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Here, we combined archived mitochondrial sequences for Ponto-Caspian gobiids with new sequences from the south Caspian basin to assess and evaluate its gobioid diversity and taxonomy, and to provide a first mitochondrial-based phylogenetic and phylogeographic framework. We demonstrate that: (i) Proterorhinus nasalis is the tubenose goby taxon in the saline waters of the southern Caspian Sea, whereas the name Pr. semipellucidus for the Azov/northern Caspian Sea/Volga River populations is likely be resurrected depending on the outcome of an integrative taxonomical approach; (ii) the deep-water goby Ponticola bathybius should be re-assigned to the genus Neogobius, as it is the sistergroup of N. melanostomus; (iii) specimens previously identified as Po. cyrius and Po. iljini from the south Caspian basin appear conspecific with Po. iranicus and Po. gorlap, respectively, and should be omitted from the checklist of Iranian and south Caspian freshwater fishes; (iv) the low stand of the Caspian Sea during the Tyurkyanian regression is inferred to have led to the isolation and evolution of Po. iranicus; and (v) similarities in genetic background, and invasion history of Rhinogobius sp. and Pseudorasbora parva in Iran and Turkmenistan indicate that the initial introduction of both species into the region possibly originated from Japan in the 1980s.

Otoliths (ear stones) of the inner ears of teleost fishes, which develop independently from the skeleton and are functionally associated with hearing and the sense of equilibrium, have significantly contributed to contemporary understanding of teleost fish systematics and evolutionary diversity. The sagittal otolith is of particular interest, since it often possesses distinctive morphological features that differ significantly among species, and have been shown to be species- and genus-specific, making it an informative taxonomic tool for ichthyologists. The otolith morphology of the Caspian Sea gobiids has not been thoroughly studied yet, with data available for only a few species. The aim of the present paper is to examine the qualitative and quantitative taxonomic and phylogenetic information in the sagittal otoliths of these species. A total of 118 otoliths representing 30 gobiid species (including 53.5% of the Caspian gobiofauna) in three gobiid lineages (i.e., Gobius , Pomatoschistus , and Acanthogobius ) and 11 genera (i.e., all Ponto-Caspian gobiid genera except Babka ) were analysed at taxonomic levels using an integrated descriptive and morphometric approach. The results indicated high taxonomic efficiency of otolith morphology and morphometry at taxonomic levels for the Ponto-Caspian gobiids. Our qualitative and quantitative otolith data also (i) support the monophyly of neogobiin gobies, (ii) along with other morphological and ecological data, offer a new perspective on the systematics of Neogobius bathybius , (iii) suggest the reassignment of Hyrcanogobius bergi to the genus Knipowitschia , and (iv) question the phylogenetic integrity of the four phenotypic groups previously defined in the tadpole-goby genus Benthophilus ; however, more studies are needed to complete these evaluations and confirm our otolith study findings.

To understand the functional meaning of morphological traits in the exploitation of natural resources, it is necessary to develop a quantitative, meaningful scheme for understanding ecophenotypes; this will facilitate management and conservation, which are the most pressing challenges in vulnerable aquatic environments. In this context, the management of cryptic and very similar species is more challenging, because of the difficulty of distinguishing them and determining their frequency in sympatry, even though they do not necessarily have the same ecologies. As such, in order to understand how morphological similarities are associated with their ecology, thirteen morphometric characteristics related to body landmark-based geometric morphometries, sagittal otolith morphology, and shape were examined in mature Chelon auratus and Chelon saliens, which were collected from the coastal waters of the southwest Caspian Sea between October 2020 and April 2021. Univariate and multivariate analysis of variance were conducted to evaluate the potential morphological differences between the species. The analyses highlight the morphological differences between C. auratus and C. saliens, and identify potentially helpful traits for using body and otolith shape for the interspecific distinction of these very similar species of Caspian mullet, which can reflect functional similarity and are an important component of community ecology.

