Oceans and Fisheries

It’s hard to imagine, but even the seeming vastness of our oceans is under the same threat as the forests. Our oceans are dying.

  1. Acidic oceans — the evil twin of climate change
  2. Hotter oceans
  3. Empty oceans — overfishing
  4. Empty oceans — inefficient fishing
  5. Plastic oceans

1. Acidic oceans — the evil twin of climate change

I used to think that ocean acidification was just one more threat to some of the ocean’s critters. I now consider it the most important of a very deadly set of threats! The wiki reports that the extra CO2 we are pumping into the atmosphere also inhibits the growth of some corals and shellfish, again weakening vital ecosystems in our oceans. The impact of deoxygenated and warmer oceans will also hurt ocean ecosystems, with various studies “that simulated the interaction of these stressors and found a catastrophic effect on the marine food web”.

TED Talk: 9 minutes — June 2017

Triona McGrath reports that 70% of cold reefs and most tropical reefs, the ecosystem base for a full quarter of the entire ocean’s life, could be gone by 2100!

2. Hotter oceans

Jeremy Jackson explains the manifold issues of overfishing, acidifying and over-heating the oceans. He starts talking about climate change and warmer oceans about 12 minutes in, but the first part of the talk covers other themes on this page really well.

3. Empty oceans — overfishing

Fishing seems to have peaked as 75% of fisheries are on the verge of collapse. Fishing provides 14-16% of humanity’s animal protein, and over 1 billion people rely on it as their primary source of protein. But we risk permanently damaging fisheries when we over-fish. The wiki explains that the world’s fishing fleets are losing $50 billion each year, and that some fisheries are no longer viable, while some species have already gone extinct.

Overfishing can permanently tip ecosystems out of balance.

“Dramatic changes in species composition can result in an ecosystem shift, where other equilibrium energy flows involve species compositions different from those that had been present before the depletion of the original fish stock. For example, once trout have been overfished, carp might take over in a way that makes it impossible for the trout to re-establish a breeding population.”

As the new documentary “End of the Line” shows, most of the world’s fisheries are in decline. While there are simple solutions to the massive problem of overfishing, the movie doubts we have the willpower to institute them in time.

We are simply harvesting too many fish too fast.

Example: The Blue Fin Tuna

For example, Blue fin tuna can grow for 30 or 40 years and weight a ton, but lately their average size has been decreasing. They are now in trouble (wiki).

From 1976 to 2006 worldwide stocks of Bluefin Tuna plummeted by 90%. Most seafood sustainability guides recommend consumers choose alternatives to bluefin tuna.

In 2010, Greenpeace International added this population to its seafood red list, saying:


The wiki on overfishing explains:


Are the world’s fisheries destined to follow the example of the Atlantic Cod in the 1990’s? (Woah, lookout, there’s another peak).

4. Empty oceans — inefficient fishing

We are also fishing inefficiently. Bottom trawling is a perverse method of fishing that scrapes the sea-floor of all life, only to sell a tiny fraction of the actual catch. The majority is just considered collateral damage. Most of the catch is then thrown back into the sea as ‘by-catch’. It also destroys important sponge ecosystems along the bottom of our oceans.

Bottom Trawling

National Geographic photographer Brian Skerry presented some of his work at TED (2010). His work is beautiful, but the subject is not. As Brian’s TED talk so graphically shows, a mere handful of 7 or 8 shrimp kills 10 pounds of ‘by-catch’.

5. Plastic oceans

The swirling ocean gyres concentrate this plastic which slowly breaks down in the sunlight, and so our oceans are filling up with microscopic plastic garbage that fish and birds mistake for plankton and food. This is also starting to affect the oceanic ecosystem with dire possibilities for food security. The various hormonal and chemical toxins accumulate through the food chain. One day ocean catches could be so toxic that seafood is banned under public health concerns.

Ocean Gyre's

It’s an estimated 8 billion tons of plastic a year! Plastic breaks down into smaller pieces that birds eat, with an estimated 90% of seabirds eating plastic. It chokes turtles and whales and other marine creatures, all of which reduces the biodiversity of the oceans, weakening it. Also, micro-plastic chemicals and hormones can bio-accumulate up the food chain. Smaller fish eat the microplastics, which accumulate in the bigger fish, and then we eat the even larger fish that have hoovered up all those toxins growing up the food pyramid. As the wiki reports:

Effect on marine life and humans[edit]

Some of these long-lasting plastics end up in the stomachs of marine animals, and their young,[5][30][31] including sea turtles and the black-footed albatrossMidway Atoll receives substantial amounts of marine debris from the patch. Of the 1.5 million Laysan albatrosses that inhabit Midway, nearly all are likely to have plastic in their digestive system.[32] Approximately one-third of their chicks die, and many of those deaths are due to being fed plastic by their parents.[33][34] Twenty tons of plastic debris washes up on Midway every year with five tons of that debris being fed to albatross chicks.[35]

Besides the particles’ danger to wildlife, on the microscopic level the floating debris can absorb organic pollutantsfrom seawater, including PCBsDDT, and PAHs.[36] Aside from toxic effects,[37] when ingested, some of these are mistaken by the endocrine system as estradiol, causing hormone disruption in the affected animal.[34] These toxin-containing plastic pieces are also eaten by jellyfish, which are then eaten by fish.

Many of these fish are then consumed by humans, resulting in their ingestion of toxic chemicals.[38] While eating their normal sources of food, plastic ingestion can be unavoidable or the animal may mistake the plastic as a food source.[39][40][41][42][43]

Marine plastics also facilitate the spread of invasive species that attach to floating plastic in one region and drift long distances to colonize other ecosystems.[16] Research has shown that this plastic marine debris affects at least 267 species worldwide.[44]
