Tag Archives: overfishing

Scientists just found humans broke a natural law of ocean life

Credit: Pixabay.

Over 50 years ago, researchers circumnavigated the Americas sampling ocean life along the way at regular intervals. In the process, they discovered a striking relationship: the abundance of a certain marine species is linked to its body size such that its collective mass is basically the same. Krill are a billion times smaller than tuna, but their numbers are a billion times more abundant. If you were to weigh all the krill in the ocean, the mass should be close to all the tuna — but not anymore.

A new study found that human activity like industrial fishing has broken this mathematical relationship known as the Sheldon spectrum, after Ray Sheldon, a marine ecologist who first reported this relationship in 1969.

Humans are at it again

The Sheldon spectrum — the total mass of a marine population stays the same even as the individual size changes — applies to virtually all ocean life, from the tiniest bacteria to the largest whales. Even though a whale is trillions of trillions of times larger than a bacterium, its population size is smaller by the same order of magnitude, so the numbers even out.

“It kind of suggests that no size is better than any other size,” Eric Galbraith, a professor of earth and planetary sciences at McGill University in Montreal, told Wired. “Everybody has the same size cells. And basically, for a cell, it doesn’t really matter what body size you’re in, you just kind of tend to do the same thing.”

But Galbraith was shocked to find that the Sheldon spectrum has been broken, specifically for larger marine creatures. Generally, the larger the fish or crustacean, the easier it is to catch. Global fisheries are notoriously unsustainable, with the United Nations’ Food and Agriculture Organization (FAO) pointing out that one-third of fish stock worldwide is experiencing depletion due to “overfishing and habitat destruction.”

Galbraith and colleagues, led by Max Planck Institute ecologist Ian Hatton, used modern satellite imagery and recent in situ ocean measurements to estimate the abundance of plankton and fish. They also used a reliable estimate of marine mammal populations from the International Union for the Conservation of Nature, the organization that designates threatened or endangered species.

“One of the biggest challenges to comparing organisms spanning bacteria to whales is the enormous differences in scale,” says Hatton.

“The ratio of their masses is equivalent to that between a human being and the entire Earth. We estimated organisms at the small end of the scale from more than 200,000 water samples collected globally, but larger marine life required completely different methods.”

These estimates were compared to those from 1850, which they modeled using records of fish and marine mammals that industrialized fishing and whaling had captured.

The Sheldon power law has been broken in the last century by human activity. Credit: Ian Hatton.

In these pre-1850 levels, the Sheldon spectrum held true across the board, with biomass staying remarkably consistent across size brackets. But when they compared these numbers to modern-day biomass, the relationship broke down in the upper one-third of the spectrum where the largest marine life can be found.

“Humans have impacted the ocean in a more dramatic fashion than merely capturing fish,” explained marine ecologist Ryan Heneghan from the Queensland University of Technology.

“It seems that we have broken the size spectrum – one of the largest power law distributions known in nature.”

Since 1800, the researchers found that the very largest size bracket of marine life experienced a reduction in biomass of nearly 90%. For instance, all whale species declined from more than 2.5 million to under 800,000 from 1890 to 2001.

In other words, a law of nature that has seemingly been true for eons has now been broken in just 100 years thanks to human activity. And overfishing isn’t the only problem we’ve brought upon ocean life. Climate-induced changes in the ocean are causing additional stress, throwing the ocean into a health crisis, which includes a loss of biodiversity.

More research is needed to understand how this huge loss in biomass affects the oceans, but it can’t be anything good. Having healthy fish stock is critical to the overall functioning of ocean ecosystems, as well as certain planetary functions. For instance, the ocean is known to play an indispensable role in regulating carbon in the atmosphere. 

Meanwhile, we already know the solution: reduce overfishing. Fish compose less than 3% of the annual human food consumption, so cutting back on fish shouldn’t be that big of a deal. But that’s of course easier said than done.

The findings appeared in the journal Science Advances.

Sawfish could soon become completely extinct if we don’t stop overfishing, says a study

A new study from the Simon Fraser University (SFU) warns that one of the most distinctive marine species — sawfish — are at real risk of extinction due to overfishing.

Image via Pixabay.

