ssb                  package:FLCore                  R Documentation

_M_e_t_h_o_d _s_s_b

_D_e_s_c_r_i_p_t_i_o_n:

     Returns the Spawning Stock Biomass of 'FLStock' and 'FLBiol'
     objects.

     For 'FLStock-class' objects the nature of the calculation depends
     on the units in the harvest slot. See details below.

_G_e_n_e_r_i_c _f_u_n_c_t_i_o_n:

     ssb(object)

_M_e_t_h_o_d_s:


      _s_i_g_n_a_t_u_r_e(_o_b_j_e_c_t=_F_L_S_t_o_c_k) : If spawning occurs at the beginning
          of the year the calculated SSB is the same regardless of the
          units of the harvest slot. If spawning occurs at any other
          time during the year such that the stock is subject to
          fishing mortality prior to spawning then the calculated SSB
          will depend on the units of the harvest slot.

          For an 'FLStock-class' with harvest units 'f' SSB is
          calculated as

          SSB = sum(N*exp(-F*propF-M*propM) * wt * mat)

          For an 'FLStock-class' with harvest units 'hr' SSB is
          calculated as

          SSB = sum(N*(1-harvest)*exp(-M*propM) * wt * mat)

          The units of the harvest slot in the 'FLStock' object must be
          specified as either 'f' for an instantaneous fishing
          mortality or else as 'hr' for a harvest rate.

      _s_i_g_n_a_t_u_r_e(_o_b_j_e_c_t=_F_L_B_i_o_l) : For an 'FLBiol-class' the spawning
          biomass at the beginning of the year is calculated.

          SSB = sum(N * wt * mat)


_A_u_t_h_o_r(_s):

     The FLR Team

_S_e_e _A_l_s_o:

     FLBiol-class FLStock-class

_E_x_a_m_p_l_e_s:

      data(ple4)
      units(harvest(ple4)) # check the units of the harvest slot
      ssb(ple4)

