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Fishes from the genus Carasobarbus , widely distributed throughout the river systems of North Africa and West Asia, are commonly referred to as Himris. In the Persian Gulf basin, they are widespread and are also found in fast-flowing rivers or the deeper regions of lakes. In this region, representation of these fishes in scientific collections is scarce, and except for C. luteus , the other species are very poorly documented and frequently misidentified due to their similarities. In this study we analysed the relationships among Carasobarbus species using mitochondrial genes (Cyt b , COI) and present morphological characters based on examinations. Our results revealed three new species which we describe here. Carasobarbus doadrioi, new species, is distinguished by 40–44 scales on the lateral line and a prominent black blotch on end of caudal peduncle in specimens < 85 mm SL. Carasobarbus hajhosseini , new species is distinguished by 32–34 scales on the lateral line and long head length (20–24% SL). Carasobarbus saadatii , new species, is distinguished by 38–40 scales on the lateral line and short head length (19–20% HL). In the Persian Gulf basin, Carasobarbus species exhibit uncorrected genetic distances of 1.6 to 5.5% in the COI barcode region and 2.6% to 9.9% in the Cyt b gene. This study highlights the importance of investigating the unexplored diversity that exists within poorly sampled and understudied freshwater fish group. Such investigations are essential for developing a comprehensive understanding of the true extent of biodiversity, which is critical for informing effective conservation and protection strategies.

Nemacheilid fishes in the genus Turcinoemacheilus are physically small members of the ichthyofauna communities of high-altitude and mountainous freshwater ecosystems. They are all distributed in Western Asia apart from a single species, described in the Himalayas. They are usually very similar in appearance, which complicates their proper identification and/or description. This is why it is important to use multidisciplinary and integrative taxonomical approaches in order to study their true diversity. In this study, three new species of Turcinoemacheilus are described from Iran, raising the total number of valid species to nine. Turcinoemacheilus ansari new species, is distinguished by the anus being situated behind the midpoint of the pelvic-fin and anal-fin origins and the short anal-fin base length. Turcinoemacheilus christofferi new species, differs by the anus being situated behind the midpoint of the pelvic-fin and anal-fin origins, with a complete lateral line reaching to the anterior part of the caudal fin. Turcinoemacheilus moghbeli new species, is distinguished by the anus being situated at or in front of the midpoint of the pelvic-fin and anal-fin origins, with a great pre-pelvic distance and a caudal peduncle length 1.5–2.3 times its length. In Western Asia, all Turcinoemacheilus species are well separated by molecular characters, showing between 3.6 and 14.1% uncorrected p genetic distances in the COI barcode region. This work shows the importance of studying the hidden diversity of under-sampled and understudied groups of organisms to have a clear image of true biodiversity in order to effectively conserve and protect it.

Channa gachua is native to the majority of streams in southeastern Iran, but reproductive parameters of the fish are barely known. Reproductive conditions are key parameters of fish populations and their assessment is very important for several reasons. To investigate reproductive biology of the native dwarf snakehead, sampling was done at monthly intervals throughout the year and 404 individuals were caught from Kajou River in Makran basin. Age, sex ratio, fecundity, oocytes diameter, gonado-somatic, modified gonado-somatic and Dobriyal indices were estimated. Regression analyses were used to find relations between fecundity and fish size (length and weight), gonad weight, and age. Sex ratio differed from unity and biased to females. The mature females and males were longer than 75 and 61 mm in total length (+2 and +1 in age, respectively). The average egg diameter was 0.50 mm, maximum 0.73 mm in April. The spawning took place from beginning of April to late June. Average GSI value at the beginning of the reproduction period was 2.89% and ranged between 0.3% and 4.4% in ripe, mature females. The average of absolute and relative fecundity was calculated 3471 and 248, respectively. The absolute fecundity was significantly related to body length and gonad weight. Based on the pattern of gonad indices, it was concluded that this fish has a prolonged active reproductive period, which is a type of adaptation by short-lived small fishes to environmental conditions.

