ABSTRACT Recent changes in sea level of the Caspian Sea and ecological impacts caused by the inva... more ABSTRACT Recent changes in sea level of the Caspian Sea and ecological impacts caused by the invasive ctenophore (Mnemiopsis leidyi) have altered the ecosystem. A consequence is the changes in the absolute and relative abundance of the commercially important anchovy kilka (Clupeonella engrauliformis) in Iranian waters. To adjust to this change more rigorous management of this fishery is required. This paper examines the maximum sustainable yield (MSY) and fishing intensity at MSY. The paper presents estimates of fMSY, yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of Fmax, F0.1 and F40%. We propose a method for estimating acceptable biological catch (ABC) that accounts for large differences in the quality and quantity of information and available data. The MSY and fMSY were estimated 44,652 mt (metric tons) and 18,609 vessel × nights (a unit of effort). The ABC was estimated at 2190 mt in 2004. In 2005, however, the catch of anchovy kilka was about 4300, over twice the estimated ABC. In 2008 (from January to October) the catch declined to 220 mt. The analyses indicate that overfishing, especially between 2005 and 2008, is the main reason of the collapse of anchovy kilka in the Caspian Sea.
Большеглазая килька Clupeonella grimmi является традиционным объектом иранского промысла в Каспий... more Большеглазая килька Clupeonella grimmi является традиционным объектом иранского промысла в Каспийском море. Индексы численности, получаемые по данным акустических съемок, представляют важнейшую информацию для оценок состояния запасов и пространственного распределения этой рыбы. Точность оценки зависит от знания «силы цели», которая в настоящее время для большеглазой кильки изучена мало. Используя доступные данные акустических наблюдений in situ, сопровождаемые траловыми выборками, исследована зависимость «силы цели» (частота 38 кГц) данного вида каспийской кильки от таких биологических параметров, как длина и вес особей, половозрелость и коэффициент упитанности. Определение зависимости «сила цели»-длина рыбы затруднено ввиду высокой вариабельности «силы цели» в естественных условиях, связанной с изменчивостью индивидуальных биологических параметров одноразмерных особей. Учет этих факторов позволяет повысить точность гидроакустических исследований. В настоящей работе исследован эффект влияния ряда биологических показателей, таких как возраст, масса, стадия зрелости, коэффициент упитанности, на «силу цели». Показана значительная зависимость «силы цели» от доли созревших самок. Полученный для большеглазой кильки коэффициент B 20 = ̶ 75,1 дБ оказался на 3,5 дБ меньше, чем рассчитанный другими исследователями без учета биологических параметров рыбы. Полученное уравнение регрессии «силы цели» от длины рыбы TS = 20 logL -75,1 сравнивается с оценками предыдущих исследований. Ключевые слова: большеглазая килька Clupeonella grimmi, акустические съемки, сила цели, Каспийское море, Иран.
Each year, at the end of the sturgeon fishing season, sturgeon management experts of Golestan pro... more Each year, at the end of the sturgeon fishing season, sturgeon management experts of Golestan province, classified as special acetra gill nets capability in the next season, according to physical features such as yarn strength and color, respectively, to 75%, 50%, 25% and obsolescent. Many past studies showed that amount of yarn twist is proportional to breaking strength. Samples of new, 75%, 50%, 25% and obsolescent special acetra gillnets were prepared and amount of yarn twists of this nets was tested. The mean and standard deviation of twist respectively was (215.4±2.28), (225.6±6.23), (223.96±3.04), (214.8±5.24) and (201.04±4.47). The mean of twist in each classes of net showed that there were significant differences among the means of twist per meter in obsolescent, with an mean of twist per meter in 25%, 50%, 75% and new (P<0.05). Also there were significant differences between mean of 25% with means of 50% and 75% (P<0.05). As well as there were significant differences between mean of new with means of 50% and 75% (P<0.05). In this study there was no significant differences between mean of 25% with new, also, between mean of 50% with mean of 75% (P>0.05). It is important to note that the rate of increase of twist gradually reduced from obsolescent to 75% net. Therefore in each net purchase the mean of yarn twist was lower than before. We suggest that, in the case of twist test, sturgeon management experts of Golestan province should have the required accuracy when purchasing new nets.
