Bur (1984) examined the population dynamics of Freshwater Drum (*Aplodinotus grunniens*) in Lake Erie in the late 1970s. In one part of his study, he measured the total length (TL) of all 1577 drum sampled and extracted scales for age estimation from a proportionate sample from each 10 mm length interval. The length and age data are recorded in **FWDrumLE2.csv** (view, download, meta).

- Separate the observed data into age- and length-samples. Construct an
**observed**age-length key. [This step would have been accomplished in this exercise.] - Use the semi-random age assignment technique from Isermann and Knight (2005) and the
**observed**age-length key to assign ages to the unaged fish in the length-sample. Combine the age-sample and the age-assigned length-sample into a single data frame, add a variable to this data.frame that contains the 10 mm TL categories, and use the combined data frame to answer the following questions.- How many fish are estimated to be age 3?
- How many fish are estimated to be age 8?
- Plot the age distribution for all fish.
- How many fish are in the 150 mm TL interval?
- What is the mean TL of age-4 fish?
- Plot the length-at-age with the mean length-at-age superimposed for all fish.

- Compare your results from the previous question to someone else’s results (or repeat the previous question). Did you both get the
*exact*same results? Why or why not? If not, how different were they?

Continue with these data here.

from Derek H. Ogle , created 08-Nov-15, updated 08-Nov-15, Comments/Suggestions.