Initialisation Seeding

Seeding

In the seeding method, the system starts from a pristine state, with no schools in the domain. For a few years (user-defined), Osmose will release some eggs for every species. The eggs progress to the different steps of the life cycle, and once the fish reach sexual maturity, the reproduction process takes over and Osmose stops seeding, unless the spawning stock biomass gets depleted. In that case Osmose resumes seeding by releasing some eggs until there are again mature individuals in the system for carrying on the reproduction process. Osmose completely ceases seeding when the simulation reaches the maximal number of years for seeding (user-defined).

By following this approach:

• No assumption is made about the structure of the populations but it emerges from individual interactions
• it reduces computing requirements for the spin-up as the first years are the fastest to run
• it reduces the number of time steps for the spin-up
• it minimises the amplitude of population oscillations

The initialisation process is controlled by three parameters:

• population.seeding.year.max defines the number of years for running the seeding process (from year 0 to population.seeding.year.max), and during which Osmose ensures that some eggs will be released even though there are no mature individuals in the system. Then, the seeding ceases completely until the end of the simulation. If the parameter is not specified, Osmose will set it by default to the lifespan of the longest lived species of the system.
• population.seeding.biomass.sp# defines the spawning stock biomass (SSB) that Osmose considers during the seeding period when there are no mature adults to ensure the reproduction process. SSB is then used to compute the number of eggs to be released in the system (cf.Reproduction section for details).