Environment compact

The overfishing will not only caused extinction of one specific species but will have a net effect on other marine species as well. To take an example, the blue-fin tuna, a valuable fish mentioned most by the environmentalists, is the main food of sharks. Due to the rapid decrease in the number of tuna, sharks have to find other source of energy to maintain life. Moreover, the population of small predator, which is the food for tuna will increase rapidly and make an imbalance in the ecosystem. 

Moreover, the modern fishery will have a bad effect on the habitat of many species. To make a example, the engine of modern fish boat will make noise in the sea water and caused a misdirection of dolphin or whale's communication. 

Bycatch is also a very serious problem as many sea mammal died every year due to bycatch. Not only fish, but sea mammals such as whales, dolphins and sea turtles as well. Here is some video about the bycatch effect on sea turtles. 

Sources:

"Bottlenose dolphin", Animal Globe, Web, Feb 25th, 2014, http://true-wildlife.blogspot.com/2011/02/bottlenose-dolphin.html

"Millions of turtle killed due to bycatch", Dicovery, Web, video, Feb 25th, 2014,http://www.youtube.com/watch?v=2cH7PYXrbAs