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Fisheries Oceanography. SST anomalies off Peru coastline. ENSO impacts on pelagic fishes: variable catch reductions (Peru). A. Bertrand. 12. 8. Catch (M. tons). El Nino. 4. 0. 1950. 1960. 1970. 1980. 1990. (Yánez et al. 1992). A. Bertrand. Space. Large scale forcing. - PowerPoint PPT Presentation
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Fisheries Oceanography
SST anomalies off Peru coastline
ENSO impacts on pelagic fishes: variable catch reductions (Peru)
A. Bertrand
0
4
8
12
1950 1960 1970 1980 1990
Cat
ch (M
. ton
s)
El Nino
(Yánez et al. 1992)
Spatio-temporal scales of effects on peruvian pelagic fisheries
A. Bertrand
Time
Space
DecadeInter-annualMonth Season YearDay
Ocean
Local
Regional
Basin Stock condition before ENSO
Adapted reproduction
Fishery pressure
Local Upwelling
ENSO strength and duration
Inter-decadal regime
Large scale forcing
Small scale forcing
Pacific Decadal Oscillations
ENSO and pelagic fisheries: regime shift
Chavez et al. 2003
ClupeidaeAmerican shadAlosa sapidissima
Engraulidaebaelama anchovyThryssa baelama
(Chavez et al. 2002)
A. Bertrand
(Chavez et al. 2002)
A. Bertrand
Pacific Decadal OscillationWarm Phase Cool Phase
Wintertime Wind (arrows) and Sea SurfaceTemp (colors)- Affect the N. Pacific, with secondary signatures in the tropics (opposite for ENSO)
Pacific Decadal Oscillation(PCA of N. Pacific SST)
20-30 year duration
A. BertrandChavez et al 2003
A. BertrandChavez et al 2003
Humans as Top Predator
Prod
uctio
n (
mill
ion
tonn
es)
50
100
1800 1840 1880 1920 1960 2000Year
EE
Zs C
laim
s
Global Trend in Landings
(Pauly et al., 2002)
Non-registered catches
Expansion of fisheries
A. Bertrand
(Pauly et al., 2002)
Non-registered catches
Expansion of fisheries
A. Bertrand
Trawling
Humans as “engineer species”
• Trawling disrupts sea bottom……
• Trawling ecosystem effects:– Decrease of spatial complexity– Decrease of target and bycatch
species– Increase of scavenger species– Overall loss of biodiversity (macro-
organism level)
Trawled Un-trawled
Trawled AreaUn-trawled Area
(bottom sonar images)
Trawling Impact
Bycatch of unwanted species
Turtle Excluder Device (TED)
Trawling frequency by german vessels between 1993 & 1996
(Rijnsdorp 1997)
P. Cury
Marine Protected
AreasNo Trawling Area
Gulf of Maine
Gillnetting
Bycatch of unwanted species
(Pauly et al., 2002)
Non-registered catches
Expansion of fisheries
A. Bertrand
Purse seining
Schooling behavior
Bycatch of unwanted species
(Pauly et al., 2002)
Non-registered catches
Expansion of fisheries
A. Bertrand
Longlining
Bycatch of unwanted species
(Pauly et al., 2002)
Non-registered catches
Expansion of fisheries
A. BertrandWhy steady increase?
Catches per 100 hooks (Japanese fleet)1952
1964
1958
1980
Myers & Worm, 2003
Shark Populations NE Atlantic
Baum et al. 2003
Fishing Down the Food Web
Fishery induced changes in world fish composition
Compensation in exploited fish communities
(Tropical Atlantic)
Myers & Worm, 2003
● Blue Marlin△ Sailfish○ Swordfish
Compensation in exploited fish communities
(Southern Grand Banks)
Myers & Worm, 2003
● Codfishes (Gadidae)○ Flatfishes (Pleuronectidae)
Seafood consumption (US)