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Vishnyakova K.,South Scientific Research Institute of Marine Fisheries and Oceanography | Gol'Din P.,Ukrainian Academy of Sciences
ICES Journal of Marine Science

In this study, we analyse seasonal aspects of harbour porpoise strandings in the Sea of Azov and discuss factors affecting the stranding rate. Data on 633 strandings were obtained frommonitoring of a 35-km long area of the south coast of the Sea of Azov in 1999-2013.Adistinct peak of strandings fell in July and August: it depended on the bycatch peak and calving season. Stranding rates depended neither on weather conditions nor on the seasonal fishing activities (including IUU fisheries). Moreover, stranding peaks in the neighbouring Black Sea were also tied to the calving season rather than to the fishing activities. We suggest that the seasonal mortality patterns are indirectly determined by nutritional stress: in Atlantic, winter-stranding oceanic populations and summer-stranding inner-sea populations occur that also possibly differ in the seasonal dynamics of body mass, weaning time or duration of mother-calf association, and dentine structure. In a typical summer-stranding population, summer is the season of nutritional stress, parturition, independent foraging of yearlings and lactation of nursing females, which leads to the risky foraging behaviour near gillnets. Another possible factor of increased bycatch is the seasonal habitat preference, corresponding to the gillnet preferences. Therefore, stranding and bycatch seasonality of porpoises can largely be explained by the aspects of their life history and foraging behaviour rather than by weather conditions and fisheries. This supports the time-area closure strategy as an adequate conservation measure, which would consider minimizing the conflict of interest with fisheries. © International Council for the Exploration of the Sea 2014. All rights reserved. Source

Gladilina E.V.,Taurida National University | Kovtun O.A.,Odessa I I Mechnikov National University | Kondakov A.A.,Russian Academy of Sciences | Syomik A.M.,South Scientific Research Institute of Marine Fisheries and Oceanography | And 2 more authors.
Marine Biodiversity Records

A grey seal (Halichoerus grypus), representative of the North Atlantic species, has been recorded in the north-east Black Sea. It is the first documented case of successful long-term survival of an exotic pinniped. We have been receiving data about regular sightings of the seal identified as the observed individual since 2001. It is a 160-170 cm long adult female. The seal used an underwater cave as a shelter. The most likely way of introduction of the grey seal to the Black Sea is escape from captivity. According to available data (body size and moulting seasonality), we tentatively identify it as a representative of the Baltic subspecies. The biotope requirements of the grey seal and monk seal are similar: Both species use coastal karst caves and grottos. In addition, the seal's presence in this region is a marker of the lack of anthropogenic disturbance. Thus, the survival of a seal in this region indicates the possibility of successful re-colonization of the Black Sea by monk seals. © Marine Biological Association of the United Kingdom 2013. Source

Vishnyakova K.,South Scientific Research Institute of Marine Fisheries and Oceanography | Gol'din P.,Ukrainian Academy of Sciences
Marine Biology

The dynamics of the endangered population of the harbour porpoise (Phocoena phocoena) in the Azov Sea is currently unknown. It can be, however, estimated by stranding analysis. In 1999–2014, the porpoise stranding rates were regularly monitored at the southern coast of the Azov Sea, particularly at the uninhabited abraded coast of the Tarkhan Cape. Specifically, the general trends and annual fluctuations in strandings were compared to the catch reports of the Azov anchovy (Engraulis encrasicolus), an important prey for porpoises. It was observed that the fluctuations in stranding rates closely correlated with the population dynamics of the anchovy stock. A cosine function, based on the data from 1999–2012, correctly predicted maximum strandings in 2013 and their substantial decline in 2014. The function worked particularly well, when possible biases affecting carcass preservation, such as discovery rate and drift conditions, were reduced. In certain environments and over established time periods, the cetacean stranding rate can be an indicator of population trends. The use of stranding rates as such indicator may be verified by external factors, including the dynamics of prey stocks. © 2014, Springer-Verlag Berlin Heidelberg. Source

Gol'din P.E.,Taurida National University | Vishnyakova K.A.,Taurida National University | Vishnyakova K.A.,South Scientific Research Institute of Marine Fisheries and Oceanography
Acta Palaeontologica Polonica

We report two partial skulls of fossil beaked whales (Odontoceti, Ziphiidae) of uncertain age trawled from the sea floor of the sub-Antarctic Indian Ocean (58 to 60°S), representing the southernmost record of the family. The skulls possess diagnostic features of the genus Africanacetus, several specimens of which have been recovered from the sea floor off South Africa, but differ from the type and only known species Africanacetus ceratupsis in their larger size. This difference may either reflect intraspecific variation or indicate the existence of a hitherto unrecognised species. The two specimens are characterised by unusually developed mesorostral ossifications, combined with maxillary crests occurring in the facial region. Both of the latter are found in a range of extant and extinct ziphiids, and known to be sexually dimorphic in extant beaked whales. These structures may be the result of hypermorphosis driven by sexual selection, and could be involved in male-specific behaviour. © 2013 P.E. Gol'din and K. A. Vishnyakova. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

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