Category Archives: food

Overfishing eats away at genetic diversity of fish

Overfishing eats away at genetic diversity of fish – environment – 15 July 2011 – New Scientist.

Plenty more fish in the sea? Maybe not for much longer. Overfishing is damaging the genetic diversity of fish to a greater degree than expected, leaving at-risk species vulnerable.

It was thought that even badly overfished species would remain genetically diverse, since millions of individual fish remain even in the most depleted species.

To test this assumption, Malin Pinsky and Stephen Palumbi of Stanford University in California gathered published data on genetic diversity in 37 overfished species and compared it with diversity in 51 of their lightly fished relatives.

To their surprise, they found that the overfished species carried, on average, about 18 per cent fewer genetic variants than their lightly fished relatives. “Contrary to what we expected, it looks like the [genetic] effects of overfishing are quite widespread,” Pinsky says.

At first glance, a drop in genetic diversity of just 18 per cent may seem small, given that some overfished species are thought to have suffered severe population crashes. However, widespread overfishing is just a few decades old, and if it continues it may lead to a further erosion of genetic diversity, says Pinsky.

Meanwhile, Michael Alfaro of the University of California, Los Angeles, and his colleagues have found another ominous sign for fish stocks.

Speedy evolution

They analysed the family tree of fish to see how quickly body size changes in each lineage, then noted which lineages are most heavily fished. The team found that species with unusually fast rates of evolution in body size are preferentially targeted by fishing.

Since changes in body size often lead to changes in other ecologically relevant traits, this means that fishing targets the most evolutionarily active groups of fish, Alfaro says.

“Humans are eating away the richest branches of the fish tree of life,” says Alfaro. “If you were going to come up with a plan to assault the fish tree of life, you would want to do it like this.”

The results add urgency to biologists’ call for more aggressive management of commercial fisheries. “These are not trends we would wish to see continue,” says Paul Bentzen, a fisheries geneticist at Dalhousie University in Halifax, Canada. “We need to be managing fisheries more effectively.”

That could involve measures such as shorter fishing seasons and an increase in the number of no-fishing zones. But the bottom line is that people need to catch fewer fish, Bentzen says.

Pinsky and Alfaro presented their findings at a meeting of the Society for the Study of Evolution in Norman, Oklahoma, last month

Dry onion skin a treasure we're tossing out?

Dry onion skin has a use.

ScienceDaily (July 14, 2011) — More than 500,000 tonnes of onion waste are thrown away in the European Union each year. However, scientists say this could have a use as food ingredients. The brown skin and external layers are rich in fibre and flavonoids, while the discarded bulbs contain sulphurous compounds and fructans. All of these substances are beneficial to health.

Production of onion waste has risen over recent years in line with the growing demand for these bulbs. More than 500,000 tonnes of waste are generated in the European Union each year, above all in Spain, Holland and the United Kingdom, where it has become an environmental problem. The waste includes the dry brown skin, the outer layers, roots and stalks, as well as onions that are not big enough to be of commercial use, or onions that are damaged.

“One solution could be to use onion waste as a natural source of ingredients with high functional value, because this vegetable is rich in compounds that provide benefits for human health,” says Vanesa Benítez, a researcher at the Department of Agricultural Chemistry at the Autonomous University of Madrid (Spain).

Benítez’s research group worked with scientists from Cranfield University (United Kingdom) to carry out laboratory experiments to identify the substances and possible uses of each part of the onion. The results have been published in the journal Plant Foods for Human Nutrition.

According to the study, the brown skin could be used as a functional ingredient high in dietary fibre (principally the non-soluble type) and phenolic compounds, such as quercetin and other flavonoids (plant metabolites with medicinal properties). The two outer fleshy layers of the onion also contain fibre and flavonoids.

“Eating fibre reduces the risk of suffering from cardiovascular disease, gastrointestinal complaints, colon cancer, type-2 diabetes and obesity,” the researcher points out.

Phenolic compounds, meanwhile, help to prevent coronary disease and have anti-carcinogenic properties. The high levels of these compounds in the dry skin and the outer layers of the bulbs also give them high antioxidant capacity.