Sawfishes have already disappeared from roughly half of their known range, the authors report, as overfishing is driving their numbers into the ground. The species used to be quite a common sight for around 90 coastal countries around the globe, but are now one of the most threatened family of ocean fish and presumed extinct in 46 of those nations. A further 18 countries presume at least one species of sawfish to be locally extinct, while 28 others presume at least two.

A fish in need

“Through the plight of sawfish, we are documenting the first cases of a wide-ranging marine fish being driven to local extinction by overfishing,” says Nick Dulvy, one of the two authors of the paper.

“We’ve known for a while that the dramatic expansion of fishing is the primary threat to ocean biodiversity, but robust population assessment is difficult for low priority fishes whose catches have been poorly monitored over time. With this study, we tackle a fundamental challenge for tracking biodiversity change: discerning severe population declines from local extinction.”

Sawfishes get their name from the highly distinctive rostra they sport. These are long and narrow noses lined by teeth, making them very similar to sawblades. According to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, three of the five species of sawfish alive today are critically endangered, with the other two being endangered.

According to the authors of this study, overfishing is to blame. The animals’ long rostra and the teeth they sport can easily become entangled in fishing nets. They can fetch a high price on the market as their fins are among the most pricy shark fins. Rostra can also be sold for a variety of reasons, from folk medicine and novelty to spurs used in cockfighting.

Although we have no reliable global account of sawfish numbers, Dulvy says that the data we do have paints a very bleak picture. Unless an effort is made to stop overfishing and protect the habitats these species live in, there’s a very real risk of them going completely extinct.

In regards to solutions, the team recommends a concerted international conservation project focusing on Cuba, Tanzania, Columbia, Madagascar, Panama, Brazil, Mexico, and Sri Lanka, where such efforts are likely to see the greatest payoff. Fishing restrictions in these countries could also help. Australia and the United States both have solid protections already in place and retain populations of sawfish — they should act as “lifeboat” nations to ensure the species doesn’t go the way of the dodo.

“While the situation is dire, we hope to offset the bad news by highlighting our informed identification of these priority nations with hope for saving sawfish in their waters,” says Helen Yan, the paper’s other co-author.

“We also underscore our finding that it’s actually still possible to restore sawfish to more than 70 percent of their historical range if we act now.”

The paper “Overfishing and habitat loss drive range contraction of iconic marine fishes to near extinction” has been published in the journal Science Advances.

The European Union agreed to drastically reform its fishing policy

fishing350 years ago, if you took a cod from European waters, you’d have to cut it to be able to cook it. Nowadays, cooks easily fit one fish in a frying pan, even with a few vegetables. As unimportant as this fact may seem,it is actually a good reflection of the huge drop in fish numbers.

Blame it on the decimation of the dinner plate on industrial overfishing of Europe’s once plentiful waters, blame it on poor regulations, blame it on whatever, but one thing’s for sure: fish populations are going down, dramatically.


But leave it to Europe to pave the way and be the first continent to take a significant measure: the European Union has backed landmark legislation that could well prevent the commercial extinction of some of the continent’s favorite fish, and protect numbers of all populations.

“This is a historic deal. It has a commitment to rebuild fish stocks and a legally-binding target to end overfishing,” said Uta Bellion of The Pew Charitable Trusts, a nonprofit organization.

The plan — backed by representatives of EU member states, the European Parliament and the executive commission — compels the fishing industry to respect scientific advice on overfishing, vastly reduce the amount of fish thrown into the sea and give additional protection to sensitive areas.

“If we carried on, potentially 90 percent of all fish stocks would be unsustainable and at risk within the next decade,” said Davies, a British Liberal Democrat who led the push for change.

Does this actually matter, or is it too little too late? Well, the main player when it comes to overfishing is China – China reports less than 10% of everything they fish, and they fish not only in Asia, but also in Africa, and even near the Americas!


But this is definitely very good news! European coasts have lots of fish – or at least they had, at the end of WWII.

“German submarines were really good for cod stocks. No one went fishing,” Davies said.

But as decades pass, population increases, and fishing vessels get bigger and bigger.

“We quickly had too many boats chasing too few fish,” Davies said.

