2732. Fish Can Get Depressed

By Heather Murphy, The New York Times, October 12, 2017

Can a fish be depressed? This question has been floating around my head ever since I spent a night in a hotel across from an excruciatingly sad-looking Siamese fighting fish. His name was Bruce Lee, according to a sign beneath his little bowl.

There we were trying to enjoy a complimentary bloody mary on the last day of our honeymoon and there was Bruce Lee, totally still, his lower fin grazing the clear faux rocks on the bottom of his home. When he did finally move, just slightly, I got the sense that he would prefer to be dead.

The pleasant woman at the front desk assured me that he was well taken care of. Was I simply anthropomorphizing Bruce Lee, incorrectly assuming his lethargy was a sign of mental distress?

When I sought answers from scientists, I assumed that they would find the question preposterous. But they did not. Not at all.

It turns out that not only can our gilled friends become depressed, but some scientists consider fish to be a promising animal model for developing anti-depressants. New research, I would learn, has been radically shifting the way that scientists think about fish cognition, building a case that pet and owner are not nearly as different as many assume.

“The neurochemistry is so similar that it’s scary,” said Julian Pittman, a professor at the Department of Biological and Environmental Sciences at Troy University in Alabama, where he is working to develop new medications to treat depression, with the help of tiny zebrafish. We tend to think of them as simple organisms, “but there is a lot we don’t give fish credit for.”

Dr. Pittman likes working with fish, in part, because they are so obvious about their depression. He can reliably test the effectiveness of antidepressants with something called the “novel tank test.” A zebrafish gets dropped in a new tank. If after five minutes it is hanging out in the lower half, it’s depressed. If it’s swimming up top — its usual inclination when exploring a new environment — then it’s not.

The severity of the depression, he says, can be measured by quantity of time at the top vs. the bottom all of which seemed to confirm my suspicions about Bruce Lee.

All of this, of course, may sound fishy to any of the one in six people who has experienced clinical depression. How could a striped minnow relate to what you’ve been through? Is “depression” the right word?

While scientists have used animals, like mice, to study emotional problems for decades, the relevance of those models to human experience is sketchy at best.

There’s the obvious issue that “We cannot ask animals how they feel,” says Dr. Diego A. Pizzagalli, the director of the Center For Depression, Anxiety and Stress Research at Harvard Medical School. Though researchers may find parallels in serotonin and dopamine fluctuations, neither fish nor rat can “capture the entire spectrum of depression as we know it,” says Dr. Pizzagalli.

There is a heated debate in the fish research community about whether anxious or depressed is a more appropriate term.

But what has convinced Dr. Pittman, and others, over the past ten years is watching the way the zebrafish lose interest in just about everything: food, toys, exploration — just like clinically depressed people.

“You can tell,” said Culum Brown, a behavioral biologist at Macquarie University in Sydney who has published more than 100 papers on fish cognition. “Depressed people are withdrawn. The same is true of fish.”

The trigger for most domestic fish depression is likely lack of stimulation, said Victoria Braithwaite, a professor of fisheries and biology at Penn State University, who studies fish intelligence and fish preferences.

Study after study shows how fish are defying aquatic stereotypes: some fish use tools, others can recognize individual faces.

“One of the things we’re finding that fish are naturally curious and seek novel things out,” said Dr. Braithwaite. In other words, your goldfish is probably bored. To help ward off depression, she urges introducing new objects to the tank or switching up the location of items.

Dr. Brown agrees, pointing to an experiment he conducted, that showed that if you leave a fish in an enriched, physically complex environment — meaning lot of plants to nibble on and cages to swim through — it decreases stress and increases brain growth.

The problem with small tanks is not just the lack of space for exploration, said Dr. Brown, but also the water quality tends to be unstable and there may not be sufficient oxygen.

“A goldfish bowl for example is the worst possible situation,” he said.

If you own fish, you might want to consider where Dr. Brown keeps his: an extensively-landscaped six-foot tank. He recommends a “two foot tank with lots of plants and stuff” for your average betta.

The last time a guest posted Bruce Lee to Instagram he was looking good and lively. Perhaps that new green leaf in his bowl had provided the enrichment he craved.

But then, my heart sank. The internet produced photos of other Bruce Lees from the same hotel in several colors — red, blue and purplish. I wondered whether the monotony would eventually drive this replacement Bruce, to hover, immobile, near his transparent rocks.

2449. Fish Recorded Singing Like Birds

By Gerta Keenan, New Scientist, September 21, 2016

Bat Fish

The ocean might seem like a quiet place, but listen carefully and you might just hear the sounds of the fish choir.

Most of this underwater music comes from soloist fish, repeating the same calls over and over. But when the calls of different fish overlap, they form a chorus.

