On the Morphology of Arrowhead Flounders of the Genus Atheresthes in the Pacific Waters of the Northern Kuril Islands and Southeastern Kamchatka

This paper presents the results of studies on the morphology of arrowhead flounders, the Kamchatka flounder Atheresthes evermanni (35 specimens), and the American arrowtooth flounder A. stomias (37 specimens) collected in Pacific waters of the northern Kuril Islands and southeastern Kamchatka in 1998–1999. The morphology of the discussed species is compared with that of arrowtooth flounders from other areas. From this comparison, available information on the sharp increase in the density of the American arrowtooth flounder in the surveyed area (since 1997), and similarities in size compositions of the fish in Kuril and Aleutian waters, a conclusion has been made about the penetration of this species from Aleutian Pacific waters into the area of the northern Kuril Islands and southeastern Kamchatka. This is a result of expansion of the geographical range of this species due to general water warming in the northwestern Pacific during the second half of the 1990s.     

Distribution and Ecology of Yellowfin Sole Limanda aspera and Sakhalin Sole L. sakhalinensis (Pleuronectidae) in the Pacific Waters of Kamchatka in Summer 2016–2020

Journal of Ichthyology - Based on materials for 2016–2020, it has been revealed that yellowfin sole Limanda aspera and Sakhalin sole L. sakhalinensis form the main aggregations in the Avacha...     

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.     

Specific features of distribution and some features of biology of Korean flounder <Emphasis Type="Italic">Glyptocephalus stelleri</Emphasis> (Pleuronectidae) in waters off Kamchatka in the Sea of Okhotsk

According to materials of 1997–2002, the characteristic of the spatial-bathymetric distribution, size and age composition, size and sex structure, and feeding of the Korean flounder Glyptocephalus stelleri in the summer period in waters off Kamchatka in the Sea of Okhotsk (the site from 51°15′ to 57°20′ N, depths of 10–300 m) is given. It is shown that throughout the observation period, maximum catches of this flatfish were constantly observed at two sites of the western Kamchatka shelf (51°20′–53°00′ N and 55°00′–56°00′ N) in the zone exposed to the effect of anticyclonic gyres in the range of depths 101–200 m at the near-bottom temperature below 2°C. Unlike other habitat areas, off the coast of western Kamchatka, G. stelleri in the summer time is quite frequently found at negative temperature values, which is obviously determined by the specifics of thermal conditions of the eastern part of the Sea of Okhotsk. It was established that, in this species of flatfish, sex dimorphism is distinctly pronounced in sizes—males are considerably smaller than females whose relative number among individuals with a length larger than 50 cm reaches 100%. The main items of feeding of G. stelleri at the western Kamchatka shelf in the summer period are oligochaetes.     

Prey selection by flounder, Platichthys flesus, in the Douro estuary, Portugal

Prey selection by the flounder, Platichthys flesus (Linnaeus, 1758), in an estuarine nursery was investigated and the major factors influencing food choice by this species were assessed. Diet breadth was narrow, reflecting the low prey diversity observed in the benthos. A gradual ontogenetic shift from small prey such as amphipods to larger prey like polychaetes and bivalves was observed. Amphipods had positive electivity values in the upper estuary and negative values in the lower estuary.Polychaetes showed the inverse pattern. Bivalve electivity values were always positive. Differential selectivity throughout the estuary was mainly related to spatial segregation of flounders according to size, with the smaller individuals concentrating in the upper estuary and larger individuals concentrating in the lower estuary. Amphipods such as Corophium spp. play a crucial role in the flounder diet because of their small size, low mobility and diel activity pattern. As prey, the polychaete value increases throughout flounder ontogeny since the flounder size range is compatible with the larger mouth gapes and detection ability of larger fish. Bivalve electivity values for flounder are mainly related to high calorific values. The absence of Crangon crangon (Linnaeus, 1758) in the diet may be due to low water temperature since the cost–benefit involved in the capture of highly mobile prey is too high at low temperatures. It was concluded that flounder must use several sensory features to detect and capture prey in turbid estuarine waters and that field studies provide important background information on the actual predator preferences under natural conditions.     