So when does it kick in ? Under this new plan, overfishing should end by 2015 for most species and by 2020 for all stocks, with a ban on approving catch quotas that are not in line with scientific advice.


China only reports 9% of what it is fishing

Just 9% of the millions of tonnes of fish caught by China’s giant fishing fleet in international waters (most notably in Africa) is reported to the UN.


Overfishing is one of the most serious issues mankind is facing – people don’t really understand that aquatic resources are not neverending, and this is probably the kind of thing which will make people 50 years from now say “how could we let this happen”.

In order to keep overfishing (at least partially) at bay, all UN countries have to respect certain limits – however, some players just don’t report how much they’re fishing. The problem is especially acute in African waters where there is a total lack of transparency.

“We can’t assess the state of the oceans without knowing what’s being taken out of them,” says Daniel Pauly, a fisheries scientist at the University of British Columbia in Vancouver, Canada, who led the study. The unreported catch is crippling the artisanal fisheries that help to feed West African populations, he says.

Fishing experts have long suspected that China catches way more fish than it reports. From 2000 to 2011, the country reported an average overseas catch of 368,000 tonnes a year. However, China has the world’s largest fishing fleet – and why would they do, if they’re only fishing this much? Pauly and his colleagues estimate that the average catch for 2000–11 was in fact 4.6 million tonnes a year, more than 12 times the reported figure. Of that, 2.9 million tonnes a year came from West Africa, one of the world’s most productive fishing grounds.


The estimate delivered by Liu Xiaobing, director of the division of international cooperation of China’s bureau of fisheries only accounts for the fish which is brought back to China – but most of the catch is actually sold abroad.

The only good thing about this is that it shows where environmental models were lacking.

“So that’s where my fish were going!” says Didier Gascuel at the European University of Brittany in Rennes, France, who is a member of the scientific committee that advises Mauritania and the EU on fishing agreements. Year after year, Mauritanian populations of bottom-dwelling species such as octopus, grouper and sea bream have remained stubbornly low — a sign of over­fishing by bottom-scraping trawlers, he says. “We had no idea the Chinese catch was so big and of course we never included it our models,” he says.

While pretty much every researcher in the field agrees that China is overfishing and the numbers they are sending in are too low, not everybody agrees with this new estimates.

“The new estimates seem far, far too high,” says Richard Grainger, chief of the fisheries statistics and information service at the FAO. He notes that a previous assessment2 estimated the total unreported catch in West Africa (by all nations) at 300,000–560,000 tonnes a year. That study tried to identify what was missing from official catch figures with a review of English-language scientific studies.

Ironically, Pauly and his team conducted another study 12 years ago, which showed that China is actually overreporting their internal production, as a result of mid-level bureaucrats in the country exaggerating their achievements.

But the problem is what they’re doing in international waters.

“It shows the extent of the looting of Africa, where so many people depend on seafood for basic protein.”

Via Nature

European Parliament supports major fishery reform

Overfishing is a dramatic problem in most areas of the oceans, and many people are desperately trying to protect what’s left of the ecosystems; thankfully though, the European Union has approved a major reform by an enormous majority.


The European Parliament was having its say in the on-going attempt to shake up Europe’s controversial Common Fisheries Policy (CFP), with many researchers warning that many fish species are fished at levels far beyond what the ecosystem can sustainably support.

As well as fulfilling (some of) the environmentalists and scientists demands, the Eurpoean Parliament has also agreed to recalculate the so-called ‘maximum sustainable yield’.

“We have shown today that the European Parliament is anything but toothless. We have used our power as a co-legislator, for the first time in fisheries policy, to put a stop to overfishing. Fish stocks should recover by 2020, enabling us to take 15 million tonnes more fish, and create 37,000 new jobs,” said Ulrike Rodust, the parliament’s rapporteur for fisheries reform rapporteur. Rodust’s report was passed by her colleagues for 502 votes for to 137 against (press release).

Campaign groups have been celebrating this decision, but this is just the first step in a larger scale issue. MEP Chris Davies said the vote would provide a “strong negotiating position” in the discussions Parliament will now have with the European Council and Commission to agree on the final legislation. If things don’t change in this direction, pretty soon, then “There’s plenty of fish in the oceanwill soon turn into an old saying.