Video Plankton Recorder estimates of copepod,
pteropod and larvacean distributions from a stratified region of
Georges Bank with comparative measurements from a MOCNESS sampler.
Mark C. Benfield1², Cabell S. Davis¹, Peter H.
Wiebe¹, Scott M. Gallager¹, R. Gregory Lough³ and
Nancy J. Copley¹
¹ Department of Biology, Woods Hole Oceanographic Institution,
Woods Hole, Massachusetts 02543
² Present Address: Coastal Fisheries Institute, Louisiana
State University, 218 Center for Wetland Resources, Baton Rouge,
Louisiana 70803
³ Northeast Fisheries Science Center, National Marine
Fisheries Service, NOAA, Woods Hole, Massachusetts 02543
A two-vessel exercise was conducted over the southern flank of
Georges Bank during the onset of vernal stratification in May 1992.
The Video Plankton Recorder (VPR), a towed video system, was used
to map out the fine-scale distributions of zooplankton to a depth
of 70 m along a trackline which described a regular grid (3.5 x 4.5
km) in Lagrangian space. A second vessel following a parallel
course conducted Multiple Opening/Closing Net and Environmental
Sensing System (MOC
NESS) sampling during the last section of the grid which provided
an opportunity to compare data from the two systems. Both the VPR
and the MOCNESS provided similar data on the taxonomic composition
of the plankton which was numerically dominated by copepods
(Calanus, Pseudocalanus, Oithona), pteropods (Limacina) and
larvaceans (Oikopleura). The absence of rare (<43.1 m^03) species
from the VPR data set was a consequence of the small volume sampled
(0.0694 m^3) by the high magnification camera, while fragile
gelatinous taxa were undersampled by the MOCNESS. Estimates of
copepod and pteropod concentrations were comparable for the two
gear types. While the species composition of the plankton did not
change statistically along the grid, abundances of the dominant
taxa varied along the transect and each taxon demonstrated
pronounced fine-scale vertical patterns which appeared to be
related to hydrographic features. The VPR represents a powerful
tool for rapid surveys of the micro-to fine-scale structure of
zooplankton assemblages either alone, or in conjunction with other
sampling techniques.