To determine whether, within a population, the
focal traits were related (i.e., whether individuals
with deep bodies also had large adipose fins or
long jaws), we employed ordinary least squares
(OLS) regression. Specifically, our analysis proceeded
in four steps. First, we regressed each of
the three focal traits (adipose size, jaw length,
body depth) against body length in three separate
regressions. Second, we used the least squares
estimates of the regression predictors (slope,
intercept) to predict the expected values of each
of the above traits for each individual, given their
body length. Third, we determined residual trait
values for each individual as the observed trait
value minus the expected trait value (determined
in step 2). Fourth, we performed three sets of
regressions for each population to determine,
within a population, whether: (a) deep bodies
were associated with long jaws, (b) deep bodies
were associated with large adipose fins, and
(c) long jaws were associated with large adipose