"Commercial overexploitation of the world's fish stocks is severe," UN Secretary General Ban Ki-moon said back in 2012. "Many species have been hunted to fractions of their original populations. More than half of global fisheries are exhausted, and a further third are depleted."
According to the UN Food and Agriculture Organization, 85 percent of global fish stocks are "overexploited, depleted, or recovering from depletion."
Yet despite these alarms having been sounded loud and clear, life in the oceans is continuing to deteriorate at an ominously rapid pace.
Fisheries for the most sought-after species of fish have already collapsed.
The populations of all large predator fish in the oceans have declined by 90 percent in the 50 years since modern industrial fishing became widespread around the world, according to a shocking paper by scientists with Dalhousie University in Halifax, Canada, published in Nature in 2003.
"We are losing species every day without ever knowing about them. Sometimes humans can be like a plague to the environment."
Three years after the paper's publication, the same scientists, along with colleagues from across the world, published an even more startling paper that predicted a total collapse of all fish that are currently caught commercially by 2048.
Many scientists, like Daniel Pauly of the University of British Columbia, have estimated that the total fish catch for the planet peaked back in the mid-1980s, and has been declining ever since.
Most scientists studying the issue agree that the three primary causes of the crisis are overfishing, plastic pollution and anthropogenic climate disruption (ACD).
But several, like Dr. Simon Boxall, an associate professor of oceanography with the University of Southampton, singled out overfishing as the largest culprit.
"The big problem is that we are overfishing," Boxall told Truthout. "The [fisheries] management isn't working, and is in fact causing just as much destruction [as] if there was no management in the first place."
Dr. Maria Salta, a biological oceanographer and lecturer in environmental microbiology in the School of Biological Sciences at the University of Portsmouth, echoed this dire outlook on the state of the oceans.
"For shrimpers, 80 percent of everything caught is bycatch and thrown back for dead. It is a mode of mass marine extinction."
"It is clear that if we continue like this, in a few years time, there is not going to be much left," she told Truthout, speaking about the impacts of ACD, pollution and overfishing. "We are losing species every day without ever knowing about them. Sometimes humans can be like a plague to the environment."
Fishing operations have expanded to, quite literally, every corner of the ocean over the last 100 years, due to the fact that technology now exists that enables humans to find and catch every single fish in the oceans, no matter where they are located on the planet.
Salta's statement might be startling to many, but ample scientific evidence exists to back it up. Overfishing is nothing more than taking wildlife from the sea at rates that are too high for the fished species to replace themselves. Atlantic cod and herring, along with California's sardines, were overfished to the brink of extinction by the 1950s, and by the late 20th century, isolated depletions had become both global and catastrophic.
Salta said sharks provide one example of this problem. The International Union for Conservation of Nature has listed approximately one-third of all open-ocean shark species as threatened with extinction because of overfishing.
"The oceanic white-tip shark populations declined by 99 percent from 1950 to 1999, making it now an endangered species," Salta said. "Also, when sharks are removed from the environment you change the balance of the ecosystem and how it functions."
According to the Pew Environment Group report "Protecting Life in the Sea," nearly one-third of the world supply of commercially caught fish has already collapsed.
Bycatch and Climate Disruption
Another major issue regarding overfishing is bycatch, which is sea life that is caught with the fish being collected in order to sell commercially, but is not used for any purpose.
Salta told Truthout she believes bycatch should be considered one of the ocean's biggest problems.
"Small vessels with small nets, catching what might be considered commercially unviable, is what we need."
"From 1994 onwards, 27 million tons of bycatch are discarded every year," she said. "Thirty percent of marine catch is thrown overboard dead. For shrimpers, 80 percent of everything caught is bycatch and thrown back for dead. It is a mode of mass marine extinction."
Hence, bycatch combines with other issues, like ACD and pollution, to create a multipronged threat to life in the seas.
"If organisms drop out of the food chain, the entire ecosystem is impacted," she said. "And temperature affects biodiversity and fish stock. Changes in this variable can impact the entire ecosystem and impact fish stocks."
The intersecting effects of ACD should not be underestimated. As Salta pointed out, just mild fluctuations in water temperatures, which are now common due primarily to ACD, have dramatic impacts on fish and other marine life.
Boxall pointed to the North Sea cod fishery as an example of this.
