http://7sage.com/lsat_explanations/lsat-25-section-4-question-07/I'm confused as to why the answer can't be C.
If supply goes down, and halibut is NOT replaced by other fish, then that means that supply has gone down, and even if demand stays the same the price will go up according to the law of supply and demand. There is nothing to suggest that demand will decrease in this scenario.