Butler,M.,Bollens,S.M.,Burghalter,B.,Madin,L.P.,Horgan,E.
Mesopelagic fishes of the Arabian Sea: distribution, abundance and diet of Journal Article
In: Deep-Sea Research Part II, vol. 48, no. 61, pp. 1369-1383, 2001.
Abstract | BibTeX | Tags: abundance, Arabian Sea, diel, diet, diets, Distribution, ecology, feeding, migration, oxygen minimum, population, populations, predation, south
@article{,
title = {Mesopelagic fishes of the Arabian Sea: distribution, abundance and diet of },
author = {Butler,M.,Bollens,S.M.,Burghalter,B.,Madin,L.P.,Horgan,E.},
year = {2001},
date = {2001-01-01},
journal = {Deep-Sea Research Part II},
volume = {48},
number = {61},
pages = {1369-1383},
abstract = {Four species of predatory fishes - Chauliodus pammelas, Chauliodus sloani, Stomias afffnis and Stomias nebulosus - were collected on two cruises to the Arabian Sea during 1995. We present data on the abundances, horizontal and vertical distributions, and diet of these fishes. We also discuss briefly the importance of the oxygen minimum zone and predation on myctophid fishes to the ecology of these mesopelagic predators. Chauliodus pammelas and C. sloani appear to have only partially overlapping horizontal distributions in the Arabian Sea, with C. pammelas more common to the north and C. sloani more common to the south. Our data support previous results suggesting that diel vertical migration is the norm for these species, with smaller individuals usually nearer to the surface and larger individuals tending to stay deeper. In contrast to Chauliodus, Stomias affinis and S. nebulosus appear to have largely overlapping horizontal distributions in the Arabian Sea. However, they may have slightly di!erent vertical distributions, with S. affinis living slightly shallower (especially at night) than S. nebulosus. All four species spend most of their time in the oxygen minimum zone, entering the surface oxygenated waters (100-150 m) only at night (if at all). The diets of C. pammelas, C. sloani, and S. affinis consisted mainly of lantern fishes, Myctophidae, and other fishes. In contrast, S. nebulosus, the smaller of the two Stomias species, ate mostly copepods and other crustaceans. This differential feeding may allow the two Stomias species to co-occur. Three of these four stomiids appear to play an important role in predation on myctophid fish populations in the Arabian Sea.},
keywords = {abundance, Arabian Sea, diel, diet, diets, Distribution, ecology, feeding, migration, oxygen minimum, population, populations, predation, south},
pubstate = {published},
tppubtype = {article}
}
Four species of predatory fishes - Chauliodus pammelas, Chauliodus sloani, Stomias afffnis and Stomias nebulosus - were collected on two cruises to the Arabian Sea during 1995. We present data on the abundances, horizontal and vertical distributions, and diet of these fishes. We also discuss briefly the importance of the oxygen minimum zone and predation on myctophid fishes to the ecology of these mesopelagic predators. Chauliodus pammelas and C. sloani appear to have only partially overlapping horizontal distributions in the Arabian Sea, with C. pammelas more common to the north and C. sloani more common to the south. Our data support previous results suggesting that diel vertical migration is the norm for these species, with smaller individuals usually nearer to the surface and larger individuals tending to stay deeper. In contrast to Chauliodus, Stomias affinis and S. nebulosus appear to have largely overlapping horizontal distributions in the Arabian Sea. However, they may have slightly di!erent vertical distributions, with S. affinis living slightly shallower (especially at night) than S. nebulosus. All four species spend most of their time in the oxygen minimum zone, entering the surface oxygenated waters (100-150 m) only at night (if at all). The diets of C. pammelas, C. sloani, and S. affinis consisted mainly of lantern fishes, Myctophidae, and other fishes. In contrast, S. nebulosus, the smaller of the two Stomias species, ate mostly copepods and other crustaceans. This differential feeding may allow the two Stomias species to co-occur. Three of these four stomiids appear to play an important role in predation on myctophid fish populations in the Arabian Sea.
Kim,H-S,Flagg,C.N.,Howden,S.D.
Northern Arabian Sea variability from TOPEX/Poseidon altimetry data: an extension of the US JGOFS/ONR shipboard ADCP study Journal Article
In: Deep-Sea Research Part II, vol. 48, no. 134, pp. 1069-1096, 2001.
