Lecture 30. December 1, Evolution of Life-History Traits & Impacts on Fisheries Lab: Quiz tomorrow, practical in 1 week. Arthur has flash cards that he is willing to share. I will forward them if folks would like. We will limit the minnows, darters, and suckers to those that we collected in the field. Final on December 15, 1:30-4:30, this room. Same format. Last paper to read for Wednesday: Pauly et al. I will send out the pdf.

Life-Table Analysis - Review - use accounting practice to figure out which life-stages / parameters have biggest effect on λ. - sensitivity & elasticity analysis. - figure out management practices effects on λ. What assumptions are we making?

We assume that life-history parameters only change in certain ways. - no density dependence - no evolution

What is density dependence? What does it mean to say that life-history parameters are density dependent? What is evolution? What does it mean when life-history parameters evolve?

Eleotris - Sleeper Goby Astyanax Crenicichla alta - Pike cichlid

What was the experimental design of Conover & Munch?

What treatments did Conover & Munch use? Which treatments produced the largest harvest & the largest sized fish? Why did this happen?

What is the interpretation of these data? Which treatment had the highest growth rate? Which treatment had the lowest growth rate?

Heritability tells you the extent to which the variation in phenotype has a genetic basis. In other words, to what extent do offspring resemble their parents. The heritability is 0.2. This means that if you use fish for parents that are 1 mm larger than another group, on average you will create babies that are 0.2 mm larger.

the selection differential is the difference between the mean for the whole population and the mean for the selected animals. mean for whole population mean for subpopulation

Heritability tells you the extent to which the variation in phenotype has a genetic basis. In other words, to what extent do offspring resemble their parents. The heritability is 0.2. This means that if you use fish for parents that are 1 mm larger than another group, on average you will create babies that are 0.2 mm larger.

Huge Problem: Conover & Munch selected the smallest guys at a given age. They didn’t select the young ones. A simple-minded response to Conover & Munch would be to go out and fish the small ones and leave the big ones. Does this duplicate what Conover & Munch did? Will this produce other problems? If so, what will they be?

Review Questions What recommendations do Conover & Munch make for increasing size of fish and total harvest? Which ones do you think seem most likely to have an effect? What is the inherent conflict illuminated by Conover & Munch’s paper? What is heritability? What are the two main assumptions that people make when using basic life-table analysis? Which of these assumptions are a problem for guppies? For silversides? For salmon? Based on Conover & Munch’s paper, what do you think will happen to a fish population where only the large individuals are harvested? What do you think will happen to a fish population where only the small individuals are harvested? Catching only the small individuals seems like a problem with modern trawls. Can you think of a way around this?

Review Questions Continued What assumptions did we make in our simple life-table analysis? What does it mean when we say that life-history parameters are density dependent? What does it mean when we say that life-history parameters are density-independent? What does it mean when we say that life-history parameters have evolved? Why do Conover and Munch make the following statement: “Moreover, the genetic changes caused by selective harvest may be irreversible; cessation of harvest does not guarantee reverse selection back to the original state.” Conover & Munch selected on the smallest guys at a given age. How does this compare with the guppy experiments? Is this what they did? Or did they do something else?