The maximum sustainable yield (MSY) is an important reference point in the exploitation of living aquatic resources. It is the theoretical maximum catch that can be taken from an exploited population (= a stock) indefinitely. Rebuilding and maintaining stocks at sizes that can produce MSY is a binding requirement under the Law of the Sea and in many national legislations. Such stock size is also called Bmsy, i.e., the smallest biomass (B) that can still deliver MSY.
Estimation of MSY and Bmsy typically requires time series of stock biomass, i.e., annual estimates of the weight of the fish in the sea. Such data are difficult to obtain and are therefore lacking for most of the stocks in the world. Here we make use of a method proposed by Martell & Froese (2012), which derives a reasonable estimate of MSY from catch data and life history traits, as contained in FishBase.
For application of the method you will need to know the scientific name of the species, a time series of representative catch data for preferably more than 10 years, and a reasonable guess about the stock status at the beginning and the end of the time series.
The method will then randomly select several thousand combinations of maximum stock size (k) and maximum rate of increase (r). It will discard all r-k combinations which let the stock either crash or overshoot the carrying capacity of the system. From the remaining "viable" r-k combinations it will calculate MSY with 95% confidence limits.
Once MSY is known, the relative catches in the final years can be used to derive a preliminary estimate of stock size and to apply a precautionary, simple harvest control rule to rebuild the stock and maintain it above the Bmsy level.