Abstract | BibTeX | Tags: acoustic, Arabian Sea, Distribution, location, nearshore, oxygen minimum, south, spatial scale
@article{,
title = {Northern Arabian Sea variability from TOPEX/Poseidon altimetry data: an extension of the US JGOFS/ONR shipboard ADCP study},
author = {Kim,H-S,Flagg,C.N.,Howden,S.D.},
year = {2001},
date = {2001-01-01},
journal = {Deep-Sea Research Part II},
volume = {48},
number = {134},
pages = {1069-1096},
abstract = {Sea-level anomalies (SLA) derived from the TOPEX/Poseidon (T/P) altimetry and inferred geostrophic currents within the northern Arabian Sea were examined for the period from March 1993 through November 1996. The primary objective of this study was to confirm and extend our understanding of the upper-ocean mesoscale variability observed in the shipboard acoustic Doppler current profiler (ADCP) data collected during the US JGOFS/ONR Arabian Sea Expedition (September 1994-January 1996). The accuracy of the T/P altimetry data (~3 cm rms) results in an uncertainty in the altimeter-derived velocities comparable to the ADCP measurement error. Thus the T/P data provide a reasonable method for extending studies of the mesoscale dynamics for the region. Comparison of the T/P-derived geostrophic velocities with concurrent ADCP data showed good correlation, with an r2 between 0.7 and 0.9 and rms di!erences of 10 cm s-1. The T/P data con"rm both the overall spatial and seasonal current patterns observed by the ADCP. The monsoonally averaged rms sea-level anomalies indicate a high degree of intraseasonal variation due to the generation of squirts, jets and eddies all along the coast, the variability of which increases in both intensity and areal extent during the Southwest Monsoon. The SLA data indicate amuch reduced degree of variability over the shelf. The SLA-derived eddy kinetic energy (EKE) fields are consistent with those derived earlier from the ADCP data in both distribution and magnitude. There is a large increase in EKE to the west and southwest and to a lesser extent to the south and a large area of relatively reduced eddy activity over much of the eastern and northern Arabian Sea. The area of reduced eddy activity coincides with the location of the most intense portions of the oxygen minimum zone found in the northern Arabian Sea. The spatial scales of the eddies responsible for the EKE distribution over the study area range between 200 and 500km in the nearshore region, decreasing to 100-200km o!shore. While there is significant energy variability in annual and semi-annual time scales, a substantial portion of the energy is found between 50 and 120 days, and the relative importance of this frequency band increases offshore. Spectra indicate a distinct break in the frequency content of the eddy field at about 15§N, with little energy at less than annual periods south of this latitude.},
keywords = {acoustic, Arabian Sea, Distribution, location, nearshore, oxygen minimum, south, spatial scale},
pubstate = {published},
tppubtype = {article}
}
Sea-level anomalies (SLA) derived from the TOPEX/Poseidon (T/P) altimetry and inferred geostrophic currents within the northern Arabian Sea were examined for the period from March 1993 through November 1996. The primary objective of this study was to confirm and extend our understanding of the upper-ocean mesoscale variability observed in the shipboard acoustic Doppler current profiler (ADCP) data collected during the US JGOFS/ONR Arabian Sea Expedition (September 1994-January 1996). The accuracy of the T/P altimetry data (~3 cm rms) results in an uncertainty in the altimeter-derived velocities comparable to the ADCP measurement error. Thus the T/P data provide a reasonable method for extending studies of the mesoscale dynamics for the region. Comparison of the T/P-derived geostrophic velocities with concurrent ADCP data showed good correlation, with an r2 between 0.7 and 0.9 and rms di!erences of 10 cm s-1. The T/P data con"rm both the overall spatial and seasonal current patterns observed by the ADCP. The monsoonally averaged rms sea-level anomalies indicate a high degree of intraseasonal variation due to the generation of squirts, jets and eddies all along the coast, the variability of which increases in both intensity and areal extent during the Southwest Monsoon. The SLA data indicate amuch reduced degree of variability over the shelf. The SLA-derived eddy kinetic energy (EKE) fields are consistent with those derived earlier from the ADCP data in both distribution and magnitude. There is a large increase in EKE to the west and southwest and to a lesser extent to the south and a large area of relatively reduced eddy activity over much of the eastern and northern Arabian Sea. The area of reduced eddy activity coincides with the location of the most intense portions of the oxygen minimum zone found in the northern Arabian Sea. The spatial scales of the eddies responsible for the EKE distribution over the study area range between 200 and 500km in the nearshore region, decreasing to 100-200km o!shore. While there is significant energy variability in annual and semi-annual time scales, a substantial portion of the energy is found between 50 and 120 days, and the relative importance of this frequency band increases offshore. Spectra indicate a distinct break in the frequency content of the eddy field at about 15§N, with little energy at less than annual periods south of this latitude.
