The population biology of Lake Superior Lake Trout (*Salvelinus namaycush*) prior to 1950 was examined in detail by Sakagawa and Pycha (1971). In Table 1 of their paper, they presented the number of Lake Trout by age (from scales) collected in 4.5-inch mesh gillnets that were set between the Keweenaw Peninsula and Munising, MI in 1948. The numbers of Lake Trout caught for ages 3 to 14 were 5, 18, 21, 10, 45, 109, 95, 63, 42, 25, 13, and 4. Use these data to answer the questions below.

- Is this an example of a cross-sectional or longitudinal catch curve?
- Plot log(catch) versus age. Which ages best represent the descending portion of the catch curve? Explain.
- Using the
*unweighted*regression method, find the following (with 95% confidence intervals):- Instantaneous total mortality rate.
- Annual total mortality rate.
- Annual survival rate.

- Repeat the previous question using the
*weighted*regression method. - Repeat the previous question using the Chapman-Robson method.
- Mathematically show how to convert the instantaneous mortality rate to an annual mortality rate.

## References

Sakagawa, G. T., and R. L. Pycha. 1971. Population biology of Lake Trout (

*Salvelinus**namaycush*) of Lake Superior before 1950. Journal of the Fisheries Research Board of Canada 28:65–71.