FMSY is calculated as r/2 where r is calculated from a demographic approach
(inc steepness). Coupled with an estimate of current abundance that gives
you the OFL.
The TAC is calculated as:
$$\textrm{TAC} = F_{\textrm{MSY}} A$$
where A is an estimate of current abundance, and \(F_{\textrm{MSY}}\) is estimated
as \(r/2\), where \(r\) is the intrinsic rate of population growth, estimated
from the life-history parameters using the methods of McAllister et al. (2001).
References
McAllister, M.K., Pikitch, E.K., and Babcock, E.A. 2001. Using
demographic methods to construct Bayesian priors for the intrinsic rate of
increase in the Schaefer model and implications for stock rebuilding. Can.
J. Fish. Aquat. Sci. 58: 1871-1890.