Sexual dimorphism and some special traits of spawning behavior of the Arctic Lamprey <Emphasis Type="Italic">Lethenteron camtschaticum</Emphasis>

The sexual dimorphism and the role of secondary sexual characters in the spawning period of the Arctic Lamprey Lethenteron camtschaticum from the Utkholok basin (Kamchatka) are studied for the first time. The importance of the urogenital papilla in males and of the keel in females during egg fertilization and in construction of the redd is shown. By visual observations, underwater and above water videography, two forms of spawning behavior are revealed: group behavior in the current and paired behavior in the inshore part of the river, where the current is slower. The typically anadromous form, the anadromous forma praecox, and river lamprey reproduce together. The strategy of the spawning behavior is directed first of all towards better fertilization of eggs and finally towards reproductive success of the species.     

Life cycle and structure of populations of three-spined stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> (Fam. Gasterosteidae) in rivers of northwestern Kamchatka (with reference to the Utkholok River)

From the end of May to mid-August 2005 and 2006, the dynamics of migrations and spawning, as well as specific features of development, growth, and feeding migration of the three-spined stickleback Gasterosteus aculeatus in the salmon river Utkholok of the mountain-tundra type were studied. Morphological characteristics, age, fecundity, dates of reproduction and spawning biotopes, structure of spawning groups, and specific features of feeding were investigated. On the basis of the obtained data, it was concluded that the riverine and migratory forms of three-spined sticklebacks from the Utkholok River belong to a single population. Biological specific features of spawners with high (2005) and low (2006) numbers of the migratory form were compared. For comparison, we also used our own data on the morphology and biological analysis of the migratory three-spined stickleback from the Kol River salmon of the mountain type.     

Population structure of the masu salmon <Emphasis Type="Italic">Oncorhynchus masou</Emphasis> from the Kol River (Western Kamchatka) and geographic variation in the species area

According to materials from original investigations in Kamchatka as well as published data, the population structure and geographical variation of the masu salmon Oncorhynchus masou are considered in the species area. The intraspecies structure, dates of their run to rivers, dates of spawning, traits of spawning, size-age and sex composition, fecundity, biological traits of parr, downstream migration of smolts are investigated. The relationship is shown between the manifestations of geographical variation of masu salmon and the factor of temperature. It is assumed that the global warming of climate would contribute to the advancement of this species to northern areas and to the increase in its abundance.     

Spawning of walleye pollock (<Emphasis Type="Italic">Theragra chalcogramma</Emphasis>) off the Southwestern coast of Kamchatka

The results of ichthyoplankton surveys conducted in 2007–2008 showed that waters off Southwest Kamchatka and North Kuril Islands were areas of mass spawning of walleye pollock. The peak spawning occurred during the last 10 days of April and in early May, which was much later than the peak at the main spawning site off West Kamchatka. The spawning activity of walleye pollock near the southwestern shores of Kamchatka is a regular event, as the analysis of archive materials shows. This gave us grounds to suspect the existence of a southern site that coincided well with the mass spawning in the Shelikhov Gulf in its timing and scale, but was missed during standard ichthyoplankton surveys conducted in early April. After analyzing the growth rates of spawners, the assumption was made that the southern spawning was performed by the East Kamchatkan walleye pollock population, whose mass spawning usually occurs in late April-early May. According to the data of 2008, the estimated biomass of walleye pollock spawning in the area of the Ozernovskaya basin in late April was nearly 600000 tons. Regular monitoring of the southern spawning is proposed by means of additional ichthyoplankton surveys south of 53° N, including the Okhotsk Sea waters of the North Kuril Islands, in late April—early May.     

Key Factors Determining the Distribution of Beluga Whales, <Emphasis Type="Italic">Delphinapterus leucas</Emphasis> (Pallas, 1776), in River Estuaries of Western Kamchatka

The results of observations on the distribution of beluga whales, Delphinapterus leucas (Pallas, 1776), in three large rivers of western Kamchatka in the summer and autumn seasons are discussed. In the summer, the number of beluga whales in the Khairyuzova, Belogolovaya, and Moroshechnaya rivers reaches 111–250 individuals. Most of the belugas enter the rivers during the flood tidal phase: the number of animals in the estuaries increases along with the rising water level to the maximum value at spring tide. The belugas do not move upstream out of the estuaries and tend to remain in the zone of mixing riverine and marine waters, where 20 species of fish and three species of invertebrates have been identified. At ebb tide, the belugas leave for the sea; however, during a large run of salmon some individuals remain in the estuaries and continue hunting in deep-water areas. The main issue that causes beluga whales to form summer aggregations in Kamchatkan rivers is the hunt for salmon. The distribution of beluga whales in river estuaries is defined by the dynamics and intensity of salmon spawning runs. The preference of beluga whales for these rivers can be explained by the channel type of their estuaries.     

