A method for accounting and identifying the linear sizes of Caspian seals

© 2020. M.T. Baimukanov (1)*, L.A  Zhdanko (1), T.T. Baimukanov (1), E.S. Dauynev (1), S.E. Ryskulov (1), A.M. Baimukanova (1).
(1)- Institute of Hydrobiology and Ecology, Irgely 040916, Kazakhstan.
*e-mail: institute_he@ihe.kz


A method for accounting and identifying the linear sizes of Caspian seals (Pusa caspica) on rookeries, using multicopters

Abstract

A method was developed for processing the pictures taken from multicopters to count the number of Caspian seals and their linear sizes on their rookeries. A special protocol records the location (coordinates), date, time, survey altitude, the cloudiness across a scale ranging from one to ten, air temperature, wind speed, and picture numbering. A photo software editor (for example, Adobe Photoshop CS5) is used for counting the individuals and taking their measurements. Each seal image is allotted an individual serial number within one picture. Through flying over and photographing a rookery at different times of the day, the daily dynamics in the number of seals is estimated. If there are lots of seal groups on a rookery, it is recommended to assess their abundance, flying over the rookery along transects. Knowing the angle of the field of vision (FOV) of the multicopter and the altitude it operates at, the following formula can be applied, “A cathetus lying opposite the angle equals to the product of the second cathetus multiplied by the tangent angle”, to calculate the distance between the extreme points of a picture’s diagonal in the International System of Units (m, cm or mm) (SI). As the resolution in pixels is also known, calculating of the size of a pixel in SI can be performed per picture. The measurements of individual seal images in the pictures are converted from pixels into SI units. As a result, the length and the maximum width of seals can be established. These parameters are important for subsequent work to determine the size structure of seals on rookeries. Subsequently, having compiled a size-age key, the age structure of the groups of seals on their rookeries can be calculated.

To download the paper (the abstract in English is on p. 222): Baimukanov et al., 2020.

Photo by M.T. Baimukanov, the Director of the Institute of Hydrobiology and Ecology (Irgeli, Kazakhstan). Caspian seals. The Komsomolsky Bay, spring, 2017.

 

 

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