08-1_total-stock-biomass.qmd

---
editor: 
  mode: source
---

## Total Stock Biomass {.unnumbered}

Total stock biomass $B_T$ is the sum over the recruitment age ($r$) to the plus-group age ($A$) of stock biomass at age on January 1^st^. The computational formula for $B_T$ in year $t$ is

$$
B_T(t) = \sum\limits_{a=r}^{A}W_{P,a}(t) \cdot N_a(t) \tag{47}\label{eq:47}
$$
where $W_{P,a}(t)$ is the population mean weight of age-a fish on January 1^st^ in year $t$.