Qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks in Iranian waters of the Caspian Sea (1991-2011)

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

Hydrology and hydrobiology data analysis collected during 1998-2007

Annually, many data of hydrology and hydrobiology of the southern Caspian Sea at Iran's coasts were collected by Caspian Sea Research Institute of Ecology. The data which had been collected by researchers submitted annually in several reports but has not been processed all at once. Fluctuations of various parameters were surveyed and the relationships between them were analyzed. The main goal of this research is to analysis the data were obtained from 1994 to 2006 and show changes the concentration of various parameters in the Caspian Sea. Physicochemical data indicated that the average trend of transparency and salinity was decreased from 1994 to 2006 annually, where the salinity value was decreased from 12.37 ppt (part per thousand) to 11.5 ppt. The average of dissolved oxygen was increased from 6.4 to 8.6mg/l. pH has slightly fluctuated from 8.15 to 8.31. However, with increasing depth from surface to bottom, the average of dissolved oxygen was sharply decreased (DO concentration in surface and 800 m was 7.18 and 1.45 mg/l, respectively). The trend of salinity and pH fluctuation was very slow with depth but the salinity has an increasing with incrementing of depth but pH has a decreased trend. The average of organic and inorganic phosphorus and TP was nearly increased. The average of Nitrate and Silica sharply increased comparing to depth but the average of Nitrite and organic Nitrogen decreased. The results showed that the temperature fluctuation in different water layers was low in winter but the dramatic decreasing of temperature was occurred at 10-20 m (in spring), 20-50 m (in winter) and 50-100 m (in autumn). With increasing of depth (Slope of the Sea), transparency and salinity values have an increasing while DO and pH showed decreased. As a whole, 335 species of phytoplankton were identified, there are 70 species in advance as these species were not seen in this period but 96 of novel's species have been recorded. The lowest and the most of phytoplankton biomass was recorded in 2006 and 2001 while the biomass was 59 and 1034 mg/m^3, respectively. Albet, the lowest biomass was recorded at the depth of 100 m (24.1 mg/m^3) but the maximum was observed in surface layer (1344.1 mg/m^3). The average of phytoplankton biomass was increased after arrival of the ctenophore. There was a significant difference between the average of biomass in different seasons before and after of the ctenophore invasion (P0.137, P>0.782). Before the presence of ctenophore, the worms had been constituted a dominate group with an approximately %45 of total abundance and also %20 of their biomass. After this period, their frequency was sharply increased (more than %85) but the maximum value pertains to Cardidae (more than %90). The species diversity, evenness and richness were varied between .69-2.51, 0.23-0.63 and .011-3.79, respectively. AMBI software, Shanon-Viner parameter was moderate in all seasons from 1994 to 1996 but this parameter was reduced in a bad limit (boundary) in the most seasons from 2002 to 2005. The main parameter of M-AMBI consists of several parameters and also approximately showed similar changes such as Shanon -viner parameter. On basis of this parameter, the ecological quality condition of Caspian Sea was superior limit in all seasons from 1994 to 1996 but after the following years were decreased from good to moderate limits (After the presence of ctenophore). Relationship between abiotic variants and phytoplankton indicated that there was a direct relationship between transparency and salinity while there was a powerful and reversal significant relationship between transparency water temperature, transparency in organic Nitrate, phytoplankton number and transparency phytoplankton biomass. The comparison between different variants average in two periods (before and after the ctenophore invasion) indicated that the average of Kilka catch was decreased, the relative frequency of clupeonella engrauliformis and clupenoella grimmi was sharply reduced but the relative frequency of Clupeonella cultriventris was sharply increased, the species diversity, evenness and richness and the number of zooplankton species were sharply decreased, the average of biomass and transparency was sharply reduced, the average of dissolved oxygen and liza saliens or liza auratus catch were increased. These difference were often significant (P<0.05). Therefore, with the ctenophore invasion into the Caspian Sea, the primary production was increased, the biomass value of zooplankton and specially Kilka which fed on zooplankton were sharply decreased while the fish such as Rutilus frisii kutum and mullet (Liza salins or Liza aurratus) which fed on benthic were increased

Biological aspects of kilka (age, growth, feeding and reproduction) in southern of Caspian Sea

