دکتر رحمان پاتیمار

Fishing nets used in aquatic environments are sometimes abandoned or lost in the sea due to sea storms, torn or undiscovered fishing nets by fishermen, but they still catch aquatic organisms. Due to the lack of sufficient information on the abandoned fishing gears in the waters of Golestan Province, a study was conducted in this regard. For this purpose, in the Gorgan Bay and the Miankaleh Peninsula, the abandoned fishing nets were collected by anchoring from the spring to the winter of 2019. A total of 43 times anchoring, 6.5 km of fishing nets with weight of 425 kg were recovered from the sampling regions. A total of 1,005 aquatic animals with weight of 15.7 kg were caught in the discovered nets. The catch composition consisted of fish, crustaceans and seabirds. The main composition of the catch consisted of 73% of crustaceans (shrimp and crabs) in terms of number and 46% of seabirds in terms of weight. The results also showed that the amount of catch per retrieved nets was significantly different between summer and other seasons and the lowest amount of catch was obtained in summer. On the other hand, there was no significant difference between the average catch of retrieved nets in two depths up to 3 meters and 3 to 6.

This study aimed to investigate inter-population variation in the population dynamics of the Caspian kutum (Rutilus frisii) based on catch data from the coastal waters of Golestan Province (southeast Caspian Sea) over 26 years (1991-2016). The biometric data of 20,438 kutum samples were analyzed, with sizes ranging from 18 to 70 cm. The average values of L∞ and k were 59.83 cm and 0.44 per year, respectively. The weight infinity (W∞) ranged from 1,738.97 to 6,380.03 grams, with an average of 2,867.96 grams. Cohort analysis revealed five distinct cohorts in the exploited population. The natural mortality rates varied between 0.60 and 0.84, with an average total mortality (Z) of 1.35. The exploitation rate (E) ranged from 0.13 to 0.73, exceeding 0.5 in 8 years. The results indicate significant temporal variability in the kutum population over the study period.

This Study was conducted to determine the growth characteristics of Caucasian species (K. caucasica) in Gorgan Bay and Gomishan wetland. 149 specimens from Gorgan Bay and 192 specimens from Gomishan wetland were collected from February 2013 to May 2014 using beach sein. The length of samples range from 07.07 to 39.41 mm and weighing from 0.01 to 0.84 gr, and 48/15 to 44/78 mm and weighing from 0.05 to 1.0 gr in Gorgan Bay and Gomishan wetland. The age of the specimens was determined by Otolith and the ranges from + 0 to +1 in the Gorgan Bay and +0 to +2 in the Gomishan wetland. The b value in the Gorgan Bay for males 3.07-3.32, for females 3.31-3.3.69 and for male 3.16-3.43 and for female 3.19-3.45 in Gomishan wetland. The growth pattern of this species was positive allometric for both sexes in Gorgan Bay and Gomishan wetland. The highest condition factor in Gorgan Bay for male and female was observed in March, and in Gomishan wetland, in May and February, respectively.

This study was conducted for estimation growth of R. kutum from October 2023 to March 2024 in fishing grounds of Hormozgan province. A total of 286 specimens were weighed and measured. 149 samples, including 65 males and 84 females, were transferred to the University of Sari and Gonad laboratories for evaluation age and gender. Length-frequency distribution of both sexes had significant differences. The Exponential relationship between Fork length and total weight were estimated of population, males and females were as W=0.0045L2.947and W=0.0191L2.894 and W = 0.0076L3.154 respectively. Age at length data were used for evaluated parameters of K and L∞ By Goland and Holt equation. K and L∞ for population male and female were calculated of R. kutum, were calculated 0.179 year-1 and 62.84 cm, 0.23 year-1 and 52.25cm, 0.164 year-1 and 64.16 cm respectively. Tmax of R. kutum for population, male and female were estimated, 15.38, 12 and 18.29 year respectively. Phi Prime ф index of population, male and female were estimated 2.94, 2.79 and 2.82 respectively. W∞  for population, male and female were estimated, 3619, 2011 and 3807gr respectively.

