جستجوی مقالات مرتبط با کلیدواژه « Stock assessment » در نشریات گروه « شیلات »

Cephalopods have short life and global distribution except freshwater that these make them importance for study of their dynamics population. So, the purpose of this study was to estimate the biomass of cephalopods (Amphioctopus marginatus, Uroteuthis (Photololigo) edulis, Uroteuthis (Photololigo) duvaucelii, Sepia saya, Sepia prashadi, Sepia omani, Sepia stellifera and Sepia pharaonis) with the catch dynamics model (generalized depletion model) in the NE Gulf of Oman at the end of the fishing season (of bottom trawlers) in the summer and autumn of 2020. The catch data of these valuable fisheries species were obtained through field sampling from commercial fishing in the depths of 74-212 meters by an industrial bottom trawler for 17 consecutive days in the "Gowater-Pasabandar-Beris" fishing grounds (at least 12 nautical miles from the shoreline according to the new move-on rule). The highest total abundance and biomass belonged to Sepia pharaonis by 23431 individuals and 27005.78 kg. Also, the lowest total abundance and biomass belonged to Uroteuthis (Photololigo) edulis by 8 individuals and Sepia saya by 0.397 kg, respectively. The abundance response for most of the stocks was a hyperdepletion (β > 1), while the fishing effort response for most of them was an effort synergy (α > 1). Also, most of the selected models were executed in the presence (open population) of perturbations (pulses). Cuttlefishes had the highest and octopuses had the lowest biomass, respectively. Probably, this study was the first survey of biomass for mentioned species in the waters of the Islamic Republic of Iran - except Uroteuthis(Photololigo)duvaucelii and Sepia pharaonis. The advantages of implementing catch dynamics model based on commercial fisheries activities are practical, operational, and close-to-reality estimates, lack of some costs of scientific surveys, also lack of additional pressure on aquatic resources (especially in nursery grounds) due to the implementation of fisheries activities (fishing operations) within the permitted limits (spatial-temporal).

Extensive lack of data and information gaps for recreational fishing necessitate knowledge of the species caught to establish aquatic reserve management. Therefore, in the present study in 2021, by collecting lenght and weight information of major recreational fishes in the main recreational fishing area was done with hooks. The results showed that between the length and weight of common carp in Golestan, Mazandaran and Golestan provinces, the equations were 0.444004x4004 and 0.4652/168x2/4652 with a correlation of 90%, 95% and 94%, respectively. Between the length and weight of grass carp in Golestan, Mazandaran and Golestan provinces, the equations 0.2398x2 / 2398 and 0.6333x2 / 1313 and 30.3x1 / 7769, respectively, with a correlation rate of 96%, 94% and 90% were established and between the length-weight of yellow fish in Golestan, Mazandaran and Golestan provinces were equations of 0.494x3 / 113, 1101x1 / 4615 and 982x1 / 1381, respectively, with a correlation of 89%, 90% and 97%. The results showed allometric growth of all three species in all studied provinces. The allometric growth rate of common and yellow carp was positive in Golestan province and negative in Guilan and Mazandaran provinces. Allometric growth rate of herbivorous carp was negative in all studied provinces .

Aras dam has ecological and socio-economic importance in the West Azerbaijan province, which freshwater crayfish (Astacus leptodactylus) is one of the pristine and important sources of export. To investigate the stock status of this species, two models CMSY and BSM were used from 2013 to 2018 and catch data were analyzed in this respect. Sampling was performed in July 2021 in Aras Dam reservoir. The average catch weight was 88.91 g, total and carapace length was 13.88 cm and 7.5 cm, respectively. The amount of CPUE (Number per trap per day) calculated per day in Station I and SII were 0.06 and 0.013, respectively. Fisheries reference points obtained from CMSY and BSM models showed that the maximum sustainable yield of Aras Dam crayfish was between 18 and 24 t. These results indicated a sharp decline in stock and fishing over the sustainable yield, during the past years. Therefore, it can be generally concluded that the freshwater crayfish stocks of Aras Dam severely damaged. Considering the population parameters, and stock status, as well as the reasons of stock depletion, it can be hoped that if the stock rebuilding program and also the exploitation is defined based on sustainable harvest and maximum allowable catch planned gathered from the results of this study. Therefore, rebuilding of the stocks of this species and prevent its extinction are possible..

