Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Colin Attwood - presentation
Document related concepts
no text concepts found
Transcript
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?
