A weekly programme featuring a mix of sound-rich stories about science, the environment and medical research, recorded around New Zealand in laboratories and in the field. Our Changing World is broadcast nationwide on Thursday nights on Radio New Zealand National, during Nights with Bryan Crump. It is preceded in this recording by a news and sports bulletin, and weather forecast. In today's programme:
21:06
Spinetail Devil Rays
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Electronic tags used to measure the survival of spinetail devil rays released after being caught by tuna fishing boats have revealed long journeys to the tropics and deep dives
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By Alison Ballance
New research on spinetail devil rays has shown that these summer visitors to northern New Zealand waters are overwintering in the tropics, and diving to record-breaking depths during their journey.
“They provided some really fascinating information about the behaviour and movements of these animals. Two rays travelled rapidly to the tropical islands north of New Zealand – and one ended up near Vanuatu and the other one just south of Fiji.”
Dr Malcolm Francis, NIWA
Spinetail devil rays are mobula rays (Mobula japanica) and they are a smaller cousin of the well-known giant manta ray (Manta birostris), which is also found in New Zealand waters and can reach up to 7 metres across. Devil rays are up to 3.1 metres across, and they weigh up to 150 kilograms. With finely pointed fins they look a little like a caped superhero as they ‘fly’ through the water.
Few of us have heard of them, but devil rays are quite frequently caught as accidental by-catch by purse seine boats, fishing for skipjack tuna near the edge of the continental shelf between Great Barrier Island and the Bay of Islands. Kris Ramm, a science advisor for the Department of Conservation working on marine species and threats, works with the fishing industry to find ways to avoid catching protected species such as devil rays. He says that spinetail devil rays, which are found in tropical waters world-wide, have been protected in New Zealand waters since 2010.
“Most of the animals come on deck alive,” says Kris. “That means that if we do have incidence of by-catch we actually have room to try and release those animals alive, so that they aren’t injured and have a long term chance of survival.”
NIWA shark expert Dr Malcolm Francis has been collaborating with the Department of Conservation (DoC), the Ministry for Primary Industries (MPI) and the fishing industry to find out if these live devil rays survive when returned to the water. Fishery observers successfully attached ‘pop-up’ satellite tags to nine devil rays. These tags gather information on depth and temperature, and some of them also record light which can be used to estimate location. After a predetermined time, the tags ‘pop up’ to the surface where they transmit their data to orbiting satellites. While two tags failed to report any data and four of the devil rays subsequently died, the three survivors reported in with some eye-opening information.
“One of the rays ended up near Vanuatu and the other one just south of Fiji,” says Malcolm. “And we’re quite surprised at how fast they did it. They travelled between 1400 and 180 kilometres at least, and they covered that distance at a minimum speed of 50-60 kilometres per day, so they’re getting along pretty fast.”
As well as speeding along at the surface the two devil rays that headed off in late summer to spend winter in the tropics were making some record-breaking dives along the way.
“One of them was recorded going down to a thousand metres, and the other one to 1100 metres.”
The previous record for the species was 445 metres, recorded off the coast of Mexico.
The two rays that were tracked to the tropics were only followed for a month, but the third ray was followed for three months and remained near the edge of the continental shelf off north-eastern New Zealand. It spent much of its time feeding in the top 50 metres of water, but also dived as deep as 649 metres. All three tagged rays substantially exceeded the previous depth record of 445 m recorded for the same species off Mexico. They all made frequent dives to depths of 200-300 metres, usually during the day, and this behaviour is probably related to feeding on deep water prawns and small fishes.
Of concern is that four of the tagged rays appeared in good health when they were released but died within four days. It appears that the capture process may sometimes cause fatal physiological stress, and future work will try to determine what stages in the capture process are most stressful.
