ECOLOGICAL AND ENVIRONMENTAL-PHYSIOLOGICAL RESEARCHES OF PINNIPEDS OF BARENTS, WHITE AND KARA SEAS IN 2015–2019

A brief review of the most significant ecological and environmental-physiological studies of three species of true seals living in the arctic seas is presented. The results were obtained on the basis of the analysis of materials from the expeditions of Marine Mammals Laboratory in the Barents, White and Kara seas in 2015–2019. Special attention is paid to the application of satellite telemetry as well as hematological,biochemical, cytochemical methods in the study of harp seal, ringed seal, bearded seal.

Validation of a novel method to create temporal records of hormone concentrations from the claws of ringed and bearded seals

Ringed (Pusa hispida) and bearded seals (Erignathus barbatus) inhabit vast and often remote areas in the Arctic, making it difficult to obtain long-term physiological information concerning health and reproduction. These seals are experiencing climate-driven changes in their habitat that could result in physiological stress. Chronic physiological stress can lead to immunosuppression, decreased reproduction and decreased growth. Recently, keratin has become a popular matrix to measure steroid hormones, such as stress-related cortisol and reproduction-related progesterone. We developed and validated methods to extract cortisol and progesterone from the claws of adult female ringed (n = 20) and bearded (n = 3) seals using enzyme immunosorbent assays. As ringed and bearded seal claws grow, a pair of dark- and light-colored bands of keratin is deposited annually providing a guide for sampling. Two processing methods were evaluated, removal of claw material with a grinding bit or grinding followed by mechanical pulverization (102 paired samples from six claws, two each from three seals). Adding the mechanical pulverization step resulted in a 1.5-fold increase in hormone extraction. Progesterone from the proximal claw band was evaluated to biologically validate claw material as a measure of pregnancy in ringed seals (n = 14). Claws from pregnant seals had significantly higher claw progesterone concentrations than from non-pregnant seals. This suggests that the elevated progesterone associated with gestation was reflected in the claws, and that the most proximal claw band was indicative of pregnancy status at time of death. Thus, although the sample size was low and the collection dates unbalanced, this study demonstrates the potential to use claws to examine an extended time series (up to 12 yrs) of cortisol and progesterone concentrations in ringed and bearded seal claws.

Blood plasma chemistry in White Sea bearded seals across different age groups

Blood chemistry values are reported for the bearded seal species (Erignathus barbatus barbatus Erxleben, 1777) from the White Sea. 27 blood plasma indices are used to describe the state of the metabolism of proteins, carbohydrates, lipids, minerals (total protein, albumin, α-, β-, γ-globulins, urea, creatinine, uric acid, glucose, lactic acid, total lipids, triglycerides, cholesterol, calcium, phosphorus, sodium, potassium, magnesium, iron, copper, chlorides, aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, creatine kinase, alkaline phosphatase, lactate dehydrogenase) in 3-, 5- and 10-year-old seals. The values of the studied parameters are similar to published data for bearded seal populations in other Arctic regions, as well as being in close agreement with indicators of other pinniped species of the same age. The plasma content of total protein, albumin, α-, β-, γ-globulins, urea, uric acid, total lipids, calcium, magnesium, sodium, and chlorides is invariable in animals of the studied ages. In common with other pinnipeds and land-based mammals, age-related changes in metabolic rates in the studied animal groups are most pronounced in the activity level of key metabolism enzymes. While aspartate aminotransferase, alanine aminotransferase and γ-glutamyl transferase activity is higher in adult seals than in immature animals, alkaline phosphatase, creatine kinase and lactate dehydrogenase activity is lower. Changes in biochemical parameters of bearded seal blood at the ages of 3, 5 and 10 years indicate a catabolic orientation in metabolism at all studied development stages. Although more research is needed to investigate the biological significance of a number of blood indices, the data presented in this study provide initial baseline blood chemistry parameters for use in assessing the condition of individual seals, as well as informing monitoring and management efforts for wild seal populations.

Seasonal Movements and Relative Abundance of Bearded Seals (Erignathus barbatus) in the Coastal Waters of the Chukotka Peninsula

Information about bearded seal seasonal distribution in the Pacific Arctic is limited. Bearded seals (Erignathus barbatus Exleben, 1777) from coastal sites along the southern, eastern, and northern Chukotka Peninsula, Russian Federation, were observed most seasons during 1993 – 96, 1998 – 2000, 2002 – 05, and 2010 – 11. These observations provide spatial and temporal information about bearded seal seasonal distribution, movements, and relative numbers in the coastal zones. In winter, bearded seals aggregate on the young ice in the northern part of the Gulf of Anadyr. Numbers gradually increase during March. In springtime (April–May), bearded seals in the northern Gulf of Anadyr are relatively numerous around Nunligran (Cape Achen), but the number is highly variable across years. During spring bearded seals move eastward along the coast from the northern part of the Gulf of Anadyr towards the Bering Strait and then to the north, as the marginal ice edge zone retreats north. These movements to the east and north continue in ice-free water, and by August, the spring migration of bearded seals along the coast of the Chukotka Peninsula ends. In the summer months of August and September, few bearded seals are present in this coastal zone. The southward autumn migration of bearded seals is not evident near the coast, which suggests that it occurs farther from shore.