From the calculation of annual maximum sustainable yield (MSY) reference points, an average value is taken and reported in the simulated Data object. Following a similar procedure to that described in the first section for $SB_0$, we use $A_{50}$ as an approximation of generation time, and average the annual MSY values over $A_{50}$ years around the last historical year. For example, if OM@nyears = 50 and $A_{50}=5$, $SB_{\text{MSY}}$ is calculated as:

$$ SB_{\text{MSY}} = \dfrac{\sum_{y=48}^{52}{SB_y^{\text{MSY}}}}{A_{50}} $$ where $SB_y^{\text{MSY}}$ is the spawning biomass corresponding with maximum sustainable yield in year $y$. The logic behind this is, if estimates of MSY, $\text{SB}_\text{MSY}$, etc are available, they are likely calculated based on current life-history information, which would be estimated from data spanning several age classes.

The averaged MSY reference points in the Data object, i.e., in Data@OM and Hist@Ref$ReferencePoints, are not updated in the future projection years. The averaged MSY reference points and annual MSY values by year are returned in MSE@RefPoint and MSE@RefPoint$ByYear, respectively.

Note

The MSY metrics in the MSE object are always calculated using annual values. The slot MSE@SB_SBMSY returns the spawning biomass in the projections divided by $SB_\text{MSY}$ in each year of the projections. For alternative methods to calculate $\text{SB}/\text{SB}_{\text{MSY}}$, such as relative to the constant $\text{SB}_\text{MSY}$ described above, use MSE@SSB or MSE@B and the data stored in MSE@RefPoint.