scholarly journals Diving behaviour of whale sharks in relation to a predictable food pulse

2005 ◽  
Vol 3 (6) ◽  
pp. 109-116 ◽  
Author(s):  
Rachel T Graham ◽  
Callum M Roberts ◽  
James C.R Smart
Keyword(s):  
Frequency Domain Analysis ◽  
Diving Behaviour ◽  
Whale Shark ◽  
Transform Method ◽  
Fast Fourier Transform Method ◽  
Fish Spawning ◽  
Whale Sharks ◽  
Spawning Periods ◽  
Fine Resolution ◽  
Free Ranging

We present diving data for four whale sharks in relation to a predictable food pulse (reef fish spawn) and an analysis of the longest continuous fine-resolution diving record for a planktivorous shark. Fine-resolution pressure data from a recovered pop-up archival satellite tag deployed for 206 days on a whale shark were analysed using the fast Fourier Transform method for frequency domain analysis of time-series. The results demonstrated that a free-ranging whale shark displays ultradian, diel and circa-lunar rhythmicity of diving behaviour. Whale sharks dive to over 979.5 m and can tolerate a temperature range of 26.4 °C. The whale sharks made primarily diurnal deep dives and remained in relatively shallow waters at night. Whale shark diving patterns are influenced by a seasonally predictable food source, with shallower dives made during fish spawning periods.

The application of pulsation ratio preprocessing method in researching density wave instability

2018 ◽  
Vol 10 (3) ◽  
pp. 140-145
Author(s):  
Yefei Liu ◽  
Yang Liu ◽  
Xingtuan Yang ◽  
Haijun Jia
Keyword(s):  
Frequency Domain ◽  
Density Wave ◽  
Annular Channel ◽  
Frequency Domain Analysis ◽  
Wave Instability ◽  
Two Phase ◽  
Transform Method ◽  
Modified Method ◽  
Fast Fourier Transform Method ◽  
Dc Component

A modified Fast Fourier Transform method based on the pulsation ratio preprocessing is carried out in this study. When the density wave instability occurs, the method is applied to capture the characteristic signals in the frequency domain. Thus, the stable boundary in two-phase flow can be recognized accurately. In this paper, experiments are conducted in a system based on a narrow annular channel. The method is verified through two groups of experimental data collected in different conditions. The results indicate that the modified method can avoid the problem of DC component spectrum leakage in traditional frequency-domain analysis with the false value interference eliminated. Accordingly, it can improve the accuracy of boundary identification effectively when the instability occurs.

scholarly journals Changes in diving behaviour and habitat use of provisioned whale sharks: implications for management

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Gonzalo Araujo ◽  
Jessica Labaja ◽  
Sally Snow ◽  
Charlie Huveneers ◽  
Alessandro Ponzo
Keyword(s):  
Endangered Species ◽  
Habitat Use ◽  
Metabolic Rate ◽  
Sustainable Tourism ◽  
Diving Behaviour ◽  
Whale Shark ◽  
Rhincodon Typus ◽  
The World ◽  
Whale Sharks ◽  
Temperature Depth

Abstract Whale shark (Rhincodon typus) tourism is increasingly popular at predictable aggregations around the world, but only a few use provisioning to ensure close interactions. Understanding the effects of provisioning on the behaviour of this endangered species is critical to manage this growing industry. We recorded the diving behaviour and habitat use of juvenile whale sharks (n = 4) for a mean of 49.5 provisioned and 33.8 non-provisioned days using temperature-depth-recorders. We found that time spent at the surface (< 2 m) between 6 am and 1 pm increased ~ sixfold, while timing of deep dives shifted from 4–10 am to 10 am–2 pm, i.e. near or at the end of the provisioning activities. The shift might be related to a need to thermoregulate following a prolonged period of time in warmer water. These changes could have fitness implications for individuals frequently visiting the provisioning site. Based on recorded amount of time spent in warm waters and published Q10 values for ectotherms, we estimate a 7.2 ± 3.7% (range 1.3–17.8%) higher metabolic rate when sharks frequent the provisioning site. The observed behavioural, habitat use, and potential fitness shifts should be considered when developing guidelines for sustainable tourism, particularly in light of new provisioning sites developing elsewhere.

