Reproduction ecology of masu salmon <Emphasis Type="Italic">Oncorhynchus masou</Emphasis> in the Kol basin (Western Kamchatka)

In the Kol basin, one of the typical salmon rivers of Western Kamchatka, special traits of reproduction ecology of masu salmon Oncorhynchus masou are studied (characteristics and behavior of spawners during spawning, localization of spawning grounds, topography and hydrology of redds, and interaction with other species of salmonids). The masu salmon spawns in the Kol basin in tributaries of the upper reaches of the river and only in downwelling. Spawning grounds of masu samlmon are confined to stretches with overhanging banks, log jams creating shelters for spawners and favorable hydrological conditions for spawning and egg development. All over its range, masu salmon requires similar conditions for reproduction. In the north of its range, in Kamchatka, masu salmon retains the properties of the most warm-water species in the genus Oncorhynchus and selects for spawning the grounds characterized by the highest temperature in the period of spawning and development.     

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.     

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.     

Investigations of spawning migration and assessment of abundance of the Kamchatka steelhead (<Emphasis Type="Italic">Parasalmo mykiss</Emphasis>) from the Utkholok River by means of Didson dual-frequency identification sonar

Quantative estimates of abundance of anadromous Kamchatka steelhead Parasalmo mykiss in the period of its maximum spawning migration in the shallow Utkholok River by the instrumental method using Didson dual-frequency identification sonar are presented. Equipment and methods are described for the stationary observation of spawning run of Kamchatka steelhead through the river cross section and mobile surveys of the water area of the Utkholok R. As a result of stationary observations, the abundance and size composition of Kamchatka steelhead migrating to the upper reaches of the river are determined. Peculiarities of the diurnal dynamics of migration of Kamchatka steelhead characterized by two sharp peaks of run intensity in the morning and evening were revealed. During the period of observations from September 22 to October 20, 2007, in the seasonal dynamics of migration two peaks of intensity of run of Kamchatka steelhead depending on an abrupt decrease in water temperature by 2°C were also registered. Mobile surveys supplied data on the abundance and size composition of Kamchatka steelhead in the surveyed water area of the river, on its spatial distribution, and dynamics of accumulation of fish in the river. The abundance of Kamchatka steelhead in the river almost doubled every three-four days and the spatial distribution was aggregated, producing maximum concentration mainly in areas of increasing depth and channel meandering before and after riffles. Comparison of the results of assessment of abundance of Kamchatka steelhead that arrived for spawning in 2006 and 2007 showed significant fluctuations in population abundance.     

On joint spawning of anadromous and resident mykiss <Emphasis Type="Italic">Parasalmo mykiss</Emphasis> in rivers of Western Kamchatka

The fact of joint spawning of anadromous and resident mykiss Parasalmo mykiss is reliably recorded in the basin of the Kol River (Western Kamchatka). The obtained data on relationships of these forms during spawning indicate to their conspecificity. This species should be protected as a whole, in all diversity of its forms.     

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.     

Some issues related to reproduction of Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> in waters of the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka

The analysis of data collected in December 1996 and 1998 on the reproduction of cod Gadus macrocephalus in Pacific waters of the northern Kuril Islands and the southern part of Kamchatka was performed. It was shown that the individual absolute fecundity of the cod varies within 0.197–9.729 million eggs and the relative fecundity, in the range of 24-1386 eggs. The fecundity of 1000 mature females comprises 2179–2449 million eggs. The low individual fecundity of fish is related to pseudobranchial tumor growth. The main role in cod reproduction is played by females of two-three size groups characterized by the highest numbers of mature females. It is suggested that different fecundity within the range of Pacific cod is related to environmental conditions, in particular, water temperature in the spawning grounds during spawning rather than to the habitation latitude.     

Diversity of life strategies and population structure of Kamchatka mykiss <Emphasis Type="Italic">Parasalmo mykiss</Emphasis> in the ecosystems of small salmon rivers of various types

The diversity of life strategies and population structure of Kamchatka mykiss Parasalmo mykiss in the ecosystems of small salmon rivers of various types are considered. Hydrogeomorphological differences of the model rivers Kol and Kekhta are found. The preferred habitats are investigated, and their area is determined. It is shown that, in the Kol River, the mykiss having a resident life strategy predominated, and in the Kekhta River—the mykiss with migratory strategy. The key parameter controlling the prevalence of life strategies in each river is the ratio of the area of spawning grounds to the area of feeding grounds and their productivity. The hypothesis is confirmed that, in complex river systems, due to the diversity of biotopes and a higher productivity, the food resources are sufficient for maturation of mykiss and for realization of the resident life strategy (without migration to the sea for feeding). In small rivers of the channel type with their insufficient food resources, the specimens having a migratory life strategy prevail.     

