Number Of Gill Rakers Research Articles

Morphological features of round whitefish Prosopium cylindraceum lake Lama (Putorana Plateau)

The article presents materials on the meristic and plastic characteristics of the round whitefish, Prosopium cylindraceum (Pennant, 1784), in Lake Lama, which is part of the Norilo-Pyasinsky water ecosystem and the Pyasina River basin. The Yenisei and Pyasina rivers define the western boundary of this species’ habitat. While the round whitefish is a relatively rare species with a low population in the Yenisei basin, it is abundant in the Pyasina basin, especially in some of the upper water bodies. The round whitefish is a common species in the Norilo-Pyasinsky lakes and is present in all large lakes of the region, except for lake Keta, where it has not been found. Both river and lake-river forms of the round whitefish are present in these water bodies. Both forms have experienced a significant impact from non-commercial fishing, and in some parts of the basin, they have practically disappeared or significantly reduced in number. The areal of the round whitefish in the Pyasina River basin also extends to some right-hand tributaries (Dudypta, Samoyedskaya, etc.) in the northern regions of the basin. The tributaries where the round whitefish is found are typically characterized as rocky, fastflowing streams. The variability of meristic characters of the round whitefish in lake Lama, lake Sobachye, and some parts of the upper Pyasina river are examined. Current data show the round whitefish in the Pyasina River basin and other water bodies of the Taimyr region is represented by a relatively homogeneous population with close values in such basic parameters as lateral line, the number of gill rakers, and other characteristics.

The Ecosystem of Lake Tolpanjärvi, Western Karelia, Preserved in Natural State

The results of the study of Lake Tolpanjärvi’s ecosystem are reported. Its hydrological and geochemical indices, as well as the current condition of biotic communities (zooplankton, benthos and fish population), were studied and analyzed. Analysis of the chemical composition of water indicates the low organic matter content (total phosphorus 0.007 mg/l, nitrogen 0.26 mg/l) of the lake. The Tolpanjärvi is an oligotrophic lake, as indicated by the abundance of zooplankton (with a biomass of less than 1 g/m3) and zoobenthos (biomass 0.44 g/m2). The lake is of an oligosaprobic class (2nd quality class, clean natural water), as evidenced by its saprobity index estimated using Pantle–Bukk’s method. The quantitative indices of zoobenthos varied from 120 individuals/m2 and 0.08 g/m2 in the profundal zone to 1200 inds./м2 and 0.86 g/m2 in the quiet littoral zone. The lake is more similar in the chironomid index (К – 2.00) to clean natural water. It is inhabited by 8 fish species of 5 families. The fish population is dominated by the whitefish Coregonus lavaretus, the perch Perca fluviatilis and the roach Rutilus rutilus. Two ecological forms of whitefish, differing in both the number of gill rakers (sparsely-rakered 18–24 and medium-rakered 28–36) and biological indices (linear-weight growth рост, maturation, fertility and feeding), occur in the lake. Stable highly diverse ecosystems were shown to form the basis for the preservation of the gene pool and for assessment of the current condition of water bodies heavily affected by human activities.

Gill arch and raker morphology of common carp (Cyprinus carpio, Linnaeus, 1758) sampled in aquaculture system.

The study aimed to investigate the morphologic aspects of common carp's gill arch and gill rakers (Cyprinus carpio, Linnaeus, 1758), an omnivore and highest-produced aquaculture species. The study used 10 common carp (395.35 ± 45.06 g) grown entirely under aquaculture conditions. The fish tissues were fixed with Glutaraldehyde (2.5%) for scanning electron microscopy and with formalin (10%) for stereomicroscopic examination. In the SEM examination, two types of taste papillae (Type II and Type III) were observed in the pharyngeal mucosa. Microridge-like structures in the epithelial layer were found to have two forms. The study findings indicate a significant decrease in gill arch lengths from cranial to caudal and a significant increase in rakers per unit area, as determined through digital calliper measurements and stereomicroscopic examinations (p < 0.05). However, there was no significant difference in measurements of gill arches and raker numbers between the bilateral symmetry of the gill arches (p > 0.05). In conclusion, it was observed that the epithelial structure on the common carp gill arch contained two types of microridge-like structures: the gill arch length decreased from cranial to caudal, and the rake density on these arches increased caudally.