Study on Measurement of Thin Film Thickness with Lateral Shearing Interferometry

2013 ◽  
Vol 718-720 ◽  
pp. 848-852
Author(s):  
Jun Hong Su ◽  
Ying Shi ◽  
Jin Man Ge
Keyword(s):  
Film Thickness ◽  
Transform Method ◽  
Shearing Interferometry ◽  
Platform Process ◽  
Fast Fourier Transform Method ◽  
Lateral Shearing ◽  
Phase Unwrap ◽  
Technical Indicator ◽  
Lateral Shearing Interferometry ◽  
Shearing Interference

The film thickness is an important technical indicator of film devices, and its accuracy directly affects various performances of optical components. In fabrication process of film device, fast and accurate measurement of film thickness has positive significance on product quality control. In this paper, measure film thickness with lateral shearing interferometry. Collect interferograms through structured lateral shearing interference platform, process interferogram with Fast Fourier Transform method to extract phase, unwrap the wrapped phase to achieve phase value. Finally, calculate film thickness based on lateral shearing interference principle. The thickness of sample is 119.6800nm measured by this method, basically the same with the result 120.6036nm that measured by ZYGO interferometer. This experiment shows that lateral shearing interferometry not only suit to measurement of film thickness, but also abundant high-precision method of measuring film thickness, and has high practical value.

An Approach to the Use of an External Magnetic Field As a Diagnostic Sign of an Asynchronous Motor Malfunction

2021 ◽  
Vol 64 (3) ◽  
pp. 18-23
Author(s):  
Ildar Yamansarin ◽  
◽  
Mikhail Salikov ◽  
Alexander Padeev ◽  
Dmitry Surkov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Short Circuit ◽  
Asynchronous Motor ◽  
Technical Condition ◽  
Stator Winding ◽  
Electric Motors ◽  
Transform Method ◽  
Fast Fourier Transform Method ◽  
Measurement Location

The article deals with the issues related to the possibility of diagnosing the technical condition of an asyn-chronous electric motor by an external magnetic field. The justification of the problems associated with the di-agnosis of electric motors is given. The difficulties that arise when measuring the external magnetic field of electric motors, as well as the devices with which it is possible to carry out measurements, are described. The re-lationship between the EMF of the sensor and the external magnetic field is shown. The results of processing the EMF waveforms induced by an external magnetic field in an inductive sensor for various electric motors are presented. The processing was carried out by the fast Fourier transform method. The external magnetic field contains the first harmonic and various harmonics that are multiples of the combination of the stator teeth, or the sum of the stator and rotor teeth that fall on one pair of poles. The ratio of the amplitudes of the first and tooth harmonics is affected by the measurement location and the orientation of the sensor. Diagrams showing the ratio of the main and tooth harmonics at different points of the motor body are constructed. The depend-ences of the harmonic amplitudes on the magnitude of the magnetizing current of the stator are given. Changes in the amplitudes and spectrum of harmonics in the presence and absence of an inter-turn short circuit in the stator winding are shown. Diagrams of the circular external magnetic field for the main and higher harmonics are constructed. The study shows the possibility of using an external magnetic field to detect inter-turn short circuits of the stator winding.

scholarly journals Sizing and scarring of whale shark (Rhincodon typus Smith, 1828) in the Cenderawasih Bay National Park

2021 ◽  
Vol 21 (3) ◽  
pp. 199-213
Author(s):  
Yusup A Jentewo ◽  
Roni Bawole ◽  
Tresia S Tururaja ◽  
Mudjirahayu Mudjirahayu ◽  
Zeth Parinding ◽  
...  
Keyword(s):  
National Park ◽  
The Body ◽  
Whale Shark ◽  
Gill Slit ◽  
Rhincodon Typus ◽  
Photo Identification ◽  
Dorsal Fin ◽  
Total Length ◽  
Whale Sharks ◽  
Photo Collection

This study aims to determine the total length and scar condition of the body of whale sharks (Rhincodon typus) in Cendrawasih Bay National Park (TNTC), Papua-Indonesia. Photo-identification was used to identify individuals of the whale shark R. typus based on spot patterns behind the last gill slit of each individual. Photo-identification was also used to determine the scar of the whale shark. The total length of whale sharks were estimated based on the length of a snorkeller (assumed to be 1.6 m) swimming alongside the whale shark. We identified 21 individuals of R. typus. Of these 21 individuals, 14 were new sightings and seven were re-sightings that have been recorded in the previous photo collection database. R. typus ranged in size from 2 to 5 m total length (average 3.78 m, ±0,86, N= 21). Based on their size, all individuals of whale shark were categorized as juvenile. 52% of R. typus identified had scars and 38 % were not and 10% were unknown. The majority of whale sharks had amputation (12 individuals) and abrasion (7 individuals) scars. Scars occurred most often on the caudal fin and dorsal fin, five and four individuals respectively. This information is useful for understanding potential threats and designing better management programmes for R. typus conservation in TNTC.

scholarly journals presence of whale sharks based on oceanographic variations in Cenderawasih Bay National Park, Papua, Indonesia

