Qualitative Assessment of Golden Gray Mullet Stocks (Liza aurata Risso, 1810) in the Caspian Sea (1991-2011)

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.