ABSTRACT: Through most of the last century, three endemic kilka species supported major commercia... more ABSTRACT: Through most of the last century, three endemic kilka species supported major commercial species in the Caspian Sea. It is clear that catches and abundance of all species have changed, but catch and sampling data are limited and stock assessments are ...
One of the major sources of impacts on marine resources comes from climate variability and regime... more One of the major sources of impacts on marine resources comes from climate variability and regime shifts. In this context, the present study pinpoints the role of climatic and environmental parameters on the dynamic of kilka in the Caspian Sea. During the last decades, landings and stocks of the main pelagic species of kilka had been changed dramatically in the Caspian Sea. This study focuses on the last three decades of the climate regime and tries to explain the part of the changes in the recruitment (R) and spawning stock biomass (SSB) of three kilka species. Based on the statistical analysis of data series, it is found that regime changes in the global and regional environmental variables started in the mid-1995s, however, the shift of the late 1990s (1998) was more strong in the Caspian Sea. The study further reveals that the global climatic indices changes in the late 1990s are triggering the regional and local indices induced regime shifts in the late 1990s and 2000s. The stu...
This study aimed to investigate the impact of fishing in Iranian part of the Caspian Sea during 1... more This study aimed to investigate the impact of fishing in Iranian part of the Caspian Sea during 1991-2017 years using fishing-in-balance (FiB), mean trophic level (MTI), ratio of pelagic and demersal fish landings (P/D) and piscivory (PI) indices. The mean (±S.D) of MTI were 2.91±0.38 (95% C.I =3.14-2.67). Its value is first reduced and then increase happened and ultimately stays constant. The mean of FiB was 0.13 (95% C.I=0.28-(-0.02)) and its trend was similar to that of total landing. The mean of Pi index, P/D index, pelagic fish and demersal fish were 0.04±0.02 (95% C.I=0.09-(-0.012)), 3.16±2.31 (95% C.I = 0.6-(-0.52)), 38529±22883 (95% C.I=38585-38472) and 13380±3314 (95% C.I= 3401-13358), respectively. The results revealed that the fish stock in the Iranian waters of the Caspian Sea have been over-exploited. Considering that fishing impacts on the trophic level, we suggest that the fishery management should not continue this trend.
Iranian Journal of Fisheries Sciences, Sep 10, 2021
One of the major sources of impacts on marine resources comes from climate variability and regime... more One of the major sources of impacts on marine resources comes from climate variability and regime shifts. In this context, the present study pinpoints the role of climatic and environmental parameters on the dynamic of kilka in the Caspian Sea. During the last decades, landings and stocks of the main pelagic species of kilka had been changed dramatically in the Caspian Sea. This study focuses on the last three decades of the climate regime and tries to explain the part of the changes in the recruitment (R) and spawning stock biomass (SSB) of three kilka species. Based on the statistical analysis of data series, it is found that regime changes in the global and regional environmental variables started in the mid-1995s, however, the shift of the late 1990s (1998) was more strong in the Caspian Sea. The study further reveals that the global climatic indices changes in the late 1990s are triggering the regional and local indices induced regime shifts in the late 1990s and 2000s. The study concludes that the changes in populations of fish species, especially for kilka, could be due to the regime shift.
Water reservoirs have an important role in providing water for drinking and agriculture. It is ne... more Water reservoirs have an important role in providing water for drinking and agriculture. It is necessary to protect these resources. This study was conducted to determine water quality of Azad Reservoir (Kordestan-Sanandaj) based on Iranian Water Quality Index (IRWQI) and Carlson's Trophic State Index (TSI). Sampling was carried out at five stations during different months in 2015-2016. Results showed that trophic status of Azad dam was mesotrophic based on chlorophyll-a parameters and eutrophic to hypertrophic based on other variables (TP, SDD and DO % at bottom layers). Mean of Carlson's Trophic State Index represented mesotrophic state (high quality) at Azad dam. Based on IRWQI, water quality of dam was classified as excellent quality. Although, mean of indices indicated the suitability of this lake for drinking and agriculture activities but due to declining water quality and increasing trophic level in some months, it is necessary to apply appropriate management strategies for maintaining water quality in the reservoir.