Sturgeon, renowned for its prized caviar, plays a vital role in aquatic ecosystems and holds significant economic value. Breeding sturgeon is a delicate process that necessitates specific conditions for success. Factors such as temperature, dissolved oxygen levels, pH, and ammonia concentration in water quality substantially impact sturgeon breeding outcomes. Ensuring the ideal water quality is critical for sturgeon populations' health and successful breeding. Understanding and efficiently controlling these factors is crucial to guaranteeing the long-term viability of sturgeon populations and the preservation of this symbolic animal. This study investigates the growth indices and physicochemical water parameters in earthen ponds to raise juvenile beluga, Huso huso.

Four earthen ponds, each covering an area of 2 hectares with an average depth of 2 meters and a rectangular shape, were utilized for rearing beluga at the Shahid Marjani Breeding Center, Northeastern Iran. The test period lasted 45 days. The growth performance and water physicochemical parameters were measured during six weekly treatments from mid-March 2013 to mid-April 2014. Fish sampling was carried out using a trawl net at specific time intervals of the experiment. The length and weight of the fry were recorded, followed by the dissection of the fish. The length and weight of the digestive tract were measured in both full and empty states. Water samples were collected weekly, and physicochemical parameters were analyzed using standard methods.

Temperature (12.5 to 16.6°C), turbidity (0.50 to 50.92 NTU), dissolved oxygen (10.90 to 6.25 mg/L), pH (7.62 to 8.92), alkalinity (160 to 223 mg/L), phosphate (0.17 to 0.73 mg/L), nitrate (0.24 to 1.67 mg/L), and electrical conductivity (1240 to 1342 µmhos/cm) levels for the growth of beluga were within the optimal ranges. Additionally, the growth pattern of the sturgeon juveniles was characterized by negative allometry, indicating that as the fish grew, their weight increased at a slower rate compared to their length. There was a significant elevation in total length and weight over time, demonstrating effective growth conditions during the study period. The total length and weight of the fingerlings showed significant upraise over time (p<0.05). The highest total length (36.70 ± 7.47 mm), weight (2674.54 ± 678.04 mg) and gastrosomatic weight (431.35 ± 75.97 mg) of fingerlings were recorded during the sixth sampling period. However, the highest condition factor (0.94 ± 1.11) was measured during the second sampling period (p<0.05).

The results indicated that precise water quality management and continuous monitoring of its parameters, especially in sturgeon farming, are essential and can help improve growth conditions and reduce mortality rates. Ensuring optimal environmental conditions, particularly in earthen ponds, can increase productivity in the sturgeon fish farming industry.

To investigate the relationship between the length and weight of Neogobius melanostomus, 5145 fish were captured using nets from March to February 2018. The maximum total length and weight for females were recorded at 12.2 cm and 28.08 grams, while for males, the maximum total length and weight were 11.3 cm and 33.17 grams, respectively. The length-weight relationship for both female and male populations of N. melanostomus in Gorgan Bay across the four seasons (spring, summer, autumn, and winter) showed a high coefficient of determination. The regression slope values (b) for this species in different seasons were significantly different from the isometric growth coefficient of 3 (p < 0.05). Specifically, the t-values were 3.73 for the winter population, 10.80 for the autumn population, 21.25 for the summer population, and 21.71 for the spring population, indicating positive allometric growth throughout the year. The Pauli test confirmed this growth pattern in the N. melanostomus population of Gorgan Bay. Seasonal condition coefficients showed that females had the highest values in summer and winter, while males displayed the highest values in winter.

