The use of moored inverted echo sounders for monitoring meso-zooplankton and fish near the ocean surface

2005 ◽  
Vol 62 (5) ◽  
pp. 1004-1018 ◽  
Author(s):  
Mark V Trevorrow
Keyword(s):  
Acoustic Scattering ◽  
Near Surface ◽  
Strait Of Georgia ◽  
Abundance Estimates ◽  
Weak Evidence ◽  
Inverted Echo Sounder ◽  
Ocean Station Papa ◽  
And Behavior ◽  
Scatterer Size ◽  
Northeast Pacific Ocean

This study evaluates the effectiveness of a 200-kHz inverted echo sounder for monitoring the abundance and behavior of near-surface zooplankton and fish. Data from both oceanic and littoral environments are examined: first from an 81-day deployment at Ocean Station Papa (OSP) in the northeast Pacific Ocean during the spring of 1996, and second from an 8-day deployment in the southern Strait of Georgia in September 1998. The analysis combines calibrated backscatter intensity, echo-amplitude statistics, and acoustic-scattering models to produce estimates of mean scatterer size and abundance. The identity of the various scatterer classes is deduced from local net trawls and reference to previous studies. At the OSP site the dominant scatterers were found to be euphausiids, pteropods, and myctophid fishes, with mean lengths of 15, 1.5, and 28 mm, respectively. At the Strait of Georgia site three fish size classes were identified: juvenile herring with mean length near 10 cm, juvenile salmon with mean length of 20 cm, and there was weak evidence for an adult salmon class. Overall, the acoustically derived abundance estimates were in reasonable agreement with the local net trawls and results from previous studies. The usefulness of sustained monitoring over diurnal and seasonal time scales is demonstrated with the OSP zooplankton data.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Life History ◽  
Pacific Coast ◽  
Puget Sound ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Dietary Analysis ◽  
Strait Of Georgia ◽  
Food Items ◽  
Abundance Estimates ◽  
Commercial Species

Abstract.—Spiny dogfish <em>Squalus acanthias </em>have been an important commercial species on Canada’s Pacific coast for more than 130 years. In this study we show that the spiny dogfish life history results in juveniles remaining in pelagic waters for 10–15 years after birth, with lengths up to about 60 cm. Abundance estimates show that the numbers of these young dogfish, as well as some older dogfish in the pelagic waters, appear to represent a relatively large percentage of the population in these two regions. Dietary analysis shows that while euphausiids and teleosts constitute the major food items, regardless of size/age, dogfish feed on a number of species within the ecosystem. After about 15 years, there is a movement into demersal habitats where individuals eventually mature. Because dogfish are long lived, and because they are found throughout the pelagic zone and demersal habitats, it is probable that they play a key role in the Strait of Georgia and Puget Sound ecosystems.

scholarly journals Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins

2019 ◽  
Author(s):  
Patricia Levasseur ◽  
Sean Sterrett ◽  
Chris Sutherland
Keyword(s):  
Count Data ◽  
Hierarchical Modeling ◽  
Spatial Scales ◽  
Promising Method ◽  
Diamondback Terrapin ◽  
Imperfect Detection ◽  
Modeling Framework ◽  
Abundance Estimates ◽  
Diamondback Terrapins ◽  
And Behavior

Generating a range-wide population status of the diamondback terrapin (Malaclemys terrapin spp.) is challenging due to a combination of species ecology and behavior, and limitations associated with traditional sampling methods. Visual counting of emergent heads offers an efficient, non-invasive and promising method for generating abundance estimates of terrapin populations across broader spatial scales and can be used to explain spatial variation in population size. We conducted repeated visual head count surveys at 38 predetermined sites along the shoreline of Wellfleet Bay in Wellfleet, Massachusetts. We analyzed the count data using a hierarchical modeling framework designed specifically to analyze repeated count data: the so-called N-mixture model. This approach allows for simultaneous modeling of imperfect detection to generate estimates of true terrapin abundance. We found detection probability was lowest when skies were overcast and when wind speed was highest. Site specific abundance varied but we found that abundance estimates were, on average, higher in unexposed sites compared to exposed sites. We demonstrate the utility of pairing visual head counts and N-mixture models as an efficient method for estimating terrapin abundance and show how the approach can be used to identifying environmental factors that influence detectability and distribution.

Influence of long-term aqueous leaching of irradiated graphite on surface properties and behavior of radionuclides

MRS Advances ◽  
2020 ◽  
Vol 5 (3-4) ◽  
pp. 177-184
Author(s):  
Andrey A. Shiryaev ◽  
Anna G. Volkova ◽  
Stanislav Dvoryak ◽  
Maximillian S. Nickolsky ◽  
Elena V. Zakharova
Keyword(s):  
Surface Morphology ◽  
Surface Oxidation ◽  
Underground Water ◽  
Nuclear Spectroscopy ◽  
Secondary Phases ◽  
Near Surface ◽  
Waste Forms ◽  
Irradiated Graphite ◽  
And Behavior

AbstractSamples of real irradiated (i-)graphite from bushings of RBMK reactor after several types of decontamination treatments were put in contact with aqueous solutions modelling underground water of Nizhnekansky massif (Russia) equilibrated with bentonite for periods up to 1.5 years. Leach rates of radionuclides and evolution of graphite surface morphology and oxidation state were monitored using nuclear spectroscopy, SEM and XPS. After the experiment, less than one third of surface carbons remains unoxidised. Extensive precipitation of secondary phases (alumosilicates, carbonates) was observed on some samples and is possibly correlated with surface oxidation extent. The leach rates of dose-forming 14C and 36Cl are comparable with the leach rates of radionuclides in glassy waste forms. According to the current study i-graphite could be regarded as a waste form, which is suitable for near-surface disposal.