In the changing environmental of the Caspian Sea specifically pelagic zone following the introduction of the comb jelly Mnemiopsis leidyi has been continued ,particularly kilka catch ,biological characteristic and feeding . In this investigation which had been done in commercial catch regions (where discharged theirs catch) in three ports Babolsar ,Amirabad (in Mazandaran) and Anzali (in Guilan), estimated catch and catch per unit effort, the age structure of catch ,length- weight relationship, von Bertalanffy growth parameters, condition factor, sex ratios ,maturity stags ,age at first capture and spawning and feeding .The result shown that catch of kilka in Iranian coastal in 2006 decreased from 22300 ton to 16700 ton in 2008.But CPUE increased from1.7 ton (Vessel ×Night) to 2.5 ton at that time due to dropped effort .The length frequency of kilka is close and the juvenile fish did not see in catch as increased the length mean (P>0.000).The age frequency had the same situation as fish low than 2 years did not see for anchovy and bigeye ,so collapse juvenile stock cause poor recruitment in the species .The parameters of the von Bertalanffy growth curve were For common kilka L_∞= 136.5mm k= 0.249y t0= 1.890y Q= 3.883; For bigeye kilka L_∞= 131.7mm k= 0.346 t0= 1.123y Q= 3.688; And for anchovy kilka L_∞= 148mm k= 0.375 t0= 1.243y Q= 3.814 The exploitation rate of anchovy, bigeye and common kilka were 0.51, 0.58 and 0.6 respectively. The highest of GSI recorded in May and March for common and bigeye and in Jul, Nov for anchovy kilka .Main prey was Acartia tonsa by anchovy and common kilka and Cypris balanus by bigeye kilka. We concluded that the ecological problem causes by Mnemiopsis leidyi as well as overfishing has been collapsed kilka stocks, particularly anchvy.so sustainable fisheries management and conservation biodiversity in the Caspian Sea are real challenges now

The study of feeding, reproduction and biological parameters of kilka fishes in the Iranian waters of the Caspian Sea

The overfishing and changing environmental following the introduction of the comb jelly Mnemiopsis leidyi in the Caspian Sea, the population structure has a strong influence on kilka fishes in the Caspian Sea and therefore to in this investigation which had been done in commercial catch regions (where discharged theirs catch) in three ports Babolsar, Amirabad (in mazandaran) and Anzali (in Guilan), stimated catch and catch per unit effort, the age structur of catch, length- weight relationship, von Bertalanffy growth parameters, condition factor, sex ratios, maturity stags, spawning and feeding. The result shown that catch of kilka in Iranian coastal in 2012 decreased from 24080 ton to 22696 ton in 2013. But CPUE increased was 2.7 ton (Vessel ×Night) and there was no significant changes. Common kilka was the predominant all months of the year, 98.1 and 98.9 percent in 2012 and 2013 respectively. The mean length was 104.4±10.5 and 101.6±11.2 at the same time and range length 92/ 5 – 117/5 mm were the dominant population(about 75%). Relative abundance of fish less than 77.5 mm and more than 127.5 mm is very low. Age abundance during this period have not been substantially changed and always fishes with 3 and 4 year olds had the highest frequency73.6 and 73.5 percent respectively. The parameters of the Von Bertalanffy growth curve were (8.141) 048.1 for common kilka. The instantaneous coefficient of natural mortality (M) was 0.506 yr-1. The instantaneous coefficient of fihing mortality and total mortality were 0.694 yr-1 and 1.2 yr^-1 , respectively. The exploitation rate of common kilka varied during 2012-2013 between 0.41-0.50. The mean condition factor 1.41±0.14 (n=5801) and 1.38±0.16 (n=6754) at the same time respectively. According to statistical analysis Anova oneway were a significant difference between condition factor at the same time . Main prey common kilka was Acartia tonsa accounting for over 80%. It seems Common kilka due to a decrease in the frequency of other zooplankton species depend more than ever on Acartia tonsa and this species is probably a concentration of prey for Common kilka

Questioning the rise of gelatinous zooplankton in the World's oceans

During the past several decades, high numbers of gelatinous zooplankton species have been reported in many estuarine and coastal ecosystems. Coupled with media-driven public perception, a paradigm has evolved in which the global ocean ecosystems are thought to be heading toward being dominated by “nuisance” jellyfish. We question this current paradigm by presenting a broad overview of gelatinous zooplankton in a historicalcontext to develop the hypothesis that population changes reflect the human-mediated alteration of global ocean ecosystems. To this end, we synthesize information related to the evolutionary context of contemporary gelatinous zooplankton blooms, the human frame of reference forchanges in gelatinous zooplankton populations, and whether sufficient data are available to have established the paradigm. We conclude that the current paradigm in which it is believed that there has been a global increase in gelatinous zooplankton is unsubstantiated, and we develop a strategy for addressing the critical questions about long-term, human-related changes in the sea as they relate to gelatinous zooplankton blooms