This study aimed to study the survival rate and stock assessment of Salmo trutta in Taleghan River using regional sampling and Binns and Eiserman methods (developped for assessment of trout fishes in the streams). For this purpose, the samplings were performed in 40 stations, but S. trutta was found only in three tributaries of Grab, Gateh-Deh and Deh-Dar in the Taleghan River using regional sampling and Binns and Eiserman methods. Therefore, the stock assessment study was delimited to these tributaries. Based on the results, the survival rate was calculated in the first –third year as 0.21, 0.6 and 0.25. Regional sampling method estimated biomass values of 3.98, 9.16, 0.84 kg/km for this fish in Grab, Gateh-Deh and Deh-Dar streams and Binns and Eiserman method estimate biomass values as 18.97, 32.89 and 12.39 for these three studied streams indicating a limited distribution and lower abundance of S. trutta stocks in the Taleghan River.

Clupeidae particularly Engraulidae is one of the most valuable supplies in the Persian Gulf, which plays an important role in the ecological and nutritional chain. The present study was done during from October 2015 to September 2016 with the aim of determining the amount of reserves of anchovies and adjusting its sustainable harvest pattern in Qeshm Island. Sampling was carried out in the southern shores of Qeshm Island in the fishing ports of Raش0165 Qeshm Island from October machah, Suza, Mesen and Salakh. In this research, 2553 fish samples were weighted. The caught fish were in the fork length range of 4.22-8.79 cm, with a mean fork length of 6.42 cm and an average weight of 2.2 g. The maximum weight of the fish caught was 6.36 g and the lowest total weight was 0.56 g. In the study of the frequency of fish in the 5 cm classes, the highest frequency was found in the range of 5.7-6 cm with 36.5%. The fish were in the range of 0 to 3 years old with an average age of 1.76 years. In terms of age composition, most of the fish were two years old with 68.78%. The maximum fork  length was 11.3 cm and the value of K was determined by using the Shepherd method of 0.52 × time -1 and the value of t0 was -0.88 years. Also, their natural (M), fishing (F) and total (Z) mortality rates were 1.2, 0.94 and 2.14 respectively, and the exploitation was equal to 0.44. Based on the Thompson-Bell equation, the maximum fishing mortality (Fmax) was 1.9, the maximum sustainable yield was about 38,000 kg and the total biomass was 89400 kg, while the amount of fishing carried out during the fishing period is equivalent to 35.400 kg, indicating an increase of 10% in catches. However, at present, the supply of anchovies is relatively good. Due to the importance and special position of anchovies in the Persian Gulf ecological chain, especially Qeshm Island, it is recommended that catching should not exceed more than 40,000 kg.

In this study, Meyghan Wetland in Arak City (Central Iran) was evaluated to estimate the cyst and biomass stocks of Artemia and their relationship with various factors, abiotic such as WT, DO, pH, water depth, salinity and transparency and numbers of phytoplankton as biotic factors. For this purpose, monthly sampling was performed during 2019 from 18 stations in Mighan Wetland. The amount of cyst (28.875 t), and biomass (23.673 t) artemia in the water of Mighan wetland were determined. The density and type of phytoplankton were also measured. The results showed that the maximum amount of cyst and biomass was observed in December, 1076 and 457.11 per liter respectively. Inverse relationship between cyst and biomass with water temperature, pH, and phytoplankton density and in contrast a positive and significant relationship was observed with dissolved oxygen and salinity. In general, the results showed the possibility of cyst harvesting (5.405 tons according to the method of preserving 22 cysts per liter of water or 2.8875 tons according to the method of 10% harvesting possibility) in October, December, February and March, which the best month for exploitation was in December. The possibility of biomass harvesting (9.469 tons after calculation of 4.3 tons of biomass needed for feeding Felamingo and Shelduck) was also recommended only in December based on the depth of the Secchi disc.

In this study population dynamic of Acipenser persicus with age structure model by Monte Carlo and Bootstrap approach was studied. Length frequency data a total of 4376 specimens collected from beach seine, fixed gill net and conservation force in coastal Guilan province during 2002 to 2012. Data imported to FiSAT II for length frequency analyze by ELEFAN 1. K, L∞ and t0 estimated 203, 0.08 and -0.94 respectively. Total and natural mortality estimated 0.26 and 0.14 year-1 respectively. The exploitation rate (E) was computed 0.61. Confidence limit of Z was obtained 0.195-0.327 year-1 by Bootstrap method. At Monte Carlo simulation method, confidence limit of Z was calculated 0.169-0.289 year-1 with considering sampling error. Result of the present paper demonstrating that considering the uncertainty of population parameters of selected species could be useful for increasing the accuracy at stock assessment models.

