جستجوی مقالات مرتبط با کلیدواژه « فراوانی » در نشریات گروه « زیست شناسی »

This study aimed to investigate the catch composition, length frequency, fishing effort and distribution of Sepia pharaonis caught by pot in the fishing grounds of Ramin and Konarak (Sistan and Baluchestan Province). During October, November, December, and January 2021, 387 specimens were collected in depths of 20 to 40 meters in Ramin and 368 specimens were collected in Konarak. In the Ramin region, the highest number (129 specimens) and the highest range of length (17.3-40.6cm) and weight (367.3-3847.5g) were observed in January. The highest number of squids caught belonged to the length class of 24.8-27.2cm (54 specimens) and the lowest number belonged to the length class 39.8-42.2cm (2 specimens). In the Konarak region, the highest number was observed in January (113 specimens), and the highest ranges of length (18.2-41.2cm) and weight (426.17-3886.24g) were observed in October. The highest number of caught squid belonged to the length class of 29.3-32cm (49 specimens) and the lowest number belonged to the length class of 39.9-42.4cm (6 specimens). In the Ramin region showed that 14 species were caught in October, 11 species in November, 14 species in December and 16 species in January. Also, in Konarak, 16 species were caught in October, 15 species in November, 13 species in December and 16 species in January. The values of a, b and R2 parameters of length and weight, in the Ramin region, were 0.2085, 2.6422, and 0.9791, respectively. The values of a, b and R2 parameters of length and weight, in Konarak, were 0.17038, 2.6962, and 0.9842 respectively. Comparison of CPUE values showed that the highest values in these two regions were observed in January and the lowest values were observed in October. The results of this study have enhanced comprehension of the population dynamics of Sepia pharaonis in these fishing grounds and provide valuable insights into the ecological conditions of the studied areas.

Identifying and introducing the plants of a region is particularly and locally important, which includes the possibility of accessing specific plant species in a certain place and time, determining the potential and vegetative capabilities of the region, the possibility of increasing the density of the species of the region, the possibility of obtaining a new plant species or species, and identifying the destructive factors of the region’s plants. The most obvious classification to explain and describe the structure of plants is to specify the life form of each plant species in each different plant community. The purpose of this research is to investigate the flora, life form, geographical distribution and some characteristics of plants in plant communities. in order to analyze the vegetation status at the central Alborz protected area in Alborz province. In this research, 101 plots were collected and a total of 152 plant species were identified. The identified species belong to 103 genera from 30 families. Asteraceae family with 16 genera and 21 species includes the largest existing taxon in the study area, followed by Poaceae and Fabaceae families with 14 and 12 genera and 18 and 17 species, respectively. The genera Salvia with 8 species and Astragalus with 7 species had the highest species diversity among the identified genera. The dominant vegetative form among the identified species was herbaceous, and tree and shrub elements had the least identified form. According to the Raunkiaer system, hemicryptophyte plants with 51.3% (79 species), therophyte plants with 29% (44 species), cryptophyte plants with 9.9%, chamaephyte plants with 6.6%, and phanaerophyte plants with 2.6% were the most abundant biological forms in this range, respectively. Also, the highest abundance of plant species according to the vegetation area is Irano-Touranian (81 species) and Irano-Touranian/ Hyrcanian (33 species). In general, it can be concluded from this study that the plant community in this area is heterogeneous because all the identified species were in presence code class I with an abundance percentage of 0 to 20%. Also, considering that the study area has a relatively high flora, it can be used to evaluate the current situation and predict the future situation of the region.

The aim of this study was to investigate the changes in the structure of the plankton community in the southwestern Caspian Sea and its relationship with the reduction of Rutilus frisii and Chelon auratus catches. The current study was conducted seasonally in the coasts of Guilan provience from 2020 to 2021. A total number of 48 genera and species of phytoplanktons were identified. Tthe findings showed that the non-native species Pseudo-nitzschia seriata from chrophyta and the toxic species Nodularia spumigena from cyanobacteria formed the highest density. The increase of water temperature and nutrition and the decrease of wind speed were directly related to the bloom of phytoplanktons, especially cyanobacteria in the Caspian Sea, which caused the third bloom of N. spumigena in Anzali shores in July 2021. The results showed an increase in the abundance of phytoplankton by more than 7-folds compared to 1996. The highest abundance of phytoplankton was observed in Anzali shores in 5 m depth. The pattern of phytoplankton abundance and the abundance of R. frisii and C. auratus juveniles were similar to each other.  The food eaten by C. auratus and R. frisii juveniles showed that these fish species fed on phytoplankton detritus. Probably the reduction of Cerastoderma glucaum biomass, illegal fishing with gillnet, the quality and quantity of R. frisii release by Iranian fisheries, and the lack of restoration of the rivers where the natural reproduction occurs are the factors affecting the reduction of the R. frisii catch in recent years.