The Study of biology (age, feeding and, reproduction of Rutilus rutilus caspicus in south coast of the Caspian Sea (Iranian waters)

The Caspian Sea is an important source of water in terms of having valuable resources of sturgeon and bony fish is taken into consideration roach(Rutilus rutilus caspicus (L.)) is one of the most important commercial species in the southern coast of the Caspian Sea in Iran , the catch of this species has declined substantially in the last 10 years, The management and exploitation need of comprehensive review of its biology .This study as part of a comprehensive study of feeding , spawning and growth of this species.In this study, using samples caught in beach seine along the southern coast of the Caspian Sea coastal ( Iranian waters ) took place. The fork length and total weight ranged between 12.5 to29.5(cm) and 29 to293( grm),10.5 to23(cm) and17.2 to21(grm) in Golestan and Gilan Province respectively. The b value of the length-weight relationship ranged 3.02 to 3.25 and 3.28 to 3.75 for female and male, in Golestan and Gilan Province respectively. The age composition of the catch was from 1 to 4 year in both Province, there was one spawning peak and Fecundity variations were high and ranged 7260 to 231965 eggs. Average growth in length was described with the Von Bertalanffy growth model: L (t) = 30.94(1-exp (0.42(t-0.18) and L (t) = 20.49(1-exp (0.53(t-1). The percent of empty stomach and prey dominant evaluated during different seasons by specific formula. Result showed that gastropod, Polychaete worms and molluscs were dominated and specific food items respectively. Shrimp, fish, insects, zooplankton and clams were scare of prey

Study on biology (age, feeding and, reproductive) of (Cyprinus carpio, Linnaeus 1758) in south coastal line Caspian Sea (Iranian waters)

The Caspian Sea is the biggest lacustrine water source. Common carp is very important commercially in south coastal line of Iranian Caspian Sea waters, especially in east coastal line, because eighty percent annual catch of this species has been caught in this area in particular. Despite the common carp importance and value in Iran, but there is a little information about its biology in natural system. This study is comprehensive research on reproduction, growth and feeding. The specimens were caught by beach seine net in coastal line of Iranian waters. The fork length ranged between 5.6 and 2866.2 g. The b value of the length-weight relationship ranged from 2.843 to 2.924 for female and male, respectively. The age composition of the specimens was from 1 to 11 year. The Gonadosomatic ratio (GSR) changed from 2 to 12. There were two peaks of GSR in April and December, so that the latter peak was much shorter than the first that. Fecundity variations were high and ranged 77448 to 430745 eggs. It observed linear significant correlation in fecundity- weight (r=0.98) and fecundity-length (r=0.88) relationships. Average growth in length was described with the Von Bertalanffy growth model: L (t) = 60.5(1-exp (0.19(t-0.65). The percent of empty stomach and prey dominant evaluated during different seasons by specific formula result showed that in Cyprinus carpio prey Molluscs was dominated and specific food items. Empty stomachs in winter and spring were higher and lower, respectively

A survey of feeding habits of economic benthic feeder fishes in the southern of Caspian Sea (Rutilus frissi kutum, Rutilus rutilus caspicus, Cyprinus carpio, Liza auratus and Liza saliens)