Effect of incubation temperature on green sturgeon embryos, <Emphasis Type="Italic">Acipenser medirostris</Emphasis>

Regulation of river flow and the amount of winter rainfall are the major factors affecting the water temperature of the spawning grounds, for green sturgeon in the Klamath River. During the primary spawning period of green sturgeon, mid-April to June, the water temperature may vary from 8 to 21°C. To estimate the potential implications of this modified thermal regime, we examined the survival and development in three progeny groups of green sturgeon embryos from zygote to hatch, at constant incubation temperatures (11–26°C). Temperatures 23–26°C affected cleavage and gastrulation and all died before hatch. Temperatures 17.5–22°C were suboptimal as an increasing number of embryos developed abnormally and hatching success decreased at 20.5–22°C, although the tolerance to these temperatures varied between progenies. The lower temperature limit was not evident from this study, although hatching rate decreased at 11°C and hatched embryos were shorter, compared to 14°C. The mean total length of hatched embryos decreased with increasing temperature, although their wet and dry weight remained relatively constant. We concluded that temperatures 17–18°C may be the upper limit of the thermal optima for green sturgeon embryos, and that the river thermal regime during dry years may affect green sturgeon reproduction.     

Reproduction of the Siberian salamander, <Emphasis Type="Italic">Salamandrella keyserlingii</Emphasis> (Amphibia,Caudata, Hynobiidae), in water bodies on permafrost in Northeastern Asia

The possibility for Siberian salamanders to reproduce in the permafrost zone of Eurasia is due to specific thermal conditions in small water bodies (pools) freezing to the bottom, rather than to the adaptive properties of the species. These conditions are as follows: (1) meltwater in freezing marshland pools appears relatively early; (2) the rate of water warming increases in the south-north direction due to the lengthening of the daylight period; (3) water temperature is higher than air temperature but does not reach the values critical for S. keyserlingii eggs and larvae; and (4) the thawed silt layer prevents water cooling by the underlying permafrost bed. Reproduction of Siberian salamanders in different parts of the species range begins under similar thermal conditions, which are formed 1.5–2 months earlier in the south (the Jewish Autonomous Region) than in the north (the Chaun Bay coast). In any region, the onset of spawning may vary by up to 30 days. The existence of Siberian salamanders in the tundra zone is facilitated by continuous daylight during the polar day, which provides for rapid water warming to relatively high temperatures and creates additional opportunities for larval feeding. These factors may account for the acceleration of amphibian ontogeny in the North, noted by Shvarts and Ishchenko (1971). The northern boundary of the Siberian salamander range in Eastern Siberia is defined by the sum of water temperatures over the warm season, which should be no less than 850–900°/day. This boundary in the tundras of Europe, Western Siberia, and the Chukchi Peninsula is shifted southward, with its location being apparently dependent on some other factors.     

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 strategies of mykiss <Emphasis Type="Italic">Parasalmo mykiss</Emphasis> and trout <Emphasis Type="Italic">Salmo trutta</Emphasis> introduced in water bodies of Chili

Materials of preliminary investigations of the life strategy of mykiss Parasalmo mykiss and trout Salmo trutta introduced to water bodies of Chili are considered. Analysis of the structure of scales demonstrated that, in mykiss and trout, the estuarine and riverine-estuarine types of life strategy prevail. This seems to be related to good feeding conditions in fjords. The hypothesis is suggested that, in the area of Chilean fjords, the successful introduction to rivers and artificial rearing in cages in brackish water resulted in the formation of a peculiar and highly dynamic population system. Elements of this system are from both fish of natural self-reproducing populations and fish grown in cages. There is a continuous exchange with genetic information between them as the fish that have escaped from cages attain maturity, arrive to rivers for spawning, and reproduce together with wild fish.     

