Fisheries Glossary

agricultural runoff

water leaving areas of agricultural land use, usually enriched in nutrients, sediment, and agricultural chemicals.

algal bloom

the rapid excessive growth of algae, generally caused by high nutrient levels. Algal blooms can result in decreased oxygen in a body of water when the algae die, threatening the health of local marine life.

aquaculture

the cultivation of aquatic organisms (as fish or shellfish) especially for food; fish farming.

beam trawling

the simplest method of bottom trawling in which the mouth of the net is held open by a solid metal beam. The beam is attached to two "shoes" (solid metal plates), that are welded to the ends of the beam, and slide over and disturb the seabed. This method is mainly used on smaller vessels, fishing for flatfish or prawns, relatively close inshore.

billfish

fish with long, spear-like protrusions at their snouts, such as swordfish and marlin, that live near the upper layers of the ocean.

biodiversity

the number and variety of organisms found within a specified geographic region.

biomass

the total mass of living matter in a given environmental area.

bottom trawling

fishing method that involves towing trawl nets along the sea floor.

by-catch

unwanted marine creatures that are caught in the nets while fishing for another species.

cetacean

member of the group of marine mammals that includes whales, dolphins and porpoises.

climate

the weather in some location averaged over some long period of time.

climate change

variation in the Earth's global climate or in regional climates over time. Climate change involves changes in the variability or average state of the atmosphere over time periods ranging from decades to millions of years. These changes can be caused by natural processes on Earth, external factors including variations in sunlight intensity, and more recently by human activities.

climate variability

the way climatic variables (such as temperature and precipitation) depart from some average state, either above or below the average value, without significant changes to long-term averages.

collapse

significant depletion of a particular fish population, often cited as the point at which a population is down to 10 percent of previous levels.

dead zone

an area in an ocean or large lake where oxygen levels are extremely low, often due to the process of eutrophication. Observed incidences of dead zones have been steadily increasing since the 1970s.

demersal

living at or near the bottom of a body of water.

diadromous

fish that migrate between fresh and salt waters.

ecosystem

a community of living things and the environment in which they live.

ecosystem-based fisheries management (EBFM)

approach to fisheries management that that integrates ecosystem impacts into the management of fisheries. Thus, habitat, predators, and prey of the target species, as well as other ecosystem components and interactions, are taken into account in managing fisheries. This approach both ensures that ecosystems will be sustained, and provides the foundation for long-term sustainability of fisheries.

ecosystem-based fisheries management (EBM) tool

software or another highly documented method that can help implement EBFM by providing models of ecosystems or key ecosystem processes; generating scenarios illustrating the consequences of different management decisions on natural resources and the economy; or facilitating stakeholder involvement in planning processes.

El Niño

an abnormal warming of surface ocean waters in the eastern tropical Pacific. This climatic phenomenon occurs somewhat irregularly, but generally every 3 to 7 years, beginning around Christmastime (El Niño means Christ child). El Niño involves seasonal changes in the direction of the tropical winds over the Pacific and abnormally warm surface ocean temperatures; these changes can disrupt weather patterns and the migration habits of fish.

eutrophication

an increase in chemical nutrients—typically compounds containing nitrogen or phosphorus—in an ecosystem. Eutrophication in water often results in an increase in algae growth and decay, which can lead to decreased levels of oxygen and severe reductions in water quality and in fish and other animal populations.

fishing mortality rate (F)

a technical fishery science term that refers to the rate at which animals are removed from a stock by fishing (as opposed to natural causes).

global warming

the increase in the average temperature of the Earth's near-surface air and oceans in recent decades, as well as the projected continuation of this trend.

groundfish

fish that live on the bottom of the ocean, such as cod, haddock, or flounder.

harmful algal bloom (HAB)

an algal bloom that produces toxins which are detrimental to plants and animals.

hotspot

region with a high level of native species.

hypoxia

oxygen depletion; a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration and is harmful to aquatic organisms.

landing

the part of the fish catch that is put ashore. Most often, landings provide the only record of total catch; i.e. the landings plus discards.

marine managed area (MMA)

refers generally to an area of the marine environment with a marine resource conservation purpose. It includes both natural and cultural marine resources.

marine protected area (MPA)

officially, an MPA is any area of the marine environment that has been reserved by federal, state, tribal, territorial, or local laws or regulations to provide lasting protection for part or all of the natural and cultural resources therein. In practice, MPAs are defined areas where natural and/or cultural resources are given greater protection than the surrounding waters.

maximum fishing mortality threshold (MFMT or F_Threshold)

the fishing mortality rate that defines overfishing; a fishing mortality rate above F_Threshold for one year or more constitutes overfishing.

maximum sustainable yield (MSY)

the largest long-term average catch or yield that can be taken from a fish stock on a continuing basis without compromising the sustainability of the stock.

minimum stock size threshold (MSST or SSB_threshold)

usually 1/2 the stock biomass level that can produce Maximum Sustainable Yield (SSB_MSY).

nitrate

a water-soluble molecule made up of nitrogen and oxygen, commonly found in agricultural fertilizers.

overfished

status of a fish stock when the population size is smaller than the sustainable target set by the National Marine Fisheries Service.

overfishing

occurs when a fish stock is being fished at a fishing mortality rate that exceeds a sustainability threshold set by the National Marine Fisheries Service.

pelagic

belonging to the upper layers of the open ocean.

phosphate

a chemical compound containing phosphorous and oxygen, commonly found in agricultural fertilizers.

phytoplankton

tiny, free-floating, photosynthetic organisms in aquatic systems.

red tide

a common name for an algal bloom that the human eye perceives as discoloration in the water. The term "red tide" is a bit of a misnomer because blooms can appear greenish, brown, and even reddish orange depending upon the type of organism, the type of water, and the concentration of the organisms, and because they are not actually associated with tides.

single species management

fisheries management approach that focuses on the health of one species at a time.

spawning stock biomass (SSB)

the total weight of the fish in a stock that are old enough to spawn; the biomass of all fish beyond the age or size class in which 50% of the individuals are mature.

species density

the number of species in a sampled area.

stakeholder

anyone who has a stake or interest in the outcome of the project, as well as anyone one who is affected by the project.

sustainable yield

the number or weight of fish in a stock that can be taken by fishing without reducing the stock biomass from year to year, assuming that environmental conditions remain the same.

trade wind

a wind blowing almost constantly in one direction; especially a wind blowing almost continually toward the equator.

trawling

fishing by dragging a net behind a boat along the sea floor, weighted by anchors. This method can result in significant bycatch and habitat destruction.

upwelling

the rising of cold, nutrient-rich water from the deeper areas of the ocean to the surface.