4.8. Movement parameters

movement.distribution.method.sp# is the type of spatial distribution (either ‘random’ or ‘maps’).

If ‘random’ OSMOSE will look for the parameter movement.distribution.ncell.sp#.

If ‘maps’ OSMOSE will use the maps parameters. See below how to define a map.

4.8.1. Map definition

Here are all the parameters required to define a map of distribution in Osmose:

movement.map#.file = maps/mymap.csv
movement.map#.species = euphausiids
movement.map#.age.min = 0
movement.map#.age.max = 1
movement.map#.year.min = 0
movement.map#.year.max = 40
movement.map#.season = 0;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20;21;22;23

One map is associated to a unique species for given age span, year span and season. The full spatial distribution of a species can be represented using as many maps as necessary to cover different age spans and/or year spans and/or seasons. Let’s now have a look at each parameter in detail.

The movement.file.map# parameter is the path to the CSV file that defines the geographical extent of the map. The CSV file has the same number of lines and columns as the OSMOSE grid. Land is always indicated with -99. The distribution area can be defined using either a presence/absence map (1 for presence, 0 for absence) or a map of probability of presence (containing values ranging from 0 to 1, the sum of the probabilities should never exceed 1).

The same CSV file can be used to define different maps.

If the file path is set to null it means that the schools concerned by this map are out of the simulated domain (e.g., migrating species). See the parameter mortality.out.rate.sp for mortality rate of species momentarily out of the simulated area. When a school comes back to the simulated area, it will be randomly located on a new map (the one corresponding to the species and age class of the school at the current time step of the simulation).

The movement.species.map# is the name of the species associated to the map. The name must be one of the species.name.sp# parameters.

movement.map#.age.min and movement.map#.age.max define the age span of the schools associated to the map such as age.min <= age < age.max

movement.map#.year.min and movement.map#.year.max define the year span of the schools associated to the map such as year.min <= current year of the simulation < year.max If these two parameters are not provided, OSMOSE assumes year.min = 0 and year.max = simulation.nyear

movement.map#.season defines the vectors of the time step over one year associated to the map.

4.8.2. Several maps of distribution for one species

Several maps can be defined for representing the spatial distribution of a single species. For example:

#Map 0
movement.map0.species = euphausiids
movement.map0.file = maps/mymap_euphau1.csv
movement.map0.age.min = 0
movement.map0.age.max = 0.2
movement.map0.year.min = 0
movement.map0.year.max = 40
movement.map0.season = 0;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20;21;22;23

#Map 1
movement.map1.species = euphausiids
movement.map1.file = maps/mymap_euphau2.csv
movement.map1.age.min = 0.2
movement.map1.age.max = 1
movement.map1.year.min = 0
movement.map1.year.max = 40
movement.map1.season = 0;1;2;3;4;5;6;7;8;9

#Map 2
movement.map2.species = euphausiids
movement.map2.file = maps/mymap_euphau3.csv
movement.map2.age.min = 0.2
movement.map2.age.max = 1
movement.map2.year.min = 0
movement.map2.year.max = 40
movement.map2.season = 10;11;12;13;14;15;16;17;18;19;20;21;22;23

By increasing the number of maps, the description of the spatial distribution can be as detailed and refined as you want, as long as you have such information. It will allow for instance to create some maps for eggs (an egg in Osmose is a new school of age zero that is created during the reproduction process), some maps for the juveniles and some maps for the adults, as many as necessary to describe ontogenetic migrations.

From one time step to an other, the movement manager checks whether a given school remains in the same map or should “jump” to an other map (e.g. eggs map to juvenile map or adults in summer to adults in winter). In the latter case - change of map -, the schools are relocated randomly in the new map. In the former case - same map -, the movement manager mimics foraging movement with a random-walk that moves schools to immediately adjacent cells within their distribution area. See the parameter movement.randomwalk.range.sp# for details.