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Population dynamics of sturgeon in the southern part of the Caspian Sea / SEYED TAGHAVI-MOTLAGH

Swansea University Author: SEYED TAGHAVI-MOTLAGH

Abstract

Five years' data of the Beluga, Huso huso, Stellate Sturgeon, Acipenserstellatus, Persian Sturgeon, A. persicus and Russian Sturgeon, A. guldenstadti, in thesouthern Caspian Sea were analysed for sex and age, and length and weightcomposition. The von Bertalanffy growth parameters, and total, na...

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Published: Swansea 2024
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Ryland, John S.
URI: https://cronfa.swan.ac.uk/Record/cronfa68604
Abstract: Five years' data of the Beluga, Huso huso, Stellate Sturgeon, Acipenserstellatus, Persian Sturgeon, A. persicus and Russian Sturgeon, A. guldenstadti, in thesouthern Caspian Sea were analysed for sex and age, and length and weightcomposition. The von Bertalanffy growth parameters, and total, natural and fishingmortalities were estimated. Yield-per-recruit curves were derived for each species,based on growth parameters and mortality rates, and the optimum fishing mortality interms of yield-per-recruit was calculated as a basis for sturgeon fishery management inthe Caspian Sea.Age of the sturgeons was determined from the fin ray sections. In all fiveyears, for all the species, there were more females than males in the catches. Catchesof fish older than 20 years were a very low percentage.Von Bertalanffy growth parameters for each species were estimated for sexesseparately. For female Beluga, the values of L„ and K were estimated for threegrowth stanzas as 320 cm and 0.065 for juveniles, 450 cm and 0.029 for the middlestanza and 533 cm and 0.023 for older fish. For male Beluga and other species thevalues of and K were estimated both from Lmax and by using the Fishery ScienceApplication System (FSAS) computer program. and K for male Beluga wereestimated as 270 cm and 0.086 using Lmax 302 cm and 0.072. For female StellateSturgeon and K were 213 cm and 0.062 using Lmax, 188 cm and 0.104; and formales 190 cm and 0.083 from Lmax, 171 cm and 0.113. For female Persian SturgeonLm and K were 225 cm and 0.066 from Lmax, 207 cm and 0.079; and for males 197 ci aand 0.084, 186 cm and 0.105 respectively. For female Russian Sturgeon and Kwere 201 cm and 0.073 from Lmax, 192 cm and 0.082; and for males 189 cm and.077, 178 cm and 0.092 respectively. The value of total mortality (Z) depended on method of estimation. Forfemale Beluga Z was 0.21-0.67, for males 0.22-0.75; for female Stellate Sturgeon0.52-1.1, males 0.62-1.1; for female Persian Sturgeon 0.24-0.57, males 0.40-1.1; andfor female Russian Sturgeon 0.33-0.67, males 0.46-0.82.Natural mortality (M) was estimated from the growth parameters and K: forfemale and male Beluga 0.03 and 0.05; for female and male Stellate Sturgeon 0.07and 0.08; for female and male Persian Sturgeon 0.04 and 0.06; and for female andmale Russian Sturgeon 0.05 and 0.07.Fishing mortalities (F) were estimated as 0.45 and 0.33 for female and maleBeluga; 1.03 and 0.54 for female and male Stellate Sturgeon; 0.47 and 0.34 for femaleand male Persian Sturgeon; and 0.62 and 0.39 for female and male Russian Sturgeon.The optimum fishing mortalities (Fs) derived from yield-per-recruit calculations were0.07 and 0.16 for female and male Beluga; 0.42 and 0.30 for female and male StellateSturgeon; 0.16 and 0.34 for female and male Persian Sturgeon; and 0.21 and 0.37 forfemale and male Russian Sturgeon respectively.The population of the Beluga, probably because of higher quality of its caviar,is most depleted, and the number of spawners has become limited. To maintain thespawning stock, harvesting should be restricted for a period of several years.The sturgeon populations of the Caspian Sea are in need of protection. Fishingeffort needs to be reduced in all species to conserve stocks and, ultimately, to increaseyields.
Keywords: Sturgeons, South Caspian Sea, Fish populations
College: Faculty of Science and Engineering

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