Determine the age of fish like the aging of a tree, because it permanently forms deposits of growth. Investigators research special structures that expands progressively when the fish gets older. One commonly finds that accurately through looking at scales or watching of otoliths, so the internal ears of bones.
By means of reading of the rings of growth, also called annuli, in various parts it is possible to estimate age quite a lot exactly. Between those parts is scale, otolith, opercular bone, vertebra and slices of fin rays either dorsal except dorsal spine. Except that, teeth, eye lens, fin spines, jaw bones, pectoral girdle and opercular sequence also served for the same.
How to Tell the Age of a Fish
Every pair of annuli on scale normally points one year of growth. They show as black and white strips. The first black strip usually shows the finish of the first year, when the fish passed winter in freshwater.
New growth occasionally covers older rings, but those show if you break the otolith by means of two. The use of method for estimate age depend of fish species and of its habitat. For instance clear seasons, as heat to cold or moisture to dryness, ease the cause.
Sciado of age matter for management of populations. Number of fishes in crowd, so group born in one year, decline annually. Known age gives measure about mortality because of natural causes and capture.
That does not lack in fisheries, where some species bear in two years and others in three. Too much capture in two years risk that they perish before bear and replace themselves. In bigger age fishes usually grasiĝas and move more slowly.
Because of that predators more commonly choose them, and so many do not reach old age.
Different species have different lifetimes. Some fishes live only one year, others until 50 years. Most of Pacific salmon dies after creation, between 2 and 7 years age.
Some little fish species last of three until seven years.