Summer distribution of the purplegray sculpin <Emphasis Type="Italic">Gymnocanthus detrisus</Emphasis> (Cottidae) in Waters of Primorsky Krai,Sea of Japan

Results of trawl catches show that in the summer period, in the waters of Primorsky Krai, Russia, Sea of Japan, the purplegray sculpin Gymnocanthus detrisus occurs at depths of 20 to 411 m, preferring the range 80–250 m. The temperature of the species’ habitat varies from 0.8 to 8.6 ° C, and the optimal one is 1.2–2.2 °C. G. detrisus occurs at the preferred depths more frequently in the southern area—the Peter the Great Bay, which is more favorable for foraging; in the area of North Primorsky Krai it was found both at greater and lesser depths. The latter is probably determined by the more limited spreading of waters with unsuitable temperatures for the species there. The body size of the purplegray sculpin grows with depth. Juveniles avoid depths over 200 m, where inflow of low-temperature waters is recorded. G. detrisus, which inhabits waters of Primorsky Krai, is represented mainly by females; the proportion of males exceeds that of females only in the 21–27 cm size group. This may be related to the lower growth rate in males after maturation as compared to females.     

Biological features of common fish species in Olyutorsky-Navarin region and the adjacent areas of the Bering Sea: 3. Righteye flounders (Pleuronectidae)

Biological features of the seven abundant commercial species—the Pacific halibut Hippoglossus stenolepis, the Greenland halibut Reinhardtius hippoglossoides, the Alaska plaice Pleuronectes quadrituberculatus, the northern rock sole Lepidopsetta polyxystra, the yellowfin sole Limanda aspera, the flathead sole Hippoglossoides elassodon, and the Bering flounder H. robustus (Pleuronectidae)—have been studied for a 20-year period (1995?2015). These species are present in the northwestern Bering Sea in the summer–autumn season; they form the gatherings in Olyutorsky-Navarin region. The size-weight spectra of the fish caught by different fishing gear has been analyzed, the peculiarities of the linear growth and the weight gain, as well as the spawning period and scale and the spawning conditions, have been described. The largest halibut specimens have been registered in the bottom setlines and gill nets, while flounders were in snurrevad catches; the smallest specimens have been observed in trawl catches. The abundant year-class in most of the studied species is seen well on the long-term plots of the fish size spectra and is tracked by the decrease of their biological parameters. The species that demand vast growing grounds (Pacific halibut, Alaska plaice, northern rock sole, and yellowfin sole) are characterized by a smaller average body size of the fish sampled in the coastal waters due to the prevalence of the young specimens in this area.     

Phylogenetic relationships of sculpin <Emphasis Type="Italic">Cottus volki</Emphasis> Taranetz, 1933 (Scorpaeniformes,Cottidae) according to the results of analysis of control region in mitochondrial DNA

Sequencing of the fragment of control region in mitochondrial DNA in sculpin Cottus volki and the comparison of obtained data with homologous nucleotide sequences in the other species from genus Cottus demonstrated that C. volki occupies the basal position in the “poecilopus” group, which includes also typical sculpin C. poecilopus Heckel, 1837 from water bodies of Europe, sculpin C. szanaga Dybowski, 1869 from the Amur River basin, and sculpin Cottus cf. poecilopus from the Lena River basin. Early separation of C. volki line from common trunk of “poecilopus” group explains the presence in C. volki of several primitive (plesiomorphic for this group) morphological characters: long interior ray of ventral fin, practically complete lateral body line, and well-developed dentition of palatine bones.     

