نشریه پژوهش های ماهی شناسی کاربردی
سال نهم شماره 1 (بهار 1400)

Today, invasive species are considered as one of the major threats to biodiversity and ecosystem functions. The suitable habitats of these species are expected to be expanded under the effects of future climate change hence it is likely to threaten the existence of native species. Consequently, identifying the current and potential distribution range of invasive species is essential for management of such species. In this study, suitable habitat of Gambusia holbrooki was predicted by using Maximum Entropy (MaxEnt) under optimistic and pessimistic (RCP 4.5 and RCP 8.5) scenarios of 2050 and 2080 at the scale of Iran. According to the modeling predictions, the suitable habitats of this species not only will include its current distribution range but also may expand in some other basins. In other words, it is expected to extend to new favorable regions under future climate change scenarios. Our study showed that the distribution of this invasive species in the 19 main basins is relatively high. If preventive measures are not employed, the negative effects of invasive species on biodiversity and ecosystem dynamics will be high. Therefore, this study will be helpful to policymakers for management of this invasive species and the conservation of biodiversity.

Capoeta sevangi is a native species of the Cyprinidae family in the Caspian Sea basin (Arass River) and is ecologically and economically important. The main purpose of this study to investgate the relationship between absolute and relative fecundity with length, weight and age of this species in the Arass River and sampling was carried out from March to June 2012 using cast-net and gill-net. The result of the study on 72 female specimens of previous stages to prepare spawning showed that the absolute fecundity of this fish is 3056 to 21213 (10590.7±4085.0) eggs and the relative fecundity is 23.5 to 98.3 (41.1±11.9) eggs per gram of body weight and the egg diameter is 0.95 to 1.85 mm measured

The objective of the present study was to determine the effects of fish aggregation device (FAD) deployment on biodiversity, catch composition and length frequency distribution in the Qeshm Island handline fishery. Two FADs were deployed in the Qeshm Island. Four biodiversity indices including Margalef, Shannon-Weaver, Simpson and Pielou and also catch composition and length frequency distribution were calculated and compared between FAD and non-FAD area among spring and fall seasons. Comparing catch composition between FAD and non-FAD area by simper analysis showed that Scomberoides commersonnianus, Acanthopagrus latus, Scomberomorus commerson, Argyrops spinifer, Nemipterus japonicas and Caranx sexfasciatus were responsible for 78.03 dissimilarity. However, Comparing catch composition between spring and fall seasons indicate that A. spinifer, C. sexfasciatus, Netuma thalassina, S. commerson N, japonicas and Pomadasys kaakan were responsible for 82.77 dissimilarity. Length frequency distribution of all species (except P. kaakan) was differed significantly between FAD and non-FAD area (P<0.05). All of the biodiversity indices were lower significantly around the FAD area (P<0.05). But no significant difference was found in biodiversity indices between spring and fall seasons (P>0.05). In other mean, limited species comprise the catch dominantly. Quantifying biodiversity on the basis of diversity indices is essential both for sustainable development policies and for addressing ecological issues, such as the relationship between biodiversity and ecosystem functions.

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.

Oxynoemacheilus kurdistanicus related to the Tigris and Euphrates basins and has been distributed in a wide range of Iran, Iraq and Turkey, There is limited information on the biology of this fish in Iranian waters. This study was carried out to evaluated growth pattern of this species with 209 fish samples that obtained from May up to October 2015 with Electroshocker devices. Sex ratio of male to female was 1: 0.62 that showed significant difference between sex ration of male to female in population (X2 = 11.49, p < 0.05). The weight - length relation of female was W = 0.0157 TL2.77 (r2 = 0.90) and the weight- length relation of male was W = 0.0127 TL2.86 (r2 = 0.93) and the total relation was W = 0.0141 TL2.81 (r2 = 0.98). The results showed positive allometric growth (t-test, tmale= 2.07, tfemale = 2.15, tpopulation= 3.33, p < 0.05).

