Thursday, January 22, 2015

Sandeels: another Seneca cliff

Once you start looking for "Seneca Cliffs" in the exploitation of natural resources, you find them all over the scientific literature. This is my latest find of a production curve where decline is much more rapid than growth: the landings of sandeels. If you don't know what a sandeel is, here is one: 

In the report (2007), where I found the curve shown above, the authors discuss the causes for the collapse of the fishery, especially in view of climate change. They don't seem to arrive to any definitive conclusion and they don't use the dreaded term "overfishing". But from the fact that trawlers were used in this fishery, I think it is clear that the fish stock was being destroyed in a process similar to the one that led to the collapse of the whole UK fishing industry. The more resources were aggressively thrown at trying to maintain production, the more the fish stock was depleted. The end result was the rapid collapse observed.

So, as in several other cases, we have a classic example of the "Seneca Collapse", that is a production curve where decline is much more rapid than growth. Below, you can see the Seneca curve as shown in a simulation carried out by system dynamics that takes into account the increased capital expenditure in fishing equipment (the model is described here). 

As Seneca said, "the road to ruin is rapid", indeed.


  1. The other side of the coin : in Italy increases the area of woods and forests

  2. Give people a fish and you feed them for a day and maybe make them dependent. Teach people to fish and they will deplete the ocean. Now it may take time to do it but with modern technology it will happen in the blink of a species eye. Just add in high-tech ships with all kinds of electronics, powerful engines, and the accoutrements that make technology a weapon.

  3. Ugo
    The faster we go, the quicker we get there ... ouch.

    (btw: "Sandeels" not as in the title "Land...."

    I have been looking at reports on sandeel fisheries (and effect on sea birds of crash in sandeel stocks) and on industrial trawling techniques, particularly "bottom trawling". This latter technique is especially damaging and is a global threat ("desertification") and not just to sandeels . And we should not forget "dredging for scallops" e.g. another Canadian fishery.

    Bottom trawling has been used in sandeel fisheries - and therefore one must assume significant collateral damage. Quote: "The summer sandeel fishery is the most important fishery for the [Danish] fleet. Those vessels undertaking bottom gear sandeel trawls could potentially switch to mid-water gear and still target sandeels;" ... from impact assessment for N Sea regulation (rMCZs) questionnaire in 2011.

    Ironically the North Sea sandeel fishery provides feed for 'farmed salmon'. The profound waste of primary fish protein when fed to an obligate carnivore like salmon ought to cause a twitch or two in the convoluted justifications for present trophic levels in our hierarchical human ecology where the richest 'take the best'. It ought to frighten the 'bejesus' out of us, but I guess it won't.

    And this from a December 2005 RSPB briefing (British mainstream environmental activist organisation with >1 million members focussed on conservation of birdlife) to Scottish Parliament - the situation would not appear to have improved this last 10 years.
    "Industrial fishing for North Sea sandeels
    The sandeel fishery is not for human consumption, but instead is used in producing fish meal and oil mainly for use in aquaculture. ‘Real time monitoring’ has allowed scientists to assess the strength of the sandeel stock, which is prone to short-term fluctuations, and make urgent management recommendations. The North Sea sandeel population is at such a historic and perilous low level that in 2005 the EC were forced to take unprecedented action in closing the fishery for the remainder of the year. However, the closure was not implemented until July, when the season was over and the Danish fleet – which has the lion’s share of the massive sandeel quota – had returned home. In recent years, the Danish fleet has been unable to find enough sandeels to fish out their quota, and one of Esbjerg’s largest fishmeal factories has been forced to close."


    1. Ooops...yes. "Sandeels". A "Landeel" would be a curious creature, indeed!. Thanks

  4. Ugo,

    Are you familiar with the following paper on critical transitions in systems?

    I think it would be very interesting to analyse the time series of, for example, eels or cod landings to see if they show the expected characteristics (increasing lag autocorrelation, variance etc).

    I have performed the same calculations on inflation adjusted oil prices, and they display all the characteristics of a system approaching a catastrophic state shift. It is a very worrying result indeed. I'm going to try extending it to other commodity and price time series to see if they display similar behavior.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)