OSMOSE

This page contains documentation and notes about the OSMOSE modeling platform.

On the terminology of functional groups

Functional groups rather than individual species are considered in OSMOSE. Species of a given functional group exhibit similar life history traits, body size ranges, diets and exploitation patterns. Some individual species constitute their own group, as they are emblematic to the modeled ecosystem and of high economic importance. Typically, one distinguishes between: (1) “high trophic level functional groups” or "HTL groups", which are explicitly considered in OSMOSE; and (2) “low trophic level groups” or "LTL groups", which are implicitly considered in OSMOSE and simply serve as potential food source (e.g., phytoplankton and zooplankton groups, low-trophic level benthic groups).

Currently, a new paradigm is being introduced in the OSMOSE modeling approach. This new paradigm distinguishes between: (1) “focal functional groups”, which are explicitly considered in OSMOSE; and (2) “background functional groups”, which are implicitly considered in OSMOSE and serve as potential food source and/or have the potential to exert predation pressure on some schools of the focal functional groups.

This new paradigm was created by Dr. Caihong Fu from the Department of Fisheries and Oceans of Nanaimo (Canada) for her Pacific North Coast Integrated Management Area (PNCIMA) OSMOSE model. Arnaud Grüss strongly defends this new paradigm, because: (1) it turns out that, in some OSMOSE applications, some "LTL groups" have a higher trophic level than some "HTL groups"; and (2) forage fish (e.g., anchovies, sardines) are often referred to as "LTL groups" in the ecological literature, while they belong to the HTL groups in OSMOSE applications. Talking about "focal" and "background" functional groups better reflects the distinction that is being made between marine organisms in OSMOSE: some are considered explicitly (their whole life cycle is modeled), while the others are considered implicitly (fields of biomass for these groups are used to force OSMOSE models).

Maximum annual ingestion rate

Currently, in all OSMOSE applications, the maximum annual ingestion rate (Q/B) of all focal functional groups is set to 3.5 g of food per g of individual and per year for all focal functional groups. This is obviously open to criticism (especially from researchers like Daniel Pauly and Deng Palomares!). Therefore, the bridge between FishBase/SeaLifeBase and OSMOSE should provide the user with estimates of maximum annual ingestion rate (Q/B) for the different focal functional groups represented in his/her OSMOSE model.

Age or size at sexual maturity

In the “osm_param-species.csv” file, for each focal functional group, both an age at sexual maturity ("species.maturity.age.sp" parameter) and a size at sexual maturity (“species.maturity.size.sp” parameter) are provided. If a value is given to both the "species.maturity.age.sp" and “species.maturity.size.sp” parameters, then OSMOSE will use only the information provided for the “species.maturity.size.sp” parameter, since this information appears last in the “osm_param-species.csv” file. Therefore, it is necessary to indicate that the "species.maturity.age.sp" parameter or the “species.maturity.size.sp” parameter is “null”, depending on the information that the user wants OSMOSE to use; for example, in the West Florida Shelf case study, if the user wants OSMOSE to use a size at sexual maturity for Scomberomorus cavalla (sp0), then “species.maturity.age.sp0” must be set to "null", while the “species.maturity.size.sp0” parameter must be set to 73.4.

In the West Florida Shelf case study, a size at sexual maturity is needed for all the focal functional groups represented in the model (i.e., all the “species.maturity.age.sp” must be "null"). However, there may be OSMOSE applications where a size at sexual maturity is needed for some of the HTL groups represented in the model, while an age at sexual maturity is needed for all the other HTL groups represented in the model.