Reproductive Cycle of Females and Reproduction of the Siberian Salamander (<Emphasis Type="Italic">Salamandrella keyserlingii</Emphasis>, Caudata,Hynobiidae) on the Coast of the Sea of Okhotsk

The sexual cycle of Siberian salamander females (Salamandrella keyserlingii Dybowski 1870) has been studied in the tundra of the northern coast of the Sea of Okhotsk. Spawning starts soon after the end of wintering (in the second half of May) and ends up in the first half of June. At the end of June, the ovaries show obvious features of a new ovogenic cycle; i.e., pigment starts accumulating in large vitellogenic oocytes. By the end of July, the ovaries in most individuals are already filled with pigmented follicles and the oviduct epithelium is restored. The time from spawning to the appearance of a new generation of mature oocytes lasts a little more than two months (i.e., half of the whole activity season). In the second half of August, the state of the genital system is identical to that in spring before spawning, this proving their annual reproduction. The average fecundity in the studied water bodies varies from 102 to 123 eggs and is comparable to that in other parts of the distribution range. Oogenesis both in the vast majority of females that reach pubescence (subadultus) and in those that spawn in spring occurs simultaneously, but in some subadults it is completed almost a month or a month and a half earlier. By this phenological feature, the female subadults differ considerably from the male subadults, in which completion of spermatogenesis extends much more strongly into the season. A study of the ecology of the Siberian salamander in the conditions of a short season of activity with low temperatures allows for the coast of the Sea of Okhotsk to be considered not as extreme, but, in contrast, rather favorable for its habitation. Many population characteristics in this area are typical for the species in general. The main features of the male and female sexual cycles appear to be similar to those observed in species of the same family that live in the south of the region. The short period of germinal cell development, coupled with the outstanding winter cold hardiness of the species, partially accounts for its unique adaptive potential, which allows it to colonize vast territories of northern Eurasia and successfully thrive in the territories with short and cold summer period.     

Parasites of underyearling kamchatka mykiss Parasalmo mykiss mykiss (Osteichithyes:Salmonidae) in the Utkholok River (North-Western Kamchatka)

Eight species of parasites, Apiosoma piscicolum piscicolum, Apatemon sp., Diplostomum sp., Bunoderidae gen. sp., Crepidostomum metoecus, Hysterothylacium gadi aduncum, Salvelinema salmonicola, and Cucullanus truttae had been found in underyearling Kamchatka mykiss (with fork length 28-41 mm) from the Utkholok River, North-Western Kamchatka. Infestation rate of the fishes with each parasite species was rather low. Presence of C. truttae in underyearling Kamchatka mykiss could not be explained by the conceptual model of its life cycle proposed by Moravec (1979). Spatial and temporal isolation of underyearling Kamchatka mykiss and ammocoetes, as the elements of a local food web, suggest that the lamprey larvae do not participate in the transmission of C. truttae to underyearling Kamchatka mykiss.     

Assessing the relative importance of temperature,discharge, and day length on the reproduction of an anadromous fish (Alosa alosa)

1. Climate change threatens anadromous fishes such as the allis shad (Alosa alosa) populations of which have declined since the 20th century in Europe. Sensitivity to climate change could be quantified by determining the fish’s spawning behaviour, defined as the timing of reproduction (i.e. spawning events) as a function of temporally variable environmental factors. The cues that fish use to time reproduction could determine their response to climate change.
2. A machine learning technique (boosted regression tree) was calibrated using a 14-year dataset composed of daily measures of environmental factors and fish occurrences during reproduction. The boosted regression tree provides complete insight into the complex relationship between the spawning probability, i.e. the probability for a fish to reproduce, and environmental factors that might evolve with climate change.
3. The spawning probability was positively related to day length (44.6%) and water temperature (34.7%) and negatively related to river discharge (20.7%). Optimal reproductive conditions corresponded to a difference in day length between 0 and 0.04 hr, a water temperature between 15 and 26°C and a river discharge between 55 and 665 m³/s; these conditions are currently being utilised by allis shad populations in the Garonne and Dordogne rivers, France.
4. This study highlights the relative influence of environmental factors on the observed spawning period as well as the evolution of habitat suitability during the 14-year period. The novelty of this study stems from assessing population process data, i.e. the occurrence of fish reproduction, rather than mere occurrence data in an ecological niche model study. Climate change may lead to a shift in spawning phenology, as the water temperature and river discharge will also change. Therefore, conservation plans need to integrate these effects on spawning grounds.

