Briefing on Maximum Sustainable Yield

Ocean2012 produces a Briefing on “maximum sustainable yield” with respect for the CFP and fish stocks

The principle, indeed the concept, of “maximum sustainable yield” (MSY) is now central to fisheries management and reform of the EU Common Fisheries Policy (CFP). MSY has become the technical procedure by which fishing limits (total allowable catch/quotas) are being set.

However, how is “maximum sustainable yield” defined? Ocean2012 has produced a Briefing which seeks to address this question.

The Ocean2012 Briefing identifies two principal means by which “maximum sustainable yield” can be defined. One is on the basis of the total biomassbiomass The amount of living matter. This is therefore a different measure to numbers of organisms. So, for example, there is much more biomass in 1 elephant than there is in 1000 fleas and there may be more biomass in 100 large cod than you would find in 150 small (because of over fishing) cod. (size) of the stock, and the other is on the basis of fishing mortality (rate at which the stock is fished). In the former case, the acronym BMSY is used, and in the later the acronym FMSY. The Ocean2012 Briefing states:
“BMSY: BMSY is the biomass that enables a fish stock to deliver the maximum sustainable yield. In theory, BMSY is the population size at the point of maximum growth rate. The surplus biomass that is produced by the population at BMSY is the maximum sustainable yield that can be harvested without reducing the population.”
“FMSY: FMSY is the maximum rate of fishing mortality (the proportion of a fish stock caught and removed by fishing) resulting eventually, usually a very long time frame, in a population size of BMSY. FMSY is a constant and can be applied to any stock that is not impaired in its reproductive capacity.”

The EU Commission and a reformed CFP is proposing to require all fish stocks to attain a level capable of producing MSY by 2015. Yet, is this target and thinking actually adequate in order to rebuild fish stocks?

The Ocean2012 Briefing observes: “Stocks that are already at or below BMSY levels should be fished at rates slightly below FMSY, to account for scientific uncertainty and fluctuations in stocks sizes. Fishing below FMSY would also bring economic benefits. In order to restore stocks that are below BMSY to above levels where they can produce maximum sustainable yield, fishing pressure needs to be further relieved to enable the stocks to recover. The larger the reduction, the faster the recovery.”

MARINET observes: “Whilst the two definitions of Maximum Sustainable Yield [ BMSY and FMSY ] are scientifically correct in a technical sense, they are definitely not adequate in a practical sense. The truth is that over-fishing has been so great, and for such a long period of time, that today nearly all fish stocks are very heavily depleted and a mere shadow of their former selves. Even more significantly, these stocks are just a fraction of what the ecological conditions in the sea can actually sustain if these stocks were to be better managed.

“In other words, if we accept that the primary purpose of fisheries management (the CFP) is to manage fish stocks in such a way that they can deliver food security i.e. the ability of the stocks to feed the population for all 12 months of the year, year after year [Note: currently EU stocks are so depleted they can only feed us for 6 months of the year] — then a fundamental question arises: is the idea of fixing catch levels (total allowable catch/quotas) on the basis of “maximum sustainable yield” referenced to these current depleted stocks levels sensible?

“The short answer is, no. If we fix MSY (catch levels) at current depleted stock levels — which are only able to yield catches that can feed us for just six months of the year — then we are never going to be able to re-establish food security (the ability of our stocks to feed us for all 12 months of the year).

“Instead, what responsible fisheries management requires is that we rebuild fish stocks to the maximum levels of abundance that current ecological conditions in the sea will permit (i.e. to the largest size possible taking the changes in habitat, sea temperature, acidity and other factors into account). Then, when we have rebuilt stocks sizes to levels that the sea can genuinely and realistically support, we must set the “maximum sustainable yield” (the catch) at a level linked to the size of these newly rebuilt stocks. Very simply, when we have rebuilt stock levels to their maximum levels of abundance, we will then once more be able deliver food security.

“This is responsible fisheries management. Achieving this objective is what fisheries management based on “maximum sustainable yield” should really be about. This is a practical, rather than a technical, view of fisheries management. This approach, and its definition of MSY, is the only one that makes genuine sense.

“Therefore MARINET has, with the support of Chris Davies MEP, Linda McAvan MEP and Julie Girling MEP, secured the tabling of an amendment to the proposed new CFP Basic Regulation to be voted upon when this matter is considered by the European Parliament’s Fisheries Committee in early July. The amendment to the draft text of the new CFP Basic Regulation seeks to redefine the definition of “maximum sustainable yield” to read as follows: ‘maximum sustainable yield’ means the maximum catch that may be taken from a fish stock indefinitely and that provides for the restoration of stocks to maximum levels of abundance that current ecological conditions will permit [amendment to the definition is in bold], ref. Article 5(1).

“MARINET believes that the CFP Basic Regulation must legally embrace this revised definition of MSY. If it does, then we can rebuild fish stocks in EU seas to the level where they can once again deliver food security, and thereby guarantee that the fishing industry will also survive and become a major economic force once again.

“MARINET will be lobbying MEPs on the Parliament’s Fisheries Committee for this amendment in the period prior to the July vote, and asks all people who agree with this amendment to do so too. To assist you, the membership and contact details of the MEPs on the European Parliament’s Fisheries Committee can be seen here.


Please do share this

  • Facebook
  • Twitter
  • Delicious
  • StumbleUpon
  • Add to favorites
  • email hidden; JavaScript is required
  • RSS