Are there plenty more fish in the sea? Reports of falling hoki stocks off the West Coast and the near-disappearance of crayfish from the Hauraki Gulf suggest that our ‘best in the world’ fisheries management may not be living up to the hype. Three decades ago, the right to catch and sell fish became a property right, one that has now accumulated in the hands of a few. How has that worked out for people—and for fish?
Normally, more than 200 sightings of great white sharks are recorded every year in False Bay, near Cape Town, South Africa. This year, that number is zero. Receivers that are supposed to ‘ping’ when a tagged shark passes by remain silent, while whale carcasses usually found in the bay are free of shark bite marks. False Bay is a renowned great white hotspot, and shark scientists are puzzled by the predators’ absence. It’s possible that orcas are the culprits—they’re known to attack great whites, and have a particular taste for their livers. Indeed, sightings of great whites decreased after two orcas visited False Bay in 2015. Alleged victims of orca predation have washed up along the South African coast, their livers removed with surgical precision—the orca’s calling card. This is also consistent with observations from Australia and California, where orcas on the prowl have led to a mass exodus of great whites. But there’s another suspect in this case: humans. It’s possible that changing prey distribution, pollution or overfishing could also be responsible for the missing sharks.
It’s time to go back—to the Kimberley.
Warming seas will make life much harder for pāua, a NIWA study has found. Scientists raised young pāua in seawater of various temperatures and pH levels, then monitored their growth. “Essentially, seawater of the future will be warmer, with lower pH levels,” said Vonda Cummings, pictured, who led the study. “We found that the outer layer of pāua shells gets etched by seawater with lower pH, especially if the water was warmer.” The pāua were sensitive to temperature variations as small as 2ºC, “and that will affect the thickness of pāua shells, which could mean they are not as resistant to waves and predators”.
If you take away one thing from this issue’s story on fisheries, it’s that most of what you hear about fishing is an oversimplification. Claims by lobby groups, industry bodies and non-profits abound, but there are a few voices missing from the conversation: those of the people on the water catching the fish, and the people studying what’s happening beneath the waves. It’s incredibly difficult to count fish—like trying to count trees, except the trees are invisible and keep moving around, as British scientist John Shepherd once said—so anyone who sounds pretty sure about how many fish there are is automatically suspect. Scientists measure what they can—the number of juveniles, for instance, or the abundance of fish in one area—and then they add fishing data, the technology used to find fish, how many fish may have been discarded. (My explanation, too, is an oversimplication). They create a sophisticated model that guesses at the number of fish. Is the model right? You’d have to catch all the fish in the sea to find out. “That’s basically the only way to figure these things out for sure,” fisheries scientist Darcy Webber told journalist Kate Evans. “There have been lakes in North America, where they were doing stock assessments of freshwater fish, and then they dried up the entire lake and counted all the fish, and that’s the only way they actually ever validated a stock assessment model.” Science is expensive, so we only study the species that are important to us—important because there are a lot of them (snapper), or because we make a lot of money from them (crayfish), or both (hoki). That means we don’t know much about some fish at all, especially the ones we don’t want to eat. “I think when people think about the quota management system they assume that quotas are actually acting as a cap on the amount of fishing, and for many species that’s just not the case,” says Evans. “The levels at which those catches are set are based on how much fish people were able to get in the early 1980s, not based on what we actually know about the sustainability of that species. “The fact that we do not know whether fishing is sustainable for a considerable number of species—that doesn’t seem right to me.” In fact, we know less about our seas and coastlines than any other domain, write the authors of the government’s 2019 marine environment report. That’s despite the fact that we govern one of the largest areas of ocean in the world. There are criticisms to be made of the quota management system, and one of the most important is how it transformed the right to catch and sell fish into a form of property. This means that the commercial exploitation of our fish resources doesn’t return a profit to the government, like a mining license would. Instead, the government gave away all the fishing licenses, for good, in 1986. Fisheries debates involve arguments about values as much as arguments over whose model is right. If we want to eat fish, we have to decide which of the impacts of fishing we’re happy with—bycatch of seabirds (90 per cent of which are threatened) and marine mammals (22 per cent)? The destruction caused by bottom-trawling? The price of fish increasing? More government spending in innovation or research? Or, perhaps, the fate of fish? “There are trade-offs to be made and there’s no perfect solution that would suit all people and all fish,” says Evans. “It’s just one of those things that’s really hard. It’s something that we do have to decide what we as a country value most. Different people value things differently, so it’s inevitably going to be a compromise of some kind.”