Madhupratap,M.,Gopalakrishnan,T.C.,Haridas,P.,Nair,K.K.C.
Mesozooplankton biomass, composition and distribution in the Arabian Sea during the Fall Intermonsoon: implications of oxygen gradients Journal Article
In: Deep-Sea Research Part II, vol. 48, no. 146, pp. 1345-1368, 2001.
Abstract | BibTeX | Tags: Arabian Sea, depth, diel, Distribution, migration, oxygen minimum, seasonal variation, south, thermocline
@article{,
title = {Mesozooplankton biomass, composition and distribution in the Arabian Sea during the Fall Intermonsoon: implications of oxygen gradients},
author = {Madhupratap,M.,Gopalakrishnan,T.C.,Haridas,P.,Nair,K.K.C.},
year = {2001},
date = {2001-01-01},
journal = {Deep-Sea Research Part II},
volume = {48},
number = {146},
pages = {1345-1368},
abstract = {Mesozooplankton biomass and distribution of calanoid copepods were studied for the upper 500m between 3 and 21§N along an open-ocean transect in the Arabian Sea during the Fall Intermonsoon (September-October 1992, 1993). The region studied has strong gradients in the oxygen minimum zone (OMZ), being acutely deficient in oxygen in the north and with increasing concentrations towards the south. In the upper layers, mesozooplankton biomass was higher in the northern latitudes, above the thermocline, apparently avoiding the OMZ. In the deeper strata, relatively higher biomass was observed in the more oxygenated southern latitudes. Highest mesozooplankton biomass in open waters of the Arabian Sea was observed during the intermonsoon seasons. Calanoid copepods occurred at all depths, and surface-living species did not undertake conspicuous diel migrations, even when they occurred in the deeper waters of the more southern latitudes. A few species belonging to the families Metridinidae and Augaptilidae appeared to be characteristic of the poorly oxygenated mid-depths of the more northern latitudes. Seasonal variations in the composition of the copepod community were negligible. The evolution of the OMZ in the Arabian Sea and its implications are discussed.},
keywords = {Arabian Sea, depth, diel, Distribution, migration, oxygen minimum, seasonal variation, south, thermocline},
pubstate = {published},
tppubtype = {article}
}
Mesozooplankton biomass and distribution of calanoid copepods were studied for the upper 500m between 3 and 21§N along an open-ocean transect in the Arabian Sea during the Fall Intermonsoon (September-October 1992, 1993). The region studied has strong gradients in the oxygen minimum zone (OMZ), being acutely deficient in oxygen in the north and with increasing concentrations towards the south. In the upper layers, mesozooplankton biomass was higher in the northern latitudes, above the thermocline, apparently avoiding the OMZ. In the deeper strata, relatively higher biomass was observed in the more oxygenated southern latitudes. Highest mesozooplankton biomass in open waters of the Arabian Sea was observed during the intermonsoon seasons. Calanoid copepods occurred at all depths, and surface-living species did not undertake conspicuous diel migrations, even when they occurred in the deeper waters of the more southern latitudes. A few species belonging to the families Metridinidae and Augaptilidae appeared to be characteristic of the poorly oxygenated mid-depths of the more northern latitudes. Seasonal variations in the composition of the copepod community were negligible. The evolution of the OMZ in the Arabian Sea and its implications are discussed.
Böhm,E.,Morrison,J.M.,Manghnani,V.,Kim,H-S,Flagg,C.N.
The Ras al Hadd Jet: remotely sensed and acoustic Doppler profiler observations in 1994-1995 Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 46, pp. 1531-1549, 1999.
