DynF {DLMtool} | R Documentation |
The Fratio MP with a controller that changes the level of F according to the estimated relationship between surplus production and biomass. Ie lower F when dSP/dB is positive and higher F when dSP/dB is negative.
DynF(x, Data, reps = 100, plot = FALSE, yrsmth = 10, gg = 2)
x |
A position in the data object |
Data |
A data object |
reps |
The number of stochastic samples of the MP recommendation(s) |
plot |
Logical. Show the plot? |
yrsmth |
The number of historical recent years used for smoothing catch and biomass data |
gg |
A gain parameter that modifies F according to the gradient in surplus production with biomass |
The method smoothes historical catches and biomass and then infers the relationship between surplus production and biomass (as suggested by Mark Maunder and Carl Walters). The approach then regulates a F based policy according to this gradient in which F may range between two different fractions of natural mortality rate.
The core advantage is the TAC(t) is not strongly determined by TAC(t-1) and therefore errors are not as readily propagated. The result is method that tends to perform alarmingly well and therefore requires debunking ASAP.
The catch limit (TAC) is calculated as:
\textrm{TAC}=F B
where F is fishing mortality and B is the estimated current biomass.
F is calculated as:
F = F_{\textrm{MSY}} \exp{-gG}
where F_{\textrm{MSY}} is calculated from assumed values of \frac{F_{\textrm{MSY}}}{M} and M, g is a gain parameter and G is the estimated gradient in surplus production (SP) as a function of biomass (B). Surplus production for year y is calculated as:
SP_y = B_{y+1} - B_y + C_y
Trends in historical catch (C) and biomass (B) are both estimated using a loess smoother, over the last yrsmth
years,
of available catch and a time-series of abundance, calculated from an index of abundance (Data@Ind
)
and an estimate of abundance (Data@Abun
) for the current year.
An object of class Rec-class
with the TAC
slot populated with a numeric vector of length reps
See Data-class
for information on the Data
object
DynF
: Abun, Cat, FMSY_M, Ind, Mort, Year
See Online Documentation for correctly rendered equations
T. Carruthers
Made-up for this package.
Other Fmsy/M methods:
Fadapt()
,
Fratio()
DynF(1, Data=MSEtool::Atlantic_mackerel, plot=TRUE)