Zip, pip, chuck, goes the call of Aotearoa’s smallest bird. It may turn out to be one of the earliest forms of language.
Embryonic turtles can choose what they’ll be when they grow up: male or female. In particular turtle species, the temperature of the egg appears to determine the sex of the hatchling. Research published in August in Current Biology found that embryos are able to move around within the egg to find different temperatures. Wei-Guo Du and colleagues at the Chinese Academy of Sciences incubated turtle eggs at a range of temperatures, finding that an embryo could experience a gradient of up to 4.7°C within its egg. (A temperature change larger than 2°C can alter the sex ratio of many turtle species.) In half the eggs, researchers applied a chemical that blocked the embryos’ temperature sensors. When the eggs hatched, the embryos that weren’t able to sense temperature were either almost all males or almost all females. But the temperature-sensing embryos developed about half and half males and females. “The most exciting thing is that a tiny embryo can influence its own sex by moving within the egg,” says Du. This indicates that turtles may have the ability to shield themselves against extreme thermal conditions. Du warns that this may not be enough to protect them from rapid climate change, which is predicted to create female-biased populations. “However, the discovery of this surprising level of control in such a tiny organism suggests that in at least some cases, evolution has conferred an ability to deal with such challenges.”
Did our ancestors really chase animals until they collapsed from fatigue?
As the sun sets on New Zealand’s manufacturing industries, a photographer visits a foundry and steel mill that represent the last of their kind.
A sea sponge may one day save millions of lives, according to a study published in Scientific Reports in October. Tuberculosis kills 1.8 million people each year, more than any other disease, and current vaccines are struggling to contain it. That’s because Mycobacterium tuberculosis, the organism that causes TB in humans, is quick to mutate, meaning it can soon evolve drug resistance. The quest for a better vaccine has led scientists beneath the waves, looking for bioactive molecules in sponges: compounds that might one day comprise the basis of new vaccines. Over three years, the Centenary Institute and the University of Sydney analysed around 1500 sponges, and discovered that a species of Tedania, a genus found around Australia and New Zealand, possesses potent powers against M. tuberculosis. The active component, Bengamide B, was able to halt drug-resistant TB strains, and did not harm human cells. “Bengamide B shows significant potential as a new class of compound for the treatment of tuberculosis,” said the study’s lead author, Diana Quan, “and also importantly, for the treatment of drug-resistant TB.”
Giant carnivorous land snails don’t ask for much: moist leaf litter to burrow into, earthworms to suck up like spaghetti. But if the lower layer of the forest is nibbled away, if sunlight reaches the soil, and if one month of drought follows another, molluscs relying on damp homes struggle to survive.
Just after midnight on November 14, 2016, more than 24 fault lines around Kaikōura ruptured in spectacular fashion. One of these rifts—the previously unmapped Papatea Fault—threw up a few extra surprises for scientists. Normally, the rupture of a fault is caused by a build-up of stress. But Papatea was stress-free until its rupturing neighbours squeezed it, triggering a violent fracture. In a matter of seconds, the earth split open along 19 kilometres and sections of mountainous land were shifted upwards by eight metres. Of the 24 fault lines, Papatea produced the largest vertical movement. At first, Papatea’s behaviour confused scientists, because the fault wasn’t under strain. In a study published in Science Advances in October, New Zealand and Canadian researchers used before-and-after images of the fault line to create a model and figure out what happened. It’s another unusual aspect of the most complex earthquake ever studied, with implications for assessing seismic risk. Current earthquake forecasting is based on the strain model, where faults accumulate tension until they fail, but Papatea shows that displacement is also a risk, says Mark Stirling, chair of earthquake science at the University of Otago: “A ten-metre displacement in a built-up area or beneath a critical facility, such as a large dam, would have significant consequences.”
Artificial intelligence can spot diseases with about the same accuracy as human professionals, according to a systematic review and meta-analysis published in The Lancet Digital Health in September. Across 14 studies, ‘deep learning’ algorithms correctly detected conditions ranging from cancers to eye diseases in 87 per cent of cases, compared to 86 per cent by doctors. Artificial intelligence was also marginally better at identifying patients who had a clean bill of health.