2021 ◽  
Vol 22 (11) ◽  
Author(s):  
JAFRY FERDINAN Manuhutu ◽  
DEWA GEDE RAKA WIADNYA ◽  
ABU BAKAR SAMBAH ◽  
ENDANG YULI HERAWATI
Keyword(s):  
National Park ◽  
Additive Model ◽  
Environmental Parameters ◽  
Analysis Data ◽  
Current Speed ◽  
Habitat Modeling ◽  
Sea Surface ◽  
Observation Data ◽  
Whale Shark ◽  
Whale Sharks

Abstract. Manuhutu JF, Wiadnya DGR, Sambah AB, Herawati EY. 2021. The presence of whale sharks based on oceanographic variations in Cenderawasih Bay National Park, Papua, Indonesia. Biodiversitas 22: 4948-4955. Oceanographic factors have an important role in the study of estimating the distribution of fish resource habitats. Sea Surface Temperature (SST), Sea Surface Chlorophyll (SSC), Current Speed, Sea Surface Height (SSH), and bathymetry are important parameters that have been used in estimating the habitat of certain species. Through analyzing these environmental factors, research on the appearance and distribution of whale shark habitats in the Cenderawasih Bay National Park in Papua, Indonesia, utilized field observation data and satellite imagery. This study applied data on the presence of whale sharks and oceanographic parameter data from satellite recordings during 2019 – 2020. Analysis of the relationship and habitat modeling between the monthly presence of whale sharks and environmental parameters was carried out through the Generalized Additive Model (GAM) statistical approach and spatial analysis through the Geographic Information System approach. In the GAM analysis, data on the presence of whale sharks was used as a response variable. In contrast, the predictor variables consisted of SST, SSC, current speed, SSH, and bathymetric data. The results showed that the highest frequency of whale shark presence occurred in the transitional monsoon, with an average presence of 31.77 ± 4.00 %. The study also showed that all predictors showed a highly significant relationship (P < 0.001) to the number of whale sharks present. SST values range from 30.3 – 31.3 °C, SSC of 0.39 – 0.86 mg/L, the current speed of 0.46 – 0.65 m/s, SSH showed 0.63 to 1.00 cm, and bathymetry between 40 – 50 m . In the GAM model, the SST and SSC parameters were the two most important parameters that affect the presence of whale sharks, followed by SSHD, depth (bathymetry), and current parameters.

scholarly journals Regional connectivity of whale sharks demonstrated using photo-identification – Western Atlantic, 1999 - 2013

2013 ◽  
Author(s):  
Jennifer McKinney ◽  
Eric R Hoffmayer ◽  
Jason Holmberg ◽  
Rachel Graham ◽  
Rafael de la Parra ◽  
...  
Keyword(s):  
Population Size ◽  
Transition Probabilities ◽  
Regional Cooperation ◽  
Individual Heterogeneity ◽  
Whale Shark ◽  
Western Atlantic ◽  
Entire Study ◽  
Photo Identification ◽  
Initial Identification ◽  
Whale Sharks

Background: Although whale sharks (Rhincodon typus) occur circum-globally, most studies focus on feeding aggregations in small regional areas. Photo identification is a proven tool in assessing population size and structure. While population estimates have been obtained for individual aggregation sites, there has been a lack of broader estimates despite known movement. The aim of this work is to demonstrate connectivity throughout the Gulf of Mexico (GOM) and Caribbean, and provide the first regional population estimate. Methods: Photographs submitted to the ECOCEAN Whale Shark Photo-ID Library Sightings were used to identify individual sharks using techniques described in Holmberg et al. (2009). Sightings data were used to assess the lagged identification rate (LIR) in order to investigate residency, regional mixing, population size, and transition probabilities using modules within SOCPROG 2.4. Results: Identifications from 1998 – 2013, were obtained from Belize (n =132), Mexico (n=3642), Honduras (n = 360), and the USA (n=147). Fifty-four individual sharks were seen in more than one country and used for analysis. For the entire study area, LIR decreased rapidly between one and 64-127 (mean 94.4) days then slightly increased between 256-511 (mean 381.2) days, suggesting a near-annual resighting periodicity. Estimates of mean population size from the best-fitting model were 1897.39 ± 414.30 S.E. (95% C.I. 1191.77 – 2784.03). Evidence suggests individual heterogeneity in movement patterns. Resightings were most likely to occur in the country where initial identification occurred, with the exception of Belize. The highest site fidelity was in Mexico, followed by USA. Conclusions: This study demonstrated individual heterogeneity, fidelity to initial identification site and regional linkages. These data suggest that national and regional cooperation is required for successful whale shark management in the West Atlantic.

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