Presented is a review of published materials and reports on aerial abundance surveys, satellite tracking of seasonal movements, and genetic studies of the Okhotsk Sea beluga whale in 2007-2012. Current situation with removal of this biological resource from the Okhotsk Sea and possible outcomes of such exploitation are described. In the absence of harvest, removal quota for scientific-research and control, and educational and cultural-display purposes is proposed to be calculated considering biological peculiarities of the species by the method of potential biological removal (PBR). A calculation of PBR for the annually exploited Sakhalin-Amur beluga whale stock is exemplified.

In 2000 the Scientific Committee of the International Whaling Commission (IWC) determined 29 sustainable summer beluga aggregations. In his report at the committee’s meeting, Vladimir Melnikov mentioned three beluga aggregations in the Sea of Okhotsk: Shelikhov, Sakhalin-Amur and Shantarsk aggregations, with a total of 18,000-20,000 cetaceans. He pointed out that despite an absence of hunting since the 1960s the strength of these populations has not changed substantially in the last few decades. The information presented was not sufficient to determine a conservation status for beluga whales in the Sea of Okhotsk. There were no genetic data or materials on toxicology. Specialists pointed to the need to conduct genetic and telemetric studies, examine the condition of their health and count the number of these populations.

There are other estimates of the beluga population in the post-hunting period in the Sea of Okhotsk that differ from the data presented at the meeting of the IWC Scientific Committee. Some of these data differ substantially: from 6,000 -8,000 species to 35,000-45,000. Beluga whales were hunted with varying intensity in the Sea of Okhotsk until the middle of the 20^th century. Since the 1980s and until the present they have been removed only from the Sakhalin Gulf for scientific, monitoring and educational purposes. The quota for their removal could be calculated on the basis of any estimate cited above and could vary by more than seven times. There is an obvious need to obtain current accurate data on the beluga populations in the Sea of Okhotsk.

This is a review of our recently published materials and reports on air surveys of population abundance and studies of seasonal migrations and population structure of beluga whales in the Sea of Okhotsk. They describe live-capture removals of beluga whales in the Sakhalin Gulf and contain recommendations on the sustainable harvest of the studied aggregations.

Estimates of the abundance of beluga whales in the Sea of Okhotsk in 2009-2010

Air surveys to count the beluga populations were conducted in August-September 2009-2010 in the coastal basins of the Sea of Okhotsk with the exception of the Kurile Islands. Based on the available data of the beluga summer distribution, the basin was divided into western and north-eastern parts of the Sea of Okhotsk and further into smaller population sections. Beluga whales were counted four times in the Sakhalin-Amur and Shantarsk regions: twice each year. In the south of the Sakhalin Gulf and the Amur estuary, which were covered by parallel transects, the number of beluga whales was calculated by the extrapolation method described in the Beluga-2 programme. In other areas, the direct counting method was used during coastal aerial surveys. In other words, it was assumed that the number of visually registered beluga whales represented a complete abundance. For large aggregations, the visual assessment was adjusted by counting beluga whales in photos. The results submitted by Dmitry Glazov and his team of authors reflect the minimal count of belugas in the Sea of Okhotsk because they did not adjust their count for the number of submerged mammals that were invisible to observers and cameras during aerial surveys. The estimates of beluga abundance in 2010 were used as a point of departure. Researchers counted 1,333 belugas in the north-eastern part of the Sea of Okhotsk. Thus, there are at least 6,113 individuals in the Sea of Okhotsk.

Olga Shpak and her co-authors pointed out that up to half of belugas are likely to be invisible to observers. Later on a group of independent experts from the International Union for Conservation of Nature confirmed this conclusion. Hence, the received estimates should be adjusted to account for the number of submerged mammals. If observers registered only 50% of all belugas, their total number in the Sea of Okhotsk would amount to 12,226.

Satellite monitoring in 2007-2010

To study the seasonal migrations of beluga whales in the Sakhalin-Amur aggregation, researchers caught 22 belugas (13 females and nine males of different ages) and outfitted them with satellite transmitters near the islands of Chkalov and Baidukov in the Sakhalin Gulf in 2007-2010. One of these females tagged in 2008 was caught again and tagged in 2010. Migrations of belugas were different in different seasons. In summer belugas mostly stayed near islands, close to the place where they were caught and tagged. They behaved differently during fall. Researchers assumed that all monitored mammals (10 belugas tagged in 2007-2008) spent fall in the eastern part of the Shantarsk area, in the Gulf of Nikolai. But satellite observations showed that only four out of nine of these belugas spent time in the Gulf of Nikolai, and one of them was tagged twice.

