Glossary of Fishery Terms - H

H

• Habitat - the place where an organism lives.

• Halocline - a zone in which salinity changes rapidly.

• Harmful algal bloom (HAB) - an algal bloom that produces toxins detrimental to plants and animals. Scientists prefer this term to red tide, since not all algal blooms are harmful, nor do all algal blooms cause discoloration, and the blooms are not associated with tides.

• Harvest - the number or weight of fish caught and retained from a given area over a given period of time. Note that landings, catch, and harvest are different.

• Hatchery - the process of cultivating and breeding a large number of juveniles in an enclosed environment. The juveniles are then released into lakes, rivers or fish farm enclosures.

• High seas - waters outside national jurisdictions.

• Highly migratory species - a term which has its origins in the United Nations Convention on the Law of the Sea. It refers to fish species which undertake ocean migrations and also have wide geographic distributions. It usually denotes tuna and tuna-like species, shark, marlins and swordfish. See also transboundary stocks and straddling stocks.

• Husbandry - the farming practice of breeding and raising fish stock.

• Hypoxia - occurs in aquatic environments when dissolved oxygen becomes depletion to a level which is harmful to aquatic organisms.