Estimation fisheries Return of Sturgeon fishes with use of tagging method
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AbstractTo understand fisheries return of sturgeon fishes a project with use of tagging method was approved in 1997 and its first phase started in 1999. Total of 266796 juveniles of Persian sturgeon, stellate sturgeon, Russian sturgeon, ship and Huso huso in 3 weight categories of under 3 gr., 3-5 gr. and over 5 gr. were tagged in the Shaheed Dr. Beheshti, Shaheed Marjani and Shaheed Rajayee sturgeon hatcheries were tagged using CWT tags and released into the rivers entering the Caspian Sea. Other than CWT tags some 192000 juvenile of Persian sturgeon, Russian sturgeon and ship sturgeons between 2-10gr. weight were tagged by barbel dissection. Trawl, gill net and beach seines were used to catch tagged sturgeons at the depths below 10 meters in the Caspian Sea. Trawling was carried out in 2000- 2001 and 35 juvenile of Persian sturgeon and 8 juvenile of stellate sturgeon were caught however none of them carried CWT tags. Gill net was sued in 2002 in Gilan and 2003 in Mazandaran and Golestan provinces and total of 1690 fish were caught including 1562 persian sturgeon, 99 stellate sturgeon, 17 ship sturgeon, 8 Russian sturgeon and 4 Husu huso. Nine specimens of Persian sturgeon over 5 gr. 11 specimens between 3- 5 gr. and 6 specimens below 3 gr. and 2 specimens of stellate sturgeon over 5 gr. were found to carry CWT tags. Based on formulas used for estimation of fish population, number of juvenile Persian sturgeon and stellate sturgeon in coastal areas of the Caspian Sea were estimated to be 1317750 and 470000 in 2002 and 5452772 and 91000 in 2003 respectively (calculations were based on CTW tags). Number of Persian sturgeon caught in beach seine in Gilan province in 2003 (1 st October- -21st December) was 2978 of which 37 specimens had their barbel dissected. Based on the formulas number of sturgeon juveniles in Gilan below 10 m in the year 2003 (with dissected barbel) estimated to be 4420000. Considering number of fish caught with dissected barbel this method along with CTW tagging method could be used as a tagging method to study fisheries return. As for suitable weight for release the obtained data (taking into account the limited duration of tagging and sampling) were not enough and the obtained results could be used as guideline for further work.
Publisher or UniversityIranian Fisheries Science Research Institute
Series : Nr84.1456;