closedpop_ratio: A closed population function that calculates metrics 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 closed population. It also calculates metrics of the transient response of an MPA using the methods described in White et al. 2013 'Transient responses of fished populations to marine reserve establishment' published in conservation letters. It uses a Leslies matrix and the output is metrics that evaluate the transient dynamic for a closed population

Usage

closedpop_ratio(tf, maxage, Lmat, Lfish, M, Fi, Linf, k, a0, pW, qW, lambda)

Arguments

tf:	the time step 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 growth rate used in von-Bertallanfy growth equation, can find on fishbase
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
lambda:	the population growth rate in the MPA

Value

P1: the period of oscillations

rho: the rate of return to the stable age distribution in the MPA

theta: the angle between the initial conditions of the fished state and the stable age distribution in the MPA

Nratio: the abundance changes over time

Bratio: the biomass changes over time

fm_ratio: the fishing mortality rate to natural mortality rate ratio

transient_length: the approximate length of the transient duration

Examples

closedpop_ratio(tf=50, maxage=25,Lmat=18,Lfish=25,M=0.2,Fi=0.17, Linf=37.8,k=0.23,a0=-0.7,pW=6.29e-06,qW=3.172,lambda=1)
closedpop_ratio()

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