Population diversity and the portfolio effect in fisheries
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Population diversity and the portfolio effect in fisheries Daniel Schindler Keeler Professor of Aquatic and Fishery Sciences University of Washington Seattle, WA 98195 [email protected] Thanks to:

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Population diversity and the portfolio effect in fisheries Daniel Schindler

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Population diversity and the portfolio effect in fisheries daniel schindler

Population diversity and the portfolio effect in fisheries

Daniel Schindler

Keeler Professor of Aquatic and Fishery Sciences

University of Washington

Seattle, WA 98195

[email protected]

Thanks to:

National Science Foundation, Gordon and Betty Moore Foundation, Alaska Salmon processors


Population diversity and the portfolio effect in fisheries daniel schindler

Biological diversity is important for ecosystem stability…

…but does this apply to individual species?


Population diversity and the portfolio effect in fisheries daniel schindler

9 major rivers

Bristol Bay

each with

many

populations

L.A. Rogers

Salmon habitat in Bristol Bay

North Pacific Ocean

Wood River


Population diversity and the portfolio effect in fisheries daniel schindler

data from ADFG

Commercial fisheries for sockeye salmon in Bristol Bay have been

sustained for over 120 years

- record catches have occurred within the last 20 years -

Number of sockeye salmon caught in Bristol Bay (1893-2010)

Commercial catch


Population diversity and the portfolio effect in fisheries daniel schindler

Different dynamics in stocks of Bristol Bay sockeye produce portfolio effects in fisheries

Sockeye salmon returns to Bristol Bay rivers

10

1

Relative run size

Relative run size

0.1

0.01

1956

1961

1966

1971

1976

1981

1986

1991

1996

2001

2006

Year


Population diversity and the portfolio effect in fisheries daniel schindler

Bristol Bay

Major rivers

Streams

All the same age

Total return (relative)

Age diversity

1

2

1960 2010

year

3

Salmon returns to Bristol Bay are two times more reliable than the individual components of the portfolio

Eroded portfolio

2.2 times more variable than the Bristol Bay salmon portfolio


Population diversity and the portfolio effect in fisheries daniel schindler

http://www.absc.usgs.gov/research/Fisheries/Lake_Clark/subsistence.htm

The front line at Egegik

How does reliability affect people dependent on fisheries?


Population diversity and the portfolio effect in fisheries daniel schindler

100

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Variability in salmon increases the rate of fisheries closures

Fisheries are closed 4 years every century

Bristol Bay (intact portfolio)

average

minimum spawners

Number of returning salmon

Bristol Bay (eroded portfolio)

Fisheries are closed

40 times every century

Time (100 years)


Population diversity and the portfolio effect in fisheries daniel schindler

L.A. Rogers

Sockeye salmon have different biological features, depending on the habitat they occupy

Lake beaches

Small streams


Population diversity and the portfolio effect in fisheries daniel schindler

Habitat conditions vary among locations in watersheds


Population diversity and the portfolio effect in fisheries daniel schindler

Locations where juvenile salmon enter the ocean

Salmon habitat is also different among locations

in the ocean

August 2000, NASA


Population diversity and the portfolio effect in fisheries daniel schindler

Portfolio effects derive from intact and viable habitat

Pacific Northwest

Bristol Bay, Alaska

NOAA


Population diversity and the portfolio effect in fisheries daniel schindler

Bristol Bay

* Conservation and management should recognize the value of diversity within individual species, and the habitat conditions that produce this diversity* Maintaining genetic diversity and viable habitat is one way to build insurance for climate change. The weak stock today may be the strong one tomorrow!* Climate change, ocean acidification, etc. make the future far more uncertain than usual, the portfolio concept is one way to build insurance for the future (How are you spreading your risk? Among species? Among stocks?)* Specific strategies will be ecosystem-specific, but do not necessarily require finer scale management.


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