In-class Exercise and Problem Set 15:

Population Interactions

In the final lab of the semester, we will be watching a program that first aired on the PBS television show NATURE in 2003.  The episode, entitled A Mystery in Alaska, delves into causes and concerns over the decline in Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska.  Since the 1970s, Steller sea lion populations have dropped 70-80%.  Are predators [e.g., killer whales (Orcinus orca)] or prey [e.g., herring (Clupea pallasii), pollock (Theragra chalcogramma), etc.] responsible for the decline?  Is competition [e.g., pollock, humpback whales (Megaptera novaeangliae), etc.] a factor?  Is the decline due to anthropogenic or natural changes (e.g., oil spills, climate change) in the environment?  Perhaps several variables are interacting to reduce sea lion populations.

While watching the show, consider what you might do as a research biologist or manager, assigned to identify causes for the population decline.  Based on what you've learned in this class and other classes, how might you attack the problem?  What sorts of experiments would you perform to clarify the issues and identify potential causes?  What types of data would you need?  How would you analyze those data?

After the conclusion of the show, please answer the following questions during the time remaining in-class:

1)    In your opinion, what are the proximate and/or ultimate causes of sea lion population declines?  Is the decline caused by a single factor or multiple factors?  These could be your own ideas or variables discussed during the show.  Explain your answers.

2)    As a researcher, what experiment might you perform to identify the cause(s) of sea lion decline and, as a manager, what management action(s) might you take to increase sea lion abundance?

3)    Identify at least 2 factors not mentioned in the film that could impact sea lion populations.  Discuss how they may influence sea lion abundance (e.g., mortality, natality, survival, population growth).

4)    Both herring populations and sea lion populations have experienced similar decreases over the same time period.  Does that mean that one has caused or is the result of the other?  Explain your answer.

Use your knowledge as a biologist to come up with meaningful answers to the numbered questions.  A few sentences in response to each question will be sufficient.  Write clearly and concisely.  Feel free to use your computer or any notes you may have to reference specific course (or other) material.

    This assignment is due at the end of the class period.  Print it and hand it in before departing.  In the event of printer problems in the lab, answers may be emailed to knicholson@uidaho.edu, but must be time-stamped before 1800 hr on the day they are due.

    Also, please fill out an evaluation form for the course prior to 11 December (see Course Evaluation website).  Thanks for a great semester and good luck to all of you!

Revised: 05 December 2011