The purpose of the study is to investigate the catch composition, the amount of by- catch, the length frequency and the catch per unit of effort of bottom gillnets for catching the Tigertooth croaker, using mesh size of 73, 85 and 90 mm in the waters of the Oman Sea in the period of winter 2018 to the late spring of 2019. 973 pieces of fish including 15 families were caught, and the highest catch rate was 63.81% for the Tigertooth croaker. The rate of by- catch was 8.76%. The amount of CPUE for the mentioned mesh size was estimated as 552.9, 808.9 and 456.9 grams per net day respectively. By examining the length frequency distribution in all the meshes, it was determined that the highest frequency is in the length of 32-36 cm with 43.67%. Also, an average length of 31.80±6.64 cm was recorded in the whole operation. According to the first maturity length of the Tigertooth croaker, it was determined that the bottom gillnets available in the Chabahar region fishing grounds had a catch below the standard size, and it seems the mesh size of the net should be reviewed and standardized.

In this study, age and growth of Golden Grey Mullet (C. auratus) was investigated during the years 1394-1397 in the coastal waters of Golestan province. This study was the first study on the modeling and implementation of three models for estimating growth parameters of golden mullet (C. auratus) in Iranian waters (Golestan province). During the sampling period, commercial fishing with a size of 27-33 springs was used, and outside of the fishing season, a net with a size of 20 and 30 was used. Biometry of fish was done including fork length with an accuracy of 1 mm, total weight with an accuracy of 1 gram. The length range for golden mullet was 15 to 59.5 cm and the weight range was 52.5 to 1401 grams. The exponential relationship of fork length and total weight (W=0.69L0023) was obtained. Based on the multi-model approach, the best model to show the growth of this fish was the Gumpertz growth model (∆AIC = 1.71, AIC = 46.13), and the logistic model was the best model to depict the growth of this fish according to the AIC information coefficient ( ∆AIC = 1.27, AIC = 50.71). Considering the pressure of legal and illegal fishing on this valuable species, it shows that the population and the amount of fishing in the south-eastern coast of the Caspian Sea are increasing. The results of this study can be used as basic information for catching and exploiting this species in the future.

The present study aimed to investigate variability in growth pattern and evaluate abundance of A. persicus based on catch data in the southern Caspian Sea water in a period of 27 years (1991-2018). The data of 72704 specimens were analyzed separately by sex (male, female and population), time (years) and region (coastal waters of Gilan, Mazandaran and Golestan provinces). The highest catch of this species was recorded in 1991 (6038 pieces of the fish) and the lowest catch was recorded in 2018 (292 pieces). During the period, the Golestan province had the highest number of catches (30851 pieces) and Gilan province had the lowest ones (11129 pieces). The maximum recorded fork length of this species was 240 cm in 2006. The results showed that the highest annual average fork length was 151 cm in 2007 and 2010 and the highest annual average total weight in 1993, 1994, 1996, 1997 and 2007, which was 26000 grams. The lowest annual average fork length was 139 cm in 2018 and the lowest annual average total weight was 600 grams in 2010 and 2012. The highest length frequency corresponded for the ranges of 136-148 and 148-160 cm in males and females, respectively. The females showed the highest catches in 1991, and the lowest in 2018, while the males had the highest in 1991, and the lowest in 2014. The females dominated the population in the period of 1991- 2013, and after that this ratio was reversed. The allometric coefficient of growth (b) varied between 1.03 and 3.49 in the study period. The growth pattern was mostly positive allometric in first decade of study (1991-2001), isometric or negative allometric in the second decade of study period (2001-2011), and negative in third decade (2011-2018). During the study period, the condition factor of the fish varied between 0.61 and 0.80, and the average of the factor for the whole period of study was 0.72. Generally, the catch of A. persicus in the southern Caspian waters decreased more than 95% from 1991 to 2018 (a period of 27 catch-years).