The purpose of this study was to investigate the population of benthic invertebrates and their relationship with environmental factors of Gorgan Bay Inlet. The abundance of benthic invertebrates during 2017 in three seasons from 9 stations in three sites, bay mouth, Ashuradeh coast and sturgeon culture area was studied using three replicates (225 cm2). In this study, in total, fauna was identified: 3 phyla, 6 classes, 12 families and 12 Genus. Streblospio gynobranchiata (2347±177, 47%) and Hediste diversicolor (873±101, 17%) had the highest abundance. The highest species abundance was observed in spring and the lowest species abundance in autumn. The lowest Shannon (1.12) and Pielu index (0.62) were obtained in the sturgeon culture area. Also, the dbRDA graph based on DistLM model showed that temperature, salinity and clay temperature variables and sand, silt and dissolved oxygen variables were responsible for causing abundance of fauna among different stations in the sampling seasons. According to these results, it can be concluded that macrobenthos in different seasons and areas have many changes in abundance and diversity index. Therefore, when using these communities to assess the impact of environmental factors, their natural changes should be considered.

Although substantial studies are available as regards the abundance, richness and composition of freshwater fish along altitudinal slops, the impact of human factors such as dam construction are rarely considered. In this study, the effects of the environmental and human factors on longitudinal patterns of fish faunal changes, species richness and fish abundance from upstream to downstream in the southern profile of the central Alborz Protected Area were examined using Redundancy Analysis (RDA) and Generalized Linear Models (GLM). The Karaj River was divided into three zones based on habitat structure, physicochemical variables and species composition. The results indicate that chemical variables can be more effective in some conditions including small changes in habitat structure and physical variables along the altitudinal slope and can be a justification for the abundance, richness and composition of species. Typically, in highly polluted rivers, chemical agents can be a good explanation for the presence or absence of species. Human disturbances, such as dams, change the expected distribution patterns of fish along the altitudinal slope by decreasing outlet water temperature and also creating homogeneous and simple habitats. Therefore, the implementation of conservation programs should be a priority for the Karaj River fishes, especially in the middle areas which are affected by these threats.

Waterbirds are among the most vulnerable species of birds, and their species richness and population size are important indicators of the quality and conservation value of aquatic ecosystems. The populations of waterbirds are severely in decline, and in recent years more species have been added to the IUCN Red List. It is therefore imperative that the populations of these birds be monitored and protected. The purpose of the present study was to investigate the trends in the diversity and density of wintering migratory waterbirds in four protected areas in the Anzali International Wetland Complex, namely Selkeh, Sorkhankol, Choukam and Siahkieshim. To this end, data from the mid-winter census during a 10-year period (2003-2005 and 2008-2013) were used. We also compared the similarity of waterbird communities among the four protected areas using the Morista Index and PCA test. In total, 65 species of waterbirds were identified in all of these four areas of the wetland. Selkeh had the highest species richness (57 species) and Siahkeshim had the highest mean abundance (31,504 individuals). Also the highest abundance of these four areas combined was in 2013 (103,332 individuals) and the lowest was in 2005 (42,842 individuals). Anatidae were represented by the highest number of species (18 species) and Threskiornithidae and Sternidae families were lowest with one species each. The results of Morista Index and PCA test also revealed that, Sorkhankol wildlife refuge had the least similarity with the other protected areas based on species richness. The results suggest the importance of the Sorkhankol area for providing habitats and supporting diving waterbird species, in particular its value for diving ducks. So, this part of Anzali Wetland may need to be protected more than before. Implementation of comprehensive wetland management plans and establishment of integrated ecosystem management systems are among the most important strategies for preserving these four areas for aquatic birds and overwintering.

In the present study, species diversity and abundance of water resources in the southeast of the province were identified and studied for 6 months. Five stations were selected and fishes were caught to various means such as gill net, manual net and, electro hemlock were caught a monthly basis and transferred to the laboratory. Their identified using reliable identity keys. The aim of this survey was to genus identify and fish species, their time and spatial distributions and abundances in the region. Result indicated that 3 families, 6 genus and 9 species were identified that 4 genus and 6 spceies belong to the cyprinidae family. The family balitorada with 2 spceies was next standing. The last family in the research poecilidae family with one genus and one spceies of gambusia holbrooki has been found.