Biological features of the common fish species in Olyutorsky-Navarin region and the adjacent waters of the Bering Sea: 1. Gadidae (cods) family

Biological features of the three common fish species, pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, and saffron cod Eleginus gracilis (Gadidae), have been studied using a 20-year dataset (1995?2015). These species inhabit the northwestern Bering Sea in the summer–autumn period and form the schoolings in Olyutorsky-Navarin region. The size–age parameters, as well as the peculiarities of the body length and body weight dynamics, spawning periods, spawning range, and conditions, of the fish caught by different sampling gear have been analyzed. Due to the construction peculiarities and catch efficiency of the different catching gear, the largest specimens are found in the setlines and snurrevads; the fish caught by the trawls are characterized by the smallest size. The body length and body weight of pollock is greater in the pelagic trawl catches compared to the bottom trawl catches. The abundant brood of Gadidae may well be tracked on the multiyear dynamics graphs reflecting the size distribution, as well as by the decrease of biological parameters of the fish. The studied species inhabit the vast growth areas, so smaller body size of them in the coastal waters may be a result of a high ratio of the young specimens there.     

Biological features of the common fish species in Olyutorsky-Navarin region and the adjacent waters of the Bering Sea: 2. Families Macrouridae,Clupeidae, and Osmeridae

Biological features of the four common fish species, giant grenadier Albatrossia pectoralis (Macrouridae), Pacific herring Clupea pallasii (Clupeidae), Pacific rainbow smelt Osmerus mordax dentex, and Pacific capelin Mallotus villosus catervarius (Osmeridae), were studied under the 20-year dataset (1995?2015). These species inhabit the northwestern Bering Sea in the summer–autumn period and form the schoolings in the Olyutorsky-Navarin region. The size–age parameters of the fish caught by different sampling gear, as well as the peculiarities of the body length and body weight dynamics, spawning periods, spawning range, and conditions, were analyzed. The largest specimens of giant grenadier, Pacific herring, and Pacific rainbow smelt were observed in the catches performed by the bottom setline and the gill nets; the smallest fish were found in the trawl catches. The body length and body weight of Pacific herring were larger in the pelagic trawls compared to the bottom trawls; an opposite pattern was observed for the Pacific capelin. The abundant year-class in the species with short life cycle (capelin and herring) is well tracked on the longterm plots of the fish body size; this is accompanied by the decrease of their biological parameters. Herring stock covers large growing grounds; smaller body size was observed for the herring grazing in the coastal waters; young specimens dominate here.     

Distribution and abundance of fish in the southwest of Caspian Sea coastal waters

This study was carried out in southwestern Caspian Sea coastal area to elucidate demersal bony fishes distribution and abundance. Twenty two species were found in shore line, which belong to 6 families. In deeper waters down to 7 meters only 5 species of Gobiidae and 1 species of Syngnathidae were identified. Two species Neogobius caspius and N. pallasi were the main components of demersal fishes; however in some regions Rutilus caspicus, Rutilus kutum and Liza spp. were dominated. Most places were dominantly occupied by Atherina boyeri, which had the highest abundance among the pelagic fishes. Conversely, the Ponticola gorlap, N. melanostomus and Proterorhinus nasalis showed the lowest abundances (less than 1 ind./100 m²). Benthophilus stellatus and P. nasali had the lowest niche overlaps with other species. Both of these two species and P. gorlap are suggested to be classified as endangered or vulnerable species based on their low abundance. The distribution of Syngnathus abaster depends on algae, while algae grow up into the stony construction of the coastal line. A negative insignificant correlation was observed between pelagic and demersal fish abundances. The commercial fisheries data of 76 beach seines in our study area during 2002–2013 was compared with our results on fish abundance and species composition. More than 93% of total fish catch constituted Liza spp. and Rutilus kutum. The relationship between the abundance and distribution of the studied species, and the restocking activities performed by Iranian fisheries organization are discussed. The high abundance and distribution of small size fish in tidal zone could be related to the distribution of crustacean, which provide a good source of food for these fish species.     