Samples caught by beach seine nets in the fishing season of 2019-2021 in the southern costal zones of the Caspian Sea were used to study reproductive biology of Cyprinus carpio. Totally, 435 sea carp, including 237 female and 198 male were sampled, and their age and maturity stages were determined over sampling period. The results indicated that age range of the sampled C. carpio varied from 1 to 6 years in males, from 1 to 9 years in females, and from 1 to 9 years in combined sexes. The highest frequency of samples was in the age group of 1 for males (54.4%), 2 for females (34%), and 4 years for combined sexes (26.6%). Frequency of fish observed in the V and VI maturity stages was 45.14% and 27.17%, respectively. According to the frequency of different maturity stages and also the trend of changes in Gonado-somatic index (GSI), two spawning peaks were observed in C. carpio, including weak peak occurred in December-January and strong peak observed in March-April. The female mean length at sexual maturity (Lm50%) was 27.7 cm. Absolute and relative fecundity (mean ± SD) of C. carpio were 429310±233479 and 668±319 eggs, respectively. Since, there was an overlap between the spawning peak of C. carpio and beach seine fishing period for bony fish, it is proposed that fishing season to be banned at the beginning of April.

The Environmental variables are considered as important factors determining habitat preference and selection by fishes in the aquatic ecosystem. Therefore, it seems essential to know the habitat requirements of inhabiting species. This study in summer on Kesilian River, one of the considerable sub-basins of the Talar River in the north of country, was selected to investigate the habitat preferences of Kora Barbel (Barbus lacerta) at various ages. According to the diverse habitat characteristics, three sites were selected on the stream, and then samplings were carried out at 211 points using an electroshocker. At each point, environmental parameters including speed, depth, and type of biotic and abiotic substrate were measured and determined. The results showed that this species has different habitat preferences at different ages. General preferences of this species took place in the speed range of 15-76 cm/s and the depth of 45-75 cm. Preference for abiotic and biotic parameters of substrates included "block", "cubble" and coarse and fine particulates organic matter, wood and living parts of terrestrial plants, respectively. Regression logistic indicated that the variables including velocity and abiotic parameters of substrate are the most important factors in presence of this species in the stream. In general, the diverse environmental conditions of the stream have provided different habitat preferences for this species at different ages.

The excessive growth of the aquaculture industry, in addition to using more natural resources, causes a disturbance to the biological and non-biological balance through effluent releases, and water quality indicators provide the possibility of better management of pollution and direction for targeted biological monitoring. The purpose of this research was to evaluate the nitrogen load of the basin and rainbow trout breeding farm on the water quality of Zarin Gol River in Golestan province, Iran, based on a standard index (WQI) by measuring water quality parameters including: pH, total phosphate, temperature, nitrate, dissolved oxygen, turbidity, and total coliform. Sampling was done seasonally at five stations (before and after the first and second fish farm and 1000 meters downstream from the second fish farm) in 2018. The results showed that the concentration of nitrogen and phosphorus in the River during the six months of fish breeding on the second farm was estimated to be 16.5 tons of nitrogen and 2.9 tons of phosphorus. According to the WQI, the results showed that the water quality values in all the studied stations are 79.7 to 87.8, which indicates excellent water quality according to the descriptive table. It seems that under the current conditions, the Zarin Gol River has the ability to self-purification the effluent of two fish farms with the expected capacity.

The kutum of the Caspian Sea has long been familiar with the life of coastal people, so that it has played a significant role in the economy of the coastal cities of the south of the Caspian Sea, and the living resources of the Caspian Sea, especially its economic fish stocks, have been seriously attacked in the past few years due to various crises. The study of growth parameters and intra-population structure makes interpretation, analysis and predictions related to the abundance of populations of a species possible, and Sefidrood River, as the most important fishing river of the country in Gilan province, plays a very important role in reproduction and stock enhancement of kutum. It was studied for a period of 10 years (2010 to 2019).The highest average total length and total weight for both males and females was obtained in 2014, which was 44.41 cm and 943.72 grams for males, and 50.49 cm and 1401.98 grams for females, respectively. Other years had significant differences (p < 0.05). The type of growth pattern for kutum population was obtained in 2013, 2014 and 2017 from isometric type, in 2010, 2011, 2012, 2015, 2016, positive allometric type and in 2018-2019 from negative allometric type. The highest value of the condition coefficient was obtained in 2019 and the lowest in 2015 (p < 0.05). The results showed that in all the studied years, total length and total weight also increased with increasing age for the population. The infinite length (L∞) in the populations in the 10-year period was between 73.11-87.74 cm. The range of growth rate (K) in this study for populations was between 0.08-0.19. Zero age index (t0) for populations was between -0.46 until -0.93, and Monro's Phi index (ф) was obtained between 6.18 until 7.28 in populations.

