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The choice of temporal resolution has high importance in ecological modeling, which can greatly affect the identification of the main drivers of an organism's distribution, considering the spatiotemporal dynamism of environmental predictors as well as organisms’ abundance. The present study aimed to identify the spatiotemporal distribution patterns of Caspian Kutum, Rutilus frisii, along the southern coast of the Caspian Sea, north of Iran, evaluating multiple temporal resolutions of data. The boosted regression trees (BRT) method was used to model fish catch distribution using a set of environmental predictors. Three temporal scales of data, including seasonal, sub‐seasonal, and monthly time frames over the catch season (October–April), were considered in our modeling analyses. The monthly models, utilizing more detailed data scales, exhibited the highest potential in identifying the overall distribution patterns of the fish, compared to temporally‐coarse BRT models. The best models were the BRTs fitted using data from March and April, which represented the final months of the catch season with the highest catch levels. In the monthly models, the main determinants of the Kutum's aggregation points were found to be dynamic variables including sea surface temperature, particulate organic and inorganic carbon, as opposed to static topographic parameters such as distance to river inlets. Seasonal and sub‐seasonal models identified particulate inorganic matter and distance to river inlets as the predictors with the highest influence on fish distribution. The geographical distributions of fish biomass hotspots revealed the presence of a stable number of fish aggregation hotspot points along the eastern coast, while some cold‐spot points were identified along the central and western coasts of the Caspian Sea. Our findings indicate that utilizing fine time scales in modeling analyses can result in a more reliable explanation and prediction of fish distribution dynamics. The investigated approach allows for the identification of intra‐seasonal fluctuations in environmental conditions, particularly dynamic parameters, and their relationship with fish aggregation. In our study, we attempted to investigate the key role of the temporal resolution of data in distribution modeling for an important fish species of the Caspian Sea, with high conservation and commercial importance. Our findings indicate that utilizing fine time scales in modeling analyses can result in a more reliable explanation and prediction of fish distribution dynamics. The investigated approach allows for the identification of intra‐seasonal fluctuations in environmental conditions, particularly dynamic parameters, and their relationship with fish aggregation.

Morphology and feature selection are key approaches to address several issues in fisheries science and stock management, such as the hypothesis of admixture of Caspian common carp (Cyprinus carpio) and farmed carp stocks in Iran. The present study was performed to investigate the population classification of common carp in the southern Caspian basin using data mining algorithms to find the most important characteristic(s) differing between Iranian and farmed common carp. A total of 74 individuals were collected from three locations within the southern Caspian basin and from one farm between November 2015 and April 2016. A dataset of 26 traditional morphometric (TMM) attributes and a dataset of 14 geometric landmark points were constructed and then subjected to various machine learning methods. In general, the machine learning methods had a higher prediction rate with TMM datasets. The highest decision tree accuracy of 77% was obtained by rule and decision tree parallel algorithms, and “head height on eye area” was selected as the best marker to distinguish between wild and farmed common carp. Various machine learning algorithms were evaluated, and we found that the linear discriminant was the best method, with 81.1% accuracy. The results obtained from this novel approach indicate that Darwin’s domestication syndrome is observed in common carp. Moreover, they pave the way for automated detection of farmed fish, which will be most beneficial to detect escapees and improve restocking programs.

The present study was conducted to investigate the morphological variations in different populations of Barbus lacerta from the Iranian part of the Tigris River drainage using the geometric morphometric method. For this purpose, a total of 133 specimens were collected from the Leileh, Bid-Sorkh, Golein, Sepid-barg, Dinavar, Kelash-bakhan, and Roudbar rivers. In the Lab, the left side of the specimens was photographed and on their 2D images, 12 landmark-points were defined and digitized using tpsDig2 software. After conducting generalized procrustes analysis, the extracted data were analyzed using multivariate statistical methods, including PCA and cluster analysis (CA). The results showed significant differences in the body shape of the studied populations except the Kelash-bakhan and Dinavar (p < 0.05). The observed differences indicated that the morphological variations are due to their phenotypic plasticity to environmental conditions, the evolution of the body shape, and the geographical distance in the Iranian part of the Tigris basin. Therefore, each population of this species should be considered as a separate stock.

Olfaction in fishes is biologically-essential chemoreceptors. It provokes important behaviors for the survival of fish such as feeding, reproduction, avoiding predator and intraspecific communication. Pesticides can affect the olfactory epithelium and genes related to olfactory transduction and impair olfactory function. The present study aims to determine how toxicity of diazinon impacts olfaction of Caspian roach, Rutilus caspicus in histological and gene levels. We exposed fish (0.7 ± 0.05 g in weight) to 0, 1, 2 and 3 mg L-1 diazinon (60 fish in each 3-replicate 60-L glass tank) for 7 days in freshwater. Diazinon concentrations were chosen based on reports on its concentration in surface waters. Mortality rate, histological events of olfactory epithelium, and genes expression at the 7th day after diazinon exposure included a significant decrease in the number of olfactory receptor cells (ORCs), while increased goblet cells (GCs). In addition, G-protein αi (Gpαi) was significantly upregulated, whereas calmodulin-dependent kinase II a (CaMKIIa) was significantly downregulated after 7 days as compared to the control group. These results indicate that diazinon can impair olfactory function through effect on the olfactory epithelium and olfactory signal transduction pathways in the Caspian roach fingerlings.

