RickerHarvest.RdContains time series simulated from a Ricker model with harvesting: $$B_{t+1}=S_{t}e^{r-S_{t}/K+\epsilon_{b}}$$ $$X_{t+1}=bB_{t+1}$$ $$u_{t+1}=((1-a)u_{t}+au_{t}(B_{t+1}-B_{t})/B_{t})(1+\epsilon_{u})$$ $$C_{t+1}=B_{t+1}u_{t+1}$$ $$S_{t+1}=B_{t+1}-C_{t+1}$$ $$\epsilon_{b} \sim N(0,\sigma_{b})$$ $$\epsilon_{u} \sim Unif(-\sigma_{u},\sigma_{u})$$ Where \(B\) is biomass, \(X\) is a survey index of biomass with catchability \(b\), \(u\) is the exploitation rate (which changes in response to changing biomass according to parameter \(a\)), \(C\) is catch, and \(S\) is uncaught biomass (escapement). For region "A", parameter values are \(r=3\), \(K=1000\), \(b=0.01\), \(a=0.1\), \(\sigma_{b}=0.1\), and \(\sigma_{u}=0.2\). The initial exploitation rate is 0.01. For region "B", parameters are indentical except \(b=0.005\) and the initial exploitation rate is 0.8. Thus, the abundance indices for each region have different catchabilities (e.g. different survey methods are used in each region) and the regions have different catch histories.
RickerHarvestA data frame with 100 rows and 4 variables:
Time index
Index of abundance, catch per unit effort
Harvest
Region ID
The simulation code is in data-raw on the GPEDM Github page.