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Are SA’s fisheries at the End of the Line? Colin Attwood, Zoology Dept. and Marine Research Institute, UCT. End of the Line Mechanisms of over-fishing, and their consequences. Massive declines in fish abundance Excessive investment in gear The effects of subsidies Discarding - PowerPoint PPT Presentation
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Are SA’s fisheries at the End of the Line?
Colin Attwood, Zoology Dept. and Marine Research Institute, UCT
End of the LineMechanisms of over-fishing, and their
consequences
•Massive declines in fish abundance•Excessive investment in gear•The effects of subsidies•Discarding •Ignoring scientific advice •Ecosystem alteration and degradation•Exploitation of Africa by 1st world nations
Carpenter
Red stumpnose
Roman
Red steenbras
Seventy-four
Dageraad
Santer
Other
1931 to 1933 1987 to 1993
Linefish Survey data: Arniston and Struisbaai
These species dominated our temperate reefs. They briefly supported a fishery. Now they are very rare!
“74” Dageraad
Red steenbras
0
200
400
600
800
1000
1200
1400
1910 1930 1950 1970 1990 2010
Cat
ch (
ton
s)
East coast sole
Not all is bad news
Australia’s south-east trawl fishery (R.J. Gowers 2008. Environ. History 14: 265–287 )
0
1000
2000
3000
4000
5000
6000
7000
8000
1910 1920 1930 1940 1950 1960 1970
Cat
ch (
ton
s)
Catch of north-sea cod (tonnes) ICES Advice. Cod in Subarea IV (North Sea), Division VIId (Eastern
Channel), and IIIa West (Skagerrak)
Fisheries management 1.01
Effort (# boats, or sea-days)
Su
sta
ina
ble
ha
rves
t
Zero catch Extinction(?)
Maximum sustainable yield
Let’s add a few other species
Effort (# boats, or sea-days)
Su
sta
ina
ble
ha
rves
t
?
A MDS plot of the similarity of each fish species’ contribution to different fisheries
N=507
Prawn trawl
Handline
Shore angling
Beach-seine
Purse-seine
Pelagic longlineTrawl
Estuarine angling
A MDS plot of the similarity of each fish species’ contribution to different fisheries
Prawn trawl
Trawl
Handline
Shore angling
Purse-seine
Pelagic longline
Estuarine angling
Beach-seine
A MDS plot of the similarity of each fish species’ contribution to different fisheries
It looks as if we are doing OK for 11 fish species.
Lets hope the other 496 are OK too.
• We need to consider cheap and robust mechanisms to protect our incredible diversity of fishes. I consider MPAs (or closed areas) to be in this category.
• The small-scale fisheries policy is pushing co-management. It is backed by some nice theory (reducing the commons, encouraging buy-in), but can we make it work?
Final thoughts
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