Question:

Sandra and Beth are friends who both enjoy fishing. One day they begin discussing the quantity of fish in two different lakes that they frequently visit. Based on their experience in fishing in the two lakes, they decide that the two lakes are equivalent in terms of the number of fish. A researcher overhears their conversation and decides to test their conclusion. Using advanced sonar sensing, the researcher counts the actual number of fish in each lake. The researcher finds that one lake has substantially more fish than the other lake does. Assuming that the findings of the researcher reflect the population truth about the two lakes, what type of error did Sandra and Beth make in their judgment - Type I or Type II error? Explain your answer.

I would like to verify if this would be considered a type II error.