Genetic reanalysis in the Amazon has revealed that the electric eel is, in fact, three different species, including one—Electrophorus voltai—that can deliver an 860-volt shock. (That won’t kill a healthy person, says ichthyologist and lead author Carlos David de Santana, from the Smithsonian National Museum of Natural History.) The new species is now officially the strongest bioelectricity generator known, making the previous record of 650 volts a mild tingle.
Painting cows with black and white stripes reduces fly bites by 50 per cent, according to a study by a team of scientists in Japan, published in PLOS One in October. The zebra-print cows displayed fewer signs of annoyance, such as tail flicking and head shaking, and attracted lower numbers of biting flies than unpainted cows. The study was inspired by previous research suggesting the zebra’s iconic striped coat functions as a fly deterrent. The stripes are thought to work by confusing the insects: the pattern interferes with flies’ motion detection, and they fail to land on the striped surface. (This is, however, just one of a number of theories attempting to explain the evolutionary advantage of the zebra’s stripes.) Biting flies are a significant pest for cattle worldwide, including in New Zealand. Their persistent attacks cause stress and prevent cattle from sleeping and eating—which in turn affects growth and milk production.
Our next-door neighbour is a cannibal. Andromeda, the closest spiral galaxy to the Milky Way, has a history of eating smaller galaxies, and we’re next on the menu—in about four billion years. Research published in Nature in October documents the leftovers of galactic meals: dense star clusters called globular clusters dotted throughout the stellar halo orbiting Andromeda. By tracing the faint remains of smaller galaxies embedded in the globular clusters on Andromeda’s outskirts, researchers reconstructed how and when the smaller star systems were gobbled up. “We are cosmic archaeologists, except we are digging through the fossils of long-dead galaxies rather than human history,” said the study’s co-author, Geraint Lewis from the University of Sydney. Andromeda is on a collision course with the Milky Way—so now we have a clearer picture of the ultimate fate of our galaxy.
Residents and emergency services could better handle earthquakes if they knew whether the worst was over, or if it were still to come. Large earthquakes are often followed by aftershocks that are difficult to predict, and can sometimes be bigger than the first. Now, Swiss researchers have devised a system to help determine whether a magnitude 6.0 or greater earthquake is the main event, or merely a precursor. Laura Gulia and Stefan Wiemer of the Swiss university ETH Zurich analysed the sequences of earthquakes in the Amatrice–Norcia region in Italy and the Kumamoto region in Japan in 2016, devising a model for predicting the threat of a larger earthquake to follow. Tested against 58 known earthquake sequences, the model identified foreshocks and aftershocks with 95 per cent accuracy.
Can humans also regenerate damaged limbs?
Scientists are finally able to confirm that quantum theory holds up even in the absence of gravity. Physicists fired quantum-entangled photons from the ground to the quantum satellite Micius, where they were remeasured. Getting quantum theory and Einstein’s Theory of General Relativity to agree has long been the holy grail of physics. Quantum mechanics is the province of atomic physics, while Einstein’s theory is concerned largely with gravity. “But a key barrier to progress on this problem,” said University of Queensland physicist Timothy Ralph, “has been the difficulty in performing experiments in which effects from both theories play a significant role simultaneously.” The team wanted to know whether quantum mechanical theories had to be rewritten to accommodate certain features of general relativity. “However, our results showed that gravity doesn’t affect quantum states in the speculated way,” said Ralph. “The bizarre predictions of quantum mechanics continue to be accurate, even under the extreme situation of transferring quantum particles many hundreds of kilometres from the Earth’s surface. “Perhaps it’s the theory of relativity that needs to evolve to reflect the scientific theories behind quantum mechanics, and not the other way around.”
Plotting sea-level fluctuations around Zealandia three million years ago has sounded a warning for the future. Using new techniques to analyse the size of particles pushed around by wave action during the Pliocene, researchers led by Georgia Grant of GNS Science have found that, at a time when carbon-dioxide concentrations were similar to today’s, and temperatures around 2ºC warmer, a third of Antarctica’s ice sheets melted, causing sea levels to rise up to 25 metres higher than at present. The scientists warn that we might expect sea-level rise of up to 20 metres should warming hit a 2ºC tipping point.
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