A new species of spiny eel of the genus Notacanthus Bloch 1788 (Notacanthiformes: Notacanthidae) from the Indian Ocean.

The deep-sea spiny eels of the genus Notacanthus Bloch 1788 are currently represented by six valid species, of which only one, Notacanthus indicus, has been described so far from the Arabian Sea, part of the Western Indian Ocean. This paper reports the discovery of a new species, described herein as Notacanthus laccadiviensis, from the outer reef drop-off, off the Kavaratti Island, Lakshadweep Archipelago, Arabian Sea. The new species differs from its congeners in the shape of the head; morphology of dorsal, pectoral and anal fins; number of gill rakers; number of vertebrae; and body colour, and specifically from N. indicus (the only known congener from the Indian Ocean) in the unusual morphology of the dorsal fin, and number of rays in the dorsal and pectoral fins.

Distribution and Some Diagnostic Properties of Capoeta damascina (Valenciennes, 1842) in Streams of the Ceyhan and Seyhan River Basins, Türkiye

This study determined the distribution and some diagnostic characteristics of Capoeta damascina, which belongs to the Cyprinidae family, in the Ceyhan and Seyhan River basins. C. damascina individuals were detected in 21 of 25 Ceyhan River Basin stations and 12 out of 15 in the Seyhan River basin stations. C. damascina show a wide distribution in the Ceyhan and Seyhan River basins. It has been determined that C. damascina lives at altitudes between 125 m (Hemite Stream) and 1620 m (Söğütlü Stream) in the Ceyhan River basins, and in streams at altitudes ranging from 165 m (Çakıt stream) to 1758 m (Sarız Stream) in the Seyhan River basins. The average total length of C. damascina individuals (n: 218) caught in the Ceyhan River Basin is 14.72 cm, and their average weight is 40.12 g. In the Seyhan River basin, the average total length of C. damascina individuals (n: 74) was found to be 17.31 cm, and their average weight was 72.24 g. The mean number of line lateral scales was 71, the number of gill rakers was 23, and the number of pharyngeal teeth was 4:3:2-2:3:4.

Parallel shifts in trout feeding morphology suggest rapid adaptation to alpine lake environments.

Eco-evolutionary interactions following ecosystem change provide critical insight into the ability of organisms to adapt to shifting resource landscapes. Here we explore evidence for the rapid parallel evolution of trout feeding morphology following eco-evolutionary interactions with zooplankton in alpine lakes stocked at different points in time in the Wind River Range (Wyoming, USA). In this system, trout predation has altered the zooplankton species community and driven a decrease in average zooplankton size. In some lakes that were stocked decades ago, we find shifts in gill raker traits consistent with the hypothesis that trout have rapidly adapted to exploit available smaller-bodied zooplankton more effectively. We explore this morphological response in multiple lake populations across two species of trout (cutthroat trout, Oncorhynchus clarkii, and golden trout Oncorhynchus aguabonita) and examine the impact of resource availability on morphological variation in gill raker number among lakes. Furthermore, we present genetic data to provide evidence that historically stocked cutthroat trout populations likely derive from multiple population sources, and incorporate variation from genomic relatedness in our exploration of environmental predictors of feeding morphology. These findings describe rapid adaptation and eco-evolutionary interactions in trout and document an evolutionary response to novel, contemporary ecosystem change.

A New Stolephorus (Teleostei: Clupeiformes: Engraulidae: Engraulinae) from the Red Sea

The new anchovy Stolephorus meteorum, formerly confused with Stolephorus indicus, is described on the basis of 19 specimens collected from the southern Red Sea. Four other species, previously confused with or placed in the synonymy of S. indicus, have been either redescribed (Stolephorus commersonnii), described as new (Stolephorus belaerius), or resurrected from its synonymy (Stolephorus balinensis and Stolephorus scitulus). The new species shares with the latter four species, plus S. indicus, a relatively short maxilla and pelvic fins, and six or fewer prepelvic scutes but differs from them in the combination of some other characters, including intermediate numbers of gill rakers (total gill rakers on first gill arch 40–43, modally 41), 41 vertebrae, a large head and narrower interorbital area, and longer pelvic fins. A genetic analysis of the mitochondrial cytochrome oxidase I gene (COI) of S. meteorum, new species, S. balinensis, S. belaerius, and S. indicus revealed each species to be genetically divergent from the others by 2.5–3.6% uncorrected distance.

