Question

the atlantic cod was once the mainstay of the united states fishing industry. however, warming of the ocean along the shores of new england has caused the stock of cod to disappear almost completely. according to scientists at the gulf of maine research institute, the gulf of maine is heating up faster than a majority of the rest of the planet oceans. as a result of warmer ocean waters, female cod produce fewer offspring, and these fish are less likely to survive to maturity. even though recreational cod fishing was banned in 2014, and strict limitations were placed on the number of fish commercial fishermen could catch, these measures have not been enough to protect the cod. what is the main, or central, idea of the passage? because cod used to be abundant in the atlantic, it was once the backbone of the u.s. fishing industry. female cod are producing fewer offspring in the gulf of maine. because the gulf of maine is warming unusually quickly, atlantic cod are disappearing.

Explanation:

The passage starts by stating the Atlantic cod's past importance in the U.S. fishing industry, then focuses on the rapid warming of the Gulf of Maine and how it is causing the cod to disappear, despite fishing - bans and limits. The main idea is centered around the cod's disappearance due to the Gulf's warming.

Answer:

Because the Gulf of Maine is warming unusually quickly, Atlantic cod are disappearing.