Diel movements of out-migrating Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) smolts in the Sacramento/San Joaquin watershed

We used ultrasonic telemetry to describe the movement patterns of late-fall run Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) smolts during their entire emigration down California’s Sacramento River, through the San Francisco Bay Estuary and into the Pacific Ocean. Yearling hatchery smolts were tagged via intracoelomic surgical implantation with coded ultrasonic tags. They were then released at four upriver locations in the Sacramento River during the winters of 2007 through 2010. Late-fall run Chinook salmon smolts exhibited a nocturnal pattern of migration after release in the upper river. This is likely because individuals remain within a confined area during the day, while they become active at night and migrate downstream. The ratio between night and day detections of Chinook salmon smolts decreased with distance traveled downriver. There was a significant preference for nocturnal migration in every reach of the river except the Estuary. In contrast, steelhead smolts, which reside upriver longer following release, exhibited a less pronounced diel pattern during their entire migration. In the middle river, Delta, and Estuary, steelhead exhibited a significant preference for daytime travel. In the ocean Chinook salmon preferred to travel at night, yet steelhead were detected on the monitors equally during the night and day. These data show that closely related Oncorhynchus species, with the same ontogenetic pattern of out-migrating as yearlings, vary in migration tactic.     

Morphological and biological specific features of two species of nine-spined sticklebacks of the genus Pungitius (Gasterosteiformes) from water bodies of Western Kamchatka

Morphological and biological specific features of populations of stickleback Pungitius pungitius and Amur (Chinese) stickleback P. sinensis from salmon rivers of the western coast of Kamchatka have been studied. With reference to the mountain-tundra Utkholok River, conditions of habitation and reproduction of nine-spined sticklebacks are described. P. pungitius is capable of reproducing at a relatively low temperature (from 4–6°C) and is represented by a large amount of spatially isolated groups with low numbers of individuals. For more warm-water P. sinensis, fluctuations in numbers at tundra sites of the lower reaches of rivers depending on temperature and water content of potential spawning grounds during the season of reproduction are typical. At the sympatry of the two species (Utkholok, Snatolvayam, Kvachina, Kol rivers), a high (up to 6%) proportion of hybrids was revealed. A geographic variability of meristic characters of Western Kamchatka and Kuril populations was traced.     

Variations of life history strategy of the arctic lamprey <Emphasis Type="Italic">Lethenteron camtschaticum</Emphasis> from the Utkholok River (Western Kamchatka)

Morphobiological traits of the lamprey from the Utkholok River (Western Kamchatka) are investigated for the first time. All present forms of lamprey (typically anadromous, anadromous early maturing forma praecox, resident) do not differ by diagnostic characters and belong to one species Lethenteron camtschaticum. Males prevail among mature specimens of various forms, smolts, and ammocoetes at later developmental stages. The forma praecox is represented by males by 92%. A hypothesis is suggested explaining the relationships of the forms and the mechanism of realization of different types of life history strategy in relation to energy resources of water bodies and the kind of feeding of different groups of ammocoetes (organic detritus or Pacific salmon carcasses decomposed after spawning).     

Interactions between endangered wild and hatchery salmonids: can the pitfalls of artificial propagation be avoided in small coastal streams?

Hatchery and wild juvenile populations of steelhead Oncorhynchus mykiss and coho salmon Oncorhynchus kisutch , in a small coastal watershed in central California, were sampled throughout the year in a stream and at a hatchery. Both species grew faster in captivity than in the wild. Hatchery fish of both species had elevated gill Na⁺, K⁺‐ATPase activity, and thus were ready to enter sea water when planted during the wild fish migration. Downstream migrant trapping and stream surveys indicated that hatchery smolts went to sea soon after planting, consequently avoiding the effects of competition and predation that commonly occur when hatchery‐bred juveniles are released. Adult steelhead were also sampled throughout the watershed. The return of hatchery steelhead was highly synchronized with that of wild steelhead, indicating that hatchery propagation had no adverse effects on the timing of the run. A disproportionate number of hatchery steelhead returned to the tributary where the hatchery was located, despite being planted throughout the watershed. Hatchery steelhead did not differ in mean age or size from wild steelhead. Observations of spawning indicated that hatchery and wild steelhead interbreed. Competition for mates or spawning substratum was rarely observed between hatchery and wild steelhead. Many of the problems commonly associated with artificial propagation can be avoided in small coastal watersheds when wild broodstock are used and fish are released as smolts.     

Characteristics of the spawning stock of chinook salmon <Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis> from the Apuka River (northeastern Kamchatka)

Biological features of chinook salmon Oncorhynchus tshawytscha from the Apuka River, the largest river of the northeastern Kamchatka inflowing Olyutorskii Bay of the Bering Sea, are studied. Chinook salmon from the Apuka River spend mainly a year in the river before downstream migration to the sea. The fish live in the sea for 1–4 years. The spawning migration of chinook salmon into the Apuka River begins in late May just after ice melting, and it continues until early August. The main part of the spawners enters the river during June. A hypothesis on the occurrence of two seasonal races in the Apuka River is proposed.     

