A recent World Wildlife Fund report has found that the planet has lost nearly half, or 49 percent, of its marine populations--including fish, birds, reptiles, and mammals--in the period spanning 1970 to 2012.

The World Wildlife Fund, with the help of London’s Institute of Zoology, has revealed some startling statistics about the world’s water-based environment in its recent Living Blue Planet Report. 
The marine Living Planet Index, which assesses 5,829 populations of 1,234 fish, bird, reptile, and mammal species, has dropped by nearly half, or 49 percent, between 1970 and 2012.
Of particular concern is the finding that there has been a 74 percent decline among 17 species of fish including mackerels and tunas which are important for food and local economies. 
Additionally, 25 percent of shark, ray, and skate species are considered endangered, largely due to overfishing, and ocean warming and aci