The Influence of Otolithes ruber Consumption on Prey and Comparison with that Harvested by Fisheries

The Otolithes ruber is considered a valuable fish in the Indo-West Pacific. Estimates of the Q/B ratio and parameters of equations to ‘predict’ Q/B values for O. ruber in northwestern part of the Persian Gulf and the effects of different age-groups (age 1 to 6 year) on prey are presented. The age and food item of O. ruber were recorded on data collected from monthly samplings by bottom trawl during Oct 2007 to Sep 2008 and size frequency data were collected from commercial catches between Apr 2002 to Mar 2012. Food composition was analyzed by quantitative method. The effects of different age-groups on prey were calculated by biomass of the predator and the consumption rate of different age-groups. Six age group were identified. The biomass of stock was dominated by age-group 2 (3069 tons). Stomach contents of O. ruber included mostly shrimps and fish. Daily consumption of shrimp and all food items were 54 and 100 tons respectively. The highest and the lowest consumption rate and ratio of consumption to the stocked biomass were in age-groups 1 and 6, respectively. The Q/B ratios for shrimp and all food items were 3 and 5.57, respectively. Age-groups 2 and 3 had the most and age-group 6 the least effect on prey community. Shrimp consumption was greater during 2008-2009 than the minimum recorded in 2002-2003. Despite increasing biomass of O. ruber and increasing the consumption of shrimp, the shrimp catch was not much affected.