Abstract
Abstract. Precipitation is the main driver of the water balance variability of the water over space and time, and changes in precipitation have very important implications for hydrology and water resources. Variations in precipitation over daily, seasonal, annual, and decadal time scales influence hydrological variability over time in a catchment. Flood frequency is affected by changes in the year-to-year variability in precipitation and by changes in short-term rainfall properties. Desiccation of the Caspian Sea is one of the world's most serious ecosystem catastrophes. The Persian Sturgeon (Acipenser persicus) caught under 10 m depth using bottom trawl net by research vessel during winter 2012, summer and winter 2013 and spring 2014 in east, central and west of southern parts of Caspian Sea, then, their diets were investigated. During 136 trawling in the aimed seasons, Persian sturgeon with 1 to 2 years old and 179.67 × 0.2 g (body weight) and 29.97 ± 0.4 cm (Total length) captured. Examination of stomach contents in the sturgeon specimens revealed that the food spectrum was composed of bony fishes (Neogobius sp., Atherina sp. and Clupeonella delicatula), invertebrates belonging to the family Ampharetidae polychaeta worms including (Hypanai sp. and Nereis diversicolor), various crustaceans (Gammarus sp. and Paramysis sp.). Investigation on stomach contents of sturgeon Acipenser persicus caught under 10 m depth in 2012 to 2013 surveys showed that there is significant difference in the consumed food. The most food diversity have been observed in winter 2013, also Polychaeta is the primary consumed food and crustacean is the secondary one (P > 0.05), no new types of food (such as bony fishes or benthics) have been observed on food chain of Acipenser persicus and shows no significant difference (P > 0.05).
Highlights
Prey abundance, feeding and food habits are important issues for both effective Caspian Sea fisheries management and conservation biology in aquatic environment, so Sturgeons one the most important and valuable fishes in the world and Caspian Sea is one of their most important habitat’s which 90 % of total world Caviar belongs to it (Ivanov et al, 1999)
In this case 115 immature Persian Sturgeons in 1 to 2 years old captured for feeding examination 90 % of caught sturgeon had food in stomach. comparative study of condition factor in sturgeon caught under 10 m depth showed the highest condition factor in eastern region (0.75 ± 0.25) in summer 2013 and the lowest one (0.26 ± 0.13) in western region of Southern part of Caspian Sea in spring
The results showed no significant differences in condition factor of Persian sturgeon (P >0.05) (Table 1)
Summary
Prey abundance, feeding and food habits are important issues for both effective Caspian Sea fisheries management and conservation biology in aquatic environment, so Sturgeons one the most important and valuable fishes in the world and Caspian Sea is one of their most important habitat’s which 90 % of total world Caviar belongs to it (Ivanov et al, 1999). In recent years sturgeon stock and catch has been decreased in their most important habitats (Pourkazemi, 1996; Ivanov et al, 1999; Moghim et al, 2006). Biological and feeding factors have great influence an sturgeon catch to determine these factors, we should investigate on sturgeon feeding competition and other relations between different habits of fishes in various places and time is of high importance (Moghim et al, 2006) should navigate the previous studies of researchers in this regards. During sturgeon stock assessment at southern part of Caspian Sea in 2006 to 2008, diets of Persian sturgeon investigated in different depths and various seasons. The aims of the study were (i) determine seasonal change on Persian sturgeon (ii) determine more details on sturgeon food composition and identification of food index to better understand Persian sturgeon feeding condition
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