Alternative community compositional and dynamical states: the dual consequences of assembly history

1. Much work on ecological consequences of community assembly history has focused on the formation of history-induced alternative stable equilibria. We hypothesize that assembly history may affect not only community composition but also population dynamics, with assembled communities differing in species composition potentially residing in different dynamical states. 2. We provided an empirical test of the aforementioned hypothesis using a laboratory microcosm experiment that manipulated both the colonization order of three bacterivorous protist species in the presence of a protist predator and environmental productivity. 3. Both priority effects and random divergence emerged, resulting in two different community compositional states: one characterized by the dominance of one prey species and the other by the extinction of the same prey. While communities in the former state exhibited noncyclic dynamics, the majority of communities in the latter state exhibited cyclic dynamics driven by the interaction between another prey and the predator. 4. Temporal variability of total prey community biovolume consequently differed among communities with different histories. 5. Changing productivity altered priority effects on the structure and dynamics of communities experiencing only certain histories. 6. Our results support the dual (compositional and dynamical) consequences of assembly history and emphasize the importance of incorporating the dynamical view into the field of community assembly.     

Coupled predator–prey oscillations in a chaotic food web

Coupling of several predator–prey oscillations can generate intriguing patterns of synchronization and chaos. Theory predicts that prey species will fluctuate in phase if predator–prey cycles are coupled through generalist predators, whereas they will fluctuate in anti-phase if predator–prey cycles are coupled through competition between prey species. Here, we investigate predator–prey oscillations in a long-term experiment with a marine plankton community. Wavelet analysis of the species fluctuations reveals two predator–prey cycles that fluctuate largely in anti-phase. The phase angles point at strong competition between the phytoplankton species, but relatively little prey overlap among the zooplankton species. This food web architecture is consistent with the size structure of the plankton community, and generates highly dynamic food webs. Continued alternations in species dominance enable coexistence of the prey species through a non-equilibrium 'killing-the-winner' mechanism, as the system shifts back and forth between the two predator–prey cycles in a chaotic fashion.     

Role of feeding and prey distribution of summer and southern flounder in selection of estuarine nursery habitats

Diets of metamorphosing larvae and early juvenile summer and southern flounder were examined during the settlement period when their distributions overlapped and during a subsequent period when the two flounders were found in different habitats. Prey abundance on tidal flats was examined along an upstream transect. Though initially similar, diets of the two species diverged prior to the development of a segregated distribution. These diet differences reflected those found in the diets of the two species following segregation. Southern flounder ate more active epifaunal prey: mysids, amphipods and calanoid copepods and appeared to be an ambush predator. The summer flounder ate primarily infauna: polychaetes, and invertebrate parts and appeared to be an active forager. Distribution of prey within the study area suggested that mysid gradients may influence movement of southern flounder to nursery grounds. The coupling of biotic and abiotic gradients are probably important in creating nursery areas and guiding fishes to species specific habitat types.     

Geographical and temporal mitochondrial DNA variability in populations of pink salmon

Pink salmon Oncorhynchus gorbuscha from odd and even year generations in rivers of Sakhalin Island, Kuril Island, Kamchatka Peninsula, and Alaska were investigated with five informative restriction endonucleases for mtDNA variation. The odd and even generations from the same rivers of South Sakhalin differed greatly. The time of divergence between the two broodlines was estimated at 0.9-1.1 Myr. The variability of mtDNA in odd year generations was higher than in even year generations and may have been due to' founder' and/or' bottleneck' effects. The differences among river populations within the Sakhalin region in 1991-1993 were not significant and this confirms the highly migratory nature of pink compared with other Pacific salmon. The mtDNA samples revealed statistically significant differences between regions. The northern populations (Kamchatka, Alaska) were less diverse in number and frequency of haplotypes than the southern populations (Sakhalin). This suggests that pink salmon originated in the Sakhalin-Kuril region and that a founder effect during the spread of this species may have restricted the mtDNA variability in other regions.     