Phylogeny, Distribution, and Biology of Pygmy Whitefish (Prosopium coulterii) in the Beringia Region (Chukotka)

The pygmy whitefish Prosopium coulterii (C. H. Eigenmann &amp; R. S. Eigenmann, 1892) is a freshwater fish with a highly disjunct distribution ranging from the middle part of North America to Chukotka. There is still no consensus regarding its phylogeny and dispersal history due to limited information from the Chukotkan part of the range. We investigated 22 lakes over Chukotka and found a much broader distribution than it was previously thought. Pygmy whitefish was found to be a common species in the lakes that belong to rivers draining into the Arctic. Cytochrome B, cytochrome oxidase subunit 1, and ATP synthase F0 subunit 6 mitochondrial sites were analyzed from 25 samples to reconstruct the phylogenetic history of pygmy whitefish. Two haplogroups belonging to the east and west Chukotkan ranges were identified; both groups are closely related to Alaskan pigmy whitefish and distant from the Cascadia-Mackenzie (Peace) populations. Combining the distribution patterns, phylogenetic network topology, and the contemporary knowledge on the glaciation history of the region, we suggest a possible colonization pathway over Beringia region and beyond it. The basic biological characteristics (fork length, number of gill rakers, and pyloric caeca, age structure, and feeding) are also presented to characterize the populations over the investigated range.

Occurrence of longfin goatfish Upeneus supravittatus (Uiblein and Heemstra, 2010) along Chennai coast, south India

Goatfishes (Family: Mullidae) are commercially important fishery resource along the Chennai coast, south-eastern India.Species-level identification of goatfishes is a challenge, particularly in the ‘vittatus’ group, as there is severe overlapof taxonomic characteristics. In 2010, Uiblein and Heemstra revised the Family Mullidae and reported the occurrenceof Upeneus supravittatus along the Indian coast. They also remarked that U. supravittatus has been misidentified asU. taeniopterus in earlier reports from India. To resolve this and verify the occurrence of U. supravittatus, 15 morphometriccharacteristics and 13 meristic characteristics of goatfish samples collected at Chennai were analysed and compared withthe corresponding data reported by Uiblein and Heemstra for U. taeniopterus and four other ‘vittatus’ group goat fishes. Theanalysis, as well as DNA bar coding and area of distribution of species confirmed the samples as Upeneus supravittatus.The gill raker count on the upper and lower limbs of first gill arch was an important key in identifying the species. Thoughthe number of gill rakers was almost similar for U. supravittatus, U. vittatus and U. taeniopterus, the size and position ofthe gill rakers confirmed that the collected samples were all U. supravittatus. The study also indicates the possibility thatU. supravittatus has been hitherto wrongly reported as U. taeniopterus. A detailed taxonomic study on the Family Mullidaeneeds to be undertaken along the Indian coast using morphometric and meristic characteristics and DNA barcoding toresolve these taxonomic issues. Keywords: DNA barcoding, Gill rakers, Species identification, ‘vittatus’ group

Foraging morphology and diet divergence of European whitefish (Coregonus lavaretus) in water courses of Murmansk region

