mesh size — a size of screen or of particles 

 passed by it in terms of the number of open- 

 ings per Hnear inch. Also known as mesh. 



microwave radiometry — a receiver for detect- 

 ing microwave thermal radiation and simi- 

 lar weak wide band signals that resemble 

 noise and are obscured by receiver noise; 

 examples include the Dicke radiometer, 

 subtraction type radiometer and two- 

 receiver radiometer. 



over-the-horizon radar — long range radar in 

 which the transmitted and reflected beams 

 are bounced off the ionosphere layers to 

 achieve ranges far beyond the line of sight. 



pelagic fish — organisms living in the open 

 sea, including both plankton and nekton. 



population — a group of organisms occupying 

 a specific geographic area. 



recruitment — young fish that just become 

 available (vulnerable) to the fishing gear. In 

 long-lived species only a portion of a year 

 class may be recruited each year until 

 finally all are vulnerable. 



remote sensing — sensing by a power supply, 

 of voltage directly at the load, so that varia- 

 tions in the load lead drop do not affect load 

 regulation. 



seine net — a net used to catch fish by encircle- 

 ment usually by closure of the two ends and 

 the bottom. 



seining — surrounding a shoal of fish with a 

 long net, suitably buoyed and gradually 

 drawn closer until the fish can be readily 

 removed. 



stock — a population of a species which oc- 

 cupies a specific geographical location, 

 especially at the time of reproduction. 



stock assessment — the study of individual 

 populations of fish in order to determine 

 the size and composition of the population 

 as well as estimates of possible yields. 



stock enhancement — procedures whereby the 

 total amount of edible product (biomass) is 

 increased by increasing the number of 

 animals and/or size of animals in the 

 population. 



trolling — method of angling whereby an ar- 

 tificial line or natural bait is drawn behind a 

 moving boat at any depth from the surface 

 to the bottom and at varying speeds accord- 

 ing to the species of fish being sought. Ac- 

 complished in all types of craft. 



trophic level — any of the feeding levels 

 through which the passage of energy 

 through an ecosystem proceeds, examples 

 are photosynthetic plants, herbivorous 

 animals, and micro organisms of decay. 



utilization — use of all fishery products both 

 edible and inedible. Estimated disap- 

 pearance of the total supply of fishery prod- 

 ucts both edible and inedible on a round- 

 weight basis without taking into considera- 

 tion beginning or end stocks. 



year class — all of the progeny of the reproduc- 

 tion from any particular year. In species 

 with fluctuatory spawning success the 

 progeny of the successful spawning of one 

 year class may dominate the population at 

 successive ages for several years. 



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