Vol 56, No 2 (2016)

An analysis of the structure of lateral musculature of the head and the basic skeletal elements was made in 14 species of genus Lampanyctus, which belong to all of its species groups. Although there are visible differences in the external morphology that are inherent in Lampanyctus from different species groups, stable anatomical differences were not revealed. Apparently, an important role in the evolution of Lampanyctus species was played by the process of paedomorphosis, which is expressed in a weak skeleton ossification, abnormal development or loss of its separate elements, a decrease in the maximum size of the body, and strong watering of body musculature. The absence of osteological differences between the species groups of Lampanyctus indirectly shows the unity of their origin and, therefore, confirms the hypothesis on the monophyly of this genus.

New findings of lower Amur grayling (Lower Amur grayling) Thymallus tugarinae and Baikal-Lena grayling Th. sp. (Th. baicalolenensis) in the basins of the upper Amur River and Zeya River are reported for 2010−2014. Lower Amur grayling has been registered in the tributaries of Argun River and in the middle stream of Ingoda River. Baikal-Lena grayling has been found for the first time in the headstream of Ingoda River. New data about the distribution of this species in the basin of upper stream of Zeya River are reported; particularly, Baikal-Lena grayling has been found in Okonon Lake; this is the first finding of a representative of Thymallidae family in the alpine lakes of the watershed area of Amur River. In the basins of upper Amur River and Zeya River, the summer ranges of upper Amur grayling Th. grubii grubii and lower Amur grayling overlap to some extent; on the other hand, the ranges of Baikal-Lena grayling and lower Amur grayling are disjoint. During the summer period, upper Amur grayling and Baikal-Lena grayling together inhabit the basin of upper stream of Zeya River, but only Baikal-Lena grayling has been found in the headstream of Zeya River. In the basin of upper Amur River (the headstream of Ingoda River), the joint range of these species is still unknown; the sympatric zone is located in Dzhermoltai River (the basin of Onon River).

Distribution, population structure, and abundance of Amur kaluga Acipenser dauricus and Amur sturgeon A. schrenckii in the Lower Amur and Amur Estuary have been considered based on the materials of two surveys performed in 2011. Both species occur along almost the entire length of the Lower Amur and in major part of the Amur Estuary. The density of their aggregations has significantly decreased in most regions of the river if compared to the 1960s. In the Amur Estuary, A. dauricus and A. schrenckii are most abundant in freshwater and light salted water bodies of its western part. In 2011, the abundance and biomass of A. dauricus and A. schrenckii in the Lower Amur and Amur Estuary was 345000 specimens and 7110 tons and 289000 specimens and 1946 tons, respectively.

The interannual and ontogenetic dynamics of the fecundity of the Baltic cod Gadus morhua callarias and the dependence of the number of the offspring on the reproduction conditions were studied. The absolute individual fecundity and the relative individual fecundity had no pronounced interannual dynamics for the period of 1994−2013. The maximal population fecundity was observed in early 1980, the minimal, in 1990−2000. Nearly every year, the highest contribution to the population fecundity belongs to the 4−5-year old females. The ranking of the survival rates and the year-class strength for the females at the age of 2 years showed that the emergence of the generations of high and average productivity (1980−1986) referred to the unfavorable and moderate survival conditions during the early ontogenesis. During the period of small stock (after 1987), the conditions were mostly favorable and moderate. It is suggested that the significant role in the offspring dynamics belongs to the factors linked to the population density. After 2005, favorable survival conditions promoted the increase of the Baltic cod abundance; this increase was also supported by the decrease of the commercial fishing and by the sporadic large-scale advective processes.

It has been revealed that fluctuations of salinity within the ecological norm positively affect the embryonic and larval development in pike Esox lucius. Within the optimal range of salinity (0−2‰ with fluctuation period of 12 h), compared to the constant optimal salinity (2‰), the growth and development rate accelerate, the survival rate of embryos and larvae increase especially during the critical stages of development, and the variability of sizes of embryos and larvae decreases.

The data on alkaline phosphatase activity in the liver of eight dominant species of Black Sea fishes are presented. The enzyme activity varies within a wide range; significant sexual differences have not been registered. The activity of the enzyme is similar in specimens of different age groups, but it decreases in old fishes. The enzyme activity increases in prespawning and spawning, which evidences for its participation in the process of sexual maturation of fish. Based on our and published data on the dependence of alkaline phosphatase activity on the degree of the environmental pollution, the enzyme can be recommended as a biomarker for bioindication, biotesting, and ichthyological monitoring.

Physiological pH values are determined in the gastrointestinal tract of the perch Perca fluviatilis from lakes Chany and Baikal. Values of pH are detected to vary significantly along the digestive tract. Such factors as a segment of the digestive tract, presence/absence of food, season of the year, and habitat affect pH values. Environmental temperature is the main factor affecting pH values that is confirmed by the decrease in pH values upon water temperature rise in spring, lower pH values in summer compared to other seasons, and lower pH in fish from the waterbody (Lake Chany) with higher temperature of water.

The experimental investigation of the effects of hyperthyroidism on the development of Labeobarbus intermedius pigmentation revealed that high level of thyroid hormone leads to changes in developmental rate and timing of early larval pigment pattern. The hyperthyroidism induces the acceleration of growth of early larval melanophores, causes changes in their physiological state, and provokes the premature onset of the adult pigment pattern formation.