Estimating The Age Of Fish

picture info	Estimating The Age Of Fish Knowledge of fish age characteristics is necessary for stock assessments, and to develop management or conservation plans. Size is generally associated with age; however, there are variations in size at any particular age for most fish species making it difficult to estimate one from the other with precision.Helfman et al 1997 Therefore, researchers interested in determining a fish age look for structures which increase incrementally with age. The most commonly used techniques involve counting natural growth rings on the scales, otoliths, vertebrae, fin spines, eye lenses, teeth, or bones of the jaw, pectoral girdle, and opercular series. Even reliable aging techniques may vary among species; often, several different bony structures are compared among a population in order to determine the most accurate method. History Aristotle (ca. 340 B.C.) may have been the first scientist to speculate on the use of hard parts of fishes to determine age, stating in ''Historica Animalium' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Yellow Perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch, American river perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Samuel Latham Mitchill from New York. It is closely related, and morphologically similar to the European perch (''Perca fluviatilis''); and is sometimes considered a subspecies of its European counterpart. Other common names for yellow perch include American perch, coontail, lake perch, raccoon perch, ring-tail perch, ringed perch, and striped perch. Another nickname for the perch is the Dodd fish. Latitudinal variability in age, growth rates, and size have been observed among populations of yellow perch, likely resulting from differences in day length and annual water temperatures. In many populations, yellow perch often live 9 to 10 years, with adults generally ranging from in length. The world record yellow perch (; ) was caught in M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic irregular bone whose complex structure is composed primarily of bone, and secondarily of hyaline cartilage. They show variation in the proportion contributed by these two tissue types; such variations correlate on one hand with the cerebral/caudal rank (i.e., location within the backbone), and on the other with phylogenetic differences among the vertebrate taxa. The basic configuration of a vertebra varies, but the bone is its ''body'', with the central part of the body constituting the ''centrum''. The upper (closer to) and lower (further from), respectively, the cranium and its central nervous system surfaces of the vertebra body support attachment to the intervertebral discs. The posterior part of a vertebra forms a vertebral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]