 In this study, in order to identify the fish fauna of Beshar River located in Kohgiluyeh and Boyer-Ahmad province, sampling was performed in summer and winter seasons during 2014. Fishes were captured by fixed fishing net and transferred to laboratory of veterinary medicine of Islamic Azad University, Kazerun Branch and identified by key identification after biometry. The results showed that 13 species belonging to four families existing in the Beshar River which including: Garra rufa, Cyprinion macrostomum, Barbus barbulus, Capoeta damascina, Capoeta barroisi, Capoeta trutta, Capoeta capoeta, Alburnus atropatenae, and Chondrostoma regium from cyprinidae, Oncorhynchus mykiss from salmonidae, Glyptothorax  silviae from sisoridae and two species Turcinoemacheilus kosswigi and Paracobitis malapterura from nemacheilidae. The frequency of fishes showed that G. rufa had highest percentage of frequency (23.49) and T. kosswigi and P. malapterura had lowest percentage of frequency (0.13). Cyprinidae including 9 species and 96.99 frequencies had highest percentage of frequency among the captured fish. There was no significant relationship between fish frequency and season sampling (p>0.05). The result is that in all fresh waters of the country, the predominant population of fish belonging to cyprinid fish.

The alien ctenophore Mnemiopsis leidyi which was transported from the Black Sea into the Caspian Sea by the end 1990s has been affecting the ecosystem in this new environment. In this study ,spatial and temporal distribution of M.leidyi was studied during 2001 to 2006 in three transects (Lisar, Bandar Anzali & Sefidroud) in the south of e Caspian Sea. Each transect had four stations located at 5, 10, 20 and 50 m bottom depth contours. Mnemiopsis leidyi achived maximum biomass (1411 ± 805 g/m2 ) in summer 2006. Minimum biomass (3.3±2.6 g/ m2 ) of the ctenophore was measured in winter 2001. The highest biomass was at stations with 20 m depth (1355±1072 g/m2 ) and lowest biomass (20-50 m layer 19.5±16.9 g/m2 ) was obtained at that 50 m depth. Small specimens (<5 mm) contributed about 90 % total abundance of the population. The maximum length was 70 mm. The greatest average biomass 461±354 g/m2 was measured in Sefidroud region and the smallest biomass (245±205 g/m2) observed in Anzali region. The variations of temperature and salinity were important parameters in fluctuation of abundance, biomass and size groups in different seasons and depth in the southwestern Caspian Sea

Alibilagh region, situated in the western side of Tandoureh National Park, is one of the impressive views in Dargaz town. In the point of view of distribution of lichens, the site is valuable because of the existence of hills, rocky highlands, old trees and broken trunks. However, the investigation of Alibolagh’s lichens is restricted to 18 species. The present research was done with the goals of the identification of more corticolous lichens and the investigation of distribution of the lichens on the bark of trunks and twigs and also finding the probable relation between the heights of the place of vegetation from the soil surface. Laboratory identifications were done on the base of standard macro-microscopy methods and the current chemical tests. The statistical analysis was done by using SPSS. 17 species identified included four new reports Lecanora albellula, Parmelia sulcata, Phaeophyscia cilita and Physcia caesia for Rzavi Khorasan province. The statistical analysis showed that Teloschistaceae and Physciaceae have the most frequency on the trunks and twigs. Also there is no meaningful relation between the height of the establishment of the thalli on the substrate and the species.

This study was directed in the four stations of the coast of Noor, Mahmoudabad and Royan cities (Mazandaran Province) located in the coast of the Caspian Sea for identification and determine some ecological factors of crab Rhithropanopeus harrrissi. Samples of each station were fixed and transported to the laboratory and were identified at the species level. The 192 collected samples were found to be Rhithropanopeus harrrissi in the laboratory analysis. In order to verifying the species, our samples compare with the metatypical crab samples in the Zoological Museum, University of Tehran. Also in this species, morphological features, sex ratio, abundance and distribution were analysis. The one ways ANOVA with LSD test showed a significant difference (p

