What is the main conflict in Cod: A Biography of the Fish That Changed the World by Mark Kurlansky?

Gadus morhua, or cod, has been an important commercial fish for about six hundred years. As early as 1620, cod fishing was as the center of international conflict as various nations attempted to monopolize rich fishing grounds. Cod's prolific reproductive rates were seen for hundreds of years as a guarantee that the species would never be negatively impacted by human activity. However, numerous technological improvements and widespread increase in the scale of fishing operations have systematically reduced the various global cod fisheries to commercial insignificance. Today, cod is a depleted fishery and rapidly is becoming increasingly scarce.