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DisMELS: A Dispersal Model for Early Life History Stages

DisMELS screenshot, see caption
Figure 2.  A screenshot of the DisMELS graphical user interface.  (click map to enlarge)

Dispersal of eggs and larvae by oceanographic currents is a critical factor in the process of recruitment for marine populations. Scientists in REFM have shown that the scope for recruitment of several flatfish species in the eastern Bering Sea is fairly well correlated with the final locations of drifters simulated using a simple surface wind drift current model (OSCURS). Other scientists at the AFSC, however, have shown that the eggs and larvae of some flatfish species are not located primarily at the surface but are concentrated below the surface and may even change depths depending on whether it’s day or night (i.e., they undergo diel vertical migrations).

In an effort to incorporate more aspects of early life history behavior into simulations of dispersal of flatfish (and other species) eggs and larvae, William Stockhausen in REFM is developing DisMELS, a dispersal model for early life history stages.

DisMELS is a new tool being developed to incorporate the behavior of early life history stages of marine fishes and invertebrates into computer simulations for the dispersal of eggs and larvae from natal sites. The tool consists of a series of graphical user interfaces (GUIs) that allows a user to easily set up and run individual-based models, as well as an application programming interface (API) that allows a user to create his/her own stage-based behavioral models for use in the dispersal simulations (Fig. 2).

Currently, one “generic” behavioral model is available that allows the user to specify preferred daytime and nighttime depth ranges, vertical swimming speed, and growth and mortality rates for each early life history stage to be included in a simulation. Ontogenetic changes in behavior can be incorporated by defining parameter values for successive stages and setting the conditions under which an individual changes from one life history stage to the following stage. Precomputed oceanographic currents, temperature and salinity fields are required to drive the dispersal simulations. Currently, output from the ROMS (Regional Oceanographic Modeling System) model for the northeast Pacific (NEP ROMS) and other ROMS models can be used to drive dispersal simulations.

In an initial application of DisMELS, Stockhausen and Janet Duffy-Anderson (Recruitment Processess Program) are developing dispersal models for northern rock sole in the eastern Bering Sea.

By William Stockhausen

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