Title: Comparison between commercial catches of Greenland halibut for trawl, longline, and gillnet

Final project
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Supervisors: Haraldur Einarsson
Greenland halibut; selectivity; trawl; longline; gillnet; distribution; mean length; depth; catch; discard.


At present, Greenland halibut in the ICES subares I and II is caught by three types of fishing gears: trawls, longlines and gillnets. This study helps to understand and estimate differences in catches using these different types of fishing gears, as well as the influence of these fisheries on the exploited stock. The material for this investigation is fishing data on the Greenland halibut which was collected by the Marine Research Institute of Iceland during the period 1970-2005. Selectivity parameters of trawl and longline are accepted from previous experimental work. Selectivity parameters for gillnet are estimated from data from the Marine Research Institute of Iceland. This study estimates the difference in mean length and sex composition for catches from trawls, longlines and gillnets. The mean length (62.5 ± 1.55) and female share (0.58 ± 0.04) of the annual catches from trawls are less than the mean lengths and female shares from gillnet and longline catches. The selectivity patterns, the length distributions of stock and the annual catches are used to estimate discard from various fishing gears. Discards from the trawl and gillnet fisheries are similar to or less than those from longline. It was determined that there was a good correlation between the mean length of catch of Greenland halibut and the sea depth. The difference between the mean lengths of industrial trawl catches and stock assessment survey catches demonstrated good selectivity of the commercial fishery. 

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