Robert McCauley and colleagues at Curtin University in Perth, Australia, recorded vocal fish in the coastal waters off Port Headland in Western Australia over an 18-month period, and identified seven distinct fish choruses, happening at dawn and at dusk. You can listen to three of them here:

The low “foghorn” call is made by the Black Jewfish (Protonibea diacanthus) while the grunting call that researcher Miles Parsons compares to the “buzzer in the Operation board game” comes from a species of Terapontid. The third chorus is a quieter batfish that makes a “ba-ba-ba” call.

“I’ve been listening to fish squawks, burble and pops for nearly 30 years now, and they still amaze me with their variety,” says McCauley, who led the research.

Sound plays an important role in various fish behaviours such as reproduction, feeding and territorial disputes. Nocturnal predatory fish use calls to stay together to hunt, while fish that are active during the day use sound to defend their territory. “You get the dusk and dawn choruses like you would with the birds in the forest,” says Steve Simpson, a marine biologist at the University of Exeter, UK.

The recordings were captured by two sea-noise loggers: the first positioned near the Port Headland shore and the second 21.5 kilometres away in offshore waters.

“This is a method that allows us to understand what’s happening at Port Headland 24/7 for a year and a half,” says Simpson. “I don’t know any scuba diver that can stay down there that long!”

Listening to choruses over a long period of time allows scientists to monitor fish and their ecosystems, particularly in low visibility waters, such as those off Port Headland.

“We are only just beginning to appreciate the complexity involved and still have only a crude idea of what is going on in the undersea acoustic environment,” says McCauley.

Journal reference: Bioacoustics, DOI: 10.1080/09524622.2016.1227940

2368. Global Fish Production Approaching Sustainable Limit, UN Warns

By Arthur Nelson, The Guardian, July 7, 2016

Super trawlers are depleting oceans of fish

Global fish production is approaching its sustainable limit, with around 90% of the world’s stocks now fully or overfished and a 17% increase in production forecast by 2025, according to the UN Food and Agriculture Organisation (FAO).

Overexploitation of the planet’s fish has more than tripled since the 1970s, with 40% of popular species like tuna now being caught unsustainably, the UN FAO’s biannual State of the world’s fisheries report says.

Manuel Barange, the UN FAO’s fisheries director, told the Guardian that overfishing rates of around 60% in the Mediterranean and Black Sea regions were “particularly worrying”.

He said: “There is an absolute limit to what we can extract from the sea and it is possibly very close to current production levels, which have stabilised over last few years. They have grown a little in recent years but we don’t expect much more growth because of the rampant increase in aquaculture production.”

Aquaculture is now forecast to overtake wild-caught fish as the source of most fish consumption in 2021, for the first time.

The rise of aquaculture has also benefitted trade, employment and diets in the developing world, with global per capita fish consumption estimated at a record 20 kilograms.

“My personal view is that it is quite momentous to have reached this level of production,” Barange said. “In the struggle to make sure we have enough food to feed more than 9 billion people in 2050, any source of nutrients and micronutrients is welcome.”

Some campaign groups though fear that aquaculture may introduce invasive species, diseases and parasites. The potential for chemical pollution and use of transgenic species are also causes for concern, as are the impacts on wild fisheries and natural habitats.

Shrimp farming is thought to have led to the destruction of 3m hectares of coastal wetlands, including many mangrove forests, and the UN FAO is currently drawing up guidelines to reduce such environmental footprints.

Lasse Gustavssin, the director of Oceana, a marine conservation body, said that sustainable fisheries management should be prioritised instead.

“We now have a fifth more of global fish stocks at worrying levels than we did in 2000,” he said. “The global environmental impact of overfishing is incalculable and the knock-on impact for coastal economies is simply too great for this to be swept under the rug any more.”

For the UK, Brexit could have a big impact on fish-eating patterns. “One thing very likely to happen is that the drop in the value of the pound will makes fish imports into the UK more expensive, and exports cheaper,” said Barange, who lived in Britain for several years. “The UK is a net importer of fish so the fish we eat might cost us more. 

The fish our industries export will benefit as they will be more competitive pricewise.”

Globally though, some of the biggest beneficiaries of the growing fish industry will be found in the developing world, where fish exports in 2014 exceeded the combined net trade revenues from meat, tobacco, rice and sugar.

Of the world’s top 30 fish consuming nations, 22 were in the UN’s “low income, food deficit” category.

Twelve percent of the world’s population now relies directly or indirectly on the fisheries industry.

1840. When Humans Declared War on Fish

By Paul Greenberg and Boris Worm, The New York Times, May 8, 2015

On Friday we humans observed V-E Day, the end to one part of a global catastrophe that cost the planet at least 60 million lives. But if we were fish, we would have marked the day differently — as the beginning of a campaign of violence against our taxonomic classes, one that has resulted in trillions of casualties.

Oddly, the war itself was a great reprieve for many marine species. Just as Axis and Allied submarines and mines made the transportation of war matériel a highly perilous endeavor, they similarly interfered with fishing. The ability to catch staple seafoods, like cod, declined markedly. Freed from human pursuit, overexploited species multiplied in abundance.