Variability in growth allometry of two prawn species Palaemon adspersus and Palaemon elegans was investigated in the Gorgan Bay, SE Caspian Sea, during a period between May 2019 and April 2020. Resalts showed that females grew to a larger size than males in both species. The weight growth of females was faster than length growth in P. adspersus (Log TW = -5.3975 + 3.2018Log TL), while in P. elegans the length growth of males was faster than weight growth (Log TW = -4.9019 + 2.8758Log TL). In P. adspersus TL – CL relationship was CL = 0.2162TL + 0.002 for females and CL = 0.2087TL + 0.0096 for males. In P. elegans TL – CL relationship was CL = 0.2451TL – 0.0908 for females and CL = 0.2043TL + 0.0372 for males. TL – CL relationships were nagative allometry in both sexes of two species. Mean condition factor (CF) of females was larger than that of males in both species, and it was observed significant difference in the mean condition factor between species and month.

Extensive lack of data and information gaps for recreational fishing necessitate knowledge of the species caught to establish aquatic reserve management. Therefore, in the present study in 2021, by collecting lenght and weight information of major recreational fishes in the main recreational fishing area was done with hooks. The results showed that between the length and weight of common carp in Golestan, Mazandaran and Golestan provinces, the equations were 0.444004x4004 and 0.4652/168x2/4652 with a correlation of 90%, 95% and 94%, respectively. Between the length and weight of grass carp in Golestan, Mazandaran and Golestan provinces, the equations 0.2398x2 / 2398 and 0.6333x2 / 1313 and 30.3x1 / 7769, respectively, with a correlation rate of 96%, 94% and 90% were established and between the length-weight of yellow fish in Golestan, Mazandaran and Golestan provinces were equations of 0.494x3 / 113, 1101x1 / 4615 and 982x1 / 1381, respectively, with a correlation of 89%, 90% and 97%. The results showed allometric growth of all three species in all studied provinces. The allometric growth rate of common and yellow carp was positive in Golestan province and negative in Guilan and Mazandaran provinces. Allometric growth rate of herbivorous carp was negative in all studied provinces .

Hypoxia stress is an unfavorable environmental condition for fish that can have several effects on immunity and antioxidant. The aim of the present study investigated the impact of hypoxia stress (Chronic; 2 to 2.5 mg/L for 36 hours) and (acute; 0.013 and 0.017 mg/L for 1.5 hours) compared to control (6 to 7 mg/L) on survival, immune and oxidative status Common carp (Cyprinus carpio) in biofloc conditions. In the first stage, the fish (21.90 ± 0.75 g) were stored in 9 tanks (50 liters) in the biofloc system for 7 weeks. In the second stage, the fish were subjected to hypoxia stress (chronic and acute) and control (normoxia). After hypoxia stress, serum lysozyme, total immunoglobulin, and ACH50 activities were significantly lower, and red blood cells (RBC), hemoglobin, and hematocrit were higher in chronic and acute stress treatments. The activity of SOD, CAT, and GPX in the fish serum exposed to hypoxic stress was significantly reduced compared to the control. In general, the results show that both chronic and acute hypoxic stress weakened the blood parameters of common carp in the biofloc system.