Distribution and diversity of the Opheliidae (Annelida,Polychaeta) on the continental shelf and slope of Iceland,with a review of the genus <Emphasis Type="Italic">Ophelina</Emphasis> in northeast Atlantic waters and description of two new species

The diversity, taxonomy and distribution of the Opheliidae (Annelida: Polychaeta) in Icelandic waters is reviewed based on material collected during the BIOICE project. Nine opheliid species are recorded from Iceland; of these, three were previously reported in the area (Ophelia limacina, Ophelina cylindricaudata and O. acuminata), four are new for Icelandic waters (Ammotrypanella cf. arctica, Ophelina abranchiata, O. helgolandica and Tachytrypane jeffreisii), and two are new to science. Ophelina basicirra sp. nov. is distinguished by having a narrow anal tube with one short proximal anal cirrus in ventral position. Ophelina bowitzi sp. nov. is characterized by the small size of its anterior branchiae, which become larger in the middle and posterior body regions, and by an upwardly bent anal tube that is wide at the base and narrowing distally. The genera Euzonus, Armandia and Polyophthalmus are not represented in the BIOICE samples. The distribution of each species off Iceland is presented; one species is restricted to shallow waters of northwestern fjords, three species are found south of the GIF Ridge, and five species are circumicelandic. Several body characters with taxonomic relevance in some species are reviewed based on SEM images. Furthermore, as a first step towards a future revision of the genus Ophelina Örsted 1843 in North Atlantic waters, the status of each species originally described or subsequently reported from the area is commented on, and a key to the currently valid species is presented. Ophelina longicephala Hartmann-Schröder, 1977, formerly a subspecies of O. delapidans (Kinberg, 1866), is raised to species status.     

Opistholobetines (Digenea: Opecoelidae) in Australian tetraodontiform fishes

Opistholebetine opecoelids are reported following examination of 1,041 individual tetraodontiform fishes, comprising 60 species and seven families, collected in Australian waters between 1986 and 2018. Nine species consistent with Opistholebes Nicoll, 1915, Heterolebes Ozaki, 1935 or Maculifer Nicoll, 1915 were recovered. However, phylogenetic analysis of sequence data, generated for some of these species, suggested that five genera, not three, are required to adequately accommodate these taxa. Thus, the concept and composition for each is revised, Pseudoheterolebes Yamaguti, 1959 nec Gupta, 1968 is resurrected and Parallelolebes n. g. is proposed. Of the nine species examined, five are new. Four new species are from fishes endemic to subtropical and temperate Australian waters for which no trematodes have previously been reported: Pa. australis n. sp. and Ps. corazonae n. sp. from the slender-spined porcupinefish Diodon nicthemerus Cuvier (Diodontidae) off Stanley, Tasmania; Pa. virilis n. sp. from the horse-shoe leatherjacket Meuschenia hippocrepis (Quoy & Gaimard) (Monacanthidae) off Stanley; and Ps. stellaglobulus n. sp. from the threebar pocupinefish Dicotylichthys punctulatus Kaup (Diodontidae) in Moreton Bay, south-east Queensland. The fifth new species is M. diodontis n. sp., collected from the spotted porcupinefish Diodon hystrix Linnaeus and the blackblotched porcupinefish D. liturosus Shaw, in tropical waters on the Great Barrier Reef. Species reported previously include the type-species of Opistholebes, O. amplicoelus Nicoll, 1915 from the rough golden puffer Lagocephalus lunaris (Bloch & Schneider) (Tetraodontidae) and the common toadfish Tetractenos hamiltoni (Richardson) (Tetraodontidae) in Moreton Bay, and three species reported for the first time from fishes in Australian waters: H. maculosus Ozaki, 1935, Pa. elongatus Ozaki, 1937 n. comb. and Ps. diodontis (Cable, 1956) n. comb., each from both D. hystrix and D. liturosus on the Great Barrier Reef. Following the revisions, Opistholebes is recognised for two species, Heterolebes for five, Maculifer for eight, Pseudoheterolebes for five and Parallelolebes for three.     

Rare species of cyclostomata and fish in the Upper Oka basin and within Kaluga oblast

The species list of fish of the Upper Oka basin is verified. Data on biology of rare species are presented (western brook lamprey Lampetra planeri, sterlet Acipenser ruthenus, bystryanka Alburnoides bipunctatus rossicus, asp Aspius aspius, undermouth Chondrostoma variabile, bitterling Rhodeus sericeus, and fresh-water sculpin Cottus gobio koshewnikowi). Their morphological characters, distribution in the Upper Oka basin relative abundances of these species, and its changes during recent decades are also commented.     

