سپیده خطیب

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.

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.

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.

Silver carp, Hypophthalmichthys molitrix, is a plankton filter feeder fish and introduced to Chitgar Lake since 9 years ago. In this study, the effect of silver carp stocking was evaluated on the phytoplankton structure of Chitgar Lake at different seasons in 2018. Samples were caught with gill-net, beach seine and cast-net gears. The results obtained from 51 individuals with a total length of 111-473 (average total length of 325.8±134.6) mm showed that coefficient of vacuity, averages of relative gut length and feeding intensity were 0.00%, 5.91±1.65 and 628.4±274.7, respectively and therefore it showed over eating, herbivory and good feeding intensity in this fish. Silver carp fed on 32 phytoplankton and 11 zooplankton genera and phytoplankton and zooplankton were observed in 100% and 88% of studied specimens, respectively. Synedra, Navicula, Staurastrum and Cyclotella were the dominant phytoplankton genera (30.0, 22.2, 13.8 and 12.1%, respectively) and Bosmina and Alona were the dominant genera of zooplankton (84.0 and 7.2%, respectively). There were no seasonal changes in feeding intensity but there were seasonal changes in food items dominance. Releasing of 20000-30000 individuals of silver carp with a weight 50-100 g is suggested in order to protect water quality of Chitgar lake annually.

Water hyacinth (Eichhornia crassipes) is native to the Amazon basin and is one of the worst aquatic weeds in the world. It has been an invasive species in aquatic ecosystems of northern Iran since 2011. The use of herbicides as a method of plant control is common and efforts are made to select a formulation with the least impact on the environment. In the current study, three types of herbicide including glyphosate (Roundup), Glufosinate-ammonium (Basta) and Bispyribac sodium (Nominee) were used to control water hyacinth and the effects of their use on the abundance and diversity of planktonic communities were investigated. Roundup treatment has an immediate effect on water hyacinth, while Basta and Nominee treatments were effective for a longer period of time. Results showed that about 90% of phytoplankton and 71% of zooplankton belonged to the diatom and protozoa, respectively. The diversity of plankton species did not change after herbicides application and the number of genera in control ponds was almost constant. The phytoplankton abundance was higher after herbicides applications, especially in the Roundup treatment. The used doses of herbicides not only had a controlling effect on water hyacinth but also had no significant negative effect on the diversity and abundance of planktonic communities.

Phytoplankton groups have specific role in the water quality of Neor Lake for living of fishes in Ardabil province. So, in order to study water quality and fish stocks assessment of Neor Lake after entering Carassius gibelio, primary products of this lake at first should be evaluated.This investigation carried out in 5 stations and 8 months during 2014. Phytoplankton sampled by 1 liter Ruttner. After that the sample fixed by formalin and after homogenizing the sample in laboratory, 5 milliliters of it precipitated for 24hr in order to further evaluation and enumeration by invert microscope 400X. According to the results, 6 phyla and 68 genera have been identified, mainly. Totally, 24, 25, 11, 2, 4, & 2 genus identified that belong to phyla Bacillariophyta, Chlorophyta, Cyanophyta, Pyrrophyta, Euglenophyta and Chrysophyta, respectively. The results show that stations 1 (Dareh Khersi) and 5 (Robero Mobish) have the most and least density of phytoplankton with annual mean of 132300500 ± 31011000 and 118575560 ± 45165997, respectively, compared to other stations. Station 3 (Mameli Dash) has the least phytoplankton density, 76071333 ± 20606342.  Phyla Cyanophyta and Bacillariophyta specially genus Oscillatoria and Synedra were dominant in all stations. Commonly, in fall, the mean density of phytoplankton is more than other seasons and in winter it is at least. According to statistical analysis Kruskal Wallis, phytoplankton density show significant differences in different months and seasons of year (P<0.05). However, there is no significant differences among stations (P>0.05). Significant differences observed in density of phyla, too (P<0.05). Generally, Neor Lake is eutrophic from nutrient material and phytoplankton density point of view after entering Carassius gibelio. The Carassius gibelio stock as the only fish of this ecosystem were 12.91 tons in 2014.

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