Yellowfin tuna, Thunnus albacares, are the most important ecological and economic fishes in the Persian Gulf. In recent decades, their populations have faced overfishing, environmental problems and climate change. In this study, using some environmental variables affecting the habitat of tuna fish, i.e. sea surface temperature at night and day, reflection of 645 nm wavelength as a water turbidity, angstrom view of aerosol 443 to 965 nm, aerosol optic thickness at 869 nm, organic and inorganic particle carbon, photosynthetic active radiation, absorption by phytoplankton at 443 nm and chlorophyll-a concentration from 2002 to 2018, on the spatial distribution of yellow-fin tuna has been modelled by fuzzy rule-based classification. Over the years, the variables had different degrees of importance in the models. There was a great variation in the spatial distribution of the species from year to year.

This study was conducted to examine the phylogenetic relationship of the genus Turcinoemacheilus in Iran based on osteological characteristics. A total of 25 fish specimens of four species belonging to the genus Turcinoemacheilus from Tigris and Isfahan basins were considered as in-group and Cobitis linea as out-group. The skeletal elements were examined after clearing and staining. A total of 19 character-states were described that showed differences between the studied taxa. Phylogenetic analysis was performed using osteological characters with the maximum parsimony method. Based on the results, the most parsimonious tree with a length of 29, the consistency index of 1, and a retention index of 1 was obtained. Turcinoemacheilus hafezi and T. bahaii with 76% support were in a sister group and the two species of T. kosswigi and T. saadii with 97% support were in another clad. The presence of the lateral fontanel in T. hafezi, the overlap of the internal lateral-wall of autoplatinii with posterior lateral-wall of the ethmoid, symmetry of the posterior part of the autoplatinii and divergence of the hemal spin’s process in T. kosswigi, ratio of the ascending process to the horizontal process of the maxillary, and beginning of the first dorsal-fin petrigiophore to vertebra 17 in T. bahaii were distinguishing osteological characters of the studied species.

Habitat suitability index (HSI) models are usually used to forecast habitat quality and species distributions and are used to develop biological studies, management priorities and anticipate possible changes under different management or climate change situations. This study was conducted to identify the habitat suitability index of three species namely, Capoeta buhsei, C. razii and C. alborzensis in the Kordan, Taleghan and Jajrood Rivers, respectively. At each station, environmental variables including temperature, dissolved oxygen, pH, EC, TDS and hydrological parameters such as flow velocity, depth, width, average diameter of stones and amount of phosphate, nitrate and ammonium were measured. The results showed that suitable habitats for these species are those with a high stone diameter, high temperature, low flow velocity and in areas where the width of the river is low. With respect to the abundance of fishes sampled in this study, the central and lower regions of the Jajrood and Kordan Rivers and the stations far from the dam (1 and 6) in the Taleghan River are favorable habitats for the studied Capoeta species.

This study investigated morphological differences, habitat preference, and ecological niche overlap in two sympatric Capoeta species i.e., Capoeta. damascina and Capoeta umbla collected from the Sirvan river drainage. Ten environmental factors, including pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), river width, river depth, flow velocity, altitude, slope, and dissolved oxygen (DO) were measured during sampling time. A total of 17 morphometric characteristics were measured using digital calipers for traditional morphometrics (TM). For the geometric morphometric method (GM), 2D pictures were taken from the left side of the fresh samples, by tpsDig2 software, and 16 landmark points were defined and digitalized to extract body shape data. The data were analyzed using t -test, Mann–Whitney, principal component analysis (PCA), and discriminant function analysis based on the P -value of Hotelling’s T-squared. The ratio of the common area under the graph to the total area of habitat suitability indices was defined as the ecological niche overlap. The results showed significant differences in eye diameter, predorsal, caudal peduncle length, preanal, preventral, ventral-pectoral, body depth, and caudal peduncle depth traits ( P  < 0.05) in TM, and those differences in the GM were related to the position of the snout, head and body depth and caudal peduncle length i.e., C. damascina had the deeper body shape and head, and anterior the snout and caudal peduncle length. Based on the results, C. damascina prefers areas with higher pH and temperature and by increasing other studied factors, its habitat suitability decreased. The preference for C. umbla with increasing river depth and DO was increased. These two species showed low niche overlap i.e., they avoid competition in their habitat by opting for different areas in terms of river width, flow velocity, and temperature that have more depth with higher slope microhabitats.

Morphological development and allometric growth patterns of reared Persian sturgeon, Acipenser persicus, were studied from hatching to 50 days post-hatching (dph). The larvae were sampled, their left sides photographed and seven morphometric characters, including total length, head length, tail length, trunk length, snout length, caudal peduncle and predorsal length were measured. Allometric growth patterns were calculated as a power function of total length and described using the growth coefficient to find important steps in early life history. The total length of the newly hatched larvae and fry were 10.59±0.8 and 38.8±2.9 mm at 1 and 50 dph, respectively. Morphogenesis and differentiation were the highest rates during the first 11 days of early development, i.e. endogenous feeding period. There were higher growth rate of head, snout and tail regions compared with those of other organs from the hatch up to yolk sac absorption, followed by positive or almost isometric patterns, after the begin of exogenous feeding, showing priority to enhance the feeding and swimming capabilities. This study confirmed that most of morphological changes of this species are occurred from hatching until the onset of exogenous feeding i.e. during the lecithotrophic phase.

The osteological characteristics is an important tool for clarification of the phylogenetic statue of the family Nemechelidae. Since any information is available about osteological features of the genus Turcinoemacheilus, hence the present study provides a detailed osteological characteristics of the Turcinoemacheilus hafezi as representative of this genus. Ten specimens of T. hafezi were collected from the Shalamzar Stream, Tigris basin, Iran and cleared and stained for osteological examination. According to the results, T. hafezi is osteologicaly characterized by absence of the preethmoideum-I and postcleithrum, having four basibranchials, presence of the sesamoid ossification, free and short epural with the reduced neural process and pleurostyle, connection of the hypural-1 to the parahypural, no connection of the hypurals 3, 4, and 5 to the pleurostyle, and no bony bridge between the parietal.