Method ssb

Description

Returns the Spawning Stock Biomass of FLStock and FLBiol objects.

For FLStock-class objects the nature of the calculation depends on the units in the harvest slot. See details below.

Generic function

ssb(object)

Methods

signature(object=FLStock) :

If spawning occurs at the beginning of the year the calculated SSB is the same regardless of the units of the harvest slot. If spawning occurs at any other time during the year such that the stock is subject to fishing mortality prior to spawning then the calculated SSB will depend on the units of the harvest slot.

For an FLStock-class with harvest units 'f' SSB is calculated as

SSB = sum(N*exp(-F*propF-M*propM) * wt * mat)

For an FLStock-class with harvest units 'hr' SSB is calculated as

SSB = sum(N*(1-harvest)*exp(-M*propM) * wt * mat)

The units of the harvest slot in the FLStock object must be specified as either 'f' for an instantaneous fishing mortality or else as 'hr' for a harvest rate.

signature(object=FLBiol) :

For an FLBiol-class the spawning biomass at the beginning of the year is calculated.

SSB = sum(N * wt * mat)

Author(s)

The FLR Team

See Also

FLBiol-class FLStock-class

Examples

 data(ple4)
 units(harvest(ple4)) # check the units of the harvest slot
 ssb(ple4)