Ultrastructure of saccular epithelium sensory cells of four sculpin fish species (Cottoidei) of Lake Baikal in relation to their way of life

Various structural elements of the apical region of hair cells and their location in the saccular macula of four sculpin fish species (Cottoidei) of Lake Baikal—two oilfish species (big golomyanka Comephorus baicalensis and small golomyanka C. dybowski), Severobaikalsk yellowfin Cottocomephorus alexandrae, and stone sculpin Paracottus knerii—were studied by scanning electron microscopy. In stone sculpin Paracottus knerii, which inhabits the coastal areas and leads a benthic lifestyle, the diversity of hair cells (in terms of the height of kinocilium and stereocilia) is big than that in the secondary pelagic species big and small golomyankas and in Severobaikalsk yellowfin, which inhabits the near-slope areas. Stereocilia of hair cells of stone sculpin and Severobaikalsk yellowfin are shorter than in the other species studied. The presence of such cells in the macula can ensure the sensitivity to more high-frequency acoustic signals and facilitate their perception by fish against the background of low-frequency noises characteristic of the coastal zone of the lake.     

Three species of <Emphasis Type="Italic">Heteromazocraes</Emphasis> Mamaev, 1981 (Monogenea: Mazocraeidae), including two new species from <Emphasis Type="Italic">Thryssa</Emphasis> spp. (Teleostei: Engraulidae) off Visakhapatnam coast,Bay of Bengal

Three species of Heteromazocraes Mamaev, 1981 including two new taxa are described from the gills of three species of engraulid fishes Thryssa mystax (Bloch & Schneider), T. setirostris (Broussonet) and T. malabarica (Bloch) collected from the coastal waters off Visakhapatnam, Bay of Bengal. Heteromazocraes thryssaensis n. sp. differs from the closely related H. dodecacantha Mamaev, 1981 in the shape of the body and ovary, the number of testes and the number and shape of the genital hooks. Heteromazocraes engrauliae n. sp. differs from all the other species of the genus in the relative sizes of the haptoral clamps, in that the four closed clamps on the left side are larger than the two open clamps on the right side, in contrast to the situation in other species where the two open clamps on the anterior right side are markedly larger than the remaining clamps. Heteromazocraes kazikodiensis (Gupta & Khullar, 1967) Mamaev, 1981 regarded as a species inquirenda is redescribed with additional details and is reinstated as a valid species. A review of Heteromazocraes including a key for identification of the species is provided.     

Reproductive features of <Emphasis Type="Italic">Upeneus margarethae</Emphasis> (Mullidae), a species recorded in the coastal zone of Vietnam for the first time

The species Upeneus margarethae described recently from the western Indian Ocean is recorded in the coastal zone of Vietnam for the first time. The reproductive features of the representatives of the species from southern Central Vietnam (Nha Trang Bay), Central Vietnam (Da Nang), and North Vietnam (Ha Long Bay) are studied. Based on the analysis of maturity stages of female’s ovaries and gonadosomatic index, the fishes spawn over the entire year in Central Vietnam, but the spawning interruption is observed in North Vietnam during a winter season. In Nha Trang Bay, 50% of females reach sexual maturity at the body length (FL) 9.8 cm. Based on histological structure of ovaries and frequency distribution of oocyte diameter before the spawning, the oogenesis is continuous. Anomalous oocyte structure is registered in 20% of the females. Egg morphology is described for 3 h after activation of ovulated oocytes. A comparison of reproductive parameters in U. margarethae and U. tragula is conducted.     

Life history traits of two dwarf cichlids species in the white waters of the Amazonian floodplain

The reproductive parameters are among the most important life history aspects of fishes influenced by environmental variation. During recent years, the main life history strategies of Amazonian fish species were defined mostly by a set of reproductive parameters. In the present work, we sought to describe important life history parameters, in particular on reproductive characteristics of Apistogramma agassizii and Apistogramma bitaeniata, found in floodplain lakes of the Brazilian Amazonia. The species presented a positive sexual dimorphism, and males were significantly bigger than females. For both sexes, four developmental phase of gonad maturation were detected, and based on those it was possible to identify mature, reproductive specimens throughout the entire period of the study. From the ovaries of mature females, fecundity and spawning type were determined. Low fecundity, short spawning periods, possibly separated only by few months, and total spawning are all good indications that A. agassizii and A. bitaeniata evolved an opportunistic strategy in their life history.     

