Find the current biomass at which it would take HZN mean generation times to reach Bfrac x SSBMSY biomass level given zero catches
getBlow(x, SSBMSY, MGThorizon, Find, Perr, M_ageArray, hs, Mat_age, Wt_age, R0,
V, nyears, maxage, mov, Spat_targ, SRrel, aR, bR, Bfrac = 0.5, ploty = F)position in a vector
vector nsim long of spawning biomass at MSY
vector nsim long of MGT x HZN
matrix of fishing mortality rate nsim x nyears
matrix of recruitment devitions nsim x nyears + maxage -1
array of natural mortality rate nsim x maxage x nyears + proyears
vector nsim long of steepness values
array nsim x nages x nyears+proyears of maturity at age
matrix nsim x nages of weight at age
vector nsim long of unfished recruitment
array of vulnerability nsim x maxage x nyears
integer: number of historical years
integer: maximum age
array of movement nsim x 2 x 2
vector of spatial targetting parameters
integer representing recruitmetn dynamics type 1: Bev Holt 2: Ricker
vector of recruitment parameters
vector of recruitment parameters
fraction of SSBMSY that is the target
logical: should a plot be produced