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Age can be determined by counting growth rings in fish scales, otoliths, cross-sections of fin spines for species with thick spines such as triggerfish, or teeth for a few species. Each method has its merits and drawbacks. Fish scales are easiest to obtain, but may be unreliable if scales have fallen off of the fish and new ones grown in their ...
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 that “the age of a scaly fish may be told by the size and hardness of its scales.” [4] However, it was not until the development of the microscope that more detailed studies were performed on the structure of scales. [5]
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages.
Biodiversity is usually plotted as the richness of a geographic area, with some reference to a temporal scale. Types of biodiversity include taxonomic or species, ecological, morphological, and genetic diversity. Taxonomic diversity, that is the number of species, genera, family is the most commonly assessed type. [7]
Leptoid scales are found on higher-order bony fish. As they grow they add concentric layers. As they grow they add concentric layers. They are arranged so as to overlap in a head-to-tail direction, like roof tiles, allowing a smoother flow of water over the body and therefore reducing drag . [ 3 ]
At the individual level, genetic identification can enable estimation of population abundance and population increase rates within the framework of mark-recapture models. . The abundance of cryptic or elusive species that are difficult to monitor can be estimated by collecting non-invasive biological samples in the field (e.g. feathers, scat or fur) and using these to identify individuals ...
These methods can be used to study fish, as genetic material, in the form of environmental DNA (eDNA) or cells, is freely diffused in the water. This allows researchers to identify which species are present in a body of water by collecting a water sample, extracting DNA from the sample and isolating DNA sequences that are specific for the ...
Population viability analysis (PVA) is a species-specific method of risk assessment frequently used in conservation biology.It is traditionally defined as the process that determines the probability that a population will go extinct within a given number of years.