European whitefish (Coregonus lavaretus) is a highly polymorphic species. In general, it is assumed that the divergence in whitefish is a form of a specialization in the use of the resources (including food) of the main limnological zones – pelagic (plankton), littoral (benthos, plankton), profundal (benthos) – and the morphological adaptations of the shape of the body and head simultaneously determine the direction of the process. The shape and number of gill rakers, which are responsible in whitefish for prey retention, are considered the most important adaptive trait and are most often used to distinguish between its sympatric morphs or ecotypes. Current study will be devoted to foraging morphology and diet divergence of whitefish in water courses of Murmansk region. Our study of the water bodies in three major river basins of Murmansk region revealed the presence of two whitefish morphs: sparsely rakered (further sr) and medium rakered (mr). The mr morph is less common and observed only alongside the sr whitefish. In general, in sr whitefish the number of gill rakers ranges between 15 and 31, and in mr whitefish between 27 and 44. Among whitefishes with 27–31 gill rakers, both sr and mr morphs were observed and distinguishable by the shape of the rakers. In the studied sr whitefish populations, relatively long and short rakered whitefish morphs were found. In Lake Kuetsjärvi (Pasvik River basin), the sr and mr whitefish formed additional slow- and fast-growing ecological morphs. In the water bodies of the Murmansk region, the greatest diversity of sympatric morphs of whitefish (from two – sr and dr to four morphs – sr1, sr2, mr1, mr2) is observed in the most polluted water bodies with higher productivity and a large abundance of such generalists as perch and European smelt. The diet of sr and mr whitefish morphs in the studied water bodies of Murmansk region in summer-autumn period is associated with hydrobiological features of fish habitats. Sr whitefish morph from the Pasvik, Tuloma and Niva Rivers basins, inhabiting mainly littoral and profundal areas of water bodies, have a benthic diet. Mr whitefish morph, inhabiting mainly littoral and pelagic areas of water bodies, have both benthic and mixed feeding types. According to our data, coexistence of four morphs of whitefish in Lake Kuetsjärvi (lower Pasvik River) – sr1, mr1, sr2 and mr2 have the low specialization and use the most abundant recourses in lake. The most extensive overlapping of feeding spectra is found in small morphs in Lake Kuetsjärvi – sr1 and mr1. On the basis of our data on whitefish from water bodies of Murmansk region we found active gill apparatus functioning in fish, as minimum length of food organisms in sr and mr whitefish morphs were sometimes less than or equal to gill rakers distances of fish.

Revision of Prodontocharax and revalidation of Amblystilbe (Teleostei: Characidae: Cheirodontinae), with description of a new species

Abstract Prodontocharax species are revised and the genus Amblystilbe is revalidated based on analysis of type-material and additional specimens. Both genera are diagnosed based on unique synapomorphies among members of the Cheirodontinae related to shape, size, number and arrangement of teeth in the jaw bones. Prodontocharax melanotus, from the upper rio Madeira basin, Brazil and Bolivia, is redescribed, and a new species is described from the rio Huallaga basin, Peru. The genus Amblystilbe and its type-species, A. howesi, are redescribed from the Amazonas River basin, Bolivia, Brazil, and Peru, and Prodontocharax alleni is considered a junior synonym of A. howesi. The two species of Prodontocharax are distinguished by the color pattern, number of lamellae of the olfactory rosette in male and female and number of gill rakers, and differ from A. howesi by the number and shape of teeth, color pattern and number of branched anal-fin rays. According to recent studies, the species of Prodontocharax and A. howesi cluster into two distinct clades among the cheirodontines.

Description of three new species previously identified as Stolephorusbengalensis (Dutt & Babu Rao, 1959) or Stolephorusinsularis Hardenberg, 1933 and a re-description of S.bengalensis (Chordata, Osteichthyes, Clupeiformes, Engraulidae).

Examination of numerous specimens characterised by predorsal scute, long maxilla, indented preopercle and pelvic scute lacking a spine and previously identified as Stolephorusbengalensis (Dutt & Babu Rao, 1959) or Stolephorusinsularis Hardenberg, 1933, revealed four distinct species, true S.bengalensis (distributed from the Bay of Bengal to Pakistan) and three new species, viz., Stolephoruseldorado sp. nov. (Taiwan to Java, Indonesia), Stolephorusdiabolus sp. nov. (Strait of Malacca, from Penang , Malaysia, to Singapore) and Stolephoruseclipsis sp. nov. (Bintan Island, Riau Archipelago, Indonesia). Characters separating the four species include numbers of gill rakers on each gill arch and vertebrae and pelvic fin and dorsal-fin ray lengths. Two molecular markers (mitochondrial cytochrome b and cytochrome oxidase I genes) demonstrated the distinction of three of the species examined morphologically and enabled a reconstruction of their phylogenetic relationships. Each species was genetically divergent from the others by 3.5%-7.7% mean uncorrected distance in the mitochondrial cytochrome oxidase I gene.

