Something Fishy – Chenopodium detestans
With its smelly reputation and equally unimpressive looks, the critically endangered New Zealand fish guts plant will likely never make it on a tourism poster or a commemorative stamp. Still, this curious little plant deserves our attention.
Commonly referred to as New Zealand fish guts, Chenopodium detestans is a native flowering plant only found on the South Island. It hails from the Amaranthaceae family of plants that includes spinach, beet, amaranth and quinoa.
Around the world, Chenopodiums are known as extreme survivalists, inhabiting some of the harshest environments, including the Andes, Himalayas and Atacama Desert. And the New Zealand fish guts are no different, acclimatising to live in the most extreme conditions. Historically found between Otago and Canterbury, today only three known populations are surviving at Lake Lyndon, Twizel and Lake Tekapo.
Until five years ago, few Kiwis had even heard of New Zealand fish guts, let alone seen or smelled one. That all changed in 2017 when the Department of Conservation (DOC) developed an algorithm to identify priority species for management. The New Zealand fish guts plant found itself in the top 150. Almost overnight, the little-known New Zealand fish guts plant was on the map. For DOC’s threatened plant ranger Daniel Kimber (Danny), it hadn’t come soon enough, with the Lake Lyndon population (which he looks after) narrowly hanging on by a thread. ‘Yeah, they stink, and they’re ugly, but the plants they live with are massively diverse and really special. Lake Lyndon is a hotbed of biodiversity. I have 17 different plants [species] that I look after, and no less than 11 are in the Waimakariri Basin.’
English-born botanist Thomas Kirk first recorded New Zealand fish guts at Lake Lyndon as early as 1877, but it wasn’t seen again for more than 100 years. In the1980s, they had managed to narrow it down to an area of one square kilometre. Thought to be extinct, the next time it surfaced was in 2010.
Danny set up monitoring lines in the lake in 2020, but lake levels have remained too high for the past couple of years due to weather conditions. The last time the plant was spotted was in February last year (2021). ‘They are weird. There is so much we don’t know about them, not helped by the fact that they don’t seem to pop up every year. When they do pop up, it’s very exciting. It gives us a short window to learn about them. One rain event and they’re gone,’ explains Danny.
‘What we know is that it’s a strange little plant that lives on lake shores, clay and salt pans. It needs seasonal flooding to prepare its muddy floor habitat and possibly set its seed for germination. If the lakes stay high and their habitat stays covered by water, they cannot grow. The seed will sit dormant for decades waiting for their chance.’
Their lifecycle seems totally dependent on water levels, he says. ‘They are an annual – living, breathing and dying all in the space of less than a month. Once they emerge, they quickly grow, flower and produce seed, then die. Hopefully, before the water retakes its habitat.
‘But what we don’t know is why sometimes the water resides with the right habitat, and they don’t emerge. There has got to be something fish guts need; it’s not just about exposure. Otherwise, you would expect to see heaps of them when the lake drops, and it’s not like that. We think there is some dormancy period for this plant.’
From the seed they’ve collected and grown successfully at the DOC nursery at Motukarara, Danny says they’ve noticed that the fresher the seed, the worse the germination. The best germination results came from seeds sitting in a plastic bag on a desk for six years.
The gaps in germination make monitoring them more difficult. They’re also hampered by plants not always coming up in previously known locations as the seed is moved by wind and the water direction, says Danny.
However, the Lake Tekapo population tends to come up in the same spot with more regularity which they assume has something to do with the lake’s water levels being more universal depending on power usage. Still, in reality, they don’t know if that has an effect or not, notes Danny.
Unfortunately, there is no getting away from the pungent smell for which the plant is named. ‘It literally smells like rotting fish, which it omits from all parts of the plant,’ he says. ‘Often, you can smell the plant before seeing it in the right conditions while monitoring. And if you touch it, the smell stays with you until you can wash your hands and clothes.’
It’s so bad that when the nursery successfully grew them, their excitement quickly turned to dismay when they started producing seeds and stinking out their entire building. ‘I quickly got a phone call to come and collect them asap,’ laughs Danny. But while the smell is clearly not its most endearing quality, it has its benefits. For example, helping to attract flies and other insects for pollination and as an adaption to ward off potential browsers, like native ducks and geese.
The New Zealand fish guts plant is also unique because it produces a spongy protective covering all over the leaves, flowers and seeds called a ‘bloom’. The blooms are modified hairs that act like bladders. Like with other members of the Chenopodium family, it’s thought the blooms work as a salt removal mechanism allowing salt inside the plant to be removed and released outside the plant, allowing it to exploit high salt environments.
Danny says the water levels are not the only problem threatening the survival of the New Zealand fish guts plant. The main issue is habitat degradation caused by the invasion of exotic weeds, which outcompete for the same habitat, and four-wheel drive vehicles ripping up the precious habitat. Powerboats also put enormous human pressure on the lake during the summer months. ‘The water acts as weed control. But once it resides, everything takes its chance [to grow], and our problem is that often the weeds are faster to get going than the natives are. Bring in the disturbance from people, and it swings even more in favour of the exotic weeds.’
DOC has worked with Environment Canterbury and Selwyn District Council to fence off the area surrounding Lake Lyndon to protect fish guts habitat from vehicles. Management of the site is focused on reducing weed competition, says Danny. One idea is to use a lawn mower to remove the cover of weeds, allowing light gaps for fish guts to grow and stopping the weeds from flowering and seeding. It’s hoped over time the exotic weeds like scentless daisy will die out, leaving room for the fish guts population to expand.
