qualitative assessment of golden gray mullet stocks (liza aurata risso, 1810) in the caspian sea (1991-2011)

Authors

حسن فضلی

بخش ارزیابی ذخایر، پژوهشکده اکولوژی دریای خزر، ساری، ایران غلامرضا دریانبرد

بخش ارزیابی ذخایر، پژوهشکده اکولوژی دریای خزر، ساری، ایران

abstract

the main objective of the present study was qualitative assessment of golden gray mullet stocks by using indicators of overfishing in iranian waters of the caspian sea during a long period (1991-2011). three fisheries indicators in catch were: 1. percentage of mature fish, with 100% as target; 2. percent of specimens with optimum length, with 100% as target; and 3. percentage of mega-spawners, with 0% as target, and if no upper size limit exists, 30-40% as representative of reasonable stock structure. over this period, the condition factor of golden gray mullet showed decreasing trends, declined from 1.16 in 1993-1994 to 1.01 in 2010-2011. the range of length with optimum yield was between 31.8-38.8 cm, using biological parameters. the mega-spawner measured as fish a size larger than 38.8 cm. according to these three indicators, the percentage of mature (fork length>28 cm), optimum size and mega-spawners were ranged between 58.6%-88.4%, 26.4%-47.6% and 6.8%-29.0%, and were averaged (±s.d) 76.0%±6.78, 36.1%±5.44 and 18.9%±5.71, respectively. therefore, for conservation and revitalization of golden gray mullet in the caspian sea, the target would be to all (100%) fish spawn at least once, using bigger mesh size in sac (e.g. 33 mm, during whole fishing season), also, the aim would be to implement a fishing strategy that result no (0%) mega-spawners being caught, and the main catch focus on optimum length. also, the start of the fishing season should be delayed in order for stocks to complete their spawning.

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شیلات

جلد ۶۵، شماره ۳، صفحات ۳۰۷-۳۱۵

Keywords
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