Meanwhile, the researchers suggest using the internal parts and whole onions that are thrown away as a source of fructans and sulphurous compounds. Fructans are prebiotics, in other words they have beneficial health effects as they selectively stimulate the growth and activity of bacteria in the colon.

Sulphurous compounds reduce the accumulation of platelets, improving blood flow and cardiovascular health in general. They also have a positive effect on antioxidant and anti-inflammatory systems in mammals.

“The results show that it would be useful to separate the different parts of onions produced during the industrial process,” explains Benítez. “This would enable them to be used as a source of functional compounds to be added to other foodstuffs.”

Is free global trade too great a threat to food supplies, natural heritage and health?

Is free global trade too great a threat to food supplies, natural heritage and health?.

ScienceDaily (June 9, 2011) — Researchers from the UK Research Councils’ Rural Economy and Land Use Programme say that we face a future of uncertainty, and possible new threats to our food supplies, natural heritage, and even human health, from animal and plant pathogens. Human behaviour, travel and trade exacerbates the problem and we may need to reconsider our approach to free trade.

We face a future of uncertainty, and possible new threats to our food supplies, natural heritage, and even human health, from animal and plant pathogens, according to researchers from the UK Research Councils’ Rural Economy and Land Use Programme.

In a special issue of Philosophical Transactions of the Royal Society B, the academics take a fresh look at infectious diseases of animals and plants, from an interdisciplinary perspective.

They conclude that increasing global trade may put us at greater risk from pathogens in the future, as more exotic diseases enter the country. This process is already happening, particularly in plant disease. Climate change is driving shifts in cropping patterns across the world and they may take pests and diseases with them. We are also seeing completely new pathogens evolve, while existing ones develop the ability to infect new hosts. During the 20th century the number of new fungal, bacterial and viral diseases in plants appearing in Europe rose from less than five per decade to over 20.

But these problems are exacerbated by human behaviour, and understanding this could be key to helping policymakers deal with risk and uncertainty.

In many cases the spread of disease is caused by increased trade, transport and travel. Trends in the international horticultural industry have been towards fewer, larger producers, supplying vast numbers of retailers. Thus, disease which begins in one location may be spread far and wide.

Changes in the livestock trade have similar effects at national level. Reduction in income per animal, and the introduction of mechanisation, means that fewer farmers manage more animals per farm, and animals are moved around more frequently. They may be born in one location but sold on and reared elsewhere. Government policy and the classification of diseases may even increase the risks. Farmers restocking to combat one disease may, unwittingly, introduce another.

Understanding the biological dimensions of animal and plant disease is important, but it is equally important to understand the role played by human beings in spreading disease. Whether the threat is from a tree disease such as Sudden Oak Death that could devastate familiar landscapes, or from zoonotic diseases such as E coli or Lyme disease that affect human health, it can only be addressed effectively if an understanding of human behaviour is part of the strategy, and people are given the information they need to reduce risks.

Director of the Relu Programme, Professor Philip Lowe said: “We live in a global economy: we have seen in the recent E. coli outbreak in Germany, how the complexity of the food chain can increase risk and uncertainty.

“Ultimately we may have to take a more precautionary approach to the movement of animal and plants, and recognise that free trade could, in some cases, pose unacceptable risks.”

Can’t Eliminate an Invasive Species? Try Eating It!

Can’t Eliminate an Invasive Species? Try Eating It. – NYTimes.com.

Erik Olsen/The New York Times

Although the lionfish appears off-putting, some see a growing place for it on American plates.”

With its dark red and black stripes, spotted fins and long venomous black spikes, the lionfish seems better suited for horror films than consumption. But lionfish fritters and filets may be on American tables soon.

Multimedia
Ty Cacek/The New York Times

Some invaders have successfully been turned into food, like tilapia.

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Vone Research/Lionfishhunters.Org

Among the less endearing qualities of the lionfish are their venomous spines.

An invasive species, the lionfish is devastating reef fish populations along the Florida coast and into the Caribbean. Now, an increasing number of environmentalists, consumer groups and scientists are seriously testing a novel solution to control it and other aquatic invasive species — one that would also takes pressure off depleted ocean fish stocks: they want Americans to step up to their plates and start eating invasive critters in large numbers.

