The qualitative index assessment of selective sturgeon gillnet fishing for sustainable exploration of the Caspian Searesources

 
In order to study the quality of the gillnets used for sturgeon fisheries in the estuaries leading to Caspian Sea, the fisheries cc of Iran (SHILAT) launched a sampling program on the types of nets currently utilized by fisherman in Anzali, Babolsar andTurkman ports, in Guilan, Mazandran andGoIestan provices respectively.Three types of nets were investigated as the following: 210 Dl18l100Imm (used to catch sevruga fish) 210 DI24l150z'mm catch Sturgeons) (used to  210 Di'60I25D!mm (used to catch Beluga) Three types of nets were used to catch sevruga sevrga, Acetra and Beluga respectively. There has been a noticeable decline in the quality of the nets, which was proportionate tothe duration of their use in actual fishing operation. The nets were classified in terms of quality decline of new nets as (100%), nets used in one fishing season as (75%), nets used in two fishing seasons as (50%) and nets used for three fishing seasons as (25%).  After having 1. Cut mashes of transverse, normal and 1DT x 10N, attempts were made to experiment the samples using dynamometer and twistmeter. The experiment entailed qualitative indexes such as the breaking power of iines, elacitlcity, Z score of twist, S twist. primary mesh bar and secondary mesh bar.  The results obtained, indicated that the average length of primary mesh bar for sevruga shows a meaningful difference at  95% of probability rate while the average '  secondary mash bar for huso huso indicates difference at 99% of probability on the normal probability curve.
 Key words:  Net, Gillnet, polyamide, Net quality, Caspian Sea.
 
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