FORAGING OF JUVENILE MONK SEALS AT FRENCH FRIGATE SHOALS, HAWAII

Emaciation and poor survivorship of juvenile Hawaiian monk seals at French Frigate Shoals atoll prompted a study of their foraging, using video camera technology ( crittercam ). Nine juveniles between the ages of 1 and 3 yr (six males, three females) were fitted with crittercam to identify their foraging habitat and feeding behavior. All feeding was directed at small (≤ 10 cm), cryptic, benthic prey. Older seals (ages 2 and 3), varied in their foraging intensity with most of their attention directed at shallow atoll depths (10–30 m). In contrast, the three yearlings focused all their feeding in the sand fields (50–100 m) on the atoll's outer slope. Bottom trawls were used to assess the prey abundance of the sand habitat and found 70% of the numerical catch was flounder ( Bothidae ). Extrapolating the yearlings' prey capture rate (0.13/min, derived from the crittercam video) over their total bottom time yielded an estimated 1–1.3 kg/day of flounder. The mean size of flounder (5 ± 1.7 cm) caught in the bottom trawls was close to the size at which larval flounder settle from the plankton (3 cm), suggesting that localized changes in oceanography could directly impact the seals' prey supply. Extensive use of sand communities by young seals may be the strongest link yet identified between juvenile survivorship and oceanographic dynamics.     

Female maturity,reproductive potential,relative distribution,and growth compared between arrowtooth flounder (Atheresthes stomias) and Kamchatka flounder (A. evermanni) indicating concerns for management

Arrowtooth flounder (Atheresthes stomias) and Kamchatka flounder (A. evermanni), major piscivorous predators in the eastern Bering Sea and Aleutian Islands, are morphologically similar. Consequently the two species have been managed together as a species complex using the length‐ and age‐at‐maturity derived from Gulf of Alaska arrowtooth flounder, which had been the only available maturity estimates. However, there could be serious management consequences if the two species matured at significantly different ages and fork lengths. Therefore, this study was conducted during 2007 and 2008 to determine if there were significant differences in maturation between the two species. Significant differences in size and age of female maturation and growth were found. The age and length of 50% maturity (A_50,L_50, respectively) for arrowtooth flounder females is 7.6 years of age and 480 mm in body length. In comparison, A_50,L₅₀ of Kamchatka flounder females is 10.1 years of age and 550 mm, meaning that Kamchatka flounder has a significantly lower reproductive potential than arrowtooth flounder. The large difference in reproductive potential indicates that managing the two species together as a species complex using the reproductive characteristics of arrowtooth flounder, was not conservative for Kamchatka flounder. This study also determined that arrowtooth flounder maturation was consistent between the Gulf of Alaska and eastern Bering Sea populations.     

The current state of populations of the common tern Sterna hirundo (Linnaeus, 1758) and the Kamchatka tern S. camtschatica (Pallas, 1811) in northern Sakhalin

This paper presents data on the numbers of nesting common and Kamchatka tern populations on the northeastern coast of Sakhalin Island over a more than 20-year period. Distribution maps of the main tern colonies (Chaika, Lyarvo, and Wrangel islands, and an unnamed island situated in Chaivo Bay) are given. Taking into account the current data concerning southern Sakhalin colonies, the total number of terns in Sakhalin Island is about 9000 pairs for the Kamchatka tern and up to 16000 pairs for the common tern. The main biotic and abiotic factors that determine the population dynamics and distribution of nesting terns in northern Sakhalin Island are enumerated.     

