جستجوی مقالات مرتبط با کلیدواژه « abundance » در نشریات گروه « شیلات »

Three species Rutilus frisii, Alburnus chalcoides and Vimba persa are the most valuable fish that migrate to southern Caspian rivers especially Sefidroud river. In this study, the temporal and spatial distribution of was investigated based on presence and abundance of fingerling fish in 8 stations of the Sefidroud River, from the estuary to the Sangar Dam, during one year from March 2021 to December 2022.</span></span></span> According to the environmental conditions of stations, the sampling was done with an electrofishing instrument and a throwing net with mesh size 6 mm. The results showed that the abundance of fish fingerlings is minimal in the winter and their maximum abundance coincides with the reproduction time and after their adult spawning. The maximum abundance of these fingerlings along with their spatial distribution, also shows their migration pattern towards the Caspian Sea. The abundance of Rutilus frisii in the pebble and gravel beds of the upstream stations was the highest in April and the abundance of the Alburnus chalcoides and Vimba persa in the gravel-mud beds of the middle stations up to the estuary was the highest in August-September. The presence of Rutilus frisii fingerling, with an average weight of 2 g. was high in near to estuary in August while the other two species were present in the middle stations with high abundance until November. Rutilus frisii with weigh more than 3 grams in different stations in autumn and winter indicate the adaptability and residency of a number of fish in the river. The present study can provide some guidelines to the fish stocks restoration centers of Caspian Sea for releasing Kutum fry in the upstream areas, or fish fingerling in the middle of the river at an earlier time. This plan can be tested in a pilot program.

More than 70 millions of Kutum (Rutilus frisii) fingerlings are released in the rivers of Guilan province annually for restoring, but there is few data about biological chracteristics about the fish during staying in the rivers downstream, thus this study has been done on abundance, growth, condition factor and diet of released fingerlings of kutum fish (Rutilus frisii) in Khoshkrud River downstream, and for this propose, 3 stations selected in the river downstream and sampling has been done using electroshocker monthly from Oct. 2022 until March 2023. Results showed Alburnoides samii, Capoeta razii, Rutilus frisii, Ponticola gorlap and Cobitis with 249.2, 108.7, 85.2, 32.2 and 31.4 individuals in 100 m2 catch effort had the most abundant. The fingerlings of kutum fish present in all months in the river downstream and its density varied 20.0 to 212.5 individuals per 100 m2. Studied fingerlings (n=119) had a weight of 2.10-15.10 (5.77±2.54g, average±s.d), total length of 6.62-12.20 (8.61±1.13cm) and condition factor 0.71-0.97 (0.86±0.05) and there was significant statistical difference only in condition factor between autumn and winter. The length-weight parameters was calculated for b-value 3.09 and correlation coefficient (r2) 0.98 and indicated isometric growth patterns. It was determined vacuity index 40.9% and 59.6%, the mean relative length of intestine 0.78±0.08 and 0.75±0.08 and the mean fullness intensity 76.1±97.1 and 71.3±118 in kutum fingerlings in autumn and winter seasons, respectively. There was 6 macro-invertebrates and 14 genera of algae in gut of kutum fingerlings and in the fish intestine were abundant Chironomidae from benthos and genera Synedra, Navicula, Diatoma and Melosira from algae cells in both seasons. In general, fullness intensity, condition factor and water temperature were no suitable for staying fish fingerlings in the stuied duration, but was not distinguished the reason of settle of fish in rivers and no emigration to sea water.

Rocky shores or artificial structures increase the diversity of sessile and mobile fauna. On the Southern shores of the Caspian Sea, these areas have been constructed artificially. The bivalve Mytilaster lineatus is one of the non-native species of the Caspian Sea, which widely distributed in the southern coasts. In this investigation, a certain level of the breakwater walls in in both regions of the Anzali port and the Caspian port were scraped and cleaned off all organisms. The population structure, growth, and abundance of M. lineatus were seasonally investigated in the sampling units. M. lineatus species was not present inside the port area of Anzali region, while it was established in the marina area of the Caspian port but its abundance was gradually decreased. A gradually increase in the abundance and biomass of the bivalves was observed in both marine parts of the mentioned regions. Five months after the beginning of survey, all length classes were observed in the population after five months and the height length of 13 mm present in the specimens. One year after the first sampling, the maximum length was 17.13 mm. The growth rate in summer-autumn was calculated at about 0.075 mm per day. After one year, the biomass was about 2 kg per square meter, which shows that this species is extremely invasive in the southern Caspian regions. The abundance of this species in areas far from the coast can provide the food resources for many species such as sturgeon fish and Kutum, which can be investigated by a pilot program with creating artificial habitats.

