Presentation on theme: "The Status of World Fisheries by Daniel Pauly Fisheries Centre, University of British Columbia Vancouver, Canada United Nations University Fisheries Training."— Presentation transcript:
The Status of World Fisheries by Daniel Pauly Fisheries Centre, University of British Columbia Vancouver, Canada United Nations University Fisheries Training Programme Institute of Marine Research Reykjavik, December 16, 2002
Everywhere one looks, fisheries are in trouble… Martell (1999) Bluefin tuna in the Atlantic … Lingcod in British Columbia … …and I could go on with hundreds of those…
We can generalize this by using simple definitions of stock status: Status of fisheryCriteria applied to 932 species (groups) in FAO’s global catch statistics UndevelopedYear before maximum year and value less than 10% of maximum value. DevelopingYear before maximum year and value 10-50% of maximum value. Fully exploitedValue larger than 50% of maximum value. OverfishedYear after maximum year and value 10-50% of maximum value. CollapsedYear after maximum year and value less than 10% of maximum value. Definitions by R. Froese, IfM, Kiel, Germany
...and applying these to FAO’s marine catch data (1951-1998). This shows a steady erosion of fisheries worldwide. Thus, fisheries are in crisis, and the problem is growing rapidly. Analysis by R. Froese, IfM, Kiel, Germany
And yet, the global catch statistics assembled by FAO so far did not seem to add up to a globally declining catch … Indeed, global catches appeared to increase in the 1990s. Based on the FAO FISHSTAT database (with approximations for discards and unreported catches).
To deal with anomalies of this sort, we usually plot things on a graph, and look for patterns, and deviations from the patterns. However: Except for tuna, fisheries data are usually not presented in spatially disaggregated form; Data on who caught ‘what and where’ usually exist only for fisheries with on-board observers, tend to be confidential, and cover only a small part of the world fisheries; Hence, to place fisheries catches on maps, we must use other things we know.
Taxon (what) FAO Area (where)Country (who) Taxon distribution database Spatial reference database Fishing access database Common spatial cells? Assign catch rate to common cells YES This algorithm now assigns over 99 % of FAO global marine catches to ½ degree spatial cells, and we are still improving the underlying databases … NO Improve databases Thus, we used a ruled-based algorithm…
The global map we got was not very exciting, except for the anomalies (red)…. 0 We had no problem with Peru and Chile. But China?
So we used a statistical model to try to reproduce the catch map, using depth, primary production, etc., to predict catches... It worked everywhere, except for Chinese waters, where the discrepancies were huge….
This allowed us to identify and quantify over- reporting of marine catches by China throughout the 1990s … (Watson and Pauly, Nature, Nov. 29, 2001).
Correcting for this resolved the global conundrum: … in reality, global marine fisheries catches have been decreasing since the late 1980s (Watson and Pauly, Nature, 2001).
Now to the ecological processes underlying overfishing. Fisheries exploit resources embedded within ecosystems … wherein each organism has its own trophic level …
Now consider that ecosystem fluxes move up ‘trophic pyramids’ … Turning this around, we can use global catches to estimate how much primary production is required to support the fisheries … Trophic level Phytoplankton Top predators Prey fish Zooplankton................... *.......... *.*. *.*....... 10% *. 4 3 2 1
Terrestrial average: 35-40% Non-tropical shelves: 35% Open ocean: 2% Tropical shelves: 35% Upwelling: 25% Rivers/ lakes: 24% Pauly and Christensen, Nature 1995 And we can estimate the percentage of total marine primary production that is appropriated by humans…
Pauly et al. Science March 1998 Marine Freshwater Similarly, we can estimate (from catch data and the trophic level of all species caught) the mean trophic level of global fisheries landings. This is declining…
In a critique, Caddy et al. (1998. Science 282:183a.) wrote we overlooked several sources of bias, notably: 1.The composition of landings does not necessarily reflect relative abundance on underlying ecosystem; 2.Trophic levels change with size or age; 3.Over-aggregated catch statistics may bias results.
