The MSY – harshly criticized and yet established

The term maximum sustainable yield (MSY) was developed in the 1930s. It is based on two findings. Firstly, there is a maximum size which the stock of an animal group can achieve within an ecosystem. Secondly, the net growth of the stock, resulting from reproduction and increased size and weight of individuals, is highest at 30 to 50 per cent of the maximum stock size. This stock size therefore allows the maximum long-term yield. However, such a maximum withdrawal is only achievable when the maximum stock size and the growth rate have been accurately determined. The current stock size must also be known. If the stock was already smaller than 30 to 50 per cent of the maximum size, the stock would be overfished. For this reason there has been much criticism of this concept, and there were recommendations that it should be abandoned. Nonetheless the term was taken up by the United Nations Convention on the Law of the Sea in 1982. With one important condition, however – that ecological and economic factors as well as the special needs of developing countries should be taken into account. For this reason the MSY concept is no longer applied in the theoretical, mathematical terms in which it was originally defined. It now also takes particular account of the above-mentioned uncertainties, species interactions and economic aspects.