Present study analyzed the stomach contents of individuals belonging to five fish’s species in order toInvestigate seasonal changes in feeding strategy and diet composition in the South coast of the Caspian Sea (Gilan and Mazandaran provinces) from late March until late May 2010 using the research ship Gillan and fishing with batoom trawl nets and fishing blades insoles bony fishes in the depths of less than 60 meters. The average length and the total weight of Rutilus frisii kutum, Rutilus rutilus caspicus, Cyprinus carpio, Liza auratus and Liza saliens respectively were 36/9 ± 8/5 cm , 562/9 ± 353/2 g, 23/2 ± 3/2 cm , 202 ± 101/6 g, 24/6 ± 8/1 cm , 249/8 ± 242 g, 32/2 ± 8/9 cm , 320/9 ± 242/8 g, 22/7 ± 2/6 cm and 82/9 ± 52/2 g repectively. Using the method of Shorygin and Costello highly nourishing food strategy and different species of fishes were studied. The results of this study showed that Rutilus frisii kutum fed generally of Balanus and Cerastorderma In order of importance after Bivalvia, Gastropoda, Crabs, Fish eggs, Filamentous alge in GI Rutilus frisii kutum presence, but feeding it of Bivalvia (in particular Cerastorderma) was much more than the other food. The results of present study showed that under the influence of compatibility and behavioral mechanisms, ecological, physiological and nutritional importance of Rutilus frisii kutum Bivalvia. The results of studies were showed that Bivalvia was feeding the dominant Rutilus frisii kutum , while the results of this study showed that despite Bivalvia present importance in feeding the of this species, it seems that its presence in such digestion decreased. As well as the dominant food of Rutilus rutilus caspicus was fish, but generally from Detrite fed. This study showed that feeding the dominant species of Cyprinus carpio, Liza auratus and Liza saliens of Detrite was. The most important food items after ditrit for the Cyprinus carpio in order of importance include the Bivalvia, Gastropoda, Oligochaeta, Abra ovata, Nereis, Fish eggs, Filamentous alge, was. The Liza auratus dietary habits also showed that after ditrit the most importance in nutrition related to Foraminifera, Porifera and Balanus, and for Liza saliens to Gastropoda, Bivalvia and Porifera. The results showed that the mullet the greater the intensity of feeding fishes than other species were, Rutilus frisii kutum in between of Cyprinidae the greater the intensity of feeding fishes than other species were (0/05 > P). The values of this indicator in the lower longitudinal in all fish species investigated were more than high longitudinal groups. The feeding intensity at different times of sampling for all species investigated showed that in all species at times extremely reduced the reproductive index (0/05 > P). As well as the diversity foods in the lower longitudinal in all fish species investigated were more than high longitudinal groups. In conclusion, our results demonstrated Food strategy have changed based on physiological changes, metabolism activity, behaviour, and the amount of food available

Stock assessment of bonyfishes in the Iranian coastal water of the Caspian Sea (2004-2005)

For gathering of data on biometry and catch statistics, 5 mobile working group in the regions of Anzali, Kiashahr , Noshahr , Babolsar and Torkmen were involved from the start (2004.10.23) to the end of fishing season (2005.04.10). Gathered data were entered to the computer based on species. For data analysis different methods were undertaken such as Bertallanfy equation for growth parameter Beverton and Holt for total mortality rates, pauly's imperical model for natural mortality rate and cohort Analysis for biomass estimation. Total catch with taking into account of poaching, was estimated 15140 tons reported by scientific committee of catch and fishing harbor relief of Iranian Fishery Company. The total recorded catch of beach seine cooperatives was 10644 tons that comprise 70.2% of the total catch. Total catch of Caspian Kutum was estimated 6612 tons that had 1856 tons (22%) decrease with comparison of the last year. Biomass of Caspian kutum in Iranian coastal Water of the Caspian Sea in 2003-2004 estimated about 20400 tons. The total catch of golden gray mullet was estimated 4425.6 tons that constitute 29.2% of total catch of bony fishes. Biomass of this species was estimated 12200 tons and based on this amount of biomass, Maximum Sustainable Yield (MSY) was calculated as 3577 tons. Long nose mullet comprised only 1.4% of the mullet catch. The catch of common carp in 2004-2005 fishing season continued its increasing trend and caught in amount of 3087 tons by beach seine cooperatives that had 2.2 fold increase in comparison of previous fishing season. Most of the catch occurred in Golestan province and was immature and undersize and the length frequency modes showed moving towards bigger size and older age groups in comparison of previous fishing season. The catch of pick perch in 2003-2004 decreased with comparison of the last year and estimated about 22.5 tons. Most of the catch of pick perch was immature and undersize. Approximately all of the catch is due to releasing of fingerling of this species by Fishery Company especially in Guilan province. Total catch of bream was estimated 27.4 tons and most of which was immature and undersize. Population of asp is critically endangered and the catch of this species is very low (500 kg). Restocking of this species must be considered by Iranian fishing company

The study on fishing and resource management of bony fisheries within southern Caspian Sea

The project of the Study on fishing and resource management of fisheries within Southern Caspian Sea was conducted on the base of an agreement made between fisheries organization (Shilat) and the Iranian fishery research organization (IFRO) signed in 2010. In this library-based study the current situation of bony fish fisheries and biology of these species has been surveyed in Iranian waters of the Caspian Sea . In this survey internal and external environmental factors of bony fishes activities were considered. Using SWOT analysis method, current situation of fisheries was investigated..One of the most important strategies for conserving anadromous species such as Caspian kutum , common carp, roach, bream and …. is rehabilitation of the natural spawning ground in rivers, coastal lagoon specially Anzali lagoon .By conducting this strategy not only restocks of bony fishes is done ,but also reduced the cost of artificial restocking programs and releasing fingerlings .In short term , it is nessesary to enhance the stocks of the species that have low catch is done by huge releasing of the fingerlings and study the qualification of the program