The marine survey for sturgeon stock assessment was conducted to estimate the abundance of each species, total abundance and their percentage composition.In this study, a sample of 5 stations from the four fishing Golestan province which since 1380, the Iranian Fisheries as fisheries was done selected. Sampling was carried out using the gillnet. The sampling in 2011, 247 specimens including 105 A. persicus specimens, 14 A. guldenstaedti, 44 A. stellatus, 71 Huso huso and 13 A. nudiventris were caught. In 2012, of 281 specimens, 143 A. persicus, 8 A. guldenstaedti, 19 A. stellatus,19 Huso huso and 52 A. nudiventris were caught. Species composition in 2011, including 42 percent of A. persicus, 6 percent of A. guldenstaedti, 18 percent A. stellatus, 29 percent Huso huso and 5 percent A. nudiventris. In 2012, Species composition, including 59 percent of A. persicus, 3 percent A. guldenstaedti, 8 percent, A. stellatus, 22 percent Huso huso and 8 percent was A. nudiventris. The average length of A. persicus in 2011, 162.62±19.8 cm, A. guldenstaedti 149.45±16.26 cm, A. stellatus 126.4±17.42 cm, Huso huso 167.69±60.72 cm and A. nudiventris 139.06±12 cm. In 2012, the average length of A. persicus and A. guldenstaedti to the 144.55±42.12 and 145.8±13.92 cm. The average weight of A. persicus in 2011, 22.38±8.57 gr, A. guldenstaedti 19.24±6.55 gr and A. stellatus 8.70±2.76 gr. In 2012, the average weight of A. persicus 18.66±11.43 gr and A. guldenstaedti 20±7.08 gr. The catch per unit effort (CPUE) in 2011 sampeling, equivalent to 5.23 and sampling in 2013 was equivalent to the 5.73.

This study carried out in the Iranian waters of the Caspian Sea during 2009-2010، and aimed to determine species composition، relative abundance، and absolute abundance estimated of biomass. Research vessels using 9 m bottom trawl for depths less than 10 m and 24. 7 m bottom trawl for depths above 10 m. Trawling was conducted in 90 stations that were selected using a stratified random design. In each station، trawling carried out up to 30 minute and 2. 5-3 knot. In 2009 and 2010، 84 and 28 sturgeon fish were caught، respectively. Persian sturgeon was more than 83 to 100 percent of the catch. The mean total length of Persian sturgeon was 61. 9±28. 7 cm (spring) and 40. 5±27. 9 cm (autumn) in 2009. This value was 54. 7±23. 5 cm and 60. 2±17. 7 cm for spring and summer in 2010، respectively. Absolute abundance of sturgeon was estimated 1. 31 million fish in the Iranian waters of the Caspian Sea during spring but it increased to 3. 46 million fish in autumn 2009. Absolute abundance in 2010 was 831100 and 779200 fishes in spring and summer 2010، respectively. Biomass of sturgeon fish was 2019. 7 and 3014. 3 tons in spring and autumn 2009، respectively. These values were estimated 760. 6 tons (spring) and 855. 0 tons (summer) for the year 2010. The results show that Iranian fisheries organization policy in production and releasing of fingerlings has been unable to prevent the loss sturgeon stocks. Therefore، it seems the only way to recover their stocks is rebuild natural spawning areas، nursery grounds and preservation of them up to they reach commercial size.

The main objective of the present study was qualitative and quantitative assessment of anchovy stock, Clupeonella engrauliformis in Iranian waters of the Caspian Sea during (1995- 2011). Over this period, total catch of anchovy kilka increased from 32000 tonnes in 2005 to 67000 tonnes in 1999 and decreased sharply to 80 tonnes in 2011. In the years 1995-1999, catch per unit effort (CPUE) was fairly constant (2.92-3.52 tonnes/(Vessels×Nights) which fell to 0.01 tonnes/(Vessels×Nights) in 2011. Total biomass and spawning stock biomass (SSB) had the same trend as CPUE. During 1995-1999, total biomass of anchovy kilka ranged between 158500-185900 tonnes which dropped to 2000 tonnes in 2007. The SSB showed a downwardtrend from 105500 tonnes in 1997 to 1950 tonnes in 2007. In age compositions of the catch, age 3+ was the largest age group. From 2001 to 2003, age 2+ predominated. Finally, number of young specimens declined and age 6+ and 7+ groups were predominated in the last years. Present study indicated that the situation of the anchovy kilka is critical. A coordinated international effort is needed to provide implementation of sustainable management and responsible fishing activities in the whole Caspian Sea.

