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Abbreviations, definitions and terms


ventral posterior section of a fish containing the viscera (other than heart and lungs)


removal of the skin or mucous membrane of a fish by friction


lack of oxygen (causing death)

beam trawl:

a trawl with the horizontal opening maintained by a beam, usually made of metal, which may be between 3 and 12 m long; beam trawls mainly are used to catch flatfish and shrimp


fauna and flora residing in or on the sea bed


materials that are capable of being degraded by biological mechanisms


rupture of the blood vessels in a tissue with leakage of blood into the immediate surrounding tissues (synonymous with contusion)


the part of the catch that is not targeted


Bycatch Reduction Device - a physical device installed in a fishing gear that is designed to reduce bycatch


the capability of a fishing gear to catch fish or other organism during a fishing operation


the posterior section (or bag) of a funnel-shaped fishing gear, where the catch is collected during the tow

codend selectivity:

the selection processes occurring in the codend

cover exposure:

the interaction between cover sampling time and towing speed with respect to fish swimming in the codend cover, and its effect on their survival


a reduction in ambient pressure (synonymous with depressurization)


the excessive loss of water from tissues


found near sea bed (demersal trawl = bottom trawl)

diamond mesh:

conventional rhomboid shape of meshes in sheet netting

discarded catch:

the component of bycatch returned to the sea, owing to economic, legal or other considerations

discard rate:

the proportion of total catch that is discarded

discard mortality:

proportion of discarded bycatch that dies as a result of capture, handling, injury and predation


the outer living layer of the skin, the epithelium, covering the body


a fish passing through a trawl into the codend and out through the codend meshes (or through a BRD)

escape mortality:

proportion of fish that die (per unit time) as a result of stress and injury incurred when selected out of the trawl codend, prior to the catch being landed on deck (= post-selection mortality)

extension (codend):

section of netting between the trawl body and the codend; may be tapered, but the taper is much less than that of the trawl body (synonymous with codend extension piece)

fish mortality:

mortality in the population of a species generated by fishing over time; usually expressed as a percentage of the initial population


species belonging to the order Perciformes including several related families such as the Gadidae, Merlucciidae etc.

gas bladder:

synonymous with swim bladder

grid (sorting grid):

BRD made of parallel bars, often used to separate fish of different sizes

ground gear:

connected sections of wire or chain, protected with rubber discs or various types of bobbins, attached to and in front of the fishing line to protect the lower leading margin of the bottom trawl from ground damage while maintaining ground contact

ghost fishing:

fish mortality associated with lost or discarded fishing gears


the main respiratory and excretory organ of fish


a carbohydrate and sugar, the main source of energy in animals; forms the basic carbohydrate component of glycogen


the main polysaccharide energy store of animal cells, consists of long chains of glucose units


a condition of limited dissolved oxygen; below levels necessary to support most animal life


International Council for the Exploration of the Sea


the invasion of a host by a living pathogen (virus, bacterium, parasite) resulting in a diseased state in the host (organism, organ, tissue or cells)


a defensive action by living tissue to injury or infection

lactic acid:

an organic acid formed by anaerobic metabolism in muscle during exercise (synonymous with lactate)

landed catch:

the portion of the catch that is landed (often the same as the retained catch)

mean retention length:

the length at which a fish has a 50 percent probability of being retained or escaping after entering the codend


Minimum Landing Size


rate of death in a population (of individuals)

Nordmøre grid:

a BRD comprising a diagonal deflecting grid placed in, or anterior to, a codend


the process by which fish maintain a stable electrolyte concentrations in their tissues and blood

osmoregulatory system:

the organs and mechanisms by which fish maintain stable electrolyte concentrations in their tissues and blood; includes the gills, kidneys and behavioural adaptations

otter trawl:

a large funnel-shaped net rigged with two hydrovanes (trawl doors or otter boards) that horizontally open the mouth during towing


any organism or substance that causes disease in a host

sampling time:

the period that the codend cover, or the collection cage attached to it, retains (samples) fish as they escape from the trawl codend

selection curve:

the percentage of fish of a particular species that are retained, for instance by the codend, expressed in graphic form against their length


the selectivity of a fishing gear is a measurement of the selection processes; it describes the relative retention rate of different sizes and species by the gear

sexual maturity:

the development of an individual with respect to its sexual organs (gonads)

skin damage:

damage to any of the multiple layers of fish skin, as determined by the staining of damaged tissues and/or the visual or image analysis assessment of the area of damaged tissue

square mesh:

mesh shape originating from mounting netting with 45° deviation from its normal direction so that the bars run

parallel and at 90° to the trawl axis

square-mesh window:

a BRD comprising a rectangular piece of netting with square-shaped meshes, usually inserted into upper panel of a codend or extension to increase the escape of non-target fish


the adaptive physiological and behavioural changes resulting from a variety of environmental or other stimuli (stressors)


fish that do not die when selected out of the gear, such as the trawl codend (and that survive at least to the end of the monitoring period of an experiment)


Spawning Stock Biomass

swim bladder:

an organe within the body of a fish that allows the fish to remain neutrally buoyant at various depths of water by adjusting the gaseous content of the space (synonymous with gas bladder)

target catch (species):

the intended catch of a fishing activity in terms of species or group of species


Total length of fish

trawl belly (body):

a series of tapering sections of the trawl between the lower wings and the extension

trawl selection:

the selection of fish by a trawl is considered to be the process that causes the catch of the trawl to have a different composition from that of the fish population in the area where the trawl is being used

unaccounted mortality:

the subcomponents of fish mortality that may include discard mortality, escape mortality, drop-out mortality, ghost fish mortality, avoidance mortality, habitat degradation mortality, and illegal, misreported and unreported catch

unobserved mortality:

mortality caused by encounters with fishing gear that do not result in capture

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