Aggregation of euphausiids and Pacific hake (Merluccius productus) along the outer continental shelf off Vancouver Island

1997 ◽  
Vol 54 (9) ◽  
pp. 2080-2096 ◽  
Author(s):  
D L Mackas ◽  
R Kieser ◽  
M Saunders ◽  
D R Yelland ◽  
R M Brown ◽  
...  
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Acoustic Doppler Current Profiler ◽  
Shelf Break ◽  
Food Density ◽  
Outer Continental Shelf ◽  
Merluccius Productus ◽  
Water Property ◽  
Current Profiler ◽  
Property Patterns

From spring through autumn, euphausiids and Pacific hake (Merluccius productus) form dense aggregations off the outer coast of British Columbia along regions of steeply sloping bathymetry such as the continental shelf break. Their spatial overlap is ecologically significant because of their very strong prey-predator interaction. We analyze high-resolution measurements of shelf-edge spatial distributions of euphausiid and Pacific hake biomass (by echo integration), water properties (from surface measurements and conductivity-temperature-depth (CTD)/Rosette profiles), and current patterns (from acoustic Doppler current profiler, CTD profiles, and nearby current meter moorings). Both euphausiids and hake share similar horizontal distributions, although separated vertically by tens of meters during daylight hours. Bathymetric and water property patterns provide good coarse-scale prediction of aggregation location. However, details of patch location are better explained by flow-field indices such as cross-shore position of the shelf break current, intensity of cross-isobath flow and upwelling at the depth of the euphausiid scattering layer, and doming of isopycnals. Under prevailing summer oceanographic conditions along the British Columbia coast, likely ecological consequences of aggregation in and beneath upwelling water include access to high food density in the overlying surface layer, reduced alongshore transport, and horizontal segregation between adult and larval euphausiids.

Aggregation of euphausiids and Pacific hake (Merluccius productus) along the outer continental shelf off Vancouver Island

1997 ◽  
Vol 54 (9) ◽  
pp. 2080-2096 ◽  
Author(s):  
D.L. Mackas ◽  
R. Kieser ◽  
M. Saunders ◽  
D.R. Yelland ◽  
R.M. Brown ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Vancouver Island ◽  
Outer Continental Shelf ◽  
Merluccius Productus

scholarly journals Acoustic Doppler Current Profiler observations in the southern Caspian Sea: shelf currents and flow field off Feridoonkenar Bay, Iran

Ocean Science ◽  
2010 ◽  
Vol 6 (3) ◽  
pp. 737-748 ◽  
Author(s):  
P. Ghaffari ◽  
V. Chegini
Keyword(s):  
Flow Field ◽  
Continental Shelf ◽  
Caspian Sea ◽  
Driving Forces ◽  
Acoustic Doppler Current Profiler ◽  
Sea Breeze ◽  
Circulation Pattern ◽  
Current Field ◽  
Astronomical Tide ◽  
Current Profiler

Abstract. The results of offshore bottom-mounted ADCP measurements and wind records carried out from August to September 2003 in the coastal waters off Feridoon-kenar Bay (FB) in the south Caspian Sea (CS) are examined in order to characterize the shelf motion, the steady current field and to determine the main driving forces of currents on the study area. Owing to closed basin and absence of the astronomical tide, the atmospheric forcing plays an important role in the flow field of the CS. The lasting regular sea breeze system is present almost throughout the year. This system performs the forcing in diurnal and semi-diurnal bands similar to tides in other regions. In general, current field in the continental shelf could be separated into two distinguishable schemes, which in cross-shelf direction is dominated by high frequencies (1 cpd and higher frequencies), and in along-shelf orientation mostly proportional to lower frequencies in synoptic weather bands. Long-period wave currents, whose velocities are much greater than those of direct wind-induced currents, dominates the current field in the continental shelf off FB. The propagation of the latter could be described in terms of shore-controlled waves that are remotely generated and travel across the shelf in the southern CS. It has also been shown that long term displacements in this area follow the classic cyclonic, circulation pattern in the southern CS.

scholarly journals Observing Directional Properties of Ocean Swell with an Acoustic Doppler Current Profiler (ADCP)

2010 ◽  
Vol 27 (1) ◽  
pp. 210-225 ◽  
Author(s):  
T. H. C. Herbers ◽  
S. J. Lentz
Keyword(s):  
Continental Shelf ◽  
Acoustic Doppler Current Profiler ◽  
Parametric Estimation ◽  
Monitoring Applications ◽  
Current Profiler ◽  
Adcp Measurements ◽  
Directional Wave ◽  
Acoustic Doppler Current Profilers ◽  
Good Agreement

Abstract Acoustic Doppler current profilers (ADCPs) are widely used for routine measurements of ocean currents and waves in coastal environments. These instruments have the basic capability to measure surface wave frequency–directional spectra, but the quality of the estimates is not well understood because of the relatively high noise levels in the velocity measurements. In this study, wave data are evaluated from two 600-kHz ADCP instruments deployed at 20- and 45-m depths on the Southern California continental shelf. A simple parametric estimation technique is presented that provides robust estimates of the gross directional wave properties, even when the data quality is marginal, as was often the case in this benign wave environment. Good agreement of mean direction and (to a lesser degree) directional spreading estimates with measurements from a nearby surface-following buoy confirms that reliable wave information can generally be extracted from ADCP measurements on the continental shelf, supporting the instrument’s suitability for routine wave-monitoring applications.

