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  1. The spatial arrangement of neritina virginea (gastropoda: neritidae) during upstream migration in a split-channel reach.

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    Author(s): JUAN F. BLANCO; FREDERICK N. SCATENA
    Date: 2007
    Source: River Res. Applic. 23: 235–245
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (196 B)

    Description

    This paper relates differences in flow hydraulics between a main channel (MC) and a side channel (SC) of a river to patterns of upstream migration by Neritina virginea (Neritidae: Gastropoda), a dominant diadromous snail in streams of Puerto Rico (Greater Antilles). Near-bed water velocity, snail density and shell size were measured on a weekly basis between August and December 2000 along cross-sections in a main channel (MC) and an adjacent channel (SC) under a bridge crossing of the Rio Mameyes of Northeastern Puerto Rico. Near-bed velocity and water depth were used to compute Reynolds (Re) and Froude (Fr) numbers, and to classify flows within each channel. During base flow conditions (<2m3 s1), flow was chaotic and supercritical (Fr>1) in the MC, and non-chaotic and subcritical (Fr<1) in the SC. Higher mean densities (>100 indm2) of relatively small snails (mean s.d., 6.3 2.8 mm) were consistently recorded in the MC. Conversely, the SC had lower mean densities(<20 indm2) and significantly larger snails (7.6 2.4 mm). Within the MC, migratory groups preferred near-bed velocities>0.8ms1. Within the SC, they preferred the channel thalweg and depths>30 cm. The spatial arrangement that was observed between and within the channels may be related to food resources, predation pressure or biomechanics. Characteristics of preferred upstream migration pathways of N. virginea must be accounted when building road crossings incoastal streams with diadromous fauna.

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    Citation

    BLANCO,JUAN F.;SCATENA,FREDERICK N. 2007. The spatial arrangement of neritina virginea (gastropoda: neritidae) during upstream migration in a split-channel reach. River Res. Applic. 23: 235–245

    Keywords

    diadromous fauna, neritid snails, hydraulic ecology, habitat selection, tropical streams, Puerto Rico

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