The length-weight relationship, breeding season and condition factor of Oxynoemacheilus bergianus from Jajrud River in the Namak Lake basin, Tehran Province, Central Iran, were investigated. Sampling was performed from March 2017 to February 2018. The biometric measurements and the body and gonad weights were monthly carried out for one year log sampling occasions, in a total of 546 specimens. The range of total length in males and females were 3.8-7.5 and 3-7.6 cm, and the range of total weight were correspondingly 0.36-3.53 and 0.2-4.67 g respectively. The calculated coefficient of determination (r2) in males and females was found to be 0.94 and 0.95, respectively reflecting a positive allometric (b > 3, p > 0.05) growth in both sexes. The gonadosomatic index and modified gonadosomatic index showed that O. bergianus spawns in the middle of spring in May. In agreement with that, the condition factor reached the minimum (0.60) in February, while the maximum (0.96) in May. Since there is poor conservation status of the species, this study aims to give a contribution for biologists and wildlife managers.

Otoliths (ear stones) of the inner ears of teleost fishes, which develop independently from the skeleton and are functionally associated with hearing and the sense of equilibrium, have significantly contributed to contemporary understanding of teleost fish systematics and evolutionary diversity. The sagittal otolith is of particular interest, since it often possesses distinctive morphological features that differ significantly among species, and have been shown to be species- and genus-specific, making it an informative taxonomic tool for ichthyologists. The otolith morphology of the Caspian Sea gobiids has not been thoroughly studied yet, with data available for only a few species. The aim of the present paper is to examine the qualitative and quantitative taxonomic and phylogenetic information in the sagittal otoliths of these species. A total of 118 otoliths representing 30 gobiid species (including 53.5% of the Caspian gobiofauna) in three gobiid lineages (i.e., Gobius, Pomatoschistus, and Acanthogobius) and 11 genera (i.e., all Ponto-Caspian gobiid genera except Babka) were analysed at taxonomic levels using an integrated descriptive and morphometric approach. The results indicated high taxonomic efficiency of otolith morphology and morphometry at taxonomic levels for the Ponto-Caspian gobiids. Our qualitative and quantitative otolith data also (i) support the monophyly of neogobiin gobies, (ii) along with other morphological and ecological data, offer a new perspective on the systematics of Neogobius bathybius, (iii) suggest the reassignment of Hyrcanogobius bergi to the genus Knipowitschia, and (iv) question the phylogenetic integrity of the four phenotypic groups previously defined in the tadpole-goby genus Benthophilus; however, more studies are needed to complete these evaluations and confirm our otolith study findings.

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.

The oriental river shrimp ( Macrobrachium nipponense ), an exotic species, has been well adapted and dispersed in Iranian freshwater ecosystems. The feeding ecology and trophic level of this species in the Anzali Wetland, southwestern Caspian Sea, was investigated by both a traditional method and the carbon and nitrogen stable isotope technique. The highest feeding index (FI) was seen in mollusca at 35.9%, followed by detritus at 31.3%. While no significant differences were observed in the preference of food items among different seasons. A Bayesian mixing model was used to estimate the contributions of the stomach contents to the isotopic signature of M. nipponense . According to mixing model results, M. nipponense obtain food from gastropod, fish, shrimp (as cannibalism), insecta, other crustacea, aquatic plants, worms, zooplankton, and unrecognizable content (as detritus) with 30.6%, 16.8%, 12.7%, 5.2%, 4.3%, 3.5%, 0.6%, 0.3%, and 25.9%, respectively. M. nipponense showed a high δ 15 N and its trophic level (TL = 3.38) was at the top of the Anzali Wetland food web, close to commercially important fish species such as pike, Esox Lucius. Being at this trophic level, this shrimp is expected to possess high nutritional quality for human consumption.