Kris Ramm says that DoC, MPI and NIWA are working with the fishing industry to develop an industry code of practise, to find better ways to avoid catching devil rays and improve the survival rate of released rays. MPI strongly supports this research, which is closely aligned with its National Plan of Action for the Conservation and Management of Sharks. Spotter planes working with the fishing boats to identify schools of tuna can report when they see devil rays, allowing fishing boats to avoid those schools. One possible mitigation measure is to empty the catch onto the boat through a large mesh cargo net, which would allow the tuna through but would catch any devil rays, which could then be easily lowered back into the water on the net. At the moment it is challenging to deal with these large, heavy animals once they are on the deck of a moving boat.
Malcom Francis says that devil rays are animals of the open ocean and don’t often come inshore, but they gather along the edge of the shelf where water depth is 150–350 m, probably to feed on swarms of small planktonic shrimp-like creatures called euphausids. They feed by swimming along with their mouths open, and filtering their small prey from the water on their comb-like gill rakers.
Previous work by NIWA’s Malcolm Francis and Clinton Duffy from DoC has used satellite tags to reveal that great white sharks migrate annually between New Zealand and the tropics, also diving regularly and to great depths on the way.
This research was presented at the NZ Marine Sciences Society and Oceania Chondrichthyan Society joint conference being held in Auckland this week.
Spinetail devil rays are classified as near threatened on the IUCN Red List.
Keeping with the theme of cartilagenous fishes (which includes sharks, skates and rays, and chimaeras) Our Changing World recently featured stories on eagle rays and rig sharks.
Topics: environment, science
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Tags: devil ray, manta ray, protected species, conservation, fisheries by-catch, fishing industry, migration, satellite tracking
Duration: 16'53"
21:20
Spookfish and Other Deep Sea Sharks
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Long-nosed spookfish and other chimaeras are among a suite of weird, little known deep sea sharks that sport spiky sex organs on their head, enormous noses, fierce spines and long tails
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By Alison Ballance
"They’re just so weird looking. When it was first suggested that I look at deep water sharks I was a little sceptical, because everyone wants to study your big typical pelagic species, the charismatic great whites and whale sharks. But spending a bit of time with them and just looking at them and all the weird features they have - there are some that glow in the dark, they have massive spines, and there’s lots we just don’t know about them so there’s lots of opportunity to learn."
Brit Finucci, PhD student and deep sea shark scientist, Victoria University of Wellington
Brit Finucci is a PhD student at Victoria University of Wellington, and she already knows more about six of New Zealand’s species of deep water sharks than almost anyone else in the world. She has spent many weeks this year dissecting more than 500 specimens of chimaeras that were accidentally caught by research boats working on the Chatham Rise and in the subantarctic, trying to find out as much as she can about these mysterious enigmatic creatures.
Chimaeras are ‘perhaps the oldest and most enigmatic groups of fishes alive today.’ Their closest living relatives are sharks, but they parted evolutionary ways about 400 million years ago. Chimaeras are deep sea sharks that are known by a number of different names, including spookfish, ratfish, rabbitfish, elephantfish and ghostsharks.
The name chimaera (or chimera) comes from Greek mythology, in which it was a fire-breathing monster composed of various animals: a lioness, a snake and a goat.
Like sharks the skeletons of chimaeras are composed of cartilage, and the males have claspers for internal fertilization of females. Unlike true sharks, chimaeras have just a single pair of gills, and most species also have a mildly venomous spine located in front of the dorsal fin.
“They’re all characterised by having this big giant spine [on their back] which is probably a defensive mechanism,” says Brit.
As well as having flexible claspers with a spiked bulbous end, male chimaeras also have small sexual organs, which resemble a hooked club at the end of a stalk – known as tenaculum - on their forehead and in front of the pelvic fins.
“It’s really odd with the chimaeras, males have this little organ on their head that’s the tenaculum,” says Brit. “When they’re mature the [tenaculum] get these tiny little hooks on them. They think it’s used to attach themselves to the female.”
Chimaeras are deep sea species. “Living in complete darkness at the bottom of the ocean they do have large eyes,” says Brit. “And they also have a tapetum, which is a reflective surface – you see that in cats, too, when you shine lights in their eyes and you get that reflection back.”
Not much is known about the diet of chimaeras. “Their teeth are more like rabbit teeth,” says Brit, “They have these tooth plates they use to grind their food.”
