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Sampling error resulting from depth‐dependent plankton distributions and current differentials in a two‐layered system
Author(s) -
ANDERSON JOHN T.,
WEBSTER IAN T.
Publication year - 1992
Publication title -
fisheries oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 80
eISSN - 1365-2419
pISSN - 1054-6006
DOI - 10.1111/j.1365-2419.1992.tb00039.x
Subject(s) - ichthyoplankton , pelagic zone , plankton , environmental science , sampling (signal processing) , current (fluid) , replicate , oceanography , abundance (ecology) , fish <actinopterygii> , hydrology (agriculture) , geology , fishery , biology , statistics , mathematics , filter (signal processing) , computer science , computer vision , geotechnical engineering
We evaluate a source of error observed in standard ichthyoplankton bongo tows in which volumes of water filtered did not result in increased catches of red‐fish. Our analyses demonstrate that, under conditions where redfish larvae are distributed in surface waters in a two‐layered system, current differentials between surface and subsurface layers resulted in biased, standardized estimates of larval abundances as a result of filtering varying amounts of subsurface waters. Analysis of standard survey results on Flemish Cap demonstrated that this source of bias was limited to the May‐June period, after waters became stratified and before redfish passed from the larvae to pelagic juvenile stage. Correcting for this source of sampling bias wIII result in more accurate absolute estimates of ichthyoplankton abundance, and we estimate that variation (CV) for replicate samples may be reduced by 10%.