Working in the Gulf of Nikolai in July 2009 and 2010, we registered two belugas with scars from transmitters installed by us in the previous summer seasons in the Sakhalin Gulf. Based on these encounters it is impossible to establish whether belugas move between the gulfs in summer or choose different gulfs in which to spend the summer in different years.

The analysis of these migrations in winter showed that the beluga whales tagged in one place (the Island of Baidukov in the Sakhalin Gulf) did not follow the same migration route, and spent the winter in different gulfs. None of the tagged belugas moved to the east of the traverse of Taui Bay (151E). In other words, none of them entered the Gulf of Shelikhov or the coastal waters of western Kamchatka. At the same time, one of the females tagged in summer off the coast of western Kamchatka in the estuary of the Moroshechnaya River did not travel west of 155E during the winter-spring period. This fact makes it possible to assume that belugas from the summer aggregations of the western and north-eastern parts of the Sea of Okhotsk follow different routes.

Earlier we assumed that aggregations from the Sakhalin-Amur area and the eastern part of the Shantarsk area occupied the same basins as the belugas of the Sakhalin-Amur aggregation during fall and moved to the north in winter, mixing with the belugas from the Gulf of Shelikhov and western Kamchatka. However, when the sampling was increased we made the following conclusions: 1) belugas from the Sakhalin-Amur aggregation do not always move to the gulfs of the eastern part of the Shantarsk area, but may bypass them migrating to the north for winter; 2) in winter and spring Sakhalin-Amur and western Kamchatka belugas may remain geographically isolated from each other.

Genetic analysis

For decades researchers have discussed how many beluga populations (from one to three) inhabit the Sea of Okhotsk. The first article on their genetic analysis was published in 2008. The nucleotide sequencing of 28 belugas in the mtDNA control region revealed substantial differences in the maternal lines of the Sakhalin-Amur aggregation and different populations of the Pacific refugium.

Later on the analysis of the allelic composition of microsatellite loci in nuclear DNA showed that belugas from the Sakhalin Gulf and Udsky Bay are a single population, while belugas that summer off western Kamchatka may be attributed with great consistency to a different population.

Using the clustering method, researchers that studied in detail all summer aggregations in the gulfs of the Sakhalin-Amur and Shantarsk areas revealed high heterogeneity of the population in the west of the Sea of Okhotsk. The division into groups (subpopulations, demes and aggregations) appeared to be independent of their geographical location. At the same time, the analysis of mtDNA of belugas from different aggregations in the west of the Sea of Okhotsk revealed statistically significant differences in nucleotide sequencing in haplotypes, with the exception of the following pair samplings: Udsky Bay / Tugursky Gulf and Gulf of Nikolai / Sakhalin Gulf. Unique maternal lines of geographically close summer aggregations point to a high degree of philopatry that is also typical of other Pacific beluga populations. Generations of belugas consistently migrate to the same places in summer. A single genetic pool is sustained during the mating of different aggregations in winter or early spring.

Current use of the beluga whale in the Sea of Okhotsk

Based on the total allowable catches, every year the Federal Fisheries Agency issues quotas on the hunting of belugas by indigenous northern minorities and live-capture removals for research, monitoring and educational purposes. Northern minorities rarely submit applications for permits to catch belugas in the fishing subzones of the Sea of Okhotsk. Thus, in 2012 the Federal Fisheries Agency granted a quota for hunting 90 belugas in the northern part of the Sea of Okhotsk to the indigenous community, but no belugas were caught.

Unsanctioned slaughter (removal) of belugas exists, but as far as we know it has not exceeded two or three mammals annually per village in the Shantarsk area in the last few years. L. Bogoslovskaya and I. Krupnik wrote in 2000 that local residents kill about 10 belugas in Kamchatka and 20-30 animals in the Amur River basin. These figures appear current for the last few years.

Since 1986 live-capture removals by local residents in the northern part of the Sea of Okhotsk have been limited to the southern part of the Sakhalin Gulf, along the coasts of the islands of Chkalov and Baidukov. The first live-capture removals were ordered by TINRO-Tsentr, and since 1990s by other organisations that upkeep and sell sea mammals. As distinct from the traditional hunting by northern minorities that prefer large male and female members of the species, mammals caught for dolphinariums are usually young individuals of two or three years, preferably females, due to the difficulties of transportation and requirements of further upkeep.