The present study considered the situation of kilka stocks using overfished biomass threshold, fi... more The present study considered the situation of kilka stocks using overfished biomass threshold, fishing effort ratio and fishing mortality proxy during 1991-2010. The CPUE index of anchovy kilka and mixed-species (three species of Kilka) indicated no overfishing from 1991 to 2000. In 2000, the CPUE ratio neared the "in danger" region, and subsequently fell into the "overfished" region from 2001 to 2007 for both anchovy and mixed-species of kilka. The CPUE ratios of common kilka have been in an overfished state during 1991-2003. During 2008-2010 the biomass increased and the CPUE ratio of common kilka and mixed-species upgraded to non-overfished region. The control rule of anchovy kilka showed that overfishing was occurred from 1998 to 2010, and overfishing-effort was exceeded the overfishing threshold (MFMT) by 12-66%. The trajectory of the phase-plot of biomass proxy (CPUE ratio) and fishing mortality proxy (effort ratio) of anchovy kilka showed that the status of the fishery of anchovy kilka has generally reduced since 1998 and collapsed to the lowest level in 2010. The trajectory for common kilka has generally increased since 1991 getting close to the fisheries management target in 2007. In conclusion, in the new condition, common kilka is the main species in the Caspian Sea. For stock recovery of anchovy kilka, the catch of three species of kilka must be restricted during reproduction periods, and also, a coordinated international effort should be put into effect.
Measurements of bioavailability responses in frogs from contaminated sites could provide valuable... more Measurements of bioavailability responses in frogs from contaminated sites could provide valuable data for environmental risk assessment. Biomarkers are sensitive to both e nvironmental pollution and confounding factors that are not related to pollution. The specimens were collected on a monthl y basis from the Babol-River from July to September 2010 to determine if monthly changes exist in condition, he patosomatic index (HSI) and frogs. Fulton condition factor (FCF range: 1.513±0.431 ‐ 1.638±0.473), hepatosomatic index ( HSI range: 3.901±0.504-5.231±1.206), Bioaccumulation factor (BAF), the highest level of copper was observed. Liver wei ght was seen to increase from July to August/Septem ber, most probably as a result of accumulation of metabolites, especia lly fat and glycogen. Furthermore, the concentratio ns of the metals found in the liver of the frog were in the order: Cu>Cr>C d>Pb>Ni. On the other hand, the concentrations of t he metals found in the water were in the order: Cu>Pb>Cd> Ni >Cr.
ABSTRACT Recent changes in sea level of the Caspian Sea and ecological impacts caused by the inva... more ABSTRACT Recent changes in sea level of the Caspian Sea and ecological impacts caused by the invasive ctenophore (Mnemiopsis leidyi) have altered the ecosystem. A consequence is the changes in the absolute and relative abundance of the commercially important anchovy kilka (Clupeonella engrauliformis) in Iranian waters. To adjust to this change more rigorous management of this fishery is required. This paper examines the maximum sustainable yield (MSY) and fishing intensity at MSY. The paper presents estimates of fMSY, yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of Fmax, F0.1 and F40%. We propose a method for estimating acceptable biological catch (ABC) that accounts for large differences in the quality and quantity of information and available data. The MSY and fMSY were estimated 44,652 mt (metric tons) and 18,609 vessel × nights (a unit of effort). The ABC was estimated at 2190 mt in 2004. In 2005, however, the catch of anchovy kilka was about 4300, over twice the estimated ABC. In 2008 (from January to October) the catch declined to 220 mt. The analyses indicate that overfishing, especially between 2005 and 2008, is the main reason of the collapse of anchovy kilka in the Caspian Sea.
Большеглазая килька Clupeonella grimmi является традиционным объектом иранского промысла в Каспий... more Большеглазая килька Clupeonella grimmi является традиционным объектом иранского промысла в Каспийском море. Индексы численности, получаемые по данным акустических съемок, представляют важнейшую информацию для оценок состояния запасов и пространственного распределения этой рыбы. Точность оценки зависит от знания «силы цели», которая в настоящее время для большеглазой кильки изучена мало. Используя доступные данные акустических наблюдений in situ, сопровождаемые траловыми выборками, исследована зависимость «силы цели» (частота 38 кГц) данного вида каспийской кильки от таких биологических параметров, как длина и вес особей, половозрелость и коэффициент упитанности. Определение зависимости «сила цели»-длина рыбы затруднено ввиду высокой вариабельности «силы цели» в естественных условиях, связанной с изменчивостью индивидуальных биологических параметров одноразмерных особей. Учет этих факторов позволяет повысить точность гидроакустических исследований. В настоящей работе исследован эффект влияния ряда биологических показателей, таких как возраст, масса, стадия зрелости, коэффициент упитанности, на «силу цели». Показана значительная зависимость «силы цели» от доли созревших самок. Полученный для большеглазой кильки коэффициент B 20 = ̶ 75,1 дБ оказался на 3,5 дБ меньше, чем рассчитанный другими исследователями без учета биологических параметров рыбы. Полученное уравнение регрессии «силы цели» от длины рыбы TS = 20 logL -75,1 сравнивается с оценками предыдущих исследований. Ключевые слова: большеглазая килька Clupeonella grimmi, акустические съемки, сила цели, Каспийское море, Иран.
