Marine life dipped by 50% in 40 years

A study by WWF shows that marine life decreased by 50% in last 40 years (ie between 1970 and 2012).
Global population sizes of the Scombridae family of food fish that includes tunas, mackerels and bonitos have fallen by 74%.

Coral Reefs:

Almost 75% of the world’s coral reefs are threatened with their cover having decreased by more than 50% in the last 30 years.
At current projected levels of ocean warming and acidification, there is mounting concern that reefs could be lost from most areas by 2050.

Mangroves:

The world’s mangroves too are in serious peril. There has been a 20% loss in mangrove cover between 1980 and 2005 equal to as much as 3.6 million hectares. The rate of loss is 3-5 times greater than average global forest loss.

Sharks:

Global catches of sharks have increased by 300%. This means that 25% of shark, rays and skates are now threatened with local extinction.
Rising temperatures and increasing acidity levels caused by carbon dioxide are further weakening a system that is already degraded through overfishing, habitat degradation and pollution.