Lecture 29, November 19, 2008. Applying life-history analysis to problem of salmon.

Lecture 29, November 19, 2008.

Applying life-history analysis to problem of salmon.

Will removing dams on the Columbia River increase salmon survival?

Have past management strategies been effective?

What can be done to help increase their numbers?

Review from last lecture.

Step 1. - Figure out # of animals living and dying at each age.

Step 2. - Calculate death rates (dx), survival rates (px), and survival to age x (lx).

Step 3. - Figure out birth rates (expected number of offspring for a female inage class X.

Step 4. - Calculate lxmx - the contribution to population growth from females in eachage group.

Step 5. - Calculate Ro which is the net reproductive rate by summing lxmx over allages.

Step 6. - Make these measures specific with respect to time.- calculate generation time T-calculate little r (growth rate of a population)-calculate λ (per-time unit rate of multiplication of a population

1t

t

NRN

R = λ

0 1 2 1* * *...x xl p p p p the link between survival at a given age (px)and survival to age x (lx)

0 x xR l m* x xT x l m

Generation time where α is age at first reproduction andω is age at last reproduction.

0ln( )RrT

re

1 2

1 2

sensitivityelement element element

1 2

1 2

ln( ) ln( )ln( )ln( ) ln( ) ln( )

elasticityelement element element

Examining the effects of the life-table parameters on λ.

Sensitivity gives us the change in lambda with respect to a given element.- problem --> survival and fecundity are in different units

Elasticity makes these measures dimensionless.

Chinook salmon, Oncorhynchus tshawytscha

Population in Columbia River is ofconcern.

How to increase population size?

Dams and stream modifications

• 75,000 dams over 2m tall, plus 2.5 million smaller dams in the U.S. alone

Biological Effects of Dams

• Interrupts fish migration (e.g., salmon)– Fish ladders

can help

– Still can have 10-20% fish loss during outmigration

Video of Salmon in ladders & spawning in streams.

http://www.youtube.com/watch?v=vWG_y7WwAmI

Transporting salmon

To breach or not to breach, that is the question.

• Some say that this paper was a hand-grenade tossed into the heated debate over whether to breach the 4 dams on the lower Snake River.

Opponents of breaching

• “We are on a course change in the region,” said Bruce Lovelin, executive director of the Columbia River Alliance, an industry group. “Two or three years ago, dam braching seemed to be the solution. Now based on this report, it seems the problem is more in the estuary and the ocean.” –Nov. 3, 2000 Oregonian.

Proponents of breaching

• “Conservationists and scientists who work for Northwest tribes and the Oregon and Idaho fish and wildlife departments have said that the four dams must be breached to save Snake River salmon from extinction.

• On Thursday, they said the biologists’ arguments in Science do not change their opinion.” - Nov. 3, 2000 Oregonian.

This matrix -- and the values that go into it -- are the heart & soul of this paper.

What do these bars tell us? Which parameters were altered in the matrix? Whatdo these parameters mean? What is the conclusion for the fish?

This matrix -- and the values that go into it -- are the heart & soul of this paper.

What is the conclusion from this graph? What parameters in the matrixwere altered? What do these parameters correspond to?

What does this graph tell us aboutthe important stages to manage?

I had problems figuring out this graph. What is this graph telling us?

How to increase first year and estuarine survival?

• “… dam breaching is unlikely to affect available spawning habitat or first-year survival

• but could improve estuarine survival considerably.”

Benefits of barging?

• “Although survival of juvenile fish during barging is quite high, barging might reduce the subsequent survival of barged fish relative to those that swim downstream.”

• Is there delayed mortality associated with barging?

Benefits of breaching the Snake River dams?

• “Breaching the lower Snake dams would mean the end of fish transportation operation and would therefore eliminate any delayed mortality from transportation.

• Additionally… might increase the physiological vigor of salmon that swim downriver, thus improving survival during the critical estuarine phase.”

Indirect mortality

• “If this indirect mortality were 9% or higher, then dam breaching could reverse the declining trend of the SRSS chinook salmon.

• Unfortunately, estimating the magnitude of any indirect mortality from passage through the Snake River dams is difficult.”

In your opinion, is it a good idea to remove the dams?

Positive aspects Negative Aspectssurvival might go up costs lots of money to take?????? down

loss of power??????

Consider the following life-table. How high would survival to age 3 (l(3)) have to be for λ to be 1 or greater?

How high would fecundity have to be at age 3 for λ to be 1 or greater?

l(x) equals survival to age X. One way to calculate it is as the proportion of individuals surviving to age X. The other way is to consider the age-specific survival p(x). In this case, l(x) =p(x-1) * p(x-2)* . . . p(0). Which age-specific survival has the largest impact on lambda?

What has a larger impact on the population growth rate - an increase in p(2) or an increase in m(2)? How do you determine this?

Review Question from last Monday

What has a bigger effect - a change in lx(2) or a change in m(2) or a change in p(2)?