The OM object contains all the information that is used to simulate the fishery dynamics.

Here we will briefly examine some of the contents of the OM object. See the OM Object page for a more detailed description of the OM object.

The OM object is an S4 class object, and the contents are stored in slots which are accessed using the @ symbol.

For example, the number of simulations that will be run is stored in the nsim slot:

ourOM@nsim # number of simulations

## [1] 48

The number of historical (the spool-up period) and projection years stored in the nyears and proyears slots respectively:

ourOM@nyears # number of historical years

## [1] 50

ourOM@proyears # number of projection years

## [1] 50

The operating model in openMSE is a fully stochastic model, where each parameter is drawn from a distribution. By default, the parameters are sampled from a uniform distribution, with the lower and upper bounds for each parameter specified in the relevant slot in the OM object (alternative distributions, including correlated samples for multiple parameters, can be used with the Custom Parameters feature).

For example, the natural mortality parameter (M) is stored in the M slot:

ourOM@M

## [1] 0.35 0.45

In this case, when the operating model is used for the simulations, there will be 48 samples of the natural mortality parameter drawn from a uniform distribution with lower bound 0.35 and upper bound 0.45:

M <- runif(ourOM@nsim, ourOM@M[1], ourOM@M[2]) # M sampled from the operating model
M # values of M used for the simulations

##  [1] 0.3858056 0.3763009 0.3961270 0.3755719 0.4126376 0.4448254 0.4425928
##  [8] 0.3550651 0.4071992 0.4294535 0.3798353 0.4169559 0.4163164 0.4449279
## [15] 0.3774734 0.3579502 0.4293925 0.4048781 0.3921581 0.4331793 0.4387676
## [22] 0.3960934 0.4145920 0.4069295 0.3770496 0.4068633 0.4017503 0.4049638
## [29] 0.3817586 0.4297536 0.4276901 0.4142439 0.4468154 0.4186154 0.4037847
## [36] 0.4224353 0.4178063 0.3686688 0.4174828 0.4408652 0.3841905 0.3651994
## [43] 0.3704076 0.3979884 0.4275526 0.4253633 0.3682858 0.3539196

The OM object includes a seed for the random number generator (ourOM@seed) so that the sampled values are identical each time the OM is used.

The OM Object page describes the contents of the OM object in more detail. For the purposes of this brief demonstration, the main thing to know is that the OM object contains all the information related to simulating the fishery.

In the next section we will select some management procedures to evaluate for the OM we constructed.