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Co-occurring biodiversity and global heating crises are systemic threats to life on Earth as we know it, especially in relatively rare freshwater ecosystems, such as in Iran. Future changes in the spatial distribution and richness of 131 riverine fish species were investigated at 1481 sites in Iran under optimistic and pessimistic climate heating scenarios for the 2050s and 2080s. We used maximum entropy modeling to predict species’ potential distributions by hydrologic unit (HU) occupancy under current and future climate conditions through the use of nine environmental predictor variables. The most important variable determining fish occupancy was HU location, followed by elevation, climate variables, and slope. Thirty-seven species were predicted to decrease their potential habitat occupancy in all future scenarios. The southern Caspian HU faces the highest future species reductions followed by the western Zagros and northwestern Iran. These results can be used by managers to plan conservational strategies to ease the dispersal of species, especially those that are at the greatest risk of extinction or invasion and that are in rivers fragmented by dams.

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.

This study aimed to provide the length–weight relations and condition factors of 34 Oxynoemacheilus species from the inland waters of Turkey: Oxynoemacheilus anatolicus Erk’akan, Özeren et Nalbant, 2008; Oxynoemacheilus angorae (Steindachner, 1897); Oxynoemacheilus argyrogramma (Heckel, 1847); Oxynoemacheilus arsaniasus Freyhof, Kaya, Turan et Geiger, 2019; Oxynoemacheilus atili Erk’akan, 2012; Oxynoemacheilus banarescui (Delmastro, 1982); Oxynoemacheilus bergianus (Derjavin, 1934); Oxynoemacheilus cf. bureschi (Drensky, 1928); Oxynoemacheilus ceyhanensis (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus ciceki Sungur, Jalili et Eagderi, 2017; Oxynoemacheilus cilicicus Kaya, Turan, Bayçelebi, Kalayci et Freyhof, 2020; Oxynoemacheilus cyri (Berg, 1910); Oxynoemacheilus ercisianus (Erk’akan et Kuru, 1986); Oxynoemacheilus eregliensis (Bănărescu et Nalbant, 1978); Oxynoemacheilus euphraticus (Bănărescu et Nalbant, 1964); Oxynoemacheilus evreni (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus frenatus (Heckel, 1843); Oxynoemacheilus germencicus (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus hamwii (Krupp et Schneider, 1991); Oxynoemacheilus hazarensis Freyhof et Özuluğ, 2017; Oxynoemacheilus insignis (Heckel, 1843); Oxynoemacheilus kaynaki Erk’akan, Özeren et Nalbant, 2008; Oxynoemacheilus mediterraneus (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus namiri (Krupp et Schneider, 1991); Oxynoemacheilus nasreddini Yoğurtçuoğlu, Kaya et Freyhof, 2021; Oxynoemacheilus paucilepis (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus samanticus (Bănărescu et Nalbant, 1978); Oxynoemacheilus seyhanensis (Bănărescu, 1968); Oxynoemacheilus seyhanicola (Erk’akan, Nalbant et Özeren, 2007); Oxynoemacheilus simavicus (Balik et Bănărescu, 1978); Oxynoemacheilus theophilii Stoumboudi, Kottelat et Barbieri, 2006; Oxynoemacheilus tigris (Heckel, 1843); Oxynoemacheilus veyselorum Çiçek, Eagderi et Sungur, 2018. Based on the results, the growth coefficient values ( b ) ranged from 2.770 ( O. argyrogramma ) to 3.285 ( O. theophilii ) with an R 2 estimate greater than 0.91. Fulton’s condition factor ( K F ) of the studied fishes ranged from 0.598 ( O. insignis ) to 1.07 ( O. nasreddini ) . Relative conditions ( K R ) were found to have a narrow distribution range (0.856–1.014 with a mean of 1.005). The form factors of these species were calculated between 0.006 and 0.14, with a mean and median value of 0.01. This study represents the first reports of LWRs parameters for 22 species, new maximum total length data were bigger than given in FishBase for 21 species, and first species listing for maximum total length for seven species. The findings of this study provide useful information for further fisheries management and fish population dynamic studies.

During 2018-2019, to investigate the sexual dimorphism in the body shape and morphological variations of Aphaniops hormozensis inhabiting in Mehran and Shur rivers of the Hormozgan basin using the geometric morphometric method, 80 specimens were collected. In the laboratory, the left side of the samples was photographed and 17 landmark points were digitalized on the 2D images. To eliminate non-shape data including size, direction, and position, the extracted data were analyzed by the generalized procrustes analysis using discriminant function analysis based on the p-value of T-test Hoteling. The results of the present study showed significant differences between the body shape of males and females within the population and male-male and female-female inter-populations (p

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.

The present study examined the morphological variations of 162 specimens of Chondrostoma regium (Heckel, 1843) collected from Beheshtabad, Shalmzar, Karoun, Gandman, Sheikh Ali Khan (Chaharmahal-e Bakhtiari Province), Tof Sefid and Seimareh (Isfahan Province), Khersan, Beshar (Kohgoluyeh and Boyer-Ahmad Province), Dinevarab, Alvand (Kermanshah Province), Homeil (Ilam Province), Doab, Kafraj (Lorestan Province) and Zab (Kurdistan Province). A total of 27 morphometric and 11 meristic characteristics were assessed. To investigate the morphological variations between the studied populations, the morphometric and meristic characteristics were analyzed using one-way analysis of variance (ANOVA), Kruskal-Wallis test, principal component analysis (PCA), multivariate analysis of variance (MANOVA), and canonical variates analysis (CVA). The results of the study showed that there were differences in regards to 20 morphometric and 10 meristic characteristics (p

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.

A new species of algae-scraping cyprinid of the genus Valenciennes, 1842 is described from the Kheyroud River, located in the southern part of the Caspian Sea basin in Iran. The species differs from other members of this genus by a combination of the following characters: one pair of barbels; predorsal length equal to postdorsal length; maxillary barbel slightly smaller than eye's horizontal diameter and reach to posterior margin of orbit; intranasal length slightly shorter than snout length; lateral line with 46-54 scales; 7-9 scales between dorsal-fin origin and lateral line, and 6-7 scales between anal-fin origin and lateral line.

The present study reports length-weight relationship (LWR) of four fish species viz. Pennahia macrophtalmus, Epinephelus bleekeri, Acropoma joponicum and Trichiurus lepturus from the Oman Sea, Iran. A total of 880 specimens were collected from December 2016 to August 2017 by trawling. The LWR parameter b for the studied species was 2.68 to 3.07.