“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.”
Overfishing - Wikipedia
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 Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries.”
[4]
Wikipedia
The
wiki on overfishing explains:
According to a 2008 UN report, the world’s fishing fleets are losing $50 billion USD each year through depleted stocks and poor
fisheries management. The report, produced jointly by the
World Bank and the UN
Food and Agriculture Organization (FAO), asserts that half the world’s
fishing fleet could be scrapped with no change in catch. In addition, the
biomass of global
fish stocks have been allowed to run down to the point where it is no longer possible to catch the amount of fish that could be caught.
[10] Increased incidence of
schistosomiasis in Africa has been linked to declines of fish species that eat the snails carrying the disease-causing parasites.
[11] Massive growth of
jellyfish populations threaten fish stocks, as they compete with fish for food, eat fish eggs, and poison or swarm fish, and can survive in oxygen depleted environments where fish cannot; they wreak massive havoc on commercial fisheries. Overfishing eliminates a major jellyfish competitor and predator exacerbating the jellyfish population explosion.
Are the world’s fisheries destined to follow the example of the Atlantic Cod in the 1990’s? (Woah, lookout, there’s another peak).
Inefficient fishing with terrible collateral damage
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. 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.
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’.
Are we being poisoned by micro-plastics in the ocean?
There are 5 oceanic gyres collecting a thick soup of micro-plastic particles, which one do you live nearest? Fish and birds end up with this plastic in their guts, and the various hormonal and chemical toxins accumulate through the food chain.
For more
What’s an Ocean Garbage Patch? : Video : Discovery News.
Wiki: Great_Pacific_Garbage_Patch
Wiki: North_Atlantic_Garbage_Patch