Fisheries

Fish as FoodCommercial FisheriesTrends in World FisheriesSolutions?

Commercial Fisheries• Traps• Trawls• Purse seines• Gillnets• Longlines• etc…

Purse seining

Trawling

Fish size-selective gridCod Fishery - Norway

Gillnetting

Longlining

Technological Improvement in Fisheries

Tuna catches under floating objects

0

1970

1990

1980

2000

10

20

30

40

Gro

ss R

egis

tere

d T

onna

ge (

106 to

ns)

1960

Non corrected

Corrected

World Fishing Fleet Capacity

0

20

40

60

80

100

1950 1960 1970 1980 1990 2000

Mill

ion

tonn

es

Capture

mariculture

Production of Marine Fisheries

Prod

uctio

n (

mill

ion

tonn

es)

50

100

1800 1840 1880 1920 1960 2000Year

EE

Zs C

laim

s

Global Trend in Landings

Catches per 100 hooks (Japanese fleet)1952

1964

1958

1980

Myers & Worm, 2003

Phase I - Undeveloped

Phase II - Developing

Phase III - Mature

Phase IV - Senescent

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1951

1953

1955

1957

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

Perc

enta

ge o

f res

ourc

esDevelopment Phases of World Fisheries

0% 10% 20% 30% 40% 50%

Fully exploited

Moderately exploited

Overexploited

Depleted

Recovering

Undeveloped

State of Fish Stocks 1999

0%

10%

20%

30%

40%

50%

60%

1970 1975 1980 1985 1990 1995 2000 2005

Fully Fished

Moderately fished: U+M

Overfished: O+D+R

Trends in States of Fish Stocks

1.00

1.00

1.00

1.00

0.94

0.92

0.87

0.86

0.83

0.81

0.73

0.71

0.44

0.43

0.39

0.14

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

IE

PNW

PSW

PCW

IW

ANE

AEC

ASW

PNE

MBS

PEC

ACW

ANW

PSE

ASE

ANT1. Antarctic2. Atlantic, Southeast3. Pacific, Southeast4. Atlantic, Northwest5. Atlantic, Western Central6. Pacific, Eastern Central7. Medit . & Black Sea8. Pacific, Northeast9. Atlantic Southwest10. Atlantic Eastern Central11. Atlantic Northeast12. Indian Western13. Pacific Central Western14. Pacific Southwest15. Pacific Northwest16. Indian Eastern

Ratio between Present & Historical Landings

Popu

latio

n Si

ze (N

)

Time (t)= Maximum Sustainable Yield

Maximum Sustainable Yield

= Growth

Maximum Sustainable Yield

Grow

th /

Yiel

d

Fishing effort

Simple Abundance Model

Single Species Models• Assessment models are biased because they do not incorporate the

predation by other species.

• Assessment models are limited because of their emphasis on equilibrium solutions, such as MSY.

• Assessment models do not usually account for environmental changes, whether interannual or interdecadal.

• A correct assessment approach requires that a multi-species framework be used.

• Harvest recommendations from single-species assessment do not consider the needs of other species.

• Harvest recommendations from single-species assessment involve the deliberate fishing down of a population and therefore adversely change the ecosystem.

• The single-species approach is invalidated, because overfishing has occurred for at least a majority of the world’s fisheries.

• Single-species approaches do not account for the indirect effects of fishing (e.g. bottom fishing on habitat quality).

PSE

AEC

MBS

ANT

ANE

ASW

PNE

PNW

ACW

PEC

IE

ANW

PCW

IW

PSW

0% 50% 100

PEC

PSW

ANT

PCW

PNW

IE

ANW

ASW

MBS

ANE

ASE

AEC

PSE

IW

ACW

50% 100 %

“GOOD”

“GOOD”“BAD”

“BAD”

A: if fishing at MSY is “good” B: if fishing at MSY is “bad”

Fishing at MSY level: is it good or bad?

Neoclassical Sustainability

Modern Sustainability

Fishery induced changes in world fish composition

Fishing Down the Food Web

Shark Populations NE Atlantic

Baum et al. 2003

• Fisheries have significantly contributed to human development and can still do so

• There are problem areas and avenues for positive change

• Change will never be at no cost; but….

Solutions?

Historical Succession of Coastal Ecosystems

Jackson et al. 2001

1. Over-exploitation of large predators2. Collapse “Ecosystem Engineering” species3. Rise of Microbes

Historical fishing consequences

Jackson et al. 2001

Historical fishing consequences

Jackson et al. 2001

Historical fishing consequences

Jackson et al. 2001

Jackson et al. 2001