Überfischung: Ein weltweites Problem
Dr. Rainer FroeseIFM-GEOMAR
Kiel
Das `Runterfischen´ mariner Nahrungsnetze(Fishing Down Marine Food Webs, Pauly et al. Science 1998)
Überfischung im Nordost-Atlantik(Froese & Pauly 2003)
0%
25%
50%
75%
100%
1974 1978 1982 1986 1990 1994 1998
Years
Perc
ent o
f ICE
S Fi
sher
ies
43%3.9 years
28%5.1 years
Undeveloped
Developing
Fully exploited
Overfished
Collapsed
(t/km2)
Biomasse von Speisefischen im Jahr 1900 Christensen et al. 2003
und im Jahr 2000…. Christensen et al. 2003
Es gab Leben am Meeresboden
Bilder: Dr. K. Sainsbury, CSIRO
vorher
nachher
Spuren der Zerstörung
Typischer Meeresboden courtesy F. Grassle
Misswirtschaft in der Ostsee
Management Empfehlung für 2006: Erhöhung des Fangs auf 28,400 t (+ 15%)!
Größe ist wichtig:Typische Längenverteilung im Fang
Commercial Landings of Nile perch in 1982
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120 140 160 180 200 220
Length (cm)
Num
bers
Die meisten Fische sind zu klein
Commercial Landings of Nile perch in 1982
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120 140 160 180 200 220
Length (cm)
Num
bers
LinfLoptLm
Wenn man sie später fängt, konnten sie wachsen und ablaichen
Commercial Landings of Nile perch in 1982
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120 140 160 180 200 220
Length (cm)
Num
bers
LinfLoptLm
Actual catch:1,218 fish9,171 kg
Potential catch:541 fish12,556 kg+ 29%
Beispiel NordseeBabyfisch in Nordseefängen 2000 - 2004
82 %
61 %
55 %54 %
36 %32 %
18 %
0
10
20
30
40
50
60
70
80
90
100
Makrele Seezunge Hering Seelachs Scholle Schellfisch Kabeljau
Proz
ent B
abyf
isch
im F
ang
(%)
Quelle: ICES Report on the Assessment of Demersal Stocks in the North Sea and Skagerrak 2005
Don‘t Eat Babies
Herring, Clupea harengus, Lm = 24 cm TL
Rainer FroeseIfM, Düsternbrooker Weg 20
24105 Kiel, [email protected]
As a result of overfishing, most fishes are now caught before they had a chance to reproduce. This results in low catches (growth overfishing) and very small spawning stocks (recruitment overfishing). We suggest that fish of a given suitable stock are only caught after the first and before the second spawning in order to obtain maximum biomass and at the same time rebuild and maintain strong spawning stocks including large, fit ‘mega-spawners‘. The percentage to be taken from this cohort will depend on the species and on the status of the stock, and should be agreed between all parties involved. As the size of the cohort can be easily determined through surveys before and during first spawning, the total allowed catch in a given year can be determined quite accurately and transparently. We suggest that such simple regulations can be easier communicated and enforced than traditional management tools. Preliminary size at first maturity can be obtained from www.fishbase.org for all commercial fishes of the world. This size is shown below for some commercial fishes of the North Sea. Similar posters can be used to educate fishers, fish dealers, and consumers.
European Sprat, Sprattus sprattus, Lm = 10 cm TL
Atlantic cod, Gadus morhua, Lm = 50 cm TL
European plaice Pleuronectes platessusLm = 28 cm TL
Atlantic mackerel, Scomber scombrus, Lm = 30 cm FL
Plakat beim Fischerei-Kongress2001
Der ‚FisherMin Ruler‘
Und Heute:
Das Fisch-O-Meter
Fragen?
