Te Papa fish experts Andrew Stewart and Thom Linley, and mollusc expert Kerry Walton, are part of a team that discovered well over 100 new animal species in the depths of the Bounty Trough, east of the South Island. The expedition was led by Ocean Census, the National Institute of Water and Atmospheric Research (NIWA), and Te Papa.

We caught up with Andrew, Thom, and Kerry to hear why this expedition was a once-in-a-lifetime opportunity.

Andrew: This three-week expedition was funded by Ocean Census, an alliance between The Nippon Foundation (Japan) and Nekton (UK). What did this expedition mean to you?

It meant that we were able to 1) sample a body of ocean that’s at the junction of the subtropical and cool temperate, and 2) sample well below the depths normally looked in.

A proportion of our fishes have come, directly or indirectly, as part of the seafood industry. This means a maximum depth of only 1,200 metres, and there has been very little incentive to go deeper than that. Being able to get down to metres to fishes we knew were there but weren’t represented in our collection was fantastic.

In addition, we were able to forge a really good working relationship with Ocean Census, and voyage co-leader Alex Rogers was very impressed with what we were able to achieve. We’re hopeful that Ocean Census will come back to sample other unexplored areas of our exclusive economic zone.

Kerry: Why was the Bounty Trough selected out of so many potential sites globally?

The Bounty Trough area was selected as it hadn’t been explored very much before. In contrast, both the Campbell Plateau to the south, and the Chatham Rise to the north, are well sampled. This presented an ideal opportunity to see what lives in between. We were on the hunt for new species, so it paid to go somewhere we hadn’t been before.

It was also a rare chance to go ‘deep’. We have relatively few samples from deeper than 2,000 metres as there are less commercial activities at those depths, and few vessels are capable of accessing those habitats.

Kerry: The team took samples as deep as 4,800 metres. What’s the environment like down there, and did it reveal any surprises?

The deep seafloor is predominantly made up of mud. However, we were surprised at the diversity of the deeper reaches of the Bounty Trough. Strong currents had scoured near-vertical walls of exposed rock, and the channels themselves contained gravels.

Thom: What equipment did you create for the expedition, and why did you need to do that?

At greater depths, it gets tricky to lower something through the water. We decided to create a pop-up fish trap for the deeper sites. This type of vehicle has a ballast weight at the bottom, and floats at the top. It isn’t lowered but released from the surface and allowed to freefall to the bottom. This is very handy as it lets the vessel go and do other things while the trap works for us.

When we are ready to call it home, we send a coded burst of sound through the water, which triggers a release to let go of the ballast. Without the ballast weight, the floats can lift the trap to the surface.

This is a very efficient method of working at these depths … but it causes me a lot of worry! That burst of sound is the only way I communicate with the trap. We can calculate how far away it is using the delay in the sound, but that could be in any direction. Separating it rising to the surface from vessel drift and a million other variables caused me some headaches!

The trap itself was unusual looking. Deep-sea fish are used to having wide open spaces to themselves. They don’t like to go into confined spaces. We designed this trap to have a ‘false bottom’ where fish would follow along the seabed and up a ramp without realising it. They would then drop down and be unable to find their way out.

But all the work and worry were worth it. The traps caught two of our three new fish species.

Video by Thom Linley. Te Papa (244110)

All: What discovery are you most excited about so far?

Andrew: Fishes, of course! Eelpouts were one of the targeted abyssal families we wanted to get, and to get three putative new species was really exciting.

Being small, thin, and really slimy means they often squeeze through the usual trawl nets and are lost. That’s if you even get them in the first place, as they are often in amongst rocks and places normally avoided because of the risk of losing gear. There are a few other species that on reflection warrant a closer look!

Thom: I really enjoyed seeing my first Aphyonid. These transparent jelly-like fish are rarely caught, and often badly damaged. We got a beautiful specimen of Sciadonus pedicellaris, the slender abyssal cuskeel, although I can admit that beauty may be in the eye of the beholder!

It was in such good condition that we took the time to suspend its gelatinous body in seawater to get some detailed photographs.

Kerry: It’s hard to pick a favourite discovery for me. Discovering new species is seldom a ‘eureka’ moment as you’re often sorting through a lot of samples under time pressure, or unsure that the new species genuinely differs from those previously known.

This trip yielded at least a dozen ‘eureka’ moments for me, and I even said it out loud for the first time when I picked up a gummy squirrel sea cucumber and turned it to see a ‘giant’ new species of eulimid snail.

Thom: What else did you see – how diverse are the species in the 19 sites sampled?

The Bounty Trough is a very variable environment. Not only did we cover a huge depth range (from 600 metres to almost 5,000 metres deep) but we also covered a wide range of habitats: the slopes and peaks of undersea mountains, deep rocky channels, soft mud, sand, and reefs. Each habitat/depth range had very different animals. Even the animals themselves were habitats, as we also found a lot of parasitic organisms.

