Materials and methods Directory UMM :Data Elmu:jurnal:J-a:Journal of Experimental Marine Biology and Ecology:Vol252.Issue1.Sept2000:
C .J. Jeffery J. Exp. Mar. Biol. Ecol. 252 2000 15 –26
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response to more concentrated conspecific cues Minchinton, 1997. It may be, however, that reduced area of patch will intensify settlement Pineda and Caswell, 1997 despite
other influences. At Cape Banks, Botany Bay, New South Wales, Australia, contrary to previously
documented cases, few larvae of the small gregarious barnacle Chamaesipho tasmanica arrive and settle relative to the space available Jeffery, 1997. The barnacles often form
continuous sheets of joined individuals or occur in isolated groups of joined or separate individuals on mid-littoral areas. In the more wave-exposed areas at Cape Banks, a
patchy distribution is prevalent whereas, in sheltered areas, cleared spaces may be scattered throughout aggregations of barnacles. Despite the amount of space differing
from place to place, there were consistent patterns in numbers of cyprids arriving from 1990 to 1993. Although the numbers of cyprids varied among places, they were
correlated with the distributions of juveniles on the substratum Jeffery, 1997; Jeffery and Underwood, 2000. Obviously, the suggestions of Pineda and Caswell 1997 that
consistent differences in rate of settlement might be explained by the proportion of the substratum available, cannot be substantiated by Chamaesipho. Other processes must
also be operating.
For example, because Chamaesipho settle gregariously in response to the presence of adults Otaiza, 1989; Jeffery, 1997, if different-sized patches were cleared within
aggregations of barnacles, it was hypothesised that the degree of exposure to adults along perimeters of patches, rather than the amount of space available, would influence
settlement of cyprids. It was therefore predicted that in plots of 6, 3 or 1.5 cm diameter cleared daily of newly-settled barnacles, there would be proportionally greatest
settlement in the smallest plots with the greatest relative exposure to adults along perimeters. This study therefore tested the hypotheses that increased availability of
substratum and or exposure to conspecific adults would influence settlement of Chamaesipho.
If free space contributed to numbers settling, it would be expected that there would be no differences in numbers settling per unit area in patches of different sizes. Alter-
natively, if adults around the perimeter of a patch influence settlement, there should be no differences in settlement per unit length of perimeter around patches of different
sizes.