Habitat assessment is the most important step in environmental decisions. One of the ways to assess habitat quality is to use habitat suitability for fish species. So, this study was conducted in Klarood River, one of the important tributaries of Babolrood River in Mazandaran Province, north of Iran to evaluate the habitat quality for Capoeta razii. At first, a site with the least anthropogenic influences was selected on the river. Then the fish was caught by electrofishing device aggregate at 100 points. At each point where the fish was caught, environmental parameters such as depth, water velocity, type of biotic and abiotic substrate were also measured. The results showed that the species prefers water velocity of 16-30 cm s\"1 and depth of 16-115 cm. Moreover, suitable abiotic and biotic substrates were Macrolithal, Mesolithal and Microlithal\" as well as LPTP (Live parts of terrestrial plants) respectively. Generally, the results of this study showed the appropriate function of the model in assessing the habitat suitability of this species and it can be used as a guide for quantitative assessment of habitat as well as recognizing the behavioral characteristics of the studied species.

Barbus urmianus from the Mahabad-Chai River in Urmia Lake basin, is distinguished from its congeners in the B. lacerta group by a well-developed middle pad of the lower lip, a shorter postdorsal length (25.2–42.0 vs. 46.4–60.7% SL), long anal fin (11.0–23.0 vs. 6.0–10.4% SL), short dorsal-fin base (9.2–15.6 vs. 16.1–22.6% SL), less scales in the caudal peduncle (14–23 vs. 25–35), and 64–85 scales on the lateral line (vs. 52–70).

Paraschistura ilamensis , new species, is described from the Tigris River drainage, Iran. It is distinguished from other species of Paraschistura in Iran by a combination of the following characters: emarginate caudal fin, stout, deep and scaled body, deep caudal peduncle, 7-10 irregular and interrupted vertical pale brown bars on flanks, two obvious dark spots on the upper and lower caudal fin unbranched rays, and moveable protuberance at the antero-ventral corner of the eye in males.

Osteological features are important to study the taxonomy and phylogenetic relationship of fishes. Since there is no information is available about osteological features of Squalius orientalis, therefore this study was aimed to provide a detailed description of the osteological features of this species from the Urmia lake basin of Iran and comparing it with population of S. orientalis from the Caspian Sea basin. For this purpose, the specimens were collected from Zarineh River of the Urmia lake basin and cleared and stained with alizarin red S and alcian blue for osteological examinations. Finally, a detailed osteological features of this species was provided and compared with those of the Caspian Sea basin. Based on the results, having a longer pre-vomer, dorsally oriented parasphenoid alar, longer ventral blade-shaped process of the orbitosphenoid, concaved masticatory plate, pointed ascending process of the palatine, concaved posterior margin of the opercle, and a small posterior process of the cleithrum can differentiate S. orientalis of the Urmia Lake basin from those of the Caspian Sea basin.

Alburnoides petrubanarescui is endemic to the Urmia Lake basin, shared by Iran and Turkey. Previously, the species was found in several rivers in this basin, however, it is currently only found in the upper part of the Nazlu Chay River. The species' extent of occurrence (EOO), which was previously estimated to be 20.000 km2, is now 300 km2. Over the past three generations (10 years), the EOO of Urmia spirlin has decreased by 98%, however, the population of the Nazlu River is stable, and there is no strong evidence to suggest that the population will decline in the future. Drought and water abstraction cause the species' population to reduce. Dam building and river pollution reduce their range, making them vulnerable to extinction. Therefore, we classified the species as Vulnerable D2.

Paracobitis vignai is a Nemacheilid loach endemic to the Sistan basin. It occurs in the Helmand River and its related reservoirs in Sistan-va-Baluchistan Province in southeastern Iran and probably in Afghanistan. This species is currently endangered due to habitat loss or degradation, damming and droughts. Therefore, this paper reviews the available data on taxonomy and distribution of P. vignai, provides its morphometric features, and recommends actions for its conservation.