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  • Stock assessment  (7)
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  • 1
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    Fishery and biological aspects of anchovy Kilka ( Clupeonella engrauliformis) in the southern Caspian Sea (2018)
    Details
    Publication Date: 2021-05-19
    Description: This paper aimed to investigate the fishery and biological characteristics of anchovy Kilka in Iranian waters of the Caspian Sea from 2005-2007, including length and age structure ,Von Bertalanffy growth parameters, length and age at first capture, condition factor, sex ratio, natural and fishing mortality. The examination of catch data approved that Kilka population in the Caspian Sea have been declined a few years ago following entrance jellyfish Ctenophora Mnemiopsis leidyi. The greatest destruction of anchovy kilka catch was occurred while the catch of anchovy from 4250 tonnes in 2005 reached to 924 tonnes in 2007. The results showed that K value and L∞ calculated 0.375/year, 131.7mm, respectively. The instantaneous coefficient of natural mortality was estimated 0.49/year.The instantaneous coefficient of fishing mortality and total mortality was 0.51 /year and 1/year, respectively. The Exploitation rate was calculated as 0.51. The length and age ranges restricted comparison to last decade and sharply decreased recruitment. In the past few years, the main reasons of disintegrates among anchovy Kilka stocks in the Caspian Sea were synchronized overfishing competitive anchovy Kilka with M. leidyi.
    Description: Published
    Keywords: Stock assessment ; Clupeonella engrauliformis ; Age ; Growth ; Sex ratio ; Overfishing
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.796-806
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  • 2
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    Age and growth of bigeye kilka (Clupeonella grimmi Kessler, 1877) in Iranian waters of the Caspian Sea (2018)
    Details
    Publication Date: 2021-05-19
    Description: Age and growth of Bigeye Kilka, Clupeonella grimmi, were studied in Iranian waters of the Caspian Sea from early May 2006 to April 2007. The sagitta otoliths were removed for each 5 mm length interval up to a total number of 262 fish. Fork length and weight ranged from 92.5 to 142.5 mm and 4.2 g to 23.4 g, respectively. The largest length-groups was observed from December to February and the lowest in April, which was coincided with spawning period and feeding during wintering, respectively. The overall sex ratio (male:female) was 0.33:1 which differed significantly from the expected ratio of 1:1. The length-weight regression was W= 0.0000744 FL3.14 for females and W=0.0000341FL3.16 for males, indicating the Caspian Bigeye grew isometrically for both sexes. Age determination based on otoliths readings showed that the population was composed of six- groups from 2 to 7 years old which observed a rapidly growth during the second year. In the age compositions, the four years old specimens with a mean fork length and weight 115.5±7.8 mm and 11.9 ± 2.8 g were the most abundant age group and accounted for 40.1%. The condition factor was 0.7-0.8 which varied in difference months and coincided to the gonad development. Age-at-length data were used to determine von Bertalanffy growth parameters for this population in both sexes, indicating that K value and L∞ of females was more than that of males. The results showed that C. grimmi is a rapidly-growing species in the southern parts of the Caspian Sea.
    Description: Published
    Keywords: Stock assessment ; Bigeye kilka ; Age ; Growth ; Clupeonella grimmi ; Parameters ; Population
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp. 1410-1424
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  • 3
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    Reproduction, sexual maturity and fecundity of anchovy kilka (Clupeonella engrauliformis Svetovidov 1941) in Iranian waters of the Caspian Sea (2017)
    Details
    Publication Date: 2021-05-19
    Description: Reproduction period, spawning peak and sexual maturity in anchovy kilka were investigated during the year 2006 for sustainable yield assessment in Iranian waters of the Caspian Sea. The mean fork length, total weight and age were 118±5.9mm, 11±1.7g and 4.6±1.2 year, respectively. Mean (±SD) absolute fecundity was 12625±5533 ovules. More than 50 percent of the fish specimens matured when their length exceeded 92.5mm. The results showed that reproduction of anchovy kilka occurred in autumn, and spawning occurred throughout the year and especially in winter. The length and age ranges were found to be shortened compared to the past years with many older fish and less younger ones (〈 2 years) in the catch which sharply decreased recruitment. This phenomenon is thought to be due to overfishing synchronized with invasion of M. leidyi pushing kilka to spawn in winter, which all cause collapse of anchovy kilka stocks in the Caspian Sea. We postulate that anchovy kilka has adopted the strategy of spawning year round to mitigate the negative effects of overfishing and invasion of M. leidyi.
