Dissertation - HQ

Discussion 87
Figure 4.11 Comparison of standardised abundance (first line), residuals of the
first model (second line), and residuals of the second model (third line), for the
four rotations. All values were centred and reduced so that their absolute value
does not confound the comparison (focus is on the spatial distribution here).
which confirms that they explain yet another form of the variance and
that they are the only spatial factors to consider for this dataset. The
third line of Figure 4.11 presents residuals of the model with longitude
included. Compared with the first model (second line), the area
of high concentration in rotation 2 is well explained and, overall, the
distribution of residuals is more random and chaotic. The increased
randomness indicates that longitude explained some of the remaining
spatial structure, and that there was indeed something special about
being to the West rather than to the East of Tetiaroa.
4.4 Discussion
The most conspicuous pattern in the distribution of coral reef fish
larvae around Tetiaroa was the high abundances in the Northwest
during rotation 1 and in the Southwest during rotation 2. They did
not seem to be caused by a bias in sampling efficiency between day
and night because during rotation 2 for example, stations 1, 2, and 12
were sampled at night, stations 3, 10 were sampled during the day,
station 11 was sampled at dusk and all held high concentrations of reef
fishes (Figure 4.6). Given the size of the grid (10 km) and the size of
larval patches previously observed (1-6 km 71,162,163 ), these regions with
several rich stations could be interpreted as regions where patches are
more concentrated and/or frequent rather than as belonging to one
Two regions where
larval patches
are frequent