Ad (1) - landing trends vs. ecosystem trends. Three counter-arguments: 1.Fish are nowadays exploited everywhere they are abundant; 2.All trawl survey data so far tested for this (e.g., Gulf of Thailand, Cantabrian Shelf, Guinea, etc.) show TL trends similar to those of the landings; 3.Work by Pinnegar et al. (Lowestoft) for the Irish Sea shows that decline of TL in landings is less pronounced than in survey data (i.e., skippers try to maintain catches of high TL fishes).
Ad (2) – ontogenic changes in TL. Trophic level tends to increase with size/age; as ‘fishing down’ is associated with high F, TL decline is faster when ontogenic changes in TL are considered. From Pauly et al. (2001; Can. J. Fish and Aquatic Sci.)
Item (3) came up because much of the world’s catch is reported in very coarse categories…
However, over-aggregating catch statistics has the effect of masking the fishing down effect. FAO Area 27 (NE Atlantic)
Indeed, there is another masking effect, overlooked by Caddy et al. (1998), illustrated by FAO Area 31 (West Central Atlantic). There, fishing down did not seem to occur, which we first attributed to the crude statistics from many countries of that region.
However, after separating the USA (‘South Atlantic’ and Gulf of Mexico) from the rest of the region (Mexico, Caribbean, NE South America), we get:
Disaggregating the tuna and billfishes group from the others in the FAO global database also shows the fishing down effect to occur in oceanic areas… This had so far been missed because we had pooled these fishes with others in our analyses by FAO areas.
The ‘fishing down’ effect is strong and everywhere.
This is why we now see increasing emphasis on products such as this. (indeed, Western companies are now beginning to export jellyfish to East Asia).
There is also a notion that some parts of the world still have large fisheries resources, thus making it superfluous to deal with ‘fishing down marine food webs.’ However, the fish wealth of West Africa has long attracted distant water fleets from other continents … Number of ‘country access years’ by area, 1960-1969
Number of ‘country access years’ by area, 1980-1989 … and these have increased tremendously over the years …
… finally reaching the present, staggering levels. Number of ‘country access years’ by area, 1990-1999
What is the impact of all this fishing on the resource base? We quantified this impact for the countries of the Northwest African sub-region using a methodology previously applied to the North Atlantic This methodology is based on maps of catch data, combined with ecosystem models, as documented at the website of the Sea Around Us Project (see ‘Reports’ at above address).
Fish biomass in 1950 (excluding small pelagics)
Fish biomass in 1975 (excluding small pelagics)
Fish biomass in 1999 (excluding small pelagics)
The reason for this is fishing intensity, which was low in 1950 …
Thus, we can assume that globally, caught seafood per person will continue to go down… 0
Aquaculture can counter the fisheries trends only if it is based on organism low in the food web… Trophic level trends of aquaculture production in selected countries: Left: major Asian producers; right: major non-Asian countries.
Here is an example of a herbivore, which can add to the global fish supply. Nile tilapia, Oreochromis niloticus
Other fishes, such as salmon (Salmo salar), do not add to world fish supply, because they (must) consume more than they (can) produce….
Our somewhat pessimistic conclusions: Fisheries resources, throughout the world, are under tremendous pressure, as are the ecosystems within which they are embedded, and we are losing stocks and increasingly, species; There is a strong tendency for these pressures to increase, i.e., we do not have mechanisms in place to control the growth of fishing effort. Indeed, most fisheries work is still devoted to various forms of ‘development;’ Aquaculture cannot replace the losses that are due to overfishing. The next lectures will address some of these issues. Thank you.
Acknowledgements… Thanks to the Pew Charitable Trusts, Philadelphia; Fisheries Centre, Faculty of Graduate Studies, UBC; Members of the Sea Around Us project; and many others.
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