Seasonal dynamics of growth and feeding of big-headed sculpin <Emphasis Type="Italic">Batrachocottus baicalensis</Emphasis> (Cottidae) in the Cape Berezovyi area (southern Baikal)

The seasonal features of the growth and feeding of one of the mass fish species of the littoral zone of Lake Baikal, big-headed sculpin Batrachocottus baicalensis, are investigated in the study area near the Cape Berezovyi (southern Baikal). It is found that the greatest increase of the linear parameters of the individuals of all age classes occurs in autumn, in the middle of the feeding period. Twenty-nine food objects, i.e., invertebrates and fishes, have been noted in the feeding spectrum of big-headed sculpin. It is found that the amphipods comprise the basic food year round. The transition of big-headed sculpin to predominant consumption of fish food is noted in the reproduction periods of other sculpins in the shallows. In general, the seasonal changing in species composition and food object ratio in the food are due to the fish life cycles, migrations of amphipods of different species, and, to a lesser extent, changing numbers of different groups of zoobenthos.     

Two new gonad-infecting species of <Emphasis Type="Italic">Philometra</Emphasis> Costa, 1845 (Nematoda: Philometridae) from <Emphasis Type="Italic">Trachinus</Emphasis> spp. (Osteichthyes: Trachinidae) in the Gulf of Hammamet,Tunisia

Based on light and scanning electron microscopical studies, two new gonad-infecting species of Philometra Costa, 1845, P. draco n. sp. and P. radiata n. sp. (Nematoda: Philometridae), are described from the marine perciform fishes Trachinus draco (Linnaeus) and T. radiatus (Linnaeus) (both Trachinidae), respectively, in the Gulf of Hammamet, off the northeastern coast of Tunisia. Philometra draco n. sp. and P. radiata n. sp. can be separated from other gonad-infecting species of this genus by the structures associated to the gubernaculum (e.g. dorsal protuberance, smooth field separating the dorsolateral longitudinal parts), as well as by the length of the body, spicules and gubernaculum. Philometra radiata n. sp. can be distinguished from P. draco n. sp. in having the dorsal side of the gubernaculum distal end provided with a median longitudinal smooth field demarcated by two dorsolateral lamellate parts. These two new species are the first philometrid species described from fishes of the family Trachinidae.     

On the diversity of fishes in mountain lakes of the Amur basin

Results of the study of 11 lakes situated in the mountainous part of the Amur River basin are reported. Six fish species, namely, blunt-snouted lenok Brachymystax tumensis, Baikal-Lena grayling Thymallus baicalolenensis, Siberian stone loach Barbatula toni, Lagowski’s minnow Rhynchocypris lagowskii, Czekanowski’s minnow Rh. czekanowskii, and Amur sculpin Cottus szanaga, were found in five lakes. Four species were found in one lake (Lake Pereval’noe, basin of the Amgun’ River), and two species were found in each of the remaining lakes. Lenok and Amur sculpin were the most common species. The fauna of Lake Okonon (basin of the river Zeya) was the most specific and did not have analogs among the lake faunas; Czekanowski’s minnow and Baikal black grayling were found in this lake. The lenok ecotype that formed in the mountain lakes differed from the river lenok in some regards. The potential pathways of formation and protection of mountain lake ichthyocenoses of the Amur basin are discussed.     

