Overfishing of tuna in our oceans has decimated populations and put several species at risk of extinction. The population of Pacific bluefin tuna, for example, has been reduced to 4% of its original size, and the remaining fish are threatened by extraordinary demand and illegal fishing. Read about conservation strategies to save the Pacific blue fin tuna in thisslideshow from the Pew Charitable Trusts. Learn about the efforts of scientists to use in vitro fertilization of mackerel to breed Pacific blue fin tuna in thisvideo.