Freshwater habitats of the Caucasus biodiversity hotspot represent a center of endemism for the gobiid genus Ponticola Iljin, 1927. Hitherto, large‐scale molecular studies, owing to restricted taxon and geographical sampling, have failed to give an elaborate picture of diversity and evolutionary history of these species. Here, to contribute to filling this gap, we assessed taxonomic diversity, phylogeography and evolutionary history for the south Caspian populations of Ponticola presently classified as P. iranicus and P. patimari, using an integrative taxonomic approach comprising an entire geographic range sampling, and analyses of mitochondrial DNA haplotypes, the head lateral line system, otolith shape, and meristic and morphometric variation. All freshwater samples of the P. syrman group belong to a monophyletic clade with two main subclades: a small subclade confined to the upper Sefidroud sub‐basin including the type locality of P. iranicus and a large subclade with three geographically constrained haplogroups (Hg1, Hg2, and Hg3), comprising the rest of the distribution. Hg1 showed an eastern distribution including the type locality of P. patimari, while Hg2 and Hg3 are sister groups with central and western‐central distributions, respectively. The freshwater clade diverged from P. syrman during the Tyurkyanian low stand (~150 m b.s.l. lasting ~0.1 Myr), while the divergence of P. iranicus and P. patimari and radiations within P. patimari took place during the Bakunian high stand (up to 50 m a.s.l. lasting ~378–480 kya). Species delimitation analyses indicated two distinct species, corresponding to each main subclade. Although the otolith shape and lateral line analyses did not reflect with phylogeographic pattern, PCA and DFA plots of meristic and morphometric data showed a clear separation of the two major subclades corresponding to P. iranicus and P. patimari, suggesting the presence of significant morphological variation meriting formal taxonomic recognition. Overall, our findings (i) reveal the presence of two freshwater endemic species in the P. syrman group, and pending further investigation, hypothesize the presence of a third cryptic species; (ii) revise and document a narrow distributional range and low diversity for P. iranicus, in contrast to a wider distributional range and high diversity for P. patimari; (iii) suggest that the climatic oscillations of the Pleistocene were associated with the cladogenesis within the P. syrman group; and (iv) allowed for the recognition of conservation units and proposition of management measures. Freshwater habitats of the Caucasus biodiversity hotspot represent a centre of endemism for the gobiid genus Ponticola Iljin, 1927. In this paper, we assessed taxonomic diversity, phylogeography and evolutionary history for the south Caspian populations of Ponticola presently classified as P. iranicus and P. patimari, using an integrative taxonomic approach. Overall, our findings reveal the presence of two freshwater endemic species in the P. syrman group, and pending further investigation, hypothesize the presence of a third cryptic species; revise and document a narrow distributional range and low diversity for P. iranicus, in contrast to a wider distributional range and high diversity for P. patimari; suggest that the climatic oscillations of the Pleistocene were associated with the cladogenesis within the P. syrman group; and allowed for the recognition of conservation units and proposition of management measures.

The South Caspian Sea sub-basin, owing to its complex paleogeographic history and habitat diversity, represents a center of endemism and a high-priority conservation area for the gobiid genus Ponticola. However, very little is currently known about most biological aspects of these species in general, and this sub-basin is highly threatened by anthropogenic activities. Here we examined the phylogeographic patterns, genetic diversity, and population structure of the endemic Caspian Sea species P. gorlap, in this evolutionary distinctive and ecologically threatened Caspian sub-basin. Mitochondrial DNA control region sequences and otolith shape variations were analyzed from 472 individuals at seven South Caspian localities. Results showed: (i) two shared and eight private haplotypes, distinguished by shallow divergences, (ii) pairwise ΦST values among locations, ranging from − 0.052 to 1.00; with most of the highest between Sefidroud/Kaboudval and the other samples, (iii) genetic diversity was generally low, smaller at Kaboudval/Nekaroud, and highest at Babolroud, (iv) non-unimodal mismatch distribution and neutrality tests both rejected a recent demographic expansion scenario, (v) otolith shape analysis revealed significant differences among samples, the highest between Sefidroud/Kaboudval and the others, and (vi) Mantel tests confirmed that both pairwise ΦST and otolith shape differences were more correlated to each other than with geographic distances. Different scenarios are discussed to explain the observed patterns of genetic and otolith shape variations and population structure of P. gorlap, including possible roles of euryhalinity, and presence of migratory and resident forms.

This study investigates length-weight relationships of six clupeid species (Alosa braschnikowi, Alosa caspia, Dussumieria acuta, Nematalosa nasus, Sardinella albella and Tenualosa ilisha) captured from three main water bodies of Iran (Persian Gulf, Oman Sea and Caspian Sea), to evaluate if the LWR parameters fit for these fishes having specific morphological characteristics. Based on the obtained results, i) the b value was influenced by recorded length (TL, SL, FL) and body shape, ii) it was within the expected range of 2.27-3.48, iii) length-weight relationships were highly correlated and significant (r2>0.82-0.98, P<0.001), and hence length-weight equations fit well with six clupeid species in the Iranian water bodies. The results presented here, would be useful for fishery biologists and fisheries stake-holders in the study area.