Fish Hatchery Management - fisheries & aquaculture

GLOSSARY 501Water HardeningProcess by which an egg absorbs water that accumulatesin the perivitelline space.Water Quality As it relates to fish nutrition, involves dissolved mineralneeds of fishes inhabiting that water (ionic strength).Water Treatment Primary: removal of a substantial amount ofsuspended matter, but little or no removal of colloidal and dissolvedmatter. Secondary: biological treatment methods (for example, bycontact stabilization, extended aeration). Tertiary (advanced):removal of chemicals and dissolved solids.Weir A structure for measuring water flow.W'estern Gill Disease See Nutritional Gill Disease.Whirling Disease A disease of trout caused by the sporozoan protozoanMyxosoma cerebralis.White Grub An infestation by the metacercarcial stage of Neodiplostomummulticellulata in the liver of many freshwater fishes.White Spot Disease A noninfectious malady of incubating eggs or onthe yolk sac of alevins. The cause of the disease is thought to bemechanical damage. Also see lch.Yellow Grub An infestation by the metacercarial stage of Clinostomummarginatum.Yolk The food part of an egg.Zooplankton Minute animals in water, chiefly rotifers and crustaceans,that depend upon water movement to carry them about, having onlyweak capabilities for movement. They are important prey for youngfish.Zoospores Motile spores of fungi.Zygote Cell formed by the union of two gametes, and the individualdeveloping from this cell.