Seven-tenths of the world is ocean and the people of the world is quickly depleating the oceans of its wildlife. We must put an end to the mass fishing of non-sustainable fish, and use non-regulated fishing practices that kills other marine animals like turtles, sharks, and even seabirds. Never mind the illegal fishing that profit from over $9 billion/year. The United States & Britain, among other nations, have seen an increase in the "Green movement" and yet people tend to overlook that taking care of the planet includes the oceans & seas. We forget that these waters are also our to maintain, protect, and sustain.
By eating only sustainable seafood. (You can find what qualifies in that handy widget below.)
By helping politicians understand there needs to be protected areas where fishing is illegal.
By getting the word out! There is a great new book & film "The End of the Line" that will tell you more.