"Those cod were overfished, but we also see climate change kicking in and warming the waters, and cod, which like a cooler climate, are being pushed further north," he told Truthout. "Our cod are migrating to Iceland."
It has now become common to see reports of mass displacements of fish due to water temperature changes caused by ACD.
According to a study published in late February, ACD is pushing fish toward both poles, which means that poorer countries near the equator have even less access to one of their primary food sources. The fish migrations are due to global temperature increases in the oceans.
ACD is also a culprit in causing marine diseases to spread, according to a recent report.
Studies show that warming waters in the oceans are promoting marine diseases, so infectious agents now have the potential to alter oceanic life in many different ways. On a global basis, salmon are now being attacked by the diseases, and increasing bacteria is present in oysters.
Coral Bleaching and Overfishing Persist
Dr. Debora Iglesias-Rodriguez is a biological oceanographer at the UK's National Oceanography Centre. She specializes in the study of how human impacts on the atmosphere are changing the chemistry of the oceans, and how this causes acidification. She emphasizes that ACD's role in lowering fish stocks must not be taken lightly.
Coral reefs rely on the calcification process to be constructed, and calcification is the process by which corals produce calcium carbonate.
"Calcifying organisms are essentially chalk-producing organisms, and when seawater becomes more acidic, this is impacted negatively by dissolving them," Iglesias-Rodriguez told Truthout. "Calcification affects fisheries because many fishes' diet is based on these organisms. So this has food security impacts as well."
"Fishing as it's running at the moment isn't sustainable."
Recent research shows that coral growth is already being weakened by increasingly acidifying oceans. One-quarter of the carbon dioxide released as a result of human activities is absorbed into the world's oceans, where it alters their chemistry and reduces coral growth.
Meanwhile, a severe coral-bleaching event in the most pristine portions of the Great Barrier Reef in Australia has caused authorities there to raise an alarm over severe local coral bleaching, caused by warm ocean temperatures.
Meanwhile, the overfishing issue persists.
Salta went so far as to warn that within the next 25 years, one-quarter of the planet's biodiversity is in danger of extinction due solely to commercial fishing.
"When fish become overfished, the human response is to fish down the species to smaller species, so this shifts the target group down, and this affects biodiversity and the ocean ecology," she said.
Another large problem associated directly with overfishing is the widespread use of trawling: a method of fishing that involves dragging a fishing net through the water behind a boat. Bottom trawling, when the fishing net drags across the seafloor, is particularly destructive.
"It's the equivalent of forest clear-cutting, but in the ocean, because when they trawl the entire bottom, whatever is there, is removed from the environment and changes the entire ecosystem," Salta said. "Biomass of the deep sea is in sharp decline because of trawling."
Salta believes the global commercial fishing industry is affecting evolution in the oceans by causing many fish species to mature earlier; which then causes them to grow to smaller overall sizes; which then causes female fish to produce smaller, poorer quality eggs; which then causes a negative feedback loop of evolution.
All of these issues, taken together, reveal an overwhelming crisis. However, while it may be impossible to restore the oceans to their healthiest state, many scientists believe there is hope, at least, for mitigation.
Boxall says that process must involve humans changing the way we treat our seas -- immediately.
"The sea is over 73 percent of our world," he said. "The scale of it means that anyone actually trying to go out and clean them is not physically possible. We have to find ways to change our impacts, because we can't change what has been done already."
He says local solutions are key: They won't solve the whole crisis, but they can certainly have a positive impact.
"A sustainable fishery looks like an artisan fishery," he said. "Small vessels with small nets, catching what might be considered commercially unviable, is what we need. One hundred small boats would be better than one large factory ship that is scraping the seabed and taking everything out of an area. On small boats, after the sorting, much of it is alive when it goes back into the water."
However, specific changes in practices are just one component of addressing this crisis: Boxall stresses that without a broad shift in consciousness, nothing will change.
"Fishing as it's running at the moment isn't sustainable," he said. "The industry will collapse because there won't be fish to catch. But if we manage it properly now, and come to agreements driven by science and not commerce and politics, we'll have fisheries in the future."
Thus, he suggests we start thinking more about the need for an environmentally driven market, as opposed to a commercially driven market.
If such a shift were to happen on a large scale, it may be possible for some of the negative trends we are seeing today to be slowed -- or even halted altogether.