to toxic algal blooms) levels.


Stewart Island, in part due to its more open system has the ability to produce salmon on a much larger scale. Where one pen at Mt. Cook would hold around 18,000 fish, a pen at Stewart Island held upwards of 100,000; almost six times as many fish. It’s not that salmon on Stewart Island were crammed into the same space, but that they were grown in significantly larger pens. This same scaled-up production was found in almost every other aspect of farming, from harvest to size grading. Almost all of the processes we did by hand at Mt. Cook would be unimaginable on such a large scale. The sheer size of production at the farm meant that many of their operations were mechanized. For example, while we hand-fed salmon for 3 hours every day at Mt. Cook, feeding was controlled via a computer and a feeding system that distributed feed from a central bay along pipes to the various cages, lasting significantly less time. At Mt. Cook, we normally harvested no more than 1,000 fish per day. At Stewart Island, they would harvest anywhere from 4,000-6,000 fish daily.

The general sentiment about large, industrial food operations (fish or otherwise) tends to be largely negative. But it was really valuable to actually visit a semi-industrial fish farm and learn more about their operations and experiences; especially after having just worked on a smaller fish farm. The operations manager and I both agreed that aquaculture can sometimes come across as a “black box” to the average consumer. What doesn’t necessarily come across at the grocery store is the amount of care for the fish and respect for the environment that many fish farmers have. He told me that he loved going to the seafood section of the grocery store to see how the final product looked, and that he took a certain amount of pride in seeing it cost slightly more than other salmon. Of course, this one farm does not stand in for other salmon farms in other parts of the world (or even other parts of New Zealand!), but it does speak to the complexity of aquaculture food production. The diversity of fish farms, like the diversity of landscapes they inhabit, is a mixed bag that is best understood on a case-by-case basis.


One thought on “Salmon Farming at the End of the World

  1. Your observations get more interesting as you keep going and are getting more informed. I look forward to each blog. Keep up the good work.
    Aunt Elaine


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