The Sefidroud River is the largest river in the north of Iran and has a special importance in the survival of Caspian anadromous fish. In this study, the biodiversity and abundance of fish were investigated in eight points of the Sefidroud River and one point on the sea coast from March 2022 to January 2023. There were identified a total of 40 species of fish from various ecological groups; riverine (26 species), migratory (6 species), and estuarine-marine (8 species). The highest and the lowest number of species were observed in the mid-region of the river and the marine area with 21 and 17 species, respectively. The spatial ecological niche was observed for some species such as three Gobiidae species Caspian goby (Neogobius caspius), Caucasian dwarf goby (Knipowitschia caucasica), and Iranian Goby (Ponticola iranicus) occupied the sea coast, the estuary, and the upstream area, respectively. Mugilidae species were also seen up to 10 km from the sea. The eggs and larvae of anadromous fish were observed in the highest station. Kutum (Rutilus frisii) and Danube bleak (Alburnus chalcoides) fry fish had the highest abundance among the identified species of with 222 and 92 number/200m2, respectively. Bream (Vimba persa), Leaping mullet (Chelon saliens), European bitterling (Rhodeus amarus), Sanias spined loach (Cobitis saniae), North Caucasian bleak (Alburnus hohenackeri) had moderate frequency between 27 to 59 number/200m2 and the abundant of other species was low between 0.014 to19 number/200m2. The lowest Shannon's diversity index was in the furthest distance from the Caspian with value 1.03, while the highest value, with significantly difference p<0.05, was observed in 5 km to the sea with value 1.6  Also, the highest and lowest values ​​of the index were observed in November 2022 and January 2023, respectively.

In this research, the frequency of coral fishes from Hengam Island were studied seasonally from summer of 2020 to the spring of 2021 by Underwater Visual Census (UVCm) and belt transect method. A total of 38 species were identified in five selected stations, of which 31 species were herbivorous fishes,  Pomacentridae and Labridae families had the highest frequency with 7 and 4 species. The abundance of herbivorous fish Thalassoma lunare was estimated at 80(±71) number per square kilometer in station two. In addition, two species of parrotfish (Scarus persicus and Scarus ghobban) were the most frequent in all stations. The highest seasonal frequency of herbivorous fishes was recorded at station 2 in winter 58(±12) numbers per square kilometer and the lowest at station 3 in summer 5(±21) numbers per square kilometer. The seasonal abundance of herbivorous fishes were significantly differ between stations, except in summer (p<0.05). The temporal and spatial changes in the abundance of herbivorous fish in the stations indicate the importance of selective performance of fishes for ecological niche. In this regard, the role of functional redundancy is more effective than the role of functional complement among these fishes in the biological future of the coral communities of Hengam Island. Therefore, it is recommended to protect the coral fish stock of the island.

According to the importance of macrozooplankton in food chain, this study was conducted with the aim of investigating the abundance and diversity of macrozooplankton in the coastal waters of Khuzestan and Bushehr provinces in the winter of 2021. For this purpose, 11 stations were sampled using 300 micrometers mesh size plankton net equipped with a flowmeter in the middle third of the net opening between the center and the edge of the net. In total, 2537.509±5.85 number per m2 of zooplankton belonging to 51 species, 27 genera, 29 families, 13 orders, 12 classes, and 5 phylum of zooplanktons were identified and counted. Arthropods phylum in the coastal waters of Khuzestan and Bushehr provinces was the predominant macrozooplankton phylum with 99.56% and 98.91%, respectively. No significant difference was observed between the coastal waters of the two mentioned provinces in the abundance and diversity of macrozooplankton (p>0.05), which can be caused by the similarity of the characteristics of the sampled areas and the homogeneity of the environment. However, there was a significant difference in the abundance of macrozooplankton among the investigated stations in each province (p<0.05), which is caused by the influence of environmental and nutritional conditions. The lower level of the Shannon and margalef indices in Khuzestan province indicates more stress in the region. Therefore, it is necessary to continuously monitoring and measuring environmental factors and pollutants in the coastal waters of Khuzestan and Bushehr provinces for four seasons to determine the most important factor of stress.