    Description: Published
    Keywords: Fishing management ; Stock assessment ; Anchovy kilka ; Clupeonella engrauliformis ; Reproduction ; Sexual ; Fecundity ; Maturity
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.21-32
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  • 4
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    Age and growth of bigeye kilka (Clupeonella grimmi Kessler, 1877) in Iranian waters of the Caspian Sea (2021)
    In:  http://aquaticcommons.org/id/eprint/22961 | 18721 | 2018-06-07 21:27:10 | 22961 | Iranian Fisheries Science Research Institute
    Details
    Publication Date: 2021-07-11
    Description: Age and growth of Bigeye Kilka, Clupeonella grimmi, were studied in Iranian waters of the Caspian Sea from early May 2006 to April 2007. The sagitta otoliths were removed for each 5 mm length interval up to a total number of 262 fish. Fork length and weight ranged from 92.5 to 142.5 mm and 4.2 g to 23.4 g, respectively. The largest length-groups was observed from December to February and the lowest in April, which was coincided with spawning period and feeding during wintering, respectively. The overall sex ratio (male:female) was 0.33:1 which differed significantly from the expected ratio of 1:1. The length-weight regression was W= 0.0000744 FL^3.14 for females and W=0.0000341FL^3.16 for males, indicating the Caspian Bigeye grew isometrically for both sexes. Age determination based on otoliths readings showed that the population was composed of six- groups from 2 to 7 years old which observed a rapidly growth during the second year. In the age compositions, the four years old specimens with a mean fork length and weight 115.5±7.8 mm and 11.9 ± 2.8 g were the most abundant age group and accounted for 40.1%. The condition factor was 0.7-0.8 which varied in difference months and coincided to the gonad development. Age-at-length data were used to determine von Bertalanffy growth parameters for this population in both sexes, indicating that K value and L∞ of females was more than that of males. The results showed that C. grimmi is a rapidly-growing species in the southern parts of the Caspian Sea.
    Keywords: Biology ; Fisheries ; Age ; Growth ; Clupeonella grimmi ; Caspian Sea ; Iran ; Stock assessment
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 1410-1424
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  • 5
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    Reproduction, sexual maturity and fecundity of anchovy kilka (Clupeonella engrauliformis Svetovidov 1941) in Iranian waters of the Caspian Sea (2021)
    In:  http://aquaticcommons.org/id/eprint/21863 | 18721 | 2018-01-15 06:25:49 | 21863 | Iranian Fisheries Science Research Institute
    Details
    Publication Date: 2021-07-03
    Description: Reproduction period, spawning peak and sexual maturity in anchovy kilka were investigated during the year 2006 for sustainable yield assessment in Iranian waters of the Caspian Sea. The mean fork length, total weight and age were 118±5.9mm, 11±1.7g and 4.6±1.2 year, respectively. Mean (±SD) absolute fecundity was 12625±5533 ovules. More than 50 percent of the fish specimens matured when their length exceeded 92.5mm. The results showed that reproduction of anchovy kilka occurred in autumn, and spawning occurred throughout the year and especially in winter. The length and age ranges were found to be shortened compared to the past years with many older fish and less younger ones (〈 2 years) in the catch which sharply decreased recruitment. This phenomenon is thought to be due to overfishing synchronized with invasion of M. leidyi pushing kilka to spawn in winter, which all cause collapse of anchovy kilka stocks in the Caspian Sea. We postulate that anchovy kilka has adopted the strategy of spawning year round to mitigate the negative effects of overfishing and invasion of M. leidyi.
    Keywords: Biology ; Fisheries ; Fishing management ; Stock assessment ; Anchovy kilka ; Caspian Sea ; Iran ; Clupeonella engrauliformis ; fish ; sexual ; Reproduction ; M. leidyi
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 21-32
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  • 6
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    Qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks in Iranian waters of the Caspian Sea (1991-2011) (2021)
    In:  http://aquaticcommons.org/id/eprint/21895 | 18721 | 2018-01-15 14:06:21 | 21895 | Iranian Fisheries Science Research Institute
    Details
    Publication Date: 2021-07-04
    Description: The main objective of the present study was qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks by using indicators of overfishing, condition factor and relative weight 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 and relative weight had a decreasing trend. The range of length with optimum yield was between 40 and 48 cm. The mega-spawner measured as fish a size larger than 48 cm. According to these three indicators, the percentage of mature (fork length〉40cm), optimum size and mega-spawners were 62.0, 40.9 and 12.5% in 1991-92 which decreased less than 50, 38.2 and 8%, in the years 1992-2011, respectively. The length structure is a matter of concern. Therefore, for reservation and rebuilt of kutum in the Caspian Sea, the target was to let all (100%) fish spawn at least once, using bigger mesh size in cod end (e.g. 35mm, during whole fishing season). The aim was also to implement a fishing strategy that result no (0%) mega-spawners being caught, and the main catch focus on optimum length.
    Keywords: Biology ; Fisheries ; Stock assessment ; Fisheries indicators ; Spawner fish ; Caspian Sea ; Iran ; Rutilus frisii kutum
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 53-64
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  • 7
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    Unknown
    Qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks in Iranian waters of the Caspian Sea (1991-2011) (2017)
    Details
    Publication Date: 2021-05-19
    Description: The main objective of the present study was qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks by using indicators of overfishing, condition factor and relative weight 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 and relative weight had a decreasing trend. The range of length with optimum yield was between 40 and 48 cm. The mega-spawner measured as fish a size larger than 48 cm. According to these three indicators, the percentage of mature (fork length〉40cm), optimum size and mega-spawners were 62.0, 40.9 and 12.5% in 1991-92 which decreased less than 50, 38.2 and 8%, in the years 1992-2011, respectively. The length structure is a matter of concern. Therefore, for reservation and rebuilt of kutum in the Caspian Sea, the target was to let all (100%) fish spawn at least once, using bigger mesh size in cod end (e.g. 35mm, during whole fishing season). The aim was also to implement a fishing strategy that result no (0%) mega-spawners being caught, and the main catch focus on optimum length.
    Description: Published
    Keywords: Rutilus frisii kutum ; Caspian kutum ; Stock assessment ; Fisheries indicators ; Spawner fish ; Fish
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.53-64
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