Otolith microchemical analysis
The concentrations of elements and isotopes in otoliths are compared to those in the water in which the fish inhabits in order to identify where it has been.In non-ostariophysian fishes, the largest of the three otoliths, or ear bones, the sagitta is analyzed by one of several methods to determine the concentrations of various trace elements and stable isotopes.If this migration is not discovered then overfishing of the stock may occur because managers assume there is double the amount of fish.Today otolith microchemistry provides a simpler way to assess migration patterns of fish.It has provided an accurate way to assess the natal origin of fish without collecting them on the spawning grounds.Calcium carbonate is diffused through the endolymph cell membrane and the aragonite layers are permanently deposited in discrete increments.While delineating fresh waters from marine is relatively straightforward, finer-scale resolution is required to examine spatial and temporal variation within biomes.All beam based techniques begin with cutting the otolith width wise through the core to reveal a cross section containing every layer from the origin outward.For temporal variation studies, a transect from the core through all the layers to the outer edge of the otolith is analyzed with the beam.