Descriptions of Two New Species, Sillago muktijoddhai sp. nov. and Sillago mengjialensis sp. nov. (Perciformes: Sillaginidae) from the Bay of Bengal, Bangladesh

Due to difficulty in recognition, many true species have been covered under the synonyms of wide-spread species. To justify the identification of a widely distributed species, Sillago sihama from the Bay of Bengal, Bangladesh, an integrated approach including morphology and DNA barcoding was used. Two unrecognized species of Sillago, i.e., Sillagomuktijoddhai sp. nov. and S. mengjialensis sp. nov., were identified from the coastal area of Bangladesh. S. muktijoddhai sp. nov. has marked differences in the body color, anal fin color, number of gill rakers, snout length, and swimbladder. S. mengjialensis sp. nov. has notable differences in the anal fin color, snout length, and swimbladder and is distinguished from S. muktijoddhai sp. nov. by the body color and swimbladder. The morphological characters of 14 documented Sillago species with two posterior extensions of the swimbladder were referenced and distinguished to accredit the two new species. Genetic analyses of partial mitochondrial cytochrome oxidase subunit I and 16S ribosomal RNA also supported the validity of the new species. This study has increased the number of recognized species of Sillago in the world and confirmed the prevailing misidentification of these two new species in Bangladesh as so-called S. sihama. Moreover, the study confirmed the misidentification of S. mengjialensis sp. nov. in Indonesia as S. sihama and the identification of unknown Sillago sp.1 in India.

Trophic Relations between Native Salvelinus malma Walb. and Introduced Oncorhynchus nerka Walb. in the Landlocked Lake Sevo, Kamchatka

Fish introductions are known to be dangerous due to the unexpected spread of diseases and disorganization of the food web. In 1986, the resident sockeye salmon Oncorhynchus nerka from Kronotskoye Lake was introduced into an isolated lake in Kamchatka inhabited by the native lacustrine Dolly Varden charr Salvelinus malma. Thirty years later, we analyzed the stomach content, stable isotope ratio and lipid fractions in muscles, as well as the parasite fauna of fish to assess the trophic relationships between the two species. It has been found that the sockeye salmon has occupied the planktivorous niche; no diversification into trophic forms depending on the number of gill rakers, like in the ancestral population, was detected. The indigenous benthivorous S. malma is represented by three trophic groups. Mature dwarf individuals, as well as the juveniles, mainly consume insect larvae on the lake slope; large fish feed on amphipods in the same habitats; and 10% of the large Dolly Varden switches to facultative piscivory. Predators die as a result of Diphyllobothrium sp. hyper invasion, which infects fish when feeding on the sockeye salmon. The diversity of parasite fauna is 3/4 poorer in the introduced sockeye in comparison with the donor population; part of the parasite species is obtained by the sockeye from the Dolly Varden.

Johnius sasakii, a new species of croaker (Perciformes: Sciaenidae) with a key to Johnius from East Malaysia, Borneo.