Population consequences of mass coming of pink salmon Oncorhynchus gorbuscha to the Northeastern Coast of Kamchatka in 2009

During mass spawning of pink salmon Oncorhynchus gorbuscha in two rivers of central Karaginskii Bay (Kamchatka), the average coverage of the spawning hillock did not vary much (0.6?C0.7 m²) even though the abundance of the spawning adults varied greatly. When the abundance of spawning females was less than 1.4 ind. per m² of spawning ground, the spawning hillocks did not interlock. When the abundance of spawning females varied from 1.7 to 1.8 ind./m², the spawning hillocks interlocked, and approximately 20?C25% of them were re-excavated. When the abundance of spawning females was higher than 2.0 ind./m², all the early-deposited spawning hillocks were re-excavated. The re-excavation of the spawning hillocks increased the population mortality also by the mass pre-spawning death of the breeders and spawning outside the spawning grounds. Meanwhile, fish-kill of the eggs in the spawning hillocks was not observed, and the mortality of embryos and larvae did not depend on the spawning intensity. The ratio of live and dead embryos in the spawning hillocks before their hatching was approximately 60%, varying from 44 up to 92% in regard to the environment of the spawning ground (autumn low water, freezing, and siltation). Significant correlation was found between the survivability and grain-size composition of the spawning hillocks when the impact of small-size fraction was a limiting factor.     

Reproduction of mykiss <Emphasis Type="Italic">Parasalmo mykiss</Emphasis> in the Kol river (Western Kamchatka) and its controlling factors

For the first time, special traits of the reproduction of mykiss Parasalmo mykiss in Kamchatka are studied: dates of spawning, localization, topography and hydrology of spawning grounds, structure and fractional composition of ground of redds, duration of incubation and larval period, and thermal conditions. Possibilities of reproduction of mykiss are constrained by a narrow range of variation of spawning conditions. Spawning occurs only in tundra rivers and tributaries. The principal factor limiting reproduction of mykiss is temperature, namely a rapid warming of water in May and attaining of a necessary sum of degree-days (over 500, from the middle of May until the middle of July) during spawning and the period of incubation. Presence of water bodies of the tundra type with their special thermal conditions predetermine a possibility of reproduction of mykiss in Kamchatka and its present-day comparatively narrow area in Asia.     

Downstream migration in ammocoetes of the Arctic lamprey <Emphasis Type="Italic">Lethenteron camtschaticum</Emphasis> in some Kamchatka rivers

This paper considers the major patterns of downstream migration in Arctic lamprey ammocoetes in Kamchatka rivers. Ammocoetes of different age groups are shown to be constantly noted in the composition of the migrant part of a river community. The greatest intensity of downstream migration in ammocoetes of the age class 0+ is noted in the period of their primary dispersion in late July-early August. The ammocoetes of the age groups 1+ and older migrate from spring to late autumn, but their concentrations are not high. The significant similarity of such a biologic feature as downstream migration in ammocoetes and juvenile salmonids serves as an example of ecological analogy.     

Considering sampling bias in close‐kin mark–recapture abundance estimates of Atlantic salmon

Genetic methods for the estimation of population size can be powerful alternatives to conventional methods. Close‐kin mark–recapture (CKMR) is based on the principles of conventional mark–recapture, but instead of being physically marked, individuals are marked through their close kin. The aim of this study was to evaluate the potential of CKMR for the estimation of spawner abundance in Atlantic salmon and how age, sex, spatial, and temporal sampling bias may affect CKMR estimates. Spawner abundance in a wild population was estimated from genetic samples of adults returning in 2018 and of their potential offspring collected in 2019. Adult samples were obtained in two ways. First, adults were sampled and released alive in the breeding habitat during spawning surveys. Second, genetic samples were collected from out‐migrating smolts PIT‐tagged in 2017 and registered when returning as adults in 2018. CKMR estimates based on adult samples collected during spawning surveys were somewhat higher than conventional counts. Uncertainty was small (CV < 0.15), due to the detection of a high number of parent–offspring pairs. Sampling of adults was age‐ and size‐biased and correction for those biases resulted in moderate changes in the CKMR estimate. Juvenile dispersal was limited, but spatially balanced sampling of adults rendered CKMR estimates robust to spatially biased sampling of juveniles. CKMR estimates based on returning PIT‐tagged adults were approximately twice as high as estimates based on samples collected during spawning surveys. We suggest that estimates based on PIT‐tagged fish reflect the total abundance of adults entering the river, while estimates based on samples collected during spawning surveys reflect the abundance of adults present in the breeding habitat at the time of spawning. Our study showed that CKMR can be used to estimate spawner abundance in Atlantic salmon, with a moderate sampling effort, but a carefully designed sampling regime is required.     