But World War II also brought a leap in human ingenuity, power and technical ability that led to an unprecedented assault on our oceans. Not only did ships themselves become larger, faster and more numerous, but the war-derived technologies they carried exponentially increased their fishing power.

Take sonar. Before the 1930s, electronic echolocation was a barely functioning concept. It allowed operators to trace the vague contours of the seafloor topography and crudely track the pathway of a large moving object. But the war pushed forward dramatic advances in sonar technology; by its end, sophisticated devices, developed for hunting submarines, had grown infinitely more precise, and could now be repurposed to hunt fish.

Schools of fish could soon be pinpointed to within a few yards, and clearly differentiated from the sea’s bottom. Coupled with high-powered diesel engines that had been developed during the global conflict, the modern fishing vessel became a kind of war machine with a completely new arsenal: lightweight polymer-based nets, monofilament long lines that could extend for miles and onboard freezers capable of storing a day’s catch for months at a time.

Even human resources developed during the war were later redirected toward fishing: Japanese fighter pilots adept at spotting subsurface Allied submarines were later retrained to look for whales. Likewise, more than a few former Allied pilots found postwar employment hunting bluefin tuna and Atlantic menhaden.

In some ways, the “war machine” wasn’t a metaphor. Across South Asia, leftover explosives were “recycled” for “bomb fishing,” an obscenely destructive way of killing coastal fish, which turned many coral reefs into rubble fields. And the technological overkill continued into the Cold War era: Satellite imagery and GPS technology originally intended to track the movements of the Soviet nuclear arsenal eventually allowed well-populated fish habitats to be clearly identified from space.

Because the war incentivized the creation of ships with much longer oceangoing ranges, it also meant that fishing was transformed from a local endeavor into a global one. “Industrial fishing,” maybe the first globalized economic enterprise, meant the wholesale, permanent occupation of marine ecosystems, instead of the local raids practiced by previous generations.

In addition, emerging economies of scale meant that it wasn’t just the target fish that suffered. With the invention of postwar super trawlers that scooped up everything in their path, a sort of scorched-earth approach to fishing became commonplace.

Taken collectively, the rise of postwar fishing technology meant that the global reported catch rose from some 15 million metric tons at war’s end to 85 million metric tons today — the equivalent, in weight, of the entire human population at the turn of the 20th century, removed from the sea each and every year.

Only the turn of the third millennium saw a new kind of reprieve, this time not caused by human adversity, but by the insight that we need to make peace with other species as well. Growing signs of exhaustion and failure in global fisheries made humans reconsider the totality of their assault.

Marine protected areas, an environmental version of a demilitarized zone, started to spring up, and now cover some 3.5 percent of the ocean. Countries formerly at war began to work together to hammer out new deals for fish, exemplified by both the recent revision of the Common Fisheries Policy in Europe and new efforts underway at the United Nations to better regulate fishing on the high seas, the 60 percent of the oceans outside national control.

Collateral damage to sharks, turtles, whales and sea birds is increasingly becoming unacceptable. And some of those same technologies once used to kill fish with precision are now being used to save them: War-inspired satellite technology is being deployed to identify and pursue rogue vessels fishing illegally.

But in remembering the end of World War II and the deliberate steps that led to a lasting peace, we might contemplate a broader Marshall Plan, which would further restrain our destructive tendencies and technological powers elsewhere, not just in fishing the oceans, but in mining, drilling and otherwise exploiting them.

To be sure, the postwar assault on fish mostly sprang from an honorable intention to feed a growing human population that boomed in a prosperous postwar world. But as in war, everybody loses when there is nothing left to fight for. Only when we fully embrace that simple fact, and act accordingly, will our celebrations resonate among what the author Henry Beston called those “other nations caught with ourselves in the net of life and time.”

Paul Greenberg is the author, most recently, of “American Catch.” Boris Worm is a professor of marine conservation biology at Dalhousie University, Nova Scotia.

1310. Chinook Salmon Navigate Using a System Like GPS

By Patricia Waldron, Science Magazine, February 6, 2014

Chinook Salmon

Despite having no life experience, young salmon in the Pacific Northwest somehow travel hundreds or thousands of kilometers from their native streams to feed and grow in the ocean. While they can use their sense of smell to get back home to spawn, Chinook salmon (Oncorhynchus tshawytscha) have an inborn sense of direction that functions like a GPS. Scientists now suspect that with no prior knowledge, they use Earth’s magnetic field to find the right ocean habitat. To make the discovery, researchers placed hatchery-raised juveniles inside a bucket and exposed them to artificially generated magnetic fields. When the angle and intensity of the field matched the southernmost part of their ocean range, the fish oriented themselves to face north or northeast. The magnetic field at the northernmost range caused them to point south or southwest. By orienting within these two extremes, the salmon can find the feeding grounds of their ancestors, the team reports today in Current Biology. Because sea turtles use a similar magnetic map, the researchers speculate that many migratory marine animals, such as eels, sharks, and seals, may also navigate using magnetic fields.