Dissertation - HQ

Choice of settlement habitat 45
larvae arriving off a reef during the daytime when they only settle at
night. Would these larvae simply continue on, past suitable habitat,
or would they sense the presence of the habitat and behave in a way
that keeps them in the vicinity until nightfall? There is little direct
information on this sort of behaviour, although circumstantial evidence
indicates that larvae do accumulate in the vicinity of settlement habitat
to wait for the appropriate time 142 . This circumstantial evidence does
not, however, help to decide over what periods of time such accumulation
might take place. Information on the swimming, orientation or
sensory abilities of the species of interest can be used to eliminate from
consideration accumulation that is beyond the capabilities of the larvae.
When habitat quality is known to influence settlement probability, it
should be represented in the model, either explicitly when the fineness
of the grid permits, or through parameterisation in each grid cell (e.g.
description of the percentage of each habitat type in the cell). Settlement
probability should be deduced from this habitat map. Caution is advised
regarding how this probability is computed. One could be tempted
to use settlement patterns observed a posteriori to compute a spatial
probability of settlement. While this would be likely to enhance the
result of the model when compared to observations, it does not rely on
a mechanistic understanding of the process, hence has no predictive
value. Instead, settlement experiments should be done in all habitat
types and probabilities should be derived from those.
Spatial probability
of settlement