Sharks are a surprisingly diverse group of animals, ranging in size from the enormous whale shark, the world’s largest fish, to dwarf pygmy sharks (Squaliolus spp). Sharks, batoids (rays, skates and sawfish) and chimaeras form a distinctive group of cartilaginous fishes collectively referred to as the Chondrichthyans. There are more than 500 species of sharks, nearly 650 batoid species and 50 chimaera species, bringing the overall total of Chondrichthyans to about 1200 species.
Te Ara - the encyclopaedia of New Zealand says ‘in 2004 there were 70 known species of sharks, 26 skates and rays, and 12 chimaeras or ghost sharks in New Zealand … and at least four undescribed species.’
Brit’s work is focusing on identifying when the six species she is looking at become mature, and she will look at stomach contents to see if she can work out what they’re eating. She is studying six different species:
The long nose spookfish (Harriotta raleighana) has a nose that can be up to half its body length. It belongs to a family of long-nosed chimaeras called Rhinochimaeridae, which has 8 known species in 3 genera.
The Pacific spookfish (Rhinochimaera pacifica) is another long-nosed chimaera.
The brown chimaera (Chimaera carophila) was only described as a distinct species in 2014. I t is only found in New Zealand, has a very blunt nose and large purple pectoral fins. There has been a resurgence in discovering and naming new shark species, both from existing specimens in museums and from new ones collected as more deep sea research is carried out. American taxonomist Dave Ebert alone has described 24 species, some of which he has found in Asian seafood markets.
The prickly dogfish (Oxynotus bruniensis) has a thick body, a prominent hump back with two very large sail-like fins and a very rough skin.
The black ghostshark (Hydrolagus homonycteris) lives at depths of 500 to 1,400 metres.
Owston’s dogfish (Centroscymnus owstonii) grows to 1.2 metres long, and is caught as by-catch in the orange roughy and oreo fisheries.
Topics: science, environment
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Tags: deep sea sharks, chimaeras, spookfish, ghost fish, cartilaginous fish, ocean, sharks
Duration: 13'36"
21:34
Improving Stent Design with MRI
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Susann Beier is using MRI and computational models to analyse flow of blood like fluid in 3D-printed replicas of coronary arteries with the aim of improving stent design
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By Ruth Beran
Each day approximately 17 New Zealanders – one every 90 minutes – die as a result of coronary heart disease.
People suffering from coronary heart disease have a narrowing or blockage of their coronary arteries by plaque formed by fat or cholesterol on the artery walls.
The preferred treatment is to insert a stent, and PhD student Susann Beier is trying to improve stent design.
A stent is a tiny meshed wire tube which has been put in the circulatory system to be entered into the narrowed arteries,” says Susann.
Stents are used to recover blood flow in an artery and they are deployed in arteries with the help of a balloon. “[The balloon] compresses the arterial plug against the vessel wall which opens the vessel up again,” says Susann.
Stents are usually inserted around the heart and this is the area where Susann Beier is focusing her research. However, stents can also be used in the carotid arteries for stroke prevention.
In particular, Susann is looking at blood flow and stented coronaries. Her aim is to improve stent design and identify predictors for coronary artery disease.
She is using two powerful tools in her research: computational modelling of stents and MRI (magnetic resonance imaging) to measure blood flow in large replicas of stented arteries.
The replicas are 3D printed, are six times the size of a human heart, and look like a piped “Y” depicting one coronary branch when it divides into two.
Just like humans look very different our arteries look very different as well,” says Susann.
For example, one replica has a very wide branching artery with 110 degrees in between the daughter branches. Another branches only by 30 degrees.
To measure the blood flow in the up-scaled artery replica, a flow circuit pumps blood-like fluid through and it is then placed in an MRI scanner. The MRI then measures flow in 4D, i.e. in three dimensions at each point in time. About 100 litres of blood like fluid is pumped along pipelines using equipment which must be located outside the MRI because nothing magnetic can be taken into the room.