Each year, at the end of the sturgeon fishing season, sturgeon management experts of Golestan pro... more Each year, at the end of the sturgeon fishing season, sturgeon management experts of Golestan province, classified as special acetra gill nets capability in the next season, according to physical features such as yarn strength and color, respectively, to 75%, 50%, 25% and obsolescent. Many past studies showed that amount of yarn twist is proportional to breaking strength. Samples of new, 75%, 50%, 25% and obsolescent special acetra gillnets were prepared and amount of yarn twists of this nets was tested. The mean and standard deviation of twist respectively was (215.4±2.28), (225.6±6.23), (223.96±3.04), (214.8±5.24) and (201.04±4.47). The mean of twist in each classes of net showed that there were significant differences among the means of twist per meter in obsolescent, with an mean of twist per meter in 25%, 50%, 75% and new (P<0.05). Also there were significant differences between mean of 25% with means of 50% and 75% (P<0.05). As well as there were significant differences between mean of new with means of 50% and 75% (P<0.05). In this study there was no significant differences between mean of 25% with new, also, between mean of 50% with mean of 75% (P>0.05). It is important to note that the rate of increase of twist gradually reduced from obsolescent to 75% net. Therefore in each net purchase the mean of yarn twist was lower than before. We suggest that, in the case of twist test, sturgeon management experts of Golestan province should have the required accuracy when purchasing new nets.
ABSTRACT: Through most of the last century, three endemic kilka species supported major commercia... more ABSTRACT: Through most of the last century, three endemic kilka species supported major commercial species in the Caspian Sea. It is clear that catches and abundance of all species have changed, but catch and sampling data are limited and stock assessments are ...
One of the major sources of impacts on marine resources comes from climate variability and regime... more One of the major sources of impacts on marine resources comes from climate variability and regime shifts. In this context, the present study pinpoints the role of climatic and environmental parameters on the dynamic of kilka in the Caspian Sea. During the last decades, landings and stocks of the main pelagic species of kilka had been changed dramatically in the Caspian Sea. This study focuses on the last three decades of the climate regime and tries to explain the part of the changes in the recruitment (R) and spawning stock biomass (SSB) of three kilka species. Based on the statistical analysis of data series, it is found that regime changes in the global and regional environmental variables started in the mid-1995s, however, the shift of the late 1990s (1998) was more strong in the Caspian Sea. The study further reveals that the global climatic indices changes in the late 1990s are triggering the regional and local indices induced regime shifts in the late 1990s and 2000s. The stu...
This study aimed to investigate the impact of fishing in Iranian part of the Caspian Sea during 1... more This study aimed to investigate the impact of fishing in Iranian part of the Caspian Sea during 1991-2017 years using fishing-in-balance (FiB), mean trophic level (MTI), ratio of pelagic and demersal fish landings (P/D) and piscivory (PI) indices. The mean (±S.D) of MTI were 2.91±0.38 (95% C.I =3.14-2.67). Its value is first reduced and then increase happened and ultimately stays constant. The mean of FiB was 0.13 (95% C.I=0.28-(-0.02)) and its trend was similar to that of total landing. The mean of Pi index, P/D index, pelagic fish and demersal fish were 0.04±0.02 (95% C.I=0.09-(-0.012)), 3.16±2.31 (95% C.I = 0.6-(-0.52)), 38529±22883 (95% C.I=38585-38472) and 13380±3314 (95% C.I= 3401-13358), respectively. The results revealed that the fish stock in the Iranian waters of the Caspian Sea have been over-exploited. Considering that fishing impacts on the trophic level, we suggest that the fishery management should not continue this trend.