Water pollution is a major global problem that affects plants and living organisms. Factors affecting water pollution include industrial, agricultural, and human pollutants. Qarasu river is very important in terms of pollution due to the use of river water in the agriculture and aquaculture sectors. In this research, the effect of intensive fish farms and the riverbed material was investigated on the abundance of macrobenthic communities. For this purpose, four stations 1) the station upstream and before the fish farms (as control station), 2) the station between the fish farms, 3) the last station of the farms, and 4) the downstream station at a distance of 4 km from the last farm were selected. A sampling of the macrobenthos and riverbeds was done in two seasons, winter and spring, and their frequency was calculated in the sampling stations and months. The highest abundance was related to the family’s Chironomidae (1456 numbers per m2) and Simolidae (2737 numbers per m2) from the Diptera order, which were observed in the effluent of station 2 and station 4 in the winter season, respectively. In addition, the type of the river bed was determined to find the correlation with macrobenthic species. The identified macrobenthos was classified into trophic groups and the relationship with the type of substrate was determined using the Pearson correlation. The correlation of different macrobenthic species with sampling stations and months was found using Canoco software and CCA statistical analysis. The present study showed that the effluent from intensive fish farms had an effect on the abundance of macrobenthos in the Qarasu River, which could be due to the increase in nutrients in the river water from the release of the effluent, and decrease in temperature and decrease in the decomposition of nutrients in the winter season. Therefore, based on the findings, the presence of different functional macrobenthic groups is affected by the type of riverbed and different seasons of the year.

The purpose of this study was to investigate the seasonal variation of distribution, abundance and biomass Streblospio gynobranchiata of substrate sediments on the Southern coasts of the Caspian Sea (Bandar Torkman and Babolsar) in 2018-2019. Sampling was done seasonally and 6 stations at depths of 5, 10 and 30 meters of the 2 transects. The results showed that the mean (±SE) of abundance and biomass were in the Babolsar transect (respectively) 207.06±51.40 ind.m-2 and 0.042±0.006 g.m-2 and seasonal study, the highest abundance and biomass in Babolsar transect with mean (respectively) 1297.47±284.95 ind.m-2 and 0.222±0.040 g.m-2. So there was a significant difference between the abundance and biomass in different seasons (p<0.05). Also showed that the mean (±SE) of abundance and biomass were in the Bandar Torkman transect (respectively) 206.51±53.07 ind.m-2 and 0.043±0.005 g.m-2. According to seasonal study, the highest abundance in Bandar Torkman transect with mean 942.27±180.07 ind.m-2 in summer and highest biomass 0.153 ± 0.03 g.m-2 recorded in spring, so there was a significant difference between the abundance and biomass in different seasons (p<0.05), which is due to their reproductive cycle. The total organic matter in different seasons was fluctuating, which could be due to the depth, substrate and ecological origin.

In order to identify and determine the distribution of economic and ornamental seashells in the northern coasts of the Persian Gulf, sampling was done in upper, middle and bottom intertidal zone in all four seasons and in mud, sand and rocky substrates. Onshore samples were collected through diving and trawling. Identification of specimens was carried out inside the country and confirmed by Institute of Malacology, Tokyo, Japan.381 species belonging to 117 families and 231 genera were identified. There was no significant difference in the warm and cold months in terms of diversity, although the density of the species was much higher in the warm seasons. In terms of species diversity, Bandar-length, Faroor and Hendurabi islands were the most diverse. In terms of size, the largest shells found were Sepia pharaonius and Pinna muricata with a total length of 45 cm and the smallest one with a size of 1 mm was Acteocina involute.

Trichiurus lepturus is considered as one of the most economically important marine fish and consumed as food in many countries. With increasing population growth, sustainable management is essential for continuing exploitation of this species.The current study was conducted to assess the amount of biomass and Catch Per Unit of Area (CPUA) as well as to determine the distribution pattern of Trichiurus Lepturus as one of the most important and commercial fish species in the north coast of the Gulf of Oman. Samples were collected from 94 trawl stations selected at stratified random procedure. The study area was stratified to five strata (A to E) covering the depth layers of 10-20, 20-30, 30-50 and 50-100 m. The catch rates of CPUA and biomass of T. Lepturus were estimated 4778.3 kg/nm2, and 2220.2 tons, respectively. The highest value of biomass for T. Lepturus was recorded in Chabahar to Ramin (D strata, 861.8 tones) in the east coast of Chabahar, and the lowest value (105.9 tones) was estimated for stratum A (west coast of Chabahar). The highest value of biomass (1634.5 tones) was observed at 50-100 depth layer. On the other hand, the highest CPUA (1604.8 kg/nm2) was recorded in stratum D and the lowest CPUA (456.4 kg/nm2) was recorded in stratum A. The highest value of CPUA (701.5 kg/mn2) was observed at 50-100 depth layer. It was concluded that stratum B and D are the best fishing area as per higher density and distribution of T. Lepturus and depth of distribution deeper than 50 m.

