Dissertation - HQ

42 Behaviour in models
Effects on patchiness,
orientation, and survival
species 127 . Although schooling is mediated primarily by visual cues
starting aggregation, formation of the lateral line canals appears to
improve coordination of school members for parallel orientation 64 .
Potter & Chitre 128 used simple numerical experiments implementing
the “many wrongs” principle 129 to demonstrate that schooling can
enhance the location of reefs by sounds, ultimately affecting the choice
of settlement and changing the end point of individual trajectories.
This principle states that individual errors in locating the source of
information (sound here) cancel out in the school resulting in a better
emerging orientation for the school as a whole. Schooling is also a
strategy to avoid predation, and may ultimately affect survival and simulated
levels of recruitment. Therefore, schooling can become important
when modelling recruitment to specific nursery areas, as well as for
testing hypotheses on orientation and sensory capabilities of larvae.
Schooling will also alter the patchiness in the distribution of pelagic
larvae, which has implications for sampling, predation, feeding and
patterns of settlement.
1.8.2 Simple modelling tests
As this behaviour may change spatial patterns of settlement, the rule of
thumb is to verify that the model grid-scale can resolve those spatial
differences. The extent of the spatial differences (with and without
schooling) can be estimated as the distance travelled by larvae at the
mean velocity of the flow field near the settlement area from the onset
of schooling to settlement.
In addition, schooling may enhance the sensibility and precision in
orientation. Therefore, in a model with orientation implemented as a
response to environmental cues, one can artificially increase the sensory
sensitivity of larvae and check if this has an influence on both survival
rates (ability to find suitable recruitment habitat before the end of the
pelagic phase) and spatial patterns of settlement.
1.8.3 How to get the relevant data?
Very little is known
regarding schooling
in larval fish
Unfortunately, there is little published information on schooling behaviour
in fish larvae. Data can be obtained through rearing experiments
127 , direct in situ observations 125,130 , and acoustic measurements
combined with net tows 126 . Development of optical and acoustic technologies
will provide new information on larval behaviour. Observations
should aim at elucidating the timing of the onset of schooling behaviour
because it would be crucial to its incorporation in models.
1.8.4 Suggested implementation
Schooling based on
swimming rules
Implementation of schooling is similar to that of orientation, in that one
needs to follow a set of rules for individual particles. The maintenance of