This is a Paradox question, so let's identify the discrepancy.
The discrepancy here is between the estimate based on commercial tonnage (increasing markedly over the last decade) and the research based estimate (decreasing over the last decade).
We are looking for a possible explanation for this difference.
The key here is understanding what these two estimates are based on.
The estimate based on commercial tonnage is the average number of tons of cod caught by various commercial vessels per unit of fishing effort expended in the past year. A unit of fishing effort is defined as one kilometer of net set out in the water for one hour.
The research based estimate is based on the number of cod caught by research vessels during a once yearly sampling of the area.
Answer choice (C) is a possible explanation to this discrepancy because if "improvements in technology over the last 10 years have allowed commercial fishing vessels to locate and catch large schools of cod more easily" this would explain both the increase in the commercial tonnage estimate (i.e. easier for commercial vessels to catch the cod) and the decrease in the research based estimate (i.e. easier for commercial vessels to catch the cod so the population of cod is decreasing).
Hope this helps! Please let us know if you have any other questions.
Ashley-TienJuly 10, 2018
How do you eliminate D?
ChristopherJuly 29, 2018
@Ashley-Tien, this could potentially describe the disparity if there had always been a disparity. However, since the two estimates used to be close but have gradually grown apart, it would suggest that something must have changed over the past few years. Since nothing tells us otherwise, it's safe to assume that the 30 day survey period has stayed consistent over the period in question. Therefore, there must be an alternate explanation.
