In a study of the effects of commercial fishing on fish populations, Hsieh et al. (2006) measured the year-to-year coefficient of variation (CV) of larval population sizes of exploited and unexploited fish species in the California current system. They compared the two groups of fish species by using a linear model that adjusted for differences between exploited and unexploited species in the age of maturation (MATURATION), which also seemed to influence the coefficient of variation. Data for 13 exploited species (open circles) and 15 unexploited species (filled circles) are shown in the following graph, along with the predicted values of the model for the two groups of fish.

CV=CONSTANT+MATURATION+EXPLOITATION. where EXPLOITATION is the explanatory variable representing the two groups of fish species (exploited and unexploited). The ANOVA results are listed in the following table.

a. Explain the steps that likely led to the authors using the model analyzed above.

b. What are the assumptions of this analysis?

c. Is there a significant difference between exploited and unexploited fish in their year-to-year coefficients of variation? Explain the basis for your conclusion.

Transcribed Image Text:

Coefficient of variation 2.5 2.0 1.5 1.0- 0.5 T 0 0 O do unexploited OD GOOD exploited 1 2 3 4 Age of maturation (yr) 5 6