Iranian Journal of Fisheries Sciences, Sep 10, 2021
One of the major sources of impacts on marine resources comes from climate variability and regime... more One of the major sources of impacts on marine resources comes from climate variability and regime shifts. In this context, the present study pinpoints the role of climatic and environmental parameters on the dynamic of kilka in the Caspian Sea. During the last decades, landings and stocks of the main pelagic species of kilka had been changed dramatically in the Caspian Sea. This study focuses on the last three decades of the climate regime and tries to explain the part of the changes in the recruitment (R) and spawning stock biomass (SSB) of three kilka species. Based on the statistical analysis of data series, it is found that regime changes in the global and regional environmental variables started in the mid-1995s, however, the shift of the late 1990s (1998) was more strong in the Caspian Sea. The study further reveals that the global climatic indices changes in the late 1990s are triggering the regional and local indices induced regime shifts in the late 1990s and 2000s. The study concludes that the changes in populations of fish species, especially for kilka, could be due to the regime shift.
Water reservoirs have an important role in providing water for drinking and agriculture. It is ne... more Water reservoirs have an important role in providing water for drinking and agriculture. It is necessary to protect these resources. This study was conducted to determine water quality of Azad Reservoir (Kordestan-Sanandaj) based on Iranian Water Quality Index (IRWQI) and Carlson's Trophic State Index (TSI). Sampling was carried out at five stations during different months in 2015-2016. Results showed that trophic status of Azad dam was mesotrophic based on chlorophyll-a parameters and eutrophic to hypertrophic based on other variables (TP, SDD and DO % at bottom layers). Mean of Carlson's Trophic State Index represented mesotrophic state (high quality) at Azad dam. Based on IRWQI, water quality of dam was classified as excellent quality. Although, mean of indices indicated the suitability of this lake for drinking and agriculture activities but due to declining water quality and increasing trophic level in some months, it is necessary to apply appropriate management strategies for maintaining water quality in the reservoir.
The present study considered the situation of kilka stocks using overfished biomass threshold, fi... more The present study considered the situation of kilka stocks using overfished biomass threshold, fishing effort ratio and fishing mortality proxy during 1991-2010. The CPUE index of anchovy kilka and mixed-species (three species of Kilka) indicated no overfishing from 1991 to 2000. In 2000, the CPUE ratio neared the "in danger" region, and subsequently fell into the "overfished" region from 2001 to 2007 for both anchovy and mixed-species of kilka. The CPUE ratios of common kilka have been in an overfished state during 1991-2003. During 2008-2010 the biomass increased and the CPUE ratio of common kilka and mixed-species upgraded to non-overfished region. The control rule of anchovy kilka showed that overfishing was occurred from 1998 to 2010, and overfishing-effort was exceeded the overfishing threshold (MFMT) by 12-66%. The trajectory of the phase-plot of biomass proxy (CPUE ratio) and fishing mortality proxy (effort ratio) of anchovy kilka showed that the status of the fishery of anchovy kilka has generally reduced since 1998 and collapsed to the lowest level in 2010. The trajectory for common kilka has generally increased since 1991 getting close to the fisheries management target in 2007. In conclusion, in the new condition, common kilka is the main species in the Caspian Sea. For stock recovery of anchovy kilka, the catch of three species of kilka must be restricted during reproduction periods, and also, a coordinated international effort should be put into effect.
Measurements of bioavailability responses in frogs from contaminated sites could provide valuable... more Measurements of bioavailability responses in frogs from contaminated sites could provide valuable data for environmental risk assessment. Biomarkers are sensitive to both e nvironmental pollution and confounding factors that are not related to pollution. The specimens were collected on a monthl y basis from the Babol-River from July to September 2010 to determine if monthly changes exist in condition, he patosomatic index (HSI) and frogs. Fulton condition factor (FCF range: 1.513±0.431 ‐ 1.638±0.473), hepatosomatic index ( HSI range: 3.901±0.504-5.231±1.206), Bioaccumulation factor (BAF), the highest level of copper was observed. Liver wei ght was seen to increase from July to August/Septem ber, most probably as a result of accumulation of metabolites, especia lly fat and glycogen. Furthermore, the concentratio ns of the metals found in the liver of the frog were in the order: Cu>Cr>C d>Pb>Ni. On the other hand, the concentrations of t he metals found in the water were in the order: Cu>Pb>Cd> Ni >Cr.
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