A new sciaenid fish, Johnius sasakii sp. nov. from the East Malaysian coastal waters of Sabah and Sarawak, Borneo is described herein. Johnius sasakii sp. nov. can be separated from the close congeners, Johnius heterolepis and Johnius carouna by having less gill rakers on the lower limb of the first gill arch (mode number 9 vs. 10 for J. heterolepis; 11 for J. carouna). It can be distinguished from J. heterolepis with the higher modal number of gill rakers on the upper limb of first gill arch (5 vs. 4), shorter anal-fin base length (9% vs. 10% of SL) and first anal-fin ray length (1012% vs. 1213% of SL) respectively. Furthermore, J. sasakii sp. nov. can be further differentiated from J. carouna by its shorter second anal-fin spine length 710% SL (usually 810%) vs. 1114% SL (usually 1112%) and slightly deeper body depth 2529% SL (usually 2628%) vs. 2328% SL (usually 2426%). Meanwhile, J. sasakii sp. nov. can be easily differentiated from J. macrorhynus by a present of molariform teeth on inner rows of jaws and stumpy gill rakers. Johnius (Johnius) sasakii sp. nov. can be clearly distinguished from species of the subgenus J. (Johnieops) by the lack of enlarged outer row teeth on upper jaw. A Kimura 2-parameter genetic distance comparison of 450 bp sequences of mitochondrial 16S rRNA and 488 bp nuclear gene S7 showed that J. sasakii sp. nov. are highly differentiated from J. heterolepis (16S: 10.4%, S7: 5.8%), J. carouna (16S:19.3%, S7:8.4%); and J. macrorhynus (16S: 16.7%, S7: 8.1%) respectively. The study highlights that the genetic approach from mtDNA and nDNA can contribute to the confirmation of taxonomic status of sympatric species in genus Johnius.

Benthic–limnetic morphological variation in fishes: Dissolved organic carbon concentration produces unexpected patterns

AbstractVariation in traits related to foraging and locomotion in benthic and limnetic habitats has been observed in many fishes. Benthic and limnetic food chain productivity in lakes is strongly influenced by the concentration of dissolved organic carbon (DOC) in the water, suggesting that DOC might indirectly impose selection on these traits and lead to classic benthic forms at low DOC concentrations and limnetic forms at high DOC concentrations. We tested this hypothesis via geometric morphometric and meristic analyses of bluegill sunfish (Lepomis macrochirus, Centrarchidae) from 14 lakes with DOC concentrations ranging from 4 to 24 mg/L. These lakes, located in close proximity to each other, straddle the drainage divide between the Mississippi River and Laurentian Great Lakes basins in northern Wisconsin, USA. Bluegill morphology was consistently related to lake DOC concentration in both drainage basins, despite differences in morphology between basins. Fish from higher DOC lakes had deeper bodies and smaller heads, among other differences, though the proportion of shape variation described by DOC was low. Gill raker length and inter‐raker spacing were positively related to DOC concentration. Although some traits were thus related to DOC concentration, the directions of these relationships did not match the predicted benthic–limnetic patterns. Further, no relationships were evident between DOC and gill raker number, eye width, pectoral fin dimensions, or pectoral fin insertion angle in univariate analyses. These variable outcomes suggest that selection linked to DOC does not map neatly onto the classic benthic–limnetic axis, that high DOC favors a benthic–limnetic generalist rather than a limnetic specialist, or that the benthic–limnetic morphological dichotomy is less clear and universal than is often suggested.

Testing the “young-species” hypothesis for Alburnus heckeli Battalgil 1944 (Teleostei: Leuciscidae) inhabiting Lake Hazar, Turkey

Alburnus heckeli Battalgil 1944 is endemic to Lake Hazar in the Euphrates-Tigris River system (Persian Gulf basin) and shares morphological and molecular characters with the widespread species A. sellal Heckel 1843, except putatively for the number of gill rakers. This study compared morphometric and meristic data for A. heckeli with lentic and lotic populations of A. sellal. The only significant difference was in the number of gill rakers in lotic populations of A. sellal (10–25) vs. lentic populations of A. sellal (26–35) and A. heckeli (28–35). Although our results are consistent with the interpretation of A. heckeli and A. sellal as “young species”, the amiguity of available morphological and molecular sequence data suggest that A. heckeli is best treated as a junior synonym of A. sellal until reliable differences are found.