It was nice to work with experts in different fields. Some non-fish critters that stuck out for me were the giant salp, the chonky little sea pig, and the spiny sea slater.

Some of the huge diversity of animals captured: giant salp, sea pig, and spiny sea slater.

Kerry: You’ve called the Bounty Trough one of Earth’s final frontiers, but is there still more to discover in the ocean around Aotearoa New Zealand?

The Bounty Trough was genuinely one of earth’s final frontiers – by this, I meant it was a place we had never sampled extensively before, as it has been now. That is not to say that we know everything we could want to know about the animals there – far from it.

Indeed, most of the species we collected were only found once on the whole trip. Many are still out there unknown to us. There is so much more to explore all around Aotearoa, and several regions remain effectively unexplored yet.

Andrew: What’s the cuisine and accommodation like onboard?

Accommodation is double bunk cabins sharing with someone on the opposite shift. Because you’re 12 hours on/12 hours off, having the cabin all to yourself in your off-swing is great to decompress and reflect on that day’s work, as well as getting uninterrupted sleep. It’s comfortable but fairly simple though. Getting home to a bed that I could stretch out in was fantastic!!!

We were below the water line so no portholes, meaning once the light went out it was pitch black, with the sound of the waves hitting the side. It was a rather strange adjustment if I got called early to come out and work on the catch when it was 4pm and a bright sunny day.

Food is incredible. Two chefs and a steward, and you have to actively resist the temptation to eat, eat, eat. Breakfast at 6.30 am was several bowls of fruit, yoghurt, cooked eggs to order, bacon, hash browns, baked beans, sausages, spaghetti, tomatoes, cereal, etc. Morning tea is about 10.30 – sausage rolls and the like. Dinner is at 11.30 and is a three-course one. There’s a soup, a cooked lunch (several options), cold meats, salads, cooked vegies, and dessert. I usually opted for just the soup and a salad for lunch (= my dinner).

It’s usually the changeover between swings so a chance to bring the incoming group up to speed. Dinner (I was asleep by then) is at 5.30 and was another cooked and/or cold meal.

If for any reason you couldn’t make the meal, one could be set aside for you. In the mess, a fridge holds a variety of cold drinks (fruit and tomato), cheeses, and cold meats. A sideboard has bread, crackers, biscuits, toasters, toastie maker, fresh fruit, and (don’t tell anyone) a freezer in the corner with ice creams. This is all available 24/7. Then there’s coffee 😊 (= thinking juice).

Thom: NIWA’s RV Tangaroa faced some wild weather – how do you work in a lurching vessel?

We did have a bit of weather down-time but that gives us old sea dogs some bragging rights. The RV Tangaroa handles the sea well. She doesn’t move too much but tends to heave (the up and down motion of the bow as it cuts through waves).

We weren’t getting thrown around, but we were finding ourselves much heavier and lighter, at times feeling like we are floating, only to be pushed into the deck as if someone has jumped on you for a piggyback. I dread to think what this is doing to our blood pressure; I could feel the pressure change in my ears!

There are lots of remedies for sea sickness. It’s like hiccups; everyone has something that works for them. I found some glasses online that were meant to work by giving you a false horizon. I am not sure they worked, but they certainly gave us all a good laugh.

As for how we work in such weather, the answer is that we don’t. Looking at a screen for too long, or even worse, looking down a microscope, can have you feeling unwell quite quickly. Bad weather days are a good chance to catch up on sleep and do some light work, like labelling/sorting all your samples. I also strongly recommend putting on the worst marine-themed film you can find and all yelling at it. I’m looking at you, Meg 2: The Trench!

There are those who can’t take it easy, though. These include the vessel crew, but in particular, the gally staff who, rain or shine, worked every day to keep us fed.

Andrew: The team collected over 1,800 samples (congratulations!). What happens next?

Work, and some groups will require more than others. Material has to be sorted, identified, and registered; new species noted and, in the case of fishes, relevant specialists contacted to sound out their interest in being involved in publishing a formal description.

With one of the lots, I’d like Lara Shepherd, one of Te Papa’s genetics experts, to do some DNA sequence comparison with the species it’s supposed to be. On reflection, the species in question should be a blue-black in colour and have a rigid body. The ones we got are all an off-white and have a squishy texture. Assuming there’s only one species that has tripped us up in the past, who knows what the genetics will throw up!!

We’ve undertaken a workshop that comprised those who were on the voyage as well as other specialists bought in from overseas and around New Zealand. The majority of these people specialise in invertebrates. The whole of March was set aside for this work, and the purpose was to get momentum on describing new species.

So often once an expedition like this returns, all the other work crowds in and no one has the dedicated time to do any more than register and make a mental note that they’ll ‘get back to it some day’. As a result, it can take decades for taxa to be properly described. The workshop seeks to circumvent this problem.

Further reading

• Visit the Ocean Census website to read more about the Bounty Trough expedition
• Read updates from the trip from NIWA
• Watch: The Bounty Trough expedition on the Ocean Census YouTube channel