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The effects of northern pike, Esox lucius, in controlling coarse fish and other pest organisms and enhancing harvest size in carp ponds was investigated. We used two treatments and one control each with three replicates. The pike density was 200 and 500 fish individuals per hectare for the first and second treatments, respectively and the control pond had no pike. The carp density in ponds was 3500 individuals per hectare and  stocking  rates  were  55% silver carp, 20% common carp, 10% bighead carp and 15% grass carp. Survival rate of the northern pike in treatments  1 and 2 was 43.8 and 40%, respectively.

The results showed that the mean (±SO) biomass of unwanted fishes (13 species) in the control treatment was 358.8±55.4kg/h and in the first and second treatments were 74.2±6.3 and 92.2±10.9kg/h, respectively in the end of the trial period. So unwanted fishes biomass reduced by 79.3% and 74.3% in the two treatments, respectively. Stomach  investigation showed that the pike fed mostly on frog juveniles and some pest fishes like Hemiculter leucisculus, Pseudorasbora parva, Carassius auratus, and few Macrobrachium and  aquatic insects. Also, the average biomass of unwanted fishes like Carassius auratus, Hemiculter leucisculus, Alburnus alburnus and Pseudorasbora parva of the first and second treatments in comparison to control showed a reduction of94, 88.9, 62.4 and 56.82 percent, respectively. A significant difference was found in the final mean weight of common carp between treatments and control ponds (P<0.05), as the weight of common carp in treatments ponds was 220% more than the control pond. Also, Esox lucius with controlling coarse fish increased cultured fish (such  as common  carp, grass carp, silver carp and  bighead  carp) production  by  about

17.9%.

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This study aimed to determine and comparison of age composition, sex ratio, growth model, and fecundity of the populations of Rhodeus amarus in Sefidrood River and Siyahrood River. In total 423 fish were caught monthly from February to June 2013. In Sefidrood River, were abundant males (58.2%) than females (41.8%) and in Siyahrood River, females (59.4%) than males (40.6%) and it was different from standard ratio (1male:1female). The fishes in Siyahrood River have had 1+ till 8+ years old and in Sefidrood River 1+ till 9. The average of total length and body weight was 47.9±10.4 mm and 1.98±1.4g in Siyahrood River and 56.3±7.3 mm and 2.88±1.0 g in Sefidrood River, respectively and there were significant statistical differences between these parameters in both rivers(p<0.001). Growth model in two rivers was positive allometric.  The condition coefficient of males was higher than of females in both rivers(p<0.05). The absolute fecundity was evaluated 67.9±35.2 in Siyahrood River females and 78.8±33.1 in Sefidrood River females and significant statistical difference was observed in studied rivers. Absolute fecundity had significant correlation with fish total length and body weight. The results of this study will help to increase the information available about this species.

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This study focused on population structure, species diversity and abundance of the Chitgar Lake fishes in October 2014. Based on the lake location fish samples were collected at 34 stations in water body. In this study , 8 families belonging to 18 species comprised of Cyprinidae (11 species), Cichlidae (one species), Loricariidae (one species), Pangasiidae (one species), Serrasalmidae (one species), Poeciliidea (one species), Salmonidae (one species), and Scaridae (one species) were identified. Among the fishes just one native fish from Capoeta bohsei species observed during the study. The dominant lake fishes were invasive species Hemiculter leucisculus, Alburnus hohenackeri, Carassius auratus, Carassius gibelio and Pseudorasbora parva. The highest abundance of fishes were H. leucisculus 62 % and A. hohenackeri 35 % by Seine net. Furthermore, those were dominant abundance (69 and 12 % respectively) in Gill net method. Finally, in Cast net method A. hohenackeri 38 %, Pseudorasbora parva 21 % and H. leucisculus 17 % were dominated in the shore region. The lowest fishes abundance were P. hypophthalmus and Parrotfish. Overall more than 90 % of the fish population were invasive and alien species. Thus, the presence of invasive fishes and lack of predator fishes in the Chitgar Lake might be reason for increasing of trophic level.

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Changes in diet during the recent years have caused a marked increase in consumption of saturated fatty acids and n-6 polyunsaturated fatty acids (PUFAs) with a concomitant decrease in the intake of n-3 PUFAs. Increased fish consumption has been shown to be one of the best way to increase dietary intake of long-chain n-3 PUFAs such as eicosapentaenoic acid and docosahexaenoic acid and more balanced n-6: n-3 ratios. Our objective in this research was to characterize fatty acid profile of 7 commonly consumed fish species with different prices, from Persian Gulf. Fishes were collected from local market of Bandar abbas. Fatty acid composition of samples was determined using gas chromatography. This analysis revealed that Pomadasys  kakkam and Pseudorhombus  elevates contained highest concentrations of n-3 PUFA, low saturated fatty acids (42.41%, 35%) and Pampus argennteus, as one of the most expensive among southern marine fishes  contained lowest concentrations of n-3 PUFA, higher saturated fatty acids (6.72% , 42%).

