Description Usage Arguments Details Value References Examples

View source: R/calc_ration_growthfac.R

Calculates the amount of food required for fish of a given species and length class to grow according to the von Bertalanffy growth curve in a time step.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | ```
calc_ration_growthfac(
k,
Linf,
nsc,
nfish,
l_bound,
u_bound,
mid,
W_a,
W_b,
phi_min,
vary_growth = TRUE,
growth_eff = 0.5,
growth_eff_decay = 0.11
)
``` |

`k` |
A numeric vector of length |

`Linf` |
A numeric vector of length |

`nsc` |
A numeric value representing the number of length classes in the model. |

`nfish` |
A numeric value representing the number of species in the model. |

`l_bound` |
A numeric vector of length |

`u_bound` |
A numeric vector of length |

`mid` |
A numeric vector of length |

`W_a` |
A numeric vector of length |

`W_b` |
A numeric vector of length |

`phi_min` |
A numeric value representing the time step of the model. |

`vary_growth` |
A logical statement indicating whether growth efficiency should vary for each species ( |

`growth_eff` |
If |

`growth_eff_decay` |
A numeric value specifying the rate at which growth efficiency decreases as length approaches |

The weight increments of the `i`

th species in the `j`

th length class is calculated by determining the amount an individual will grow in one time step, `phi_min`

, if it were to follow the von Bertalanffy growth curve

`L22=(Linf[i]-mid[j])*(1-exp(-k[i]*phi_min))`

.

The weight of a fish at the mid-point of the size class is calculated using the length-weight relationship

`wgt[j,i] = a[i]*mid[j]^b[i]`

,

and similarly the expected change in weight of the the fish is calculated as

`growth_inc = (W_a[i]*L22^W_b[i])`

.

It also has a growth efficiency

`g_eff[j, i]=(1-(wgt[j,i]/(W_a[i]*Linf[i]^W_b[i]))^growth_eff_decay)*growth_eff`

if `vary_growth==TRUE`

or `g_eff[j, i]=growth_eff`

otherwise.

`ration`

is then calculated by

`growth_inc*(1/g_eff[j, i])`

.

A list object containing `ration`

, `sc_Linf`

, `wgt`

and `g_eff`

. `ration`

is a matrix with dimensions `nsc`

and `nfish`

representing the amount of food required for fish of a given species and length class to grow according to the von Bertalanffy growth curve in a time step. `sc_Linf`

is a numeric vector of length `nfish`

representing the length class at which each species reaches `Linf`

. `wgt`

is a matrix with dimensions `nsc`

and `nfish`

representing the weight of each species in each length class. `g_eff`

is a matrix with dimensions `nsc`

and `nfish`

representing the growth efficiency of each species in each length class.

von Bertalanffy, L. (1957). Quantitative Laws in Metabolism and Growth. *The Quarterly Review of Biology*, 32:217-231

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | ```
# Set up the inputs to the function - species-independent parameters
nfish <- nrow(NS_par)
nsc <- 32
maxsize <- max(NS_par$Linf)*1.01 # the biggest size is 1% bigger than the largest Linf
l_bound <- seq(0, maxsize, maxsize/nsc); l_bound <- l_bound[-length(l_bound)]
u_bound <- seq(maxsize/nsc, maxsize, maxsize/nsc)
mid <- l_bound+(u_bound-l_bound)/2
# Set up the inputs to the function - species-specific parameters
Linf <- NS_par$Linf # the von-Bertalanffy asymptotic length of each species (cm).
W_a <- NS_par$W_a # length-weight conversion parameter.
W_b <- NS_par$W_b # length-weight conversion parameter.
k <- NS_par$k # the von-Bertalnaffy growth parameter.
Lmat <- NS_par$Lmat # the length at which 50\% of individuals are mature (cm).
# Get phi_min
tmp <- calc_phi(k, Linf, nsc, nfish, u_bound, l_bound, calc_phi_min=FALSE,
phi_min=0.1) # fixed phi_min
phi_min <- tmp$phi_min
# Calculate growth increments
tmp <- calc_ration_growthfac(k, Linf, nsc, nfish, l_bound, u_bound, mid, W_a, W_b, phi_min)
ration <- tmp$ration
sc_Linf <- tmp$sc_Linf
wgt <- tmp$wgt
g_eff <- tmp$g_eff
``` |

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