Investigation of ecological, hydrological status and habitat Suitability of river is one of the key elements in river ecosystem management. In this regard, in the present study, in order to evaluate the ecological sustainable conditions in Zarrin-Gol River of Golestan Province, during stepwise calculations, echo-hydraulic and hydromorphocological analysis of the habitat of Capoeta gracilis (Keyserling, 1861) and ecological flow were studied estimation using hydrological and flow methods (Tennant and Aquatic base Flow) during the 10-year statistical period (2009-2019), hydraulic method (wetted perimeter) and habitat simulation model in different seasons of 2017 and 2018. For this purpose, physical simulation of habitat based on habitat suitability criteria curves was performed by field studies and sampling of hydraulic (depth, velocity and bed index) and ecological (aquatic communities) parameters. First, the geometry of the river model and cross sections were created using the topographic map of Zarrin-Gol River and ARC-GIS software. Then hydraulic simulation of river was performed with HEC-RAS software. In the next step, hydraulic and habitat simulations were performed in PHABSIM model. In this ecological-hydraulic model, the relationship between hydraulic flow and habitat needs of the target species was established using the Weighted Usable Area and the flow- suitability curve of the target species was extracted in different discharges in both adult and juvenile tow age group and new method of classifying the ecological flow regime was considered according to the indices of habitat suitability (water depth, flow velocity and bed). By elicitation of flow-habitat suitability curve, suitability river in terms of quantity and location was investigated. Based on the results, the optimal ecological flow regime to provide the ecological potential of habitat of index species is different by combining different methods for the studied periods during the year and accordingly, to maintain optimal conditions and protect the ecosystem and habitat components of biological communities, The required flow between 1.43 (in July-February) to 3.76 m3/s (in April), with an mean annual bio-flow of 1.74 m3/s (equivalent to 74.3% of  natural stream of the river) should be inside of Zarrin-Gol River. Also, the susceptibility of the Capoeta gracilis species to changes in velocity and bed materials is high and the weighted usable area increases with the depth remaining in optimal conditions. According to the results of this study, the distribution of habitat suitability along the Zarrin-Gol River, under the influence of geometric, hydraulic parameters and flow rate, indicates the favorable habitat conditions of the Capoeta gracilis species in the downstream area and poor conditions in the upstream area.

The great sturgeon, Huso huso, is one of the most important cultured sturgeon species in Iran, which effective management of aquaculture production of this species requires knowledge of broodstock structure, mating patterns, and genetic diversity of broodstock. The aim of the present study was the application of microsatellite DNA analysis for genetic diversity assessment in the first generation of cultured great sturgeon farmed at two centers of the live gene bank at the International Sturgeon Research Institute and Shahid Dr. Beheshti center for restoration and conservation of genetic stocks of sturgeon in Guilan province. Fin clips were sampled from 147 spawners and pre-spawners of great sturgeon at the two centers (47 samples from gene bank and 100 samples from Shahid Beheshti) in 1397-1399. Genomic DNA for amplification of microsatellite loci was extracted using ammonium acetate. Four microsatellite loci (LS68, LS57, LS19, and LS39) were amplified for examination of the genetic diversity of the two group studied sturgeons. Within 147 individuals of the great sturgeon, 198 alleles were detected (123 alleles in genebank and 75 alleles in Shahid Beheshti stocks) and all loci were disomic. The genetic diversity in gene bank and Shahid Beheshti populations were 0.44 and 0.68, respectively. Results showed that the Shahid Beheshti Center broodstocks had good allelic richness and genetic diversity and the gene bank broodstocks had good allelic richness but with reduced heterozygosity index. The genetic differentiation index (FST) between the two populations was 0.34, which indicated a low genetic differentiation between the two populations. Also, the genetic distance and similarity of Nei based on the population matrix were 1.491 and 0.225, respectively, while based on Analysis of Molecular Variance (AMOVA) genetic diversity between the two populations of great sturgeon was 92% and within the population was 8%. Genetic study of fish populations in two important fisheries centers of the country was able to provide basic information on the genetic conditions of the stocks of these valuable fish from the point of view of conservation of stocks as well as commercial aquaculture management programs.

This experiment was conducted to evaluate the effect of different levels two commercial prebiotic(Behdam) and probiotic(Moltibehsil) on the growth performance, biochemical parameters of body extract and resistance against the challenge tests of Ctenophryngodon idella for 45 days. This experiment conducted in a completely random design with seven treatments which contain triplicates. Three levels of probiotic and prebiotic (200 mg/kg, 400 mg/kg and 600 mg/kg of ration) were added to the basic diet. At the end of the feeding trial, the results some growth performance indices(including: weight gain, specific growth rate, Thermal Growth Coefficient,  Velocity of growth body weight, daily growth coefficend and Survival rate) on the grass carps larve had significantly difference with control group (P<0.05). Subsequently, elevated Body extract biochemical (AST, ALT and Cortisol) analyses was observed in C. idella fed with probiotic and prebioticcompared to control group (P<0.05). Whiles There were no significant differences in amount of ALP, Glocose, total protein and lysozyme among experimental groups (P>0.05). Also, the addition of Behsam and Moltibehsil to the diet increased larval resistance against the challenge tests and Significant differences were observed in expermentral treatment compar with control group (P>0.05). This study highlighted that the different levels of Behsam and Moltibehsil in rearing of grass carp larvae had positive effects on growth performance and resistance to challenge tests, but had a different effect on body extract biochemical parameters in this fish.