Age and growth of the king soldier bream, Argyrops spinifer (Forsskal 1775) in the Persian Gulf (Bushehr coasts) were investigated. A total of 622 samples were obtained from June 2010 to May 2011. Total length (TL) of fish ranged from 13.5 to 64.2cm (females) and 15 to 61.2cm (males). Male and female fish age ranged between 2+ to 25+ and 2+ to 21+ years, respectively. Values of the von Bertalanffy growth function were calculated in females, males and total population by using the backcalculation method and otolith reading data. The values of these parameters according to otolith reading data were K=0.061, L∞=82.10cm (TL), t0=- 2.39 years for females and K=0.082, L∞=67.90cm (TL), t0= - 2.88 for males and K=0.065, L∞=75.50cm (TL), t0=-3.21 for total population and according to backcalculation method were K=0.088, L∞=76.37cm (TL), t0=-0.329 years for females and K=0.101, L∞=65.71cm (TL), t0=-0.168 for males and K=0.094, L∞=74.55cm (TL), t0=-0.191 for total population. The results of the study provide the direction for the future management models for the continued sustainable exploitation of this species in the Persian Gulf region.

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.

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.

This study was carried out in Turkmen fishing station to examine suitable mesh size of gill nets for Persian sturgeon, Acipenser persicus, to decrease possibility of catching immature specimens and increase catch likelihood for larger fish. The Holt model was used to determine suitable length for catch and selection of mature Persian sturgeon females. Following preliminary studies some 920 experimental gill nets (mesh size 170mm) similar to those generally used by Iranian Fisheries except for mesh size (150mm) were set up in the Caspian Sea. During the experimental period, 128 and 110 sturgeons were caught in control and experimental nets, respectively. Out of those caught in control nets, 63 specimens were Persian sturgeon (49.2%), 57 were Stellate sturgeon, Acipenser stellatus (44.5%) while in the experimental nets, 95 specimens (86.4%) were Persian sturgeon and 7 specimens (6.4%) were Stellate sturgeon. Regarding maturity status of fishes, 42 Persian sturgeon caught in control nets were mature females while this figure was 83 (87.4%) in experimental nets. Mean fork length of the Persian sturgeon was 152.9±13.8cm and 162.4±13.6cm in control and experimental nets, respectively. The mean caviar yield of the Persian sturgeon in control nets was 6.4±1.7 kg and in experimental nets was 7.4±1.9kg. One way ANOVA and Tukey’s test showed significant differences between factors like age, mean caviar yield and fork length of the Persian sturgeon caught in control and experimental nets. The results showed increasing mesh size of gill nets to 170mm for the Persian sturgeon may help achieving objectives of stock managements including decrease in catch of immature fish and increase in catch of mature and larger sturgeons which can secure optimum and sustainable stock yield.

Population parameters of Whipfin silver-biddy (Gerres filamentosus) and Longtail silverbiddy (Gerres longirostris) were studied from January to December 2006 in three creeks (Markazi, Khalasi and Gabrik) of Hara protected area in Jask, Oman Sea. All fishes were sampled by boat trawl and beach seine. Growth parameters were determined using the monthly length–frequency parameters. The Mean total length was calculated at 6.2 and 5.4cm for Whipfin silver-biddy and Longtail silver-biddy. The values of L∞ and K for Whipfin silver-biddy were 16.8cm and 0.99 yr-1 and for Longtail silver-biddy, these were 15cm and 0.77 yr-1, respectively. The value of to was calculated at -0.12 year for both species. The longevity was estimated to be 3 years for Whipfin silver-biddy and 3.8 years for Longtail silver-biddy. The length-weight relationship were determined as W= 0.0088 L3.21 and W= 0.0087L 3.18 for Whipfin silver-biddy and Longtail silver-biddy, respectively. Results showed the fish were in their juvenile stage which emphasized the supporting roles of creeks for Gerridae as nursery ground.

To study moving direction and survival index of Persian sturgeon fingerlings, a total of 390200 individuals of the fish in three weight classes: less than 3g, 3 to 5g and 6 to10g were marked by coded wire tags (CWT) during 2003 to 2008. In 2003, 101500 of these individuals were marked in Shahid Beheshti, Shahid Rajaee and Shahid Marjani Sturgeon Rearing Centers, in north of Iran and then released in Sephidrud, Tajan and Gorganrud rivers. During 2004 to 2008, 288700 pieces were marked by Shahid Beheshti Rearing Centers and released in Sephidrud River. Catch and detection of fingerlings carried out by gill net prepared from nylon with mesh sizes 22, 26, 33 (2 filaments for each mesh) and one 40mm mesh size. Totally, 175 meters of net was used to study fishes in waters under 10m depth in Guilan province. In all, 2827 pieces of this fish were caught of which 40 had CWT and these belonged to weight classes 6-10g (22 pieces), 3-5g (17 pieces) and under 3g (one piece). Results on release and catch of the fingerlings for Sephirud River showed that more than 70% of fingerlings moved to eastern parts of the estuary and eastern coasts of Guilan province (stations like 12 Bahman, Dastak and Chaboksar). Of the fingerlings released in Gorganrud and Tajan rivers, only one piece was caught in Chaboksar and another in Lisar after 15 months. Hence, we postulated that the fingerlings released in Mazandaran and Golestan provices migrated to Guilan province coasts. Statistical analysis of the survival index in different weight classes indicated that the class 6-10g had higher survival rate, twice than class 3-5g and 20 times more than that of the class under 3g. Considering these results, probably the higher weight at release time can be effective in increasing the survival rate of the Persian sturgeon fingerlings.