Diurnal and Seasonal Variability of Near‐Surface Oxygen in the Strait of Georgia

2019 ◽  
Vol 124 (4) ◽  
pp. 2418-2439 ◽  
Author(s):  
Chuning Wang ◽  
Rich Pawlowicz ◽  
Akash R. Sastri
Keyword(s):  
Seasonal Variability ◽  
Surface Oxygen ◽  
Near Surface ◽  
Strait Of Georgia

scholarly journals Variability in the density and sound-speed of coastal zooplankton and nekton

2009 ◽  
Vol 67 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Krissy A. Forman ◽  
Joseph D. Warren
Keyword(s):  
Sound Speed ◽  
Fundulus Heteroclitus ◽  
Acoustic Scattering ◽  
Large Area ◽  
Palaemonetes Pugio ◽  
Acoustic Data ◽  
Abundance Estimates ◽  
Short Period ◽  
Crangon Septemspinosa ◽  
Animal Size

Abstract Forman, K. A., and Warren, J. D. 2010. Variability in the density and sound-speed of coastal zooplankton and nekton. – ICES Journal of Marine Science, 67: 10–18. Acoustic sampling techniques provide an advantage over traditional net-sampling by increasing scientist ability to survey a large area in a relatively short period, as well as providing higher-resolution data in the vertical and horizontal dimensions. To convert acoustic data into measures of biological organisms, physics-based scattering models are often used. Such models use several parameters to predict the amount of sound scattered by a fluid-like or weakly scattering animal. Two important input parameters are the density (g) and sound-speed (h) contrasts of the animal and the surrounding seawater. The density and sound-speed contrasts were measured for coastal zooplankton and nekton species including shrimps (Palaemonetes pugio and Crangon septemspinosa), fish (Fundulus majalis and Fundulus heteroclitus), and polychaetes (Nereis succinea and Glycera americana) along with multiple physiological and environmental variables. Factors such as animal size, feeding status, fecundity, gender, and maturity caused variations in g. The variations in g observed for these animals could lead to large differences (or uncertainties) in abundance estimates based on acoustic scattering models and field-collected backscatter data. It may be important to use a range of values for g and h in the acoustic scattering models used to convert acoustic data into estimates of the abundance of marine organisms.

Near-surface circulation of the northeast Pacific Ocean derived from WOCE-SVP satellite-tracked drifters

1999 ◽  
Vol 46 (11-12) ◽  
pp. 2371-2403 ◽  
Author(s):  
Steven J. Bograd ◽  
Richard E. Thomson ◽  
Alexander B. Rabinovich ◽  
Paul H. LeBlond
Keyword(s):  
Pacific Ocean ◽  
Near Surface ◽  
Northeast Pacific ◽  
Surface Circulation ◽  
Northeast Pacific Ocean

scholarly journals Affiliation or Power: What Motivates Behavior on Social Networking Sites? And Role of Self-Consciousness on Behavior on Social Networking Sites

2016 ◽  
Vol 3 (3) ◽  
Author(s):  
Satabdee Das
Keyword(s):  
Social Networking ◽  
Social Networking Sites ◽  
Implicit Measures ◽  
Regression Analyses ◽  
Weak Evidence ◽  
Affiliation Motive ◽  
Power Motive ◽  
And Behavior ◽  
The Relationship

The present study investigated the relationship between explicit and implicit measures of affiliation, power, and achievement motives and behavior as related to social networking sites (SNS) in a sample of 40 participants. SNS appear to be designed to enable social connection via the Internet, so the potential for influence of the affiliation motive seemed self- evident. Additionally, we hypothesized that the power motive drives certain aspects of SNS behavior such that individuals with a high power motive have a larger number of friends and upload more pictures. The results of regression analyses showed that the explicit affiliation motive and the explicit power motive were related to different outcome of SNS activity. Specifically, the explicit power motive predicted number of friends and number of uploaded pictures, whereas time spent on SNS per day was predicted by the explicit affiliation motive. Only weak evidence was found for an influence of implicit motives on SNS activity.

Bias in Hydroacoustic Estimates of Fish Abundance due to Acoustic Shadowing: Evidence from Day–Night Surveys of Vertically Migrating Fish

1992 ◽  
Vol 49 (10) ◽  
pp. 2179-2189 ◽  
Author(s):  
A. R. Appenzeller ◽  
W. C. Leggett
Keyword(s):  
Fish Community ◽  
Acoustic Scattering ◽  
Fish Abundance ◽  
Diel Changes ◽  
Light Levels ◽  
Abundance Estimates ◽  
Acoustic Quantification ◽  
Acoustic Methods ◽  
Acoustic Surveys ◽  
Acoustic Shadowing

We investigated the hypothesis that fish schooling behavior leads to underestimation of fish abundance when assessed by acoustic methods. Current methods for acoustic quantification of fish abundance rely on the assumption that fish biomass and numerical fish abundance are linearly related to acoustic scattering under all natural fish densities. However, cage experiments as well as field observations have indicated that acoustic shadowing effects occur at very dense and large aggregations of fish. Acoustic surveys of the pelagic fish community of Lake Memphremagog, Quebec, were conducted when fish were aggregated and dispersed. These differences in aggregation were related to diel responses to light levels. We found that estimates of fish abundance, as measured by echo integration, were consistently and significantly lower when fish were aggregated in dense schools. This bias was not due to diel changes in average echo level per fish, which exhibited no relationship to diel changes in vertical and hortizontal distributions. We conclude that the reduced abundance estimates obtained when fish were aggregated resulted from acoustic shadowing. Our data suggest that this bias may be as large as 50%.

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