A Comparison of Computer-Based Methods for Estimating the Age of Animals
- PDF / 569,463 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 17 Downloads / 226 Views
IGINAL PAPERS
A Comparison of Computer-Based Methods for Estimating the Age of Animals V. V. Sukhanova, b, * and N. I. Selina aZhirmunsky
National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia b Far Eastern Federal University, Vladivostok, 690001 Russia *e-mail: [email protected] Received July 4, 2019; revised October 21, 2019; accepted November 28, 2019
Abstract—The advantages and disadvantages of statistical methods for estimating the age of animals that lack recording structures are discussed in the article. The discussion is supported by examples from studies on the growth of the bivalve mollusk Mizuhopecten yessoensis (Jay, 1857). The age of individuals of this species can easily be determined by morphological marks on the shell surface. This makes it possible to calculate the percentage of erroneous age estimates through various statistical procedures. The following methods have been comprehensively tested: building a histogram, cumulative frequency curve, and dendrogram, as well as K-means. The algorithms that form the basis of these methods are described in brief. Some practical recommendations on their use are provided. Keywords: cluster, identification of age groups, dendrogram, K-means method DOI: 10.1134/S1063074020050090
INTRODUCTION Assessment of the age structure of a population and the growth of its constituent individuals is an important problem that can be solved by using so-called recording structures [8]. These can be solid, often mineralized parts of the body that do not decompose during the animal’s life: fish scales, otoliths, teeth, bones, shell, etc. [2, 5, 6, 12, etc.]. Annual marks on these structures that form due to the seasonal periodicity in the growth process make it possible to estimate age of an individual. As a rule, body growth slows in the cold winter and accelerates in the warm summer. The pulsed variations in growth rate cause the formation of so-called annuli (annual rings), resembling the growth rings on cross sections of tree trunks. Many animals lack recording structures. These include arthropods, which shed their exoskeleton during each molt, as well as jellyfish, echinoderms, and some mollusks, in which solid body formations that could preserve traces of the past growth are either absent or reduced with age. The age of such organisms, if they grow in nature rather than in a laboratory, cannot be determined. Here, the following issue may be of help: in temperate latitudes, the process of reproduction of animals during the year occurs within a short period of time. As a result, newborn individuals are recruited to their population within a compact group almost simultaneously. Intermittent seasonal
breeding process often results in a gap between neighboring generations, which is found in their body size– frequency distribution. This hiatus between generations allows considering such size clusters as singleage groups. Thus, the problem arises of distinguishing these groups in the size–frequency distribution
Data Loading...
