Transcript Colin Attwood - presentation

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
•Ignoring scientific advice
•Ecosystem alteration and degradation
•Exploitation of Africa by 1st world nations
Linefish Survey data: Arniston and Struisbaai
1931 to 1933
Carpenter
Red stumpnose
Roman
Red steenbras
Seventy-four
Dageraad
Santer
Other
1987 to 1993
“74”
Dageraad
Red steenbras
These species
dominated our
temperate reefs. They
briefly supported a
fishery. Now they are
very rare!
Not all is bad news
1400
East coast sole
1200
Catch (tons)
1000
800
600
400
200
0
1910
1930
1950
1970
1990
2010
Australia’s south-east trawl fishery
(R.J. Gowers 2008. Environ. History 14: 265–287 )
8000
7000
Catch (tons)
6000
5000
4000
3000
2000
1000
0
1910
1920
1930
1940
1950
1960
1970
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
Sustainable harvest
Maximum sustainable yield
Zero catch
Effort (# boats, or sea-days)
Extinction(?)
Sustainable harvest
Let’s add a few other species
?
Effort (# boats, or sea-days)
A MDS plot of the similarity of each fish species’
contribution to different fisheries
N=507
A MDS plot of the similarity of each fish species’
contribution to different fisheries
Trawl
Pelagic longline
Handline
Purse-seine
Beach-seine
Shore angling
Prawn trawl
Estuarine angling
A MDS plot of the similarity of each fish species’
contribution to different fisheries
Trawl
Pelagic longline
Handline
Purse-seine
Beach-seine
Prawn trawl
Estuarine angling
Shore angling
It looks as if we are doing OK for 11 fish
species.
Lets hope the other 496 are OK too.
Final thoughts
• 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?