Over the past years, eutrophication due to human activities has been recognized as a major ecological problem for the coastal areas, which in turn leads to significant changes in physicochemical and biological factors. The aim of the present study was to determine the eutrophication status of the Gorgan Bay, which was evaluated using the Carlson index as one of the efficient methods for assessing the eutrophication status of water bodies. The Gorgan Bay is located in the southeast of the Caspian Sea. The sampling was carried out in 23 stations with three replications seasonally from summer 2018 to spring 2019. Nitrate, phosphate, chlorophyll α, depth, and transparency were measured in each sample. Carlson's index in terms of chlorophyll α showed that the bay is in the eutrophic status in three seasons including summer, autumn, and winter (with the numbers 53.48, 53.69, and 53.67, respectively), and the mesotrophic status in spring (with the number 42.75). In terms of phosphate concentration, the bay was eutrophic in autumn and winter, and in summer (69.22 and 55.17) and oligotroph in spring (26.75 and 35.30), while in terms of transparency the bay was categorized as eutrophic in all seasons (63.33, 61.61, 69.93 and 61.58, respectively). In general, the results showed that the bay is in the range of mesotrophic to eutrophic status and therefore, more conservation management of this unique ecosystem is essential.

This study aimed to investigate Growth modelling of the milk shark (Rhizoprionondon acutus Ruppel, 1837) from October 2019 until march 2021 for 18 months in northern waters of the Persian Gulf and the Oman Sea (Hormozgan Province). Overall, 317 shark samples of R. acutus including 137 males and 180 females were weighted. Results of the present work indicated that length-frequency distribution of both sexes were statistically different. Exponential relationship between total length and total weight of males and females were as W=0.0021L3.1508 and W=0.003L3.062 , respectively. After optimization by a non-linear regression through least square method, this relationship was obtained for males and females as W=0.0028L3.078 and W=0.0025L3.106, respectively. Males were estimated for the oldest age at 8 years with the length of 91.15 cm while females were estimated for the oldest age and tallest length at 10 years and 95.5 cm, respectively. By adoption of multi-modelling approach, the best model fittedd to indicate how to grow for the females of milk shark was Gampertz Growth Model (AIC=48.14, ∆AIC = 0). Logistic model had also a considerable protection to draw the growth of females according to AIC (AIC=50.02, ∆AIC= 1.87).  The best model fitted to show how to grow the males of milk shark was Logistic Model (AIC=36.33, ∆AIC= 0). Gampertz model had also a moderate protection to draw the growth of males (AIC=42.46, ∆AIC= 6.12), but three parameterized Von Bertalanfy model showed no efficneby to draw the gorowth of males (AIC= 53.2, ∆AIC= 16.86). . This study was performed for the first time on growth and mortality parameters of the milk shark in Iranian waters of the Persian Gulf and Oman Sea. Regarding the legal and illegal fishing pressure of this valuable species, this is recommended to apply the presented results for wider future studies as a basic study and to monitor its stock status with more precision annually, so as the managers can use these results to adopt scientific-management approaches for the protection of this precious species from extinction.

The present study was conducted to determine the body shape variation among the populations of Iranian goby (P. Iranicus) in the southern Caspian Sea basin using landmark-based geometric morphometrics. A total of 350 specimens of the species were sampled using electro-shocker, and in the laboratory, the left sides of the fish samples were photographed by a digital camera. Fourteen landmark points were digitized on two-dimensional images using TPSDige2 software. The obtained data from Landmarks were analyzed using multivariate statistical analyses including PCA, CVA, and cluster analysis (CA). The phenotype plasticity patterns of each population related to the shape of the overall average of populations were illustrated. The results of the study demonstrated that there was a significant difference among the studied populations in terms of morphological features. Dendrograms revealed that both sexes could be divided into five groups related to the localities of specimens. Analysis of MANOVA/CVA showed that females of P. Iranicus have a high separation rate among the provinces, while males of Mazanderan province had significant isolation from males of Guilan and Golestan provinces. The two provinces showed a high overlap in the morphological characteristics. The results of the study can improve understanding of growing phenotype patterns plasticity of these fishes in the water bodies of different river systems from the southern basin of the Caspian Sea as well as identifying species of P. Iranicus populations in the southern basin of the Caspian Sea rivers.