Glossary of Fishery Terms - A

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• Abundance - is a measure of how many fish are in a population or a fishing ground. See relative abundance and absolute abundance.

• Acoustic survey - a systematic gathering of information on fish availability and abundance using underwater sound.

• Acoustical oceanography - the use of underwater sound to map underwater topography and the contents of the sea.

• Aerial survey - a method of gathering information on surface fish movement and density by visual observation and photography from low-flying aircraft.

• Aggregation - is a term which can be applied to any grouping of fish, for whatever reason (or unknown reason) they are concentrating. See shoaling.

• Agricultural runoff - surplus water from agricultural land, often draining into rivers and then into the sea, and often enriched with nutrients, sediment, and agricultural chemicals.

• Alginate production - a gel substance extracted from brown algae and used industrially as a thickening agent for food and paint.

• Algal bloom - a rapid excessive growth of algae, generally caused by high nutrient levels, particularly phosphorus. When the algae die, algal blooms can deplete oxygen to the point where fish cannot survive.

• Artisan - someone who practices a craft as a livelihood, as opposed to an artist, who practices an art for its own sake.

• Artisan fishing - a term sometimes used to describe small scale commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques and traditional fishing boats.

• Anadromous - fish that live their adult lives in the ocean but migrate up fresh water rivers to spawn. Examples are Pacific salmon. Fish that migrate in the opposite direction are called catadromous.

• Anoxic sea water - sea water depleted of oxygen. See hypoxia.

• Anoxic sediments - sediments depleted of oxygen.

• Antarctic convergence - a line encircling Antarctica where cold, northward-flowing Antarctic waters meet and sink beneath the sub-Antarctic waters, creating an upwelling zone which is very high in marine productivity, especially in Antarctic krill.

• Aquaculture - the farming of freshwater and saltwater organisms including molluscs, crustaceans and aquatic plants. See also fish farming and mariculture.

• Availability - (1) the proportion of a fish population living where it can be fished. (2) catch per unit effort. (3) a term sometimes used to describe whether a given fish of a given size can be caught by a given type of gear in a given fishing area.