Сиг — пыжьян Coregonus lavaretus pidschian (Gmelin, 1788) бассейна реки Хатанги

The paper presents the results of a morphological and ecological study of three sympatric forms of the Humpback whitefish from the Khatanga River basin, Taimyr Peninsula, Krasnoyarsk krai territory. Statistically significant differences in plastic and meristic features between all compared formswere revealed.The most significant values of meristic features were found by the number of gill rakers (between riverine form and lacustrine-riverine form tₛₜ = 3.55), riverine form and lacustrine form (tₛₜ = 8.92), lacustrine-riverineform and lacustrine form (tₛₜ = 6.72). Significant differences were found in the number of scales in the lateral line when comparing riverine and lacustrine-riverine forms (tₛₜ = 3.16), riverine and lacustrine forms (tₛₜ = 2.85). Significant differences were noted in the plastic characters between riverine and lacustrineforms of Humpback whitefish: in the length of the head (between riverine and lacustrine-riverinetst = 5.49, riverine and lacustrinetst = 5.49); by antedorsal distance: riverine and lacustrine-riverine (tₛₜ = 2.67), riverine and lacustrine (tₛₜ = 4.40); in eye diameter between lacustrine-riverine and lacustrine (tₛₜ = 6.89), riverine and lacustrine (tₛₜ = 9.42).A comparison of the morphological features of lacustrine, lacustrine-riverine and riverine forms of whitefish in the Khatanga River basin with those forms from other water bodies in northern Siberia is carried out.Differences in meristic and plastic features are shown.The age range of riverine whitefish in catches is represented by 9 age groups (4+ - 12+), lacustrineriverine - 13 (6+ - 18+), lacustrine - 4 (13+ - 17+).The distribution and migration of allHumpback whitefish forms in the river basin are presented on the basis of our own observations and literary sources.The nutrition of individual forms has been studied, the basis of the Humpback whitefish diet is made up of benthic organisms: caddisflies, chironomids, mollusks and amphipods. English version of the article is available at URL: https://panor.ru/articles/siberian-whitefish-coregonus-lavaretus-pidschian-gmelin-1788-khatanga-river-basin/77293.html

Comparative morphological characteristics of spawning populations of Baikal omul (Coregonus migratorius, G.) in the Posolsky Sor, Selenga and Barguzin rivers

The morphological structure, size-age variability and dynamics of age-related fertility of producers of Baikal omul of pelagic, near-bottom and coastal morpho-ecological groups during the depressive state of the population were studied. There is an improvement in the indicators of the growth rate of fish, maturation and an increase in absolute individual fertility against the background of the dilution of the population and the release of the feeding area. A comparative characteristic of some morphological features of fish among morphological-ecological groups is given. The number of gill rakers on the first gill arch significantly distinguishes different morpho-ecological groups and ranges from 36 to 43 pieces for the near-bottom, from 40 to 46 pieces for the coastal and from 44 to 53 pieces for the pelagic morpho-ecological groups. It is noted that the spawning populations of the coastal and pelagic groups are mainly represented by young individuals. With age, the proportion of females increases in all groups. The largest indices of the pectoral, abdominal and anal fins, responsible for movement in the vertical plane, rotation and stop, are noted in the near-bottom group.

Revalidation and redescription of Serranus knysnaensis Gilchrist, 1904, (Perciformes: Serranidae) with a new distribution record.

A southwestern Indian Ocean (SWIO) percoid fish Serranus knysnaensis Gilchrist, 1904, was long synonymised with the comber, Serranus cabrilla (Linnaeus, 1758), from the eastern Atlantic Ocean, Mediterranean and Black Sea. However, when the species was brought out of synonymy by Heemstra Heemstra (2004), reasons for this decision were not given. This study aims to revalidate the present taxonomic status of S. knysnaensis using morphological and molecular assessments. The two species are distinguished by the number of circumpeduncular scales (2634 in S. knysnaensis versus 3438 in S. cabrilla) and total gill rakers (1822 versus 2224). Serranus knysnaensis is also distinct from S. novemcinctus Kner, 1864, the other SWIO species of Serranus, based on total gill raker counts (1822 versus 3135). Genetic analysis of mitochondrial DNA barcode (COI) sequences for 17 Serranus species revealed three closely-related monophyletic clusters corresponding to S. cabrilla, S. novemcinctus and S. knysnaensis that were supported (P 0.001) by species delimitation methods. Even though the genetic distances among the three species were the lowest in the genus (1.60-1.99%), these species may be ecomorphs or lineages that have only recently diverged from each other. These three species also have allopatric distributions and our morphological and molecular data thus confirm that S. knysnaensis is a valid species.