TY - JOUR
T1 - Diel vertical migration of zooplankton and mesopelagic fish in the Arabian Sea
AU - Luo, Jiangang
AU - Ortner, Peter B.
AU - Forcucci, David
AU - Cummings, Shailer R.
N1 - Funding Information:
This research was funded by the Office of Naval Research (N000149710156). We thank the crew of NOAA Ship kHz sonar deck unit; Paul Dammann (AOML/NOAA) for writing the original 12 kHz data acquisition program; Charles Greenlaw (TRACOR Applied Sciences) and Charles Flagg for their help with 12 kHz and ADCP data processing, respectively; Larry Madin (WHOI) for supplying unpublished MOC10 data; and Peter Lane and the late Leonard Hill for supplying unpublished MOC1 zooplankton data. This is US JGOFS Contribution Number 525. Malcolm Baldrige and a multitude of scientific personnel for their help at sea; John Proni (NOAA/AOML) for providing the 12
PY - 2000
Y1 - 2000
N2 - Acoustic (153 kHz ADCP and 12 kHz hull-mounted transducers) data and MOCNESS (MOC01 and MOC10) net tow samples collected in the Arabian Sea during the Spring Intermonsoon (April/May) and Southwest Monsoon (August) in 1995 documented substantial diel migrations of fish and zooplankton despite the year-round presence of an oxygen minimum (< 0.2 ml l-1 at 125-150 m). Fish and zooplankton layers were distinguished by comparing 12 kHz sonar and 153 kHz ADCP backscatter data, which indicated that the strongly migrating layers were predominantly composed of fishes. Fish vertical migration speeds were independently estimated from the slopes of the volume scattering layers and from the vertical velocity components of the ADCP, yielding average speeds of 4 and 3 cm s-1 and maximum speeds of 13 and 10 cm s-1, respectively. A few migrating zooplankton layers were identified with an average speed of about 2 cm s-1 and maximum speeds as high as 8 cm s-1. Migration depths for both zooplankton and fish differed somewhat amongst stations and appeared to be related to local hydrographic conditions (principally the vertical gradients in DO and water temperature). Zooplankton displacement volumes at individual sites suggested that zooplankton biomass during the Southwest Monsoon could be as much as fivefold greater than during the Spring Intermonsoon. This observation was confirmed for the region in general by first deriving a relationship between ADCP backscatter intensity and daytime zooplankton biomass and then comparing the latter between cruises using daytime ADCP data taken along a 1500 km transect that extended from the coast of Somalia to the center of the northern basin. (C) 2000 Elsevier Science Ltd.
AB - Acoustic (153 kHz ADCP and 12 kHz hull-mounted transducers) data and MOCNESS (MOC01 and MOC10) net tow samples collected in the Arabian Sea during the Spring Intermonsoon (April/May) and Southwest Monsoon (August) in 1995 documented substantial diel migrations of fish and zooplankton despite the year-round presence of an oxygen minimum (< 0.2 ml l-1 at 125-150 m). Fish and zooplankton layers were distinguished by comparing 12 kHz sonar and 153 kHz ADCP backscatter data, which indicated that the strongly migrating layers were predominantly composed of fishes. Fish vertical migration speeds were independently estimated from the slopes of the volume scattering layers and from the vertical velocity components of the ADCP, yielding average speeds of 4 and 3 cm s-1 and maximum speeds of 13 and 10 cm s-1, respectively. A few migrating zooplankton layers were identified with an average speed of about 2 cm s-1 and maximum speeds as high as 8 cm s-1. Migration depths for both zooplankton and fish differed somewhat amongst stations and appeared to be related to local hydrographic conditions (principally the vertical gradients in DO and water temperature). Zooplankton displacement volumes at individual sites suggested that zooplankton biomass during the Southwest Monsoon could be as much as fivefold greater than during the Spring Intermonsoon. This observation was confirmed for the region in general by first deriving a relationship between ADCP backscatter intensity and daytime zooplankton biomass and then comparing the latter between cruises using daytime ADCP data taken along a 1500 km transect that extended from the coast of Somalia to the center of the northern basin. (C) 2000 Elsevier Science Ltd.
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U2 - 10.1016/S0967-0645(99)00150-2
DO - 10.1016/S0967-0645(99)00150-2
M3 - Article
AN - SCOPUS:0034073646
VL - 47
SP - 1451
EP - 1473
JO - Deep-Sea Research Part II: Topical Studies in Oceanography
JF - Deep-Sea Research Part II: Topical Studies in Oceanography
SN - 0967-0645
IS - 7-8
ER -