Mitochondrial DNA variation pattern in larches of Eastern Siberia and the Far East

Genetic variation has been studied in 32 Eastern Siberian and Far Eastern populations of Larix Mill. with the use of three mitochondrial markers based on polymerase chain reaction. Eight multilocus haplotypes with a heterogeneous spatial distribution (G(ST) = 0.788, N(ST) = 0.829) have been found, which indicates limited gene flows between populations. Several geographic regions with specific larch haplotype sets have been determined: (1) Japan, (2) southern Sakhalin and the Kuril Islands, (3) Primor'e and Korea, (4) Kamchatka, and (5) Eastern Siberia and the northern Far East. The haplotype fixed in the Kamchatka is absent in the Magadan oblast or Chukotka but is present in southern Primor'e and Sakhalin Island. This may be explained by either the postglacial recolonization of Kamchatka by larch that spread from Primor'e through Sakhalin and the Kuril Islands or its survival through the last glacial maximum in the Kamchatka Peninsula. The biogeography of larch and other woody plants indicate that boreal species have a common history of the colonization of Kamchatka.     

A genetic analysis of the beluga whale Delphinapterus leucas (Cetacea: Monodontidae) from summer aggregations in the Russian Far East

The genetic structure of four summer aggregations of the Beluga Whale, Delphinapterus leucas, in Sakhalin Bay and Udskaya Bay, off the western coast of Kamchatka in the Sea of Okhotsk and in the Anadyr Estuary of the Bering Sea was analyzed through nucleotide sequencing of the mtDNA control region and detection of the allelic composition of nine microsatellite loci in nuclear DNA. It has been shown that each of the aggregations features a unique set of maternal lines, which indicates a high degree of philopatry in this species. Beluga whales of the Anadyr Estuary are genetically isolated from those of the Sea of Okhotsk. Beluga whales of the summer aggregations of Sakhalin Bay and those from Udskaya Bay share a common gene pool and belong to a single population, while the whales that summer off western Kamchatka with great consistency may be attributed to a different population. Comparison of nucleotide sequences of the mtDNA in beluga whales from various waters of the Russian Far East and North America allowed us to propose a hypothesis about how the structure of beluga whale populations formed in the North Pacific during the postglacial period.     

The peculiarities of foraging migrations of the Korean-Okhotsk gray whale (<Emphasis Type="Italic">Eschrichtius robustus</Emphasis>) population in russian waters of the Far Eastern seas

Photographic identification of the Korean-Okhotsk gray whale Eschrichtius robustus population has been conducted since 2002 by researchers of the Institute of Marine Biology at the Far East Branch of the Russian Academy of Sciences (IMB FEB RAS), with financial support provided by Exon Neftegas, Ltd. and Sakhalin Energy Investment Co., in order to study the migration features and biology of this species. In 2008, photo-ID studies were carried out in two areas, off the northeastern coast of Sakhalin Island and off the southeastern coast of Kamchatka. As a result of the studies, 122 whales known from the Sakhalin gray whale catalogue were photographed. Of them, 97 individuals were registered off Sakhalin, 24, off Kamchatka, and one whale was observed at both sites. In addition, 25 more gray whales that had not been sighted off Sakhalin Island before were found off the coast of Kamchatka. Based on these photographic materials, the whales physical and skin conditions were also analyzed. Cases of sightings of gray whales in areas that are remote from their traditional summer and fall feeding grounds in the Far Eastern seas of Russia are discussed.     

On the phytosociology and ecology of Isoëtes asiatica (Makino) Makino in oligotrophic water bodies of South Sakhalin