This study was carried out in line with the Caspian Sea water transportation program to the central plateau on the Southeast shores of the Caspian Sea (Goharbaran region) since 2013-2014. Sampling was performed monthly and there were 8 stations at depths of 5, 10 and 15 meters in 2 transects. The purpose of this study was to investigate the relationships between some physico-chemical parameters of water and total organic matter, distribution, abundance and biomass of Streblospio gynobranchiata (Spionoidae) in the different depths. The results showed that the highest abundance and biomass were in the Eastern transect with mean 1437.1±269.17 ind.m-2 and 0.711±0.131 g.m-2, respectively. A positive correlation was found between the abundance and biomass of S. gynobranchiata with TOM and at 0.01 level, salinity and water temperature at 0.05 level based on Pearson correlation test. The abundance and biomass of S. gynobranchiatain different seasons was fluctuating, with the highest abundance 1550.08±185.22 ind.m-2 and 0.775±0.09 g.m-2 recorded in winter and in January, respectively .So there was a significant difference between the abundance and biomass in different months (p<0.05). This could be due to the approach to the period of water disruption following the seasonal changes and the creation of a bioturbation in the seabed and a deposit feeder species.

One of the unique and important aquatic species of Anzali wetland, Anadonta cygnea, native Anzali wetland and its rivers, and the most important two-body system of this blue system, has declined sharply in recent years due to various reasons. Is this species is considered to be smuggling and has a special sensitivity to environmental changes (biological pollution assessment).Anzali Wetland is a special ecosystem for the cultivation and development of various types of aquatic animals on the southern of the Caspian Sea. On the other hand, the special position of the mollusks in relation to the use of other creatures from them and the industrial industrial applications and the role of water purification necessitates the study of the Anadonta cygnea diet in the Anzali Wetland. Of the 14 stations surveyed, only 9 stations, including the stations entrance of the West Bank , Bahambar , Shijan , Soussar Rogah , Abkenar , Mahruzha , Karkan , Siakishim, and finally Hindakhale, were caught in the Anodont shell. In the above study, the average length and weight of Anadonta cygnea, regardless of their specific situation, were 8.25 ± 1.17 cm and 58.03 ± 27.53 gr, respectively. The most frequencies and distribution in different seasons belong to the entrance stations of West Wetland, Behmbar, Shijan and Sossar Roogah and the highest average age in the spring seasons belonging to the station of Behambar (7 years old), summer related to Mahrooz station (8 years old) Autumn belonged to the Sossar Roogah (7 year old) sonar station and finally to the Shijan Station (8 years old) winter. In general, it can be said that Anadonta cygnea feed from phytoplankton branches of Chlorophyta and Bacillariophyta more than other branches throughout the year. In an experimental study of the Anzali Wetland anodentic sheath, it can be stated from the different stations that most of the phytoplankton species used from the green algae of Scenedesmus, Chlorella and Pandorina were from the branches of the Diatoma Cyclotella, Cembella and Navicula algae. Nutrition from zooplankton was detected in a small amount, from the Ciliophora of Arcella and Amiibia, from Cilliata, and finally from rotifers Brachionus, Asplachna and Rotaria. Suitable substrate type is sandy with some flowers, with the range of silt-clay changes in stations ranging from 80.8 ± 3.8 to 97.64 ± 2.2 percent. In the study of Anadonta cygnea diet, it was determined that the above Anadonta cygnea are fed by filtration (non-selective selection). Therefore, with regard to different ages and abundance in the living environment, in the first place (more than 90%), branches Microscopic phytoplankton from 5 to 20 micron (branches such as Chlorophyta, Bacillariophyta and Cyanophyta), and in the next step (about 10 percent), microscopic zooplankton from 5 to 30 microns (orders such as Ciliopoda, Rhizopoda, Rotatoria and Cladocera, as well as detritus in these dimensions).

The aim of the present study was to examine the effect of temporal variations and tidal phases on frequency of Upeneus doriae (Günther,1869) in the coast of Bandar Abbas. Sampling was performed in September 2016 to April 2017. During the lunar calendar months, the highest abundance of U. doriae  was observed in Muharram (with147/15 ± 144/37 n.G-1.day-1 ), and lowest was in Rabi Ul Awal (with 3/53 ± 3/5 n.G-1.day-1). The selected species was also most abundant in the western region of Bandar Abbas coasts (205/1 ± 137/01 n.G-1.day-1 ), and lowest frequency was observed in central region of coasts (28/55 ± 22/88 n.G-1.day-1). Data analysis approved the temporal and spatial variation of U. doriae abundance in Bandar Abbas coasts. The mean total length and weight of the specimens were also 10/57 ± 1/43 cm and 18/19 ± 5/86 gr, and the total length-weight relationship was calculated W=0/01397L3/0456. Data of Length frequency distribution also showed that length classes 10.5-11.5 and 14.5-15.5 cm had the highest and lowest abundance among the caught samples, respectively. The mean relative condition factor (Krel) and relative weights (Wr)of caught specimens were calculated as 1/005 ± 0/320 and 0/890 ± 0/178, respectively.