The present study evaluates the vertical distribution of Neritina zebra in rocky outcrops in the lower and middle intertidal, intertidal as well as the horizontal
distribution between rocky and clay substratas of an estuary in the Brazilian Amazon. The sampling areas are located in an oligohaline area in Icoaraci, Mosqueiro and Colares, at the coast of the State of Pará, Brasil. To evaluate
the vertical distribution on orocky substrata, substratamolluscs were esampled
in the lower and middle intertidal. intertidal In the lower mesolittoralmto, where
clay and rocky substrata occur, substrataoccursamples were collected to verify
the effect of the substrata on othe distribution of the mollusc.For each substrata
and intertidal zonet zone, 22 replicates were randomly sampledusing a
quadrant of 25x25cm² during the rainyrainy and dry season. An Analysis of
Variance was seasonAAVancewasperformed to test (1) the effect of the
intertidal zone and (2) the substrata onsubstratao the density of N. zebra.
Analysis Athe vertical distribution results showed that in the lower zone,
,juvenile individuals show a higher density than in the middle zone, and an
oppositeand anp pattern compared with adults appear to occur.Regarding the
distribution on the different substrata,on the differentsubstrata results showed
higher densities ono rocky substrate than onon clay substrata for young
individuals, whereas no definite pattern was detected for adultss. This variability
between the substrata and intertidal zones showed the influence of the seasons
and the sampling sites. Icoaraci showed theshowedlowest densities, which can
be associated to the anthropic activities in that area.
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