Abstract | BibTeX | Tags: acoustic, Arabian Sea, budget, Gulf of Oman, Oman, south
@article{,
title = {The Ras al Hadd Jet: remotely sensed and acoustic Doppler profiler observations in 1994-1995},
author = {Böhm,E.,Morrison,J.M.,Manghnani,V.,Kim,H-S,Flagg,C.N.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {46},
pages = {1531-1549},
abstract = {The existence of a surface barotropic front-jet system at the confluence region o! the eastern tip of Oman (Ras Al Hadd or RAH) is documented for 1994-1995 through advanced very high resolution radiometer (AVHRR) and acoustic Doppler current profiler (ADCP) observations. The thermal signature of this confluence is visible in 1995 between early May and the end of October, i.e., throughout the SW Monsoon and into the transition period between SW and NE Monsoons. The thermal characteristics are those of a NE-oriented front between cooler water of southern (upwelled) origin and warmer waters of northern Gulf of Oman origin. During the period when the thermal front is absent, ADCP data suggest that the confluence takes a more southward direction with Gulf of Oman waters passing RAH into the southeastern Oman coastal region. The thermal gradient is initially small (June-July) but later increases (August-October) into a front that exhibits small-scale instabilities. Surface current velocities within the jet, estimated by tracking these features in consecutive satellite images, are 0.5-0.7 m s-1 and in remarkable agreement with concurrent ADCP retrievals in which the seasonal maximum in velocity is 1 m s-1. ADCP observations collected during several US JGOFS cruises reveal a weakly baroclinic current in the confluence region that drives the waters into the offshore system. The fully developed jet describes a large meander that demarcates two counter-rotating eddies (cyclonic to the north and anticyclonic to the south of the jet) of approximately 150-200 km diameter. The southern eddy of this pair is resolved by the seasonally averaged, sea-level anomaly derived from TOPEX/Poseidon observations. During the SW Monsoon, the RAH Jet advects primarily cold waters along its path, but as soon as the wind system reverses with the transition to the intermonsoonal period, a warm current is rapidly established that advects the surface coastal waters of the Gulf of Oman offshore. In accordance with the interannual variation of the wind forcing phase, the reversal of the currents from NE to SW occurred earlier in 1994 than in 1995, confirming that the RAH Jet is integral part of the East Arabian Current. The transport of the Jet, estimated by combining SST information on the width with ADCP data on the velocity's vertical structure, is found to fluctuate between 2-8'106 m3 s-1 and its thickness between 150-400 m. These significant fluctuations are due to the time-variable partition of horizontal transport between eddies and the RAH Jet and are potentially important to the nutrient and phytoplankton budgets of the Arabian Sea.},
keywords = {acoustic, Arabian Sea, budget, Gulf of Oman, Oman, south},
pubstate = {published},
tppubtype = {article}
}
The existence of a surface barotropic front-jet system at the confluence region o! the eastern tip of Oman (Ras Al Hadd or RAH) is documented for 1994-1995 through advanced very high resolution radiometer (AVHRR) and acoustic Doppler current profiler (ADCP) observations. The thermal signature of this confluence is visible in 1995 between early May and the end of October, i.e., throughout the SW Monsoon and into the transition period between SW and NE Monsoons. The thermal characteristics are those of a NE-oriented front between cooler water of southern (upwelled) origin and warmer waters of northern Gulf of Oman origin. During the period when the thermal front is absent, ADCP data suggest that the confluence takes a more southward direction with Gulf of Oman waters passing RAH into the southeastern Oman coastal region. The thermal gradient is initially small (June-July) but later increases (August-October) into a front that exhibits small-scale instabilities. Surface current velocities within the jet, estimated by tracking these features in consecutive satellite images, are 0.5-0.7 m s-1 and in remarkable agreement with concurrent ADCP retrievals in which the seasonal maximum in velocity is 1 m s-1. ADCP observations collected during several US JGOFS cruises reveal a weakly baroclinic current in the confluence region that drives the waters into the offshore system. The fully developed jet describes a large meander that demarcates two counter-rotating eddies (cyclonic to the north and anticyclonic to the south of the jet) of approximately 150-200 km diameter. The southern eddy of this pair is resolved by the seasonally averaged, sea-level anomaly derived from TOPEX/Poseidon observations. During the SW Monsoon, the RAH Jet advects primarily cold waters along its path, but as soon as the wind system reverses with the transition to the intermonsoonal period, a warm current is rapidly established that advects the surface coastal waters of the Gulf of Oman offshore. In accordance with the interannual variation of the wind forcing phase, the reversal of the currents from NE to SW occurred earlier in 1994 than in 1995, confirming that the RAH Jet is integral part of the East Arabian Current. The transport of the Jet, estimated by combining SST information on the width with ADCP data on the velocity's vertical structure, is found to fluctuate between 2-8'106 m3 s-1 and its thickness between 150-400 m. These significant fluctuations are due to the time-variable partition of horizontal transport between eddies and the RAH Jet and are potentially important to the nutrient and phytoplankton budgets of the Arabian Sea.