Susann then compares the outputs from her real-scale computer simulation with the measurements from the MRI to see how closely they correlate. “This is the first time anybody has ever done this and they correlate really well,” she says.
By measuring flow, Susann can see where there is really low flow or high flow in the replicas. This in turn puts low or high stress on the arteries. “Then we can say disease is likely to grow there,” she says.
The fluid is pumped from the single inlet at the bottom of the “Y” and then it divides into the two daughter branches. “At times it creates swirls and stagnation zones. These are the things we’re looking for and then it goes back into the single pipe and comes back around,” she says.
Susann has many replicas, with stents and without. She also has idealised replicas, ones that are average, and some patient specific ones.
Ultimately, she hopes that her work will lead to improved stent design.
“If we implant a stent into a vessel in most cases it’s really helpful and it’s great,” says Susann.
However, in a very small percentage of cases the design of the stent actually changes the flow environment in a way which is not beneficial.
So if we can identify those specific stent design features then we can optimise stent design. And improve stent success,” she says.
Susann conducts her work at the Centre for Advanced MRI at the University of Auckland. CAMRI is involved in a lot of clinical studies but also allows PhD students like Susann to conduct research there.
Topics: science, health
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Tags: MRI, stents, coronary heart disease, arteries, 3D printing
Duration: 12'29"
21:46
The Sshhmute - A Practice Mute for Brass Instruments
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In his New Plymouth workshop, Trevor Bremner designs and produces the sshhmute, a practice mute for brass instruments
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By Ruth Beran
Many years ago Trevor Bremner wanted to practice his cornet at home in the evenings when his boys slept, and found that he wasn’t happy with the practice mutes available. These mutes either played out of tune, or were hard to project through.
A good practice mute should [allow] you [to] play as near to what you would do without a mute,” he says.
A musical instrument repairer by trade, Trevor wanted to create the ideal mute and it took him 3.5 years to develop one that he felt happy with. From there, the company has grown and currently sell eight different mutes around the world: the standard practice mutes for trumpet, trombone, bass trombone, flugelhorn, tenor horn, French horn, and the piccolo trumpet, as well as a whisper mute for the trumpet.
A mute is designed to fit inside the bell of a brass musical instrument and reduces the sound when played. “There are different shapes and sizes depending on the type of instrument that it is going to be used in,” says Trevor. “We are at the moment working on three larger ones for baritone and euphonium and also there’s another series of whisper mutes, that we’re working on too,” says Trevor.
The mutes are tapered with a seal around the neck of the cone. This seal makes it air tight and holds the mute in place.
As the instrument is played, the air goes into the cone of the mute, and the only way the air can get out, is through a little tube at the bottom, and that’s what reduces the sound.
Getting the length and diameter of the tube correct is very important, says Trevor, because there’s so many aspects that need to come together.
“You can get notes that don’t work, you can get notes that play out of tune, you can even get what they call split harmonics, where you can actually get two notes, half a semitone apart, so there’s lots of little problems there that you have to iron out,” he says.
The sshhmute reduces the sound from an instrument by roughly 30 decibels.
“Normally if you’re practicing or playing with the mute in, and you’re in a room with a door closed, you can only just hear it outside the room. So it is very effective,” says Trevor.
The sshhmute is made of ABS plastic which accommodates the vibrations from the instrument, is not too heavy, and doesn’t get damaged if dropped. The seal is made from cork.
Trevor admits that the design process is trial and error. For example, he’s working on a whisper mute for the trombone. Whisper mutes are designed to play a little bit louder than a practice mute. “So that’s for very quiet passages onstage,” he says.
Trevor is designing the whisper mute by changing the diameter and length of the tube, because he’s confident that the volume of the cone is right, and the seal is in the right place.
And what’s different about a whisper mute? “They have straight mutes, cup mutes, harmon mutes,” says Trevor, “but they change the colours they do not really, naturally quieten it down. That’s where this mute is really, is quite different to all the other mutes.”
Topics: science, music
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Tags: Mute, practice mute, brass instruments, cornet, music, sound
Duration: 17'50"