scholarly journals Acoustic Doppler Current Profiler observations in the southern Caspian Sea: shelf currents and flow field off Freidoonkenar Bay, Iran

2009 ◽  
Vol 6 (3) ◽  
pp. 3019-3053 ◽  
Author(s):  
P. Ghaffari ◽  
V. Chegini
Keyword(s):  
Flow Field ◽  
Continental Shelf ◽  
Caspian Sea ◽  
Driving Forces ◽  
Acoustic Doppler Current Profiler ◽  
Sea Breeze ◽  
Circulation Pattern ◽  
Current Field ◽  
Astronomical Tide ◽  
Current Profiler

Abstract. The results of offshore bottom-mounted ADCP measurements and wind records carried out from August to September 2003 in the coastal waters off Freidoonkenar Bay (FB) in the south Caspian Sea (CS) are examined in order to characterize the shelf motion, the steady current field and to determine the main driving forces of currents on the study area. Owing to closed basin and absence of the astronomical tide, the atmospheric forcing plays an important role in the flow field of the CS. The lasting regular sea breeze system is present almost throughout the year that performs motive force in diurnal and semi-diurnal bands similar to tides in other regions. In general, current field in the continental shelf could be separated into two distinguishable schemes, which in cross-shelf direction is dominated by high frequencies (1 cpd and higher frequencies), and in along-shelf orientation mostly proportional to lower frequencies in synoptic weather bands. Long-period wave currents, whose velocities are much greater than those of direct wind-induced currents, are dominating the current field in the continental shelf off FB. The propagation of the latter could be described in terms of shore-controlled waves that are remotely generated and travel across the shelf in the southern CS. It has also been shown that long term displacements in this area follow the classic cyclonic, circulation pattern in the southern CS.

The relationship between Pacific hake (Merluccius productus) distribution and poleward subsurface flow in the California Current System

2006 ◽  
Vol 63 (12) ◽  
pp. 2648-2659 ◽  
Author(s):  
Vera N Agostini ◽  
Robert C Francis ◽  
Anne B Hollowed ◽  
Stephen D Pierce ◽  
Chris Wilson ◽  
...  
Keyword(s):  
Large Scale ◽  
Current System ◽  
Acoustic Doppler Current Profiler ◽  
Fish Distribution ◽  
Temperature Conductivity ◽  
California Current System ◽  
Merluccius Productus ◽  
Current Profiler ◽  
Abundance And Distribution ◽  
National Marine Fisheries Service

In a search for ocean conditions potentially affecting the extent of Pacific hake (Merluccius productus) feeding migrations, we analyzed data collected in 1995 and 1998 by the National Marine Fisheries Service on abundance and distribution of hake (by echo integration), intensity and distribution of alongshore flow (from acoustic Doppler current profiler), and temperature (conductivity–temperature–depth profiles). Our results show that Pacific hake are associated with subsurface poleward flow and not a specific temperature range. Temporal and spatial patterns characterize both hake distribution and undercurrent characteristics during the two years of this study. We suggest that poleward flow in this area defines adult hake habitat, with flow properties aiding or impeding the poleward migration of the population. We conclude that although physical processes may not directly affect fish production, they may be the link between large-scale ocean–atmosphere variability and pelagic fish distribution.

Isotopic characterization of lifetime movement by two demersal fishes from the northeastern Gulf of Mexico

2021 ◽  
Vol 657 ◽  
pp. 161-172
Author(s):  
JL Vecchio ◽  
JL Ostroff ◽  
EB Peebles
Keyword(s):  
Gulf Of Mexico ◽  
Continental Shelf ◽  
Life Histories ◽  
Linear Mixed Model ◽  
Trophic Position ◽  
Eye Lens ◽  
Outer Continental Shelf ◽  
Red Grouper ◽  
Lens Diameter ◽  
Isotopic Characterization

An understanding of lifetime trophic changes and ontogenetic habitat shifts is essential to the preservation of marine fish species. We used carbon and nitrogen stable isotope values (δ13C and δ15N) recorded within the laminar structure of fish eye lenses, reflecting both diet and location over time, to compare the lifetime trends of 2 demersal mesopredators. Tilefish Lopholatilus chamaeleonticeps inhabit burrows on the outer continental shelf, which results in exceptional site fidelity. Red grouper Epinephelus morio are spawned on the middle to outer continental shelf, move to the inner shelf for the juvenile period, and return offshore upon sexual maturity. Both species inhabit the eastern Gulf of Mexico, a region with a distinctive offshore-inshore gradient in background δ13C values. Within individual tilefish (n = 36), sequences of δ13C values and δ15N values had strong, positive correlations with eye-lens diameter, and strong correlations between the 2 isotopes (mean Spearman r = 0.86), reflecting an increase in trophic position with growth and little lifetime movement. In red grouper (n = 30), δ15N values positively correlated with eye-lens diameter, but correlations between δ15N and δ13C were weak (mean Spearman r = 0.29), suggesting cross-shelf ontogenetic movements. Linear mixed model results indicated strong relationships between δ15N and δ13C values in tilefish eye lenses but no convergence in the red grouper model. Collectively, these results are consistent with previously established differences in the life histories of the 2 species, demonstrating the potential utility of eye-lens isotope records, particularly for investigating the life histories of lesser-known species.

Sign in / Sign up

Export Citation Format

Share Document