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In this study the biotic and abiotic characteristics of Ardalan dam reservoir was studied from 2011 to 2012. Diatoms, Bacillariophyta, was the main phylum of phytoplankton in Ardalan dam reservoir that was dominant in the most seasons and green algae, Chlorophyta, was the second dominance groups. Survey of zooplanktons showed there were 25 genus from 6 phylum, and Rotatoria constitute 64% of the zooplanktons in. The average phytoplankton and zooplankton abundance during this study were about 19.15×106 and 1863 per liter of lake water respectively. Survey of benthic communities showed that Chironomidae and Tubificidae were the main benthic groups in Ardalan dam. Average of benthic biomass during this survey was 0.9 gr/m2 which is very poor. Sediments in Ardalan dam was mostly of silt and clay. Fish structure survey by gill nets in Ardalan dam showed that common carp and silver carp, by %53 and %45 respectively were the main economical species in the dam. Hydro chemical survey showed that total phosphorus and total nitrogen were 0.073 and 0.779 mg/L respectively. The amount of chlorophyll a was 6.03 mg/m3. The range `of dissolved oxygen was 6.4-10.5 mg/L. Average of EC was 576 µs/cm. Since the water temperature just in august month was more than 20ºC, the appropriate period for warm water fish culture in this reservoir is limited.

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Acanthobrama urmianus is an endemic species of Cyprinidae family in the Urmia Lake basin and important for ecological and sport fishing. The main purpose of this study was to investigate the relationship between the fecundity with length, weight and age in two rivers of Mahabadchai and Siminerud and sampling was carried out from December to June using cast-net and gill-net. The result of the study on 107 female fish specimens from maturity stages 4 and 5 showed that the absolute fecundity of this fish is 1567 to 27228 (11954.3±6991.9) eggs with a diameter of 0.35 to 1.42 and the relative fecundity is 87.9 to 633.9 with an average of 282.6±120.7. Also, with increasing age and size of the fish body, the absolute fecundity increased. Between the absolute fecundity and the total length of equation F= .0034TL ^3.545 (r²=.789) and between the absolute fecundity and the weight of the equation F=23.272W^1.665 (r²=.766) obtained. The results showed that the rate of fecundity in Mahabadchai in the constant length range was less than Siminerud River.
 

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Lake of the Persian Gulf Martyrs has been constructed in the northwest of Tehran in 22 urban areas, which in addition to creating a recreational-tourism environment, has caused an increasing economic value to the adjacent lands. The declining water quality of the lake and the increasing abundance of rough and invader fishes such as Prussian carp (Carassius gibelio) and Sharpbelly (Hemiculter leucisculus) are a threat for ecosystem of the lake. In order to control these fishes, pike (Esox Lucius) as a predator was released in the lake. After introduction of pike was studied its diet and growth, and the changes of invasive fish population in 2018-2019. Lincoln–Petersen method showed that the population of Prussian carp was decreased from 20,000 to 8,300 individuals in lake. CPUE showed that population of Sharpbelly has been reduced from 712,000 to about 3,000 individuals in the lake. Using Jolly-Seber method, population of Sharpbelly from the lake shore did not change much during the study period. The population of Pike was estimated at 575 that with continuous feeding of invader fishes had a weight gain of 3.7±6.1 grams per day. The occurrence percentage of Prussian carp was more than other preys; Sharpbelly and topmouth gudgeon (Pseudorasbora parva). Due to the increase in the size of the Pike, the small fish in the lake do not have much nutritional benefit for the pike and in the current situation, only the Prussian carp fish are fed. In order to better control of the invader fish, the use of small-sized predatory fish seems necessary.

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About 30 species of commercial fish have been caught in the seawater of Guilan province annually and the most important species is Kutum (Rutilus frisii). The aim of this study was to determine the feeding indices, food spectrum, and dominant food items of fingerlings kutum under the investigation of feeding habits of kutum and grey mullets on the coasts of Guilan province. The fish were captured with a seine net with 6 mm mesh size from winter 2020 to autumn 2021 in the coastal areas of Talesh, Anzali, Kiashahr, and Chaboksar. The results on R. frisii with body weight 0.31-14.5 (3.64±2.8)g, total length 34.3-120 (68.3±19.0) mm and ages 0+ and 1+ years showed that the relative length of intestine is 0.59-1.16 (0.78±0.10). Vacuity index was calculated at 0, 0, 5, 0 and 1% in spring, summer, autumn, and winter seasons and the total of the year, respectively, and the mean fullness intensity was 372±267, 360±151, 230±173, 581±689 and 365±302 in spring until winter and total of the year, respectively, which showed significant differences (F=9.10, p<0.05). Detritus, filamentous algae, 26 genera of phytoplankton, 2 types of zooplankton and 13 types of benthic animals and as well as eggs and larvae of fish were observed in the gastrointestinal tract of kutum fingerlings with a frequency of presence 10, 73, 62, 5, 86 and 2 percent of all studied specimens, respectively. The phytoplanktonic genera of Cyclotella, Navicula and Nitzschia were observed in 60%, 52%, and 47% respectively, and gammaridae among the benthic animals had the most frequency in 68% of the fish. In general, according to the feeding indices, feed diversity, and dominance of feed items, kutum fingerlings are a benthic feeders and euryphagous with a good fullness intensity on Guilan coasts.

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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.