     

Effects of increasing temperatures on population dynamics of the zebra mussel <Emphasis Type="Italic">Dreissena polymorpha</Emphasis>: implications from an individual-based model

Zebra mussels (Dreissena polymorpha, Pallas, 1771) have had unprecedented success in colonizing European and North American waters under strongly differing temperature regimes. Thus, the mussel is an excellent model of a species which is able to cope with increasing water temperatures expected under global change. We study three principle scenarios for successful survival of the mussel under rising temperatures: (1) no adaptation to future thermal conditions is needed, existing performance is great enough; (2) a shift (adaptation) towards higher temperatures is required; or (3) a broadening of the range of tolerated temperatures (adaptation) is needed. We developed a stochastic individual-based model which describes the demographic growth of D. polymorpha to determine which of the alternative scenarios might enable future survival. It is a day-degree model which is determined by ambient water temperature. Daily temperatures are generated based on long-term data of the River Rhine. Predictions under temperature conditions as recently observed for this river that are made for the phenology of reproduction, the age distribution and the shell length distribution conform with field observations. Our simulations show that temporal patterns in the life cycle of the mussel will be altered under rising temperatures. In all scenarios spawning started earlier in the year and the total reproductive output of a population was dominated by the events later in the spawning period. For maximum temperatures between 20 and 26°C no thermal adaptation of the mussel is required. No extinctions and stable age distributions over generations were observed in scenario 2 for all maximum temperatures studied. In contrast, no population with a fixed range of tolerated temperatures survived in scenario 3 with high maximum temperatures (28, 30, 32°C). Age distributions showed an excess of 0+ individuals which resulted in an extinction of the population for several thermal ranges investigated. Priority programme of the German Research Foundation—contribution 14.     

Spawning population characteristics of pike <Emphasis Type="Italic">Esox lucius</Emphasis> L. in Lake Rubikiai (Lithuania)

The aim of the study was to describe the peculiarities of pike spawning in mesotrophic Lake Rubikiai, to determine the spawning population structure and evaluate the influence of some environmental factors on year-class strength formation. The data were collected in April and May (1994–2011). A total of 1586 individuals were caught. The age of pike ranged from 1 to 12 years; 2–5-yearold males (96.0%) and 3–8-year-old females (89.1%) prevailed. The overall sex ratio of females to males was 1:4.1. One-year-old spawning males (26.5–28.5 cm) and two-year-old spawning females (31.5–35.5 cm) constituted 2.1% and 2.6%, respectively. Water temperature during the spawning period was relatively stable, between 4 and 6°C, during March and increased slightly towards 10°C in the middle of April. No correlation was observed between female length and spawning date. Year-class strength did not correlate with the last day of ice presence and the minimal water level at the end of spawning (WL_min), but statistically significantly negatively correlated with the maximum water level at the beginning of spawning (WL_max) and the difference between WL_max and WL_min. The mean annual survival rate for pike (aged ≥2) was 0.74 and the mean annual instantaneous mortality rate was 0.45.     

Influence of temperature and size of females on the timing of spawning of perch,Perca fluviatilis,in Lake Geneva from 1984 to 1993

Synopsis The influence of temperature and the size of reproducing females on the timing of spawning of perch in Lake Geneva has been studied for 10 consecutive years (1984–1993) by means of artificial spawning substrates. The clutch of perch is an egg ribbon with a width proportional to the size of the reproducing female, so that the size structure distribution of the female population can be estimated from measurements of the width of the egg ribbons. The survey of egg-ribbon size revealed a succession of 3 cycles (period of increasing mean size followed by a sharp decrease) lasting 3, 3 and 4 years which were due to the occurrence of 3 strong year classes born in 1982, 1985 and 1988 respectively. This phenomenon can be explained by the effect of intraspecific predation exerted by strong year classes on the offspring of the 2 following years rather than by fluctuations in the success of reproduction in relation to climatic changes. In Lake Geneva, perch spawn in May. The water temperature exerted only a minor influence on the date of the beginning of the spawning period but had a greater effect on its intensity. A rise in temperature in May stimulated spawning while bad weather decreased spawning intensity. The larger perch had a tendency to spawn later than the small ones. The date of the mid-spawning period was well correlated with the yearly mean width of perch egg ribbons but no correlation could be detected between it and the water temperature.     

Genetic divergence of mykizha (Parasalmo (Oncorhynchus) mykiss) from Kamchatka inferred from restriction analysis and sequencing of mtDNA cytochrome b gene

The populations of mykizha Parasalmo (O.) mykiss from western and eastern coasts of Kamchatka were studied by restriction analysis of a fragment of fish mitochondrial genome that included the control region and the region of the cytochrome b gene (cytb). The restriction patterns obtained with five enzymes (MspI; Tru1I; RsaI; BsuRI; DdeI) were identical in all studied individuals. Sequencing of the cytb gene showed high similarity between all samples (99.6-100%). In general, the geographical group of mykiss from Kamchatka is monophyletic with low genetic divergence at the population level. Shantarian mykiss originates most likely from that native to Kamchatka.     

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.