“Humans are the most ubiquitous predators on earth,” said Philip Kramer, director of the Caribbean program for the Nature Conservancy. “Instead of eating something like shark fin soup, why not eat a species that is causing harm, and with your meal make a positive contribution?”

Invasive species have become a vexing problem in the United States, with population explosions of Asian carp clogging the Mississippi River and European green crabs mobbing the coasts. With few natural predators in North America, such fast-breeding species have thrived in American waters, eating native creatures and out-competing them for food and habitats.

While most invasive species are not commonly regarded as edible food, that is mostly a matter of marketing, experts say. Imagine menus where Asian carp substitutes for the threatened Chilean sea bass, or lionfish replaces grouper, which is overfished.

“We think there could be a real market,” said Wenonah Hauter, the executive director of Food and Water Watch, whose 2011 Smart Seafood Guide recommends for the first time that diners seek out invasive species as a “safer, more sustainable” alternative to their more dwindling relatives, to encourage fisherman and markets to provide them.

“What these species need now is a better — sexier — profile, and more cooks who know how to use them,” she said. She has enlisted celebrity chefs to promote eating the creatures.

Scientists emphasize that human consumption is only part of what is needed to control invasive species and restore native fish populations, and that a comprehensive plan must include restoring fish predators to depleted habitats and erecting physical barriers to prevent further dissemination of the invaders.

“We are not going to be able to just eat our way out of the invasive species problem,” Dr. Kramer said. “On the other hand, there are places where this can be a very useful part of the strategy.”

The United States Fish and Wildlife Service is now exploring where it might be helpful. Models suggest that commercial harvest of Asian carp in the Mississippi would most likely help control populations there, “as part of an integrated pest management program,” said Valerie Fellows, a spokeswoman.

In practice, it is still unclear whether commercial fishing pressure could be high enough to have a significant impact, she said. The Army Corps of Engineers has spent millions of dollars to erect electronic barriers to keep Asian carp from moving from the Illinois River into the Great Lakes.

There are risks to whetting America’s appetite. Marketing an invasive species could make it so popular that “individuals would raise or release the fish” where they did not already exist, Ms. Fellows said, potentially exacerbating the problem; tilapia were originally imported into Latin America for weed and bug control, but commercialization helped the species spread far more widely than intended.

Dr. Kramer is concerned that the marketing of lionfish might increase the number of traps on reefs, which could trap other fish as well. He said spearfishing was the sustainable way to catch lionfish, which are reef dwellers.

Cookbooks do not say much about how to filet an Asian carp, which has an unusual bony structure. And even if one developed a taste for, say, European green crab soup, there is nowhere to buy the main ingredient, though it is plentiful in the sea.

To increase culinary demand, Food and Water Watch has teamed up with the James Beard Foundation and Kerry Heffernan, the chef at the South Gate restaurant in New York City, to devise recipes using the creatures. At a recent tasting, there was Asian carp ceviche and braised lionfish filet in brown butter sauce.

Lionfish, it turns out, looks hideous but tastes great. The group had to hire fishermen to catch animals commonly regarded as pests. Mr. Heffernan said he would consider putting them on his menu and was looking forward to getting some molting European green crabs to try in soft-shell crab recipes.

Last summer, the Nature Conservancy sponsored a lionfish food fair in the Bahamas, featuring lionfish fritters and more. They offered fishermen $11 a pound — about the price of grouper — and got an abundant supply. Lionfish, native to the Indian Ocean and South Pacific, arrived in the Caribbean in the early 1990s and are spreading rapidly; voracious eaters, they even eat juveniles of native fish.

Lionfish, like grouper, can carry ciguatoxin, which causes vomiting and neurological symptoms, so they cannot be taken from water where the microbe that produces the toxin is found. The fish’s venomous spines must be removed before sale, although that is not a serious marketing obstacle.

Mitchell Davis, vice president of the Beard Foundation, said other species had moved from being pariah pests to must-have items on American plates, like dandelion greens for salads.

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