This study aimed to achieve length frequency, condition factor and length-weight relationship of the rock oyster, Saccostrea cucullata in the coastal waters of Persian Gulf. Sampling was carried out by 0.25 m2 quadrat through intertidal zone from winter 2015 to autumn 2016. According to the results, length-weight relationship calculated as W=0.000004L2.79 for both sexes. In addition, coefficient of determination (R2) value was determined as 0.94. Furthermore, b value was significantly different from 3. Condition factor was estimated as 14.36, 16.87, 20.85 and 20.76 for autumn, winter, spring and summer, respectively. Mean length and weight were 34.4±4.96, 36.8±8.46, 30.25±7.1 and 33.31±4.31 cm and 8.9±7.57, 10.4±9.8, 10.9±6.11 and 7.8±4.19 g in spring, summer, autumn and winter , respectively. Maximum and minimum length were 97mm and 2 mm in spring and autumn, respectively. Maximum dry weight was found in winter (2.21g) and the minimum was determined in autumn (0.009 g). Maximum length frequency was observed in the 35-45 mm range class in all seasons. However, range class of 40-45 mm was also frequent in the spring. According to the nMDS results based on length and weight ordination, autumn was distinct from all seasons probably due to the juvenile recruitments in this season.

In the present study, macrobenthos were sampled using a grab in Pareh Sar coast at 7 station and two depths (5 and 10 m) during 4 seasons in 2016. In total, 10472 individuals belonging to 22 Species from 13 families were counted. The highest abundance of macrobenthos (648±170.79) was seen in spring while the most biomass (36.21±2.5 gr/m2) was observed in winter. The most abundance group was bivalves (40%) followed by crustaceans (36%), annelids (22%) and gastropods (2%). PERMANOVA analysis showed that season and depth affected the abundance, biomass, species richness, species composition and community structure significantly. The results also showed that with increasing the depth from 5 to 10 m, macrobenthos abundance enhanced in spring, summer, autumn and winter by a magnitude of 4, 2, 1 and 9, respectively. Furthermore, Shannon index, spices richness and biomass increased from 5 to 10 m depth. According to our results, it can be concluded that abundance, biomass and diversity index of macrobnthic communities vary greatly with season and depth. Therefore, natural fluctuations of these variables should come into account while using macrobenthos for environmental impact assessment.

This study touches on abundance and distribution of brittle star Macrophiothrix cheneyi in the intertidal zones of Chabahar Bay in the Oman Sea, Iran, due to spatial and temporal variobility during a year from November on 2008 to September on 2009 at 5 selected stations. Sampling was randomly done bimonthly, by using 1m×1m qudrate. The result of study showed density of species in different stations and months has significant difference (P

This study was conducted to survey distribution pattern and seasonal and spatial abundance of hermit crabs in six stations located in the intertidal zones of Hormuz Island. Sampling was conducted during four seasons. Hermit crabs were fixed in 70% ethanol and were transported to the laboratory. With valid identification key, nine species in two families of hermit crabs were identified. SPSS, PAST, TAL (4.2) and R software were used for statistical analyses. ANOVA test using LSD showed that the abundance of identified species were significantly different among some of the stations (P

For the investigation about prey and predator relationships, Crab plover was selected as a model species in the Zohre river mudflats, Sajafi harbor where is located in thee Mahshahr. During nine months field study from late spring 2014 to the late winter 2015, we tried to estimate the species abundance and density as a predator and prey items as well. The most important variables affecting the bird distribution and habitat use also was investigated using logistic regression and paired T test. The main items that affect Crab Plover habitat selection and feeding strategy are Crab’s density, safety (distance to the Sajafi harbor), presence of the competitors and especially limited time of the feeding period which affect optimal foraging.

Genus Alosa Linck, 1970 is widely distributed in the Caspian Sea but in Southern region of Caspian Sea identified species has not been reconsidered during past ten years. To study the population density of Alosa species of Iranian waters of Caspian Sea, samples were collected over a period of one year (Jun 2012 to March 2013) from Chaboksar, Chaf and Kiashahr coastal water by beach seines and gill net.After collection all samples were brought to laboratory in ice boxes.for identification of different species had been done according to morphological characteristic. A total of 430 specimens were examined to identify four species namely Alosa braschnikowi, Alosa caspia, Alosa kessleri and Alosa saposchnikowi. A.braschnikowi was the most frequent species and Alosa saposchnikowi had the lowest prevalence. A.braschnikowi and A.caspia had the highest and lowest mean fork length and weight, respectively. Sex survey showed that females were dominant in all species. The obtained samples were of 2 to 7 years of age.