Glossary of Fishery Terms - B

B

• Bait fish - are small fish caught for use as bait to attract large predatory fish. See forage fish.

• Bathypelagic - the open ocean or pelagic zone that extends from a depth of 1000 to 4000 meters below the ocean surface.

• Beach - a geological landform along the shoreline of a body of water, consisting of loose particles composed of rock, such as sand, gravel, shingle, pebbles, or cobble, or of shell fragments or coralline algae fragments.

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

• Bed - the bottom of a river, or watercourse, or any body of water, such as the seabed.

• Benthic zone - the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos.

• Benthos - aquatic organisms which live on or in the seabed, also known as the benthic zone. Included are both mobile animals, such as crabs and abalone, and non mobile animals, such as corals and sponges.

• Billfish - large, predatory fish characterised by their long sword-like bill. Billfish include the sailfish, marlin and swordfish. They are important apex predators feeding on a wide variety of smaller fish and cephalopods.

• Bioacoustics - in underwater acoustics and fisheries acoustics this term is used to mean the effect of plants and animals on sound propagated underwater, usually in reference to the use of sonar technology for biomass estimation

• Bimodal - a bimodal distribution is a distribution with two different modes which appear as distinct peaks. An example in fisheries is the length of fish in a fishery, which might show two or more modes or peaks reflecting fish of different ages or species.

• Biodiversity - is the variation of life forms within an area. In the context of fisheries the number and variety of organisms found within a fishery.

• Biomass - the total weight of a fish species in a given area. Can be measured as the total weight in tons of a stock in a fishery, or are be measured per square metre or square kilometre. The most successful species worldwide, in terms of biomass, may be the Antarctic krill, with about five times the total biomass of humans.

• Biotone - a region where a distinctive transition from one set of biota to another occurs. An example is the region where tropical and temperate waters mix.

• Biotoxins - natural toxins produced by organisms, often for use as a defence mechanism.

• Bony fish - fish that have a bony skeleton and belong to the class osteichthyes. Basically, this is all fish except for sharks, rays, skates, hagfish and lampreys.

• Bottom trawling - a fishing method that involves towing trawl nets along the sea floor. Bottom trawling can cause serious damage to sea floor habitats.

• Brackish water - water that has more salinity than fresh water, but not as much as seawater. It may result from mixing seawater with fresh water, as in estuaries.

• Breach - a whale's leap out of the water.

• Breaker zone - the zone where ocean surface waves approaching the shore commence breaking, typically in water depths between five and ten metres.

• Brood - the collective offspring of a species produced in a particular time span. See also cohort.

• Buoy - a floating object usually moored to the bottom. Buoys can be used as temporary markers, called dans, during Danish seine fishing to mark the anchor position of a net, or when fishing with lobster pots to mark the position of the pots.

• Bycatch - bycatch is the harvest of marine life and seabirds during fishing operations when other fish were the target. For example, bycatch might consist of a species which was not the targeted species, such as a shark caught on a tuna longline. Or it might consist of fish of the targeted species, but not of the targeted age or size. Some shrimp fisheries have a bycatch five times the weight of the caught shrimp. See also incidental catch.