Dissertation - HQ

126 Oceanography vs. behaviour
Figure 6.3 Two examples of optimal trajectories. On the left, the larva survives
and recruits successfully nearshore (x T = 0). On the right, the larva dies before
reaching the shore. The upper plots are the trajectories. The lower panels show
energy resources. Notice that, even for the trajectories, abscissa represents time
and not a component of position (position is one-dimensional).
6.3 The balance between feeding and predation:
comparison of life history strategies
Now that the quality of the algorithm has been checked, the aim of
more elaborate versions of the model is to approach a biologically
relevant description of the pelagic larval episode of fishes. In this
first refinement, we focus on introducing three dimensional prey and
predators distributions around an deep-ocean tropical island. Literature
data allows to choose nominal size order values for the parameters used
in simulations, yet they are not intended to represent a precise field
situation. Rather, the aim of this model is to infer the relative influence
of different variables (probability to feed, to be predated upon, etc.),
varying within biologically sensible ranges.
6.3.1 Plankton and predators in a 3D current field
Three dimensional
island
An isolated tropical, deep-ocean island is represented in three dimensions
as a cylinder of 7 km diameter, rising from a horizontal sea bottom.
The island is both the spawning point and the only recruitment possibility
for larvae. All quantities are discrete, including space. The domain
is 100 km × 50 km, and the water column is 100 m high. The horizontal
mesh size is 720 m and the vertical coordinate is divided in four depth
levels. As we will explain later, the value of the mesh of this model is
determined by other parameters and is not a direct choice of the user.