Total allowable catch quotas are regularly established for belugas in western Kamchatka, although they have not been hunted for a long time, while permanent live-capture removals have never been conducted. In 2010 and 2011 belugas were removed for a short time and then released into the sea under the research programme on satellite tagging of the Russian Academy of Sciences’ Institute of Ecology and Evolution.

 Due to a lack of information, until recently the total allowable catch was based on the abundance of Sea of Okhotsk belugas in 1979-1991 without taking into account the biological characteristics of these animals. After belugas were counted in 2009 and 2010, it became clear that more conservative estimates of their abundance in the late 20^th century appeared to be correct and pointed to zero growth in the beluga populations in the Sea of Okhotsk in the last few years. Nevertheless the quotas for hunting belugas in the northern part of the Sea of Okhotsk in the second half of 2012 were increased compared to the spring of the same year by almost five times to reach 212 mammals. In 2013 the Federal Fisheries Agency issued permits for live-capture removals of 263 belugas in this subzone, including 18 belugas for research and monitoring purposes and 245 for educational needs. A quota for catching 45 belugas was issued for the western Kamchatka subzone.

The increase in quotas and customers in 2013 (14 versus 3-5 in previous years) led to the growth of catching teams and instruments only in the traditional live-capture removal zone near the islands of Baidukov and Chkalov in the southern part of the Sakhalin Gulf.

Accidental death

It is practically impossible to calculate how many belugas die as a result of anthropogenic activities. They get entangled in trawls and meshing nets and collide with small vessels. We know about several fatal cases from talking to local residents in which belugas became entangled. We witnessed three cases in 2007-2012, when belugas became stuck in trawls and stake nets. Despite these instances, belugas usually avoid fishing nets, and these accidents do not represent a serious threat for them. An analysis of photos from the Sakhalin-Amur, Shantarsk and western Kamchatka areas has shown that few whales have scars or other injuries that they may have sustained after colliding with vessels or boat engines. Although we do not have enough information on the number of fatalities caused by anthropogenic activities, it is possible to disregard the influence of this factor on the beluga populations in the Sea of Okhotsk given the precautionary approach to the use of these whales.

Belugas’ deaths during live-capture removals and accidental catch represent a special case and should not be considered as accidental deaths. Mammals also die during transportation to a temporary holding base and during holding. It is impossible to estimate how many belugas die in these cases without special monitoring by inspectors of relevant agencies, because catching teams actively engage in hiding the corpses of these animals. They take them far into the sea and sink them with weights.

Recommendations on sustainable use of the beluga whale in the Sea of Okhotsk

It was shown above that according to genetic analysis, the Sakhalin-Amur and Shantarsk belugas form a single population of the western part of the Sea of Okhotsk. However, despite this fact, belugas migrate to definite summering locations year after year. They form sustainable summer aggregations, as is reflected in unique sets of maternal lines of species from different gulfs. Independent demographic units or separate aggregations – in the Sakhalin-Amur area, Nikolai, Ulbansky and Tugursky gulfs and Udsky Bay – should be managed separately. It is important to establish total allowable catch quotas and conduct removals from each aggregation on the basis of its abundance and condition.

Although researchers did not detect authentic differences between the mtDNA of belugas in Tugursky Gulf and Udsky Bay, it is necessary to point out that the sampling from Tugursky Gulf was not representative enough to make management recommendations. Only one sampling over the course of two days was made. The local aggregation of belugas was not studied and aerial surveys in August and September of 2009 and 2010 showed its geographical isolation from other aggregations. The Tugursky Gulf aggregation should be considered a separate demographic unit until subjected to comprehensive study.

A small group of belugas spend summer in the Gulf of Nikolai (or visit it). Sometimes mammals from the neighboring Sakhalin Gulf move there. Inadequate genetic samplings (less than 10) prevent researchers from making reliable conclusions on the independence of this aggregation or its unity with the mammals from the Sakhalin-Amur basin. The beluga population of the Gulf of Nikolai is small and its status is uncertain. Therefore, live-capture removals of belugas from this area must not be allowed.

Every year the Federal Fisheries Agency calculates total allowable catch for belugas in the western Kamchatka fishing subzone and establishes quotas for live-capture removals if there are relevant applications. Information on beluga whales in the northern and north-eastern parts of the Sea of Okhotsk is inadequate; there are no data on the structure of the beluga population and distribution of current resident groups, and estimates of the health condition of the western Kamchatka