Aw. Herman et al., DETECTION AND ABUNDANCE ESTIMATION OF EUPHAUSIIDS USING AN OPTICAL PLANKTON COUNTER, Marine ecology. Progress series, 94(2), 1993, pp. 165-173
An optical plankton counter (OPC) mounted on a towed Batfish vehicle w
as used to detect and estimate the abundance of euphausiids in the Eme
rald and La Have Basins of the Scotian Shelf, northwest Atlantic Ocean
. Euphausiids (Meganyctiphanes norvegica and Thysanoessa inermis) were
identified from their characteristic diameter distributions measured
by the OPC. The diameter distributions containing euphausiid peaks wer
e compared to several depth strata known to contain these animals. The
depth strata containing euphausiids were established from acoustical
tows made on the same cruise and the identification of animals was acc
omplished by sampling these acoustical layers with the BIONESS net sam
pler. The diel migration patterns of the euphausiids were also identif
ied from these diameter distributions. Euphausiid reaction to artifici
al lights mounted on Batfish and BIONESS showed increases in abundance
estimates by a factor of 2x and 50x respectively. Experiments with ar
tificial lights mounted on a remotely operated vehicle and camera plat
forms are also described. An artificial light mounted on a towed Batfi
sh resulted in a distinct increase in euphausiid abundance estimates a
s measured by the OPC. Abundance estimates from the OPC are also compa
red to results from acoustical tows and showed agreement to within a f
actor of 2 and better.