Contribution to the study of acoustic communication in two Belgian river bullheads (<Emphasis Type="Italic">Cottus rhenanus and C. perifretum</Emphasis>) with further insight into the sound-producing mechanism

Background

The freshwater sculpins (genus Cottus) are small, bottom-living fishes widely distributed in North America and Europe. The taxonomy of European species has remained unresolved for a long time due to the overlap of morphological characters. Sound production has already been documented in some cottid representatives, with sounds being involved in courtship and agonistic interactions. Although the movements associated with sound production have been observed, the underlying mechanism remains incomplete. Here, we focus on two closely related species from Belgium: C. rhenanus and C. perifretum. This study aims 1) to record and to compare acoustic communication in both species, 2) to give further insight into the sound-producing mechanism and 3) to look for new morphological traits allowing species differentiation.

Results

Both Cottus species produce multiple-pulsed agonistic sounds using a similar acoustic pattern: the first interpulse duration is always longer, making the first pulse unit distinct from the others. Recording sound production and hearing abilities showed a clear relationship between the sound spectra and auditory thresholds in both species: the peak frequencies of calls are around 150 Hz, which corresponds to their best hearing sensitivity. However, it appears that these fishes could not hear acoustic signals produced by conspecifics in their noisy habitat considering their hearing threshold expressed as sound pressure (~ 125 dB re 1 μPa). High-speed video recordings highlighted that each sound is produced during a complete back and forth movement of the pectoral girdle.

Conclusions

Both Cottus species use an acoustic pattern that remained conserved during species diversification. Surprisingly, calls do not seem to have a communicative function. On the other hand, fish could detect substrate vibrations resulting from movements carried out during sound production. Similarities in temporal and spectral characteristics also suggest that both species share a common sound-producing mechanism, likely based on pectoral girdle vibrations. From a morphological point of view, only the shape of the spinelike scales covering the body allows species differentiation.

     

Impact of the Alien Species <Emphasis Type="Italic">Mnemiopsis leidyi</Emphasis> A. Agassiz, 1865 on Fish of the Caspian Sea

The data of long-term ecological studies (1999–2014) are used for assessing the impact of a new Caspian invader Mnemiopsis leidyi A. Agassiz, 1865 on marine and anadromous fish species. The introduction of the ctenophore and its massive development in the Caspian Sea have mainly affected planktophagous fish, especially the most abundant species anchovy sprat (Clupeonella engrauliformis Borodin, 1904) and sturgeons (Family Acipenseridae). Mnemiopsis leidyi is one of the main negative factors preventing the restoration of the populations of Caspian fishes, especially anchovy tyulka. The critical state of the resources of the spawning parts of sturgeon populations (Family Acipenseridae) has been reinforced as a result of the massive development of M. leidyi.     

Reproduction and development in some species of the weakly electric genus <Emphasis Type="Italic">Campylomormyrus</Emphasis> (Mormyridae,Teleostei)

Reproduction in captivity of four species of the mormyrid genus Campylomormyrus was investigated. Cyclical reproduction was provoked by changing water conductivity (C) alone: decreasing C led to gonadal recrudescence, an increase induced gonad regression. Data on the reproduction and development of three species are presented. All three species are indeterminate fractional spawners. Spawning intervals ranged from 6 to 66 days in C. rhynchophorus, 10–75 days in C. tshokwe, and 18 days in C. compressirostris (calculated values). Fecundities (eggs per fractional spawning) ranged from 70 to 1570 eggs in C. rhynchophorus, 100–1192 in C. tshokwe, and 38–246 in C. compressirostris. Spawnings/ovipositions occurred during the second half of the night; no parental care was observed; no special spawning substrates were necessary. C. compressirostris successfully spawned in breeding groups, C. rhynchophorus as pair. Agonistic behavior in the C. tshokwe pair forced us to divide the breeding tank; therefore, only ovipositions occurred. However, injection of an artificial GnRH hormone allowed us to obtain ripe eggs and sperm and to perform successful artificial reproduction. All three species produce yolky, slightly sticky eggs. Egg diameter ranges from 2.3–3.0 mm. Hatching occurred on day 3, feeding started on day 11. Transition from larval to juvenile stage occurred at around 20 mm total length (TL). At this size C. rhynchophorus developed a higher body than the two other species and differences between the species in the melanin pigmentation of the unpaired fins occurred. Between 32 and 35 mm TL the upper and lower jaws started to elongate.