In 1989, in the southeast of the Sakhalin Island and south of the village Okhotskoye, Isoëtes asiatica (Makino) Makino and I. beringensis Kom. were detected in 24 oligotrophic lakes for the first time on Sakhalin. These are stands of the community of Isoëtetum asiaticae ass. nov. which in the majority of the lakes form a characteristic pioneer vegetation of the shallow littoral zones. In addition to poor-species dominance stands of both of the Isoëtes species, penetration stages of both of these species as well as stages rich in Comarum palustre, Eleocharis acicularis and Potamogeton species can be differentiated. Besides the structure of the species, the site conditions, particularly of the water bodies are described. The ion content is represented by absolute and relative ion field diagrams exemplified by 7 selected water bodies. The ion content is characterized by sodium and chloride which are prevailing, while calcium and magnesium as well as hydrogen carbonate and sulphate exist in low quantitative proportions only. The indicator values of individual characteristics and the complex characteristics of the Isoëtes lakes are discussed. The hydrochemical characteristics of the Sakhalin, Kuriles and Kamchatka Isoëtes waters are compared with the Isoëtes water bodies of North America and Europe. The danger to Isoëtes water bodies is discussed, necessary protective measures are defined.     

Size and age composition of populations and growth of Mytilus trossulus (Bivalvia: Mytilidae) in the subtidal area of western Kamchatka

Fairly large Mytilus trossulus beds were found in the subtidal zone at depths to 40 m off the western coast of Kamchatka. The size and age composition of local populations and growth rates of M. trossulus in this region and at Atlasova Island were studied. Significant variability of the shell shape of mollusks was found. In the western Kamchatka subtidal, M. trossulus grew faster than in the northern Kuril Islands and eastern Kamchatka. Mussels attained commercial size (50 mm in shell length) in the fourth year of life in the former case and in the fifth-sixth year in other cases. Mollusks of different ages, from 1 to 8–9 year olds, were present in western Kamchatka populations; i.e., juvenile recruitment takes place regularly, while growth rates vary. Growth and population structure of M. trossulus are discussed in relation to the habitat conditions on the western Kamchatka shelf.     

Size-related shifts in the habitat associations of young-of-the-year winter flounder (Pseudopleuronectes americanus): field observations and laboratory experiments with sediments and prey

Field surveys and laboratory studies were used to determine the role of substrata in habitat selection by young-of-the year winter flounder. A synoptic field survey of winter flounder and sediments in the Navesink River-Sandy Hook Bay estuarine system in New Jersey demonstrated that winter flounder distribution was related to sediment grain size. Analysis using a generalized additive model indicated that the probability of capturing 10-49 mm SL winter flounder was high on sediments with a mean grain diameter of /=40 mm SL) preferred coarse-grained sediments. Burying ability increased with size and all flounders avoided sediments that prevented burial. Subsequent laboratory experiments revealed that the presence of live prey (Mya arenaria) can over-ride sediment choice by winter flounder (50-68 mm SL) indicating the complexity of interrelated factors in habitat choice.     

The parasite community infecting flounders, Platichthys flesus, in the tidal Thames.

The composition of the parasite fauna of the flounder, Platichthys flesus, retrieved from two locations in the tidal Thames is described in detail for the first time. The combined parasite species list of the flounders from Lots Road in the upper tideway and West Thurrock in the middle tideway consisted of one protozoan (Glugea stephani), one monogenean (Gyrodactylus sp.), four larval digeneans (Cryptocotyle concava, Timoniella imbutiforme, T. praeterita, and Labratrema minimus), five adult digeneans (Derogenes varicus, Lecithaster gibbosus, Podocotyle sp., Plagioporus varius, and Zoogonoides viviparus), one larval cestode (unidentified tetraphyllidean), one or possibly more larval nematodes (unidentified) plus five adult nematodes (Capillaria sp., Cucullanus heterochrous, C. minutus, Contracaecum sp. and Goezia sp.), two acanthocephalans (Pomphorhynchus laevis and Acanthocephalus anguillae), three copepods (Lepeophtheirus pectoralis, Acanthochondria sp. and Lernaeocera branchialis), and one mollusc (unidentified glochidia). The overall parasite community of flounders from Lots Road and West Thurrock were compared in terms of species richness and diversity. The parasite community in flounders from the former location in the upper tideway was found to be less diverse than that of its counterpart at West Thurrock in the middle estuary. The component community of Lots Road flounders was dominated by the acanthocephalan Pomphorhynchus laevis.