Structure of spawning school of chum salmon Oncorhynchus keta from Olutorsky Bay of the Bering Sea (Northeastern Kamchatka)

Results of studies of spawning chum salmon Oncorhynchus keta (Walbaum) in Olutorsky Bay and the Apuka River—the largest river in northeast Kamchatka—inflowing Olutorsky Bay of the Bering Sea are presented. It was established that the first individuals of the chum salmon enter the river together with early sockeye salmon and chinook salmon in the first ten-day period of June, and mass-spawning run takes place in July–August. Analysis of biological characteristics of chum salmon caught in the Apuka River and Olutorsky Bay of the Bering Sea enabled us to reveal the inhomogeneity of its spawning school represented by two seasonal forms.     

Potential changes to the biology and challenges to the management of invasive sea lamprey Petromyzon marinus in the Laurentian Great Lakes due to climate change

Control programs are implemented to mitigate the damage caused by invasive species worldwide. In the highly invaded Great Lakes, the climate is expected to become warmer with more extreme weather and variable precipitation, resulting in shorter iced‐over periods and variable tributary flows as well as changes to pH and river hydrology and hydrogeomorphology. We review how climate change influences physiology, behavior, and demography of a damaging invasive species, sea lamprey (Petromyzon marinus), in the Great Lakes, and the consequences for sea lamprey control efforts. Sea lamprey control relies on surveys to monitor abundance of larval sea lamprey in Great Lakes tributaries. The abundance of parasitic, juvenile sea lampreys in the lakes is calculated by surveying wounding rates on lake trout (Salvelinus namaycush), and trap surveys are used to enumerate adult spawning runs. Chemical control using lampricides (i.e., lamprey pesticides) to target larval sea lamprey and barriers to prevent adult lamprey from reaching spawning grounds are the most important tools used for sea lamprey population control. We describe how climate change could affect larval survival in rivers, growth and maturation in lakes, phenology and the spawning migration as adults return to rivers, and the overall abundance and distribution of sea lamprey in the Great Lakes. Our review suggests that Great Lakes sea lamprey may benefit from climate change with longer growing seasons, more rapid growth, and greater access to spawning habitat, but uncertainties remain about the future availability and suitability of larval habitats. Consideration of the biology of invasive species and adaptation of the timing, intensity, and frequency of control efforts is critical to the management of biological invasions in a changing world, such as sea lamprey in the Great Lakes.     

Spatial and temporal variation of the ichthyoplankton in a subtropical river in Brazil

Studies that assess reproduction dynamics and ichthyoplankton distributions are scarce for the upper Uruguay River, especially in environments such as tributary mouths. Therefore, this study aimed to evaluate: (i) ichthyoplankton composition; (ii) spatial and temporal variation in ichthyoplankton abundance; and (iii) relationships between environmental variables and the abundance of ichthyoplankton during one annual cycle in this region. Monthly samples were collected from September 2001 to August 2002 in 48 h cycles at 6 h intervals between each sampling. Samples of eggs and larvae were collected from three of the main tributaries of the region (Ligeiro, Palomas and Chapecó rivers) and from three stretches of the Uruguay River near the confluence of these tributaries. Surface samples were collected with a 0.5 mm mesh cylindro-conical net. In general, reproductive seasonality was well-defined between October and February. It was most intense from November to January, when the photoperiod reached its highest values, flow was decreased, and the water temperature was increased. Based on egg and larval distributions, we found that spawning occurred mainly in the Ligeiro and Chapecó tributaries and in the Uruguay/Chapecó section. In contrast, fish spawning in the sites downstream of dams was more restricted. Finally, a difference was observed between the egg and larval distributions of the main river and its tributaries: the greatest reproductive activity in the tributaries occurred during periods of high flow and increased water temperature, while in the main river, more eggs and larvae were observed when the flow decreased and the water temperature increased.     

Seasonal races of chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> and their interrelations in Kamchatka Rivers

Dates of migration and spawning, size-age structure, and fecundity of seasonal races of chum salmon Oncorhynchus keta from the Kol River are reviewed, those of early summer, late summer, and autumn races, as well as localization and structure of their spawning grounds, bed-sediment particle size in the redds, hydrological and thermal conditions on spawning grounds, and meristic characters of races. Special traits of reproduction of seasonal races within the species range and in Kamchatka in particular are discussed. The number of seasonal races in rivers depends on the presence of various habitats suitable for spawning. In rivers with complicated hydrogeomorphological structure, the number of seasonal races increases. Variations of types of seasonal races in a particular river and in the whole species area are epigenetic, i.e., they depend on the hereditary genetic program and presence of conditions providing its realization via various channels.