Stock assessment and the opening and closure seasons of the green tiger prawn were surveyed in Bushehr waters from July 2004 to September 2006. The study area encompassed Motaf area (27° 30' N" and 51° 30' E) to Daylam waters (30° 00' N and 50° 00' E) the northern part of the Iranian waters of the Persian Gulf. Assessment was conducted using 45 stations on 15 transects in water depths less than lOrn, 10-20m and 20-30m. Sampling was done by bottom trawl net.Results showed that the shortest mean length of the prawn were 11.3, 11.8 and 11.9cm in the years 2004, 2005 and 2006, respectively. Also, the maximum catch per unit effort for the prawns in these years was found to be 10.8, 14.7 and 9.7kg per hour.At the opening of fishing season in the years 2004, 2005 and 2006, the CPUE of the prawn fishing launches were 100, 150 and 120kg per day.Based on length frequency of the green tiger prawn, the opening times of prawn fishing was proposed to be 22, 11 and 20, August of years 2004, 2005 and 2006, respectively. Also, the closure times were derived from the shrimp commercial catch data and defined to be 25, 27 and 28 of September in 2004, 2005 and 2006, respectively.Investigation of the shrimp stock density in Bushehr waters hows that the green tiger prawns enter the fisheries areas from the southeastern parts of Bushehr waters. The Motaf, Nakhilou, Ras-e-khan and Mond River are the areas that green tiger prawn schools are first emerged in the Bushehr province waters.

Species composition, relative abundance, absolute abundance and biomass of sturgeon species were studied during the years 2008-2009. Eighty five stations were covered in the stratified random sampling design in depths less than 1Om using 9m bottom trawl (head line) and in depths more than 10m using 24.7m bottom trawl (head line). More than 70 specimens of Acipenser persicus were caught during the effort.CPUE decreased from 0.4 to 0.24 specimens per trawl in 2009. The mean total length of the A. persicus was 47.3±29.lcm and 61.9±28.7cm in 2008 to 2009, respectively. The smallest size of A. persicus was 9cm in 2008 and 24.5cm in 2009, while the maximum size was I 02.5cm in 2008 and 126.5±29cm in 2009. The mean total weight in 2009 in comparison with 2008 increased from 989(3- 5000g) to 1569(42-71OOg).Absolute abundance of A. persicus decreased from 2006000 specimens in 2008 to 1192000 specimens in 2009. The estimated biomass was 2010 and 1878 tons in 2008 and 2009, respectively.According to the results of study, the stock status of A. persicus is highly critical in the Caspian Sea and a timely decision has to be taken for conservation of the species.

We launched a summer and winter cruise using two fishing vessels to assess the stocks of the sturgeon fish in the southern coasts of the Caspian Sea in the year 2004-2005. Eighty five random stations were selected and sampled using a 9 meter trawl in waters less than 10 meters and a 24.7 meter trawl for the depths above 10 meters. We caught 170 sturgeons in the summer cruise which comprised 142 Acipenser persicus, 19Acipenser stellatus, 4 Huso huso, 3 Acipenser nudiventris and 2 Acipenser guldenstadtti. In the winter cruise, 118 sturgeons were caught of which 75 were Acipenser persicus, 41 were Acipenser stellatus, 1 was Acipenser nudiventris and 1 was Acipenser guldenstadtti.
Catch per unit effort (CPUE) was calculated as 2 fish for summer cruise with the Acipenser persicus being the most abundant species with 1.67 individuals per trawling while for Acipenser stellatus this was 0.22. For Huso huso, the CPUE was 0.05 and for Acipenser nudiventris it was 0.04. For winter cruise, the CPUE was calculated as 1.38 fish, again with the Acipenser persicus as the most abundant with 0.88, while that of the Acipenser stellatus was 0.48. The CPUE for Acipenser guldenstadtti and Acipenser nudiventris was 0.01 in the winter cruise.