openpop_time: An open population function that calculates the length of...

In katherinekaplan/MPApopulationmodels: Population responses to marine protected areas (MPAs)

Description

This function calculates the ratio change in a fished population after a marine protected area is implemented assuming external recruitment. The output is the approximate time to reach the abundance and biomass equilibrium. For long-lived species used longer timeframes to ensure final ratios are reached.

Usage

openpop_time(tf, maxage, M, Fi, Lfish, Linf, k, a0, pW, qW, R)

Arguments

tf	time steps to run the population
maxage:	max age of the species ie. number of age classes
Lmat:	length at maturity
M:	the natural mortality rate, if unknown generally use 0.2
Fi:	the fishing mortality rate, F, find in stock assessment if don't have more localized estimate
Linf:	asymptotic length of the fish
k:	von-bertallanfy growth parameter estimate
a0:	the age at length 0 used in the von-Bertallanfy growth equation
pW:	weight length relationship parameter, same as a on fishbase.org but need to divide by 1000 to get in kg not grams
qW:	weight length relationship parameter, same as b on fishbase.org
R:	the number of recruits entering the population

Value

N.time.to.equil= the number of years it will take for the population abundance to reach its final equilibrium abundance

Btime.to.equil= the number of years it will take for the population biomass to reach its final equilibirum

final.N.ratio= the final abundance ratio increase reached in comparison to pre-MPA abundance for fished age classes

final.B.ratio= the final biomass ratio increase reach in compared to pre-MPA biomass for fished age classes

Examples

openpop_time(tf=50,M=0.2,Fi=0.14,Lfish=25,Linf=37.8,k=0.13,a0=-0.7,maxage=25,pW=9.37e-06,qW=3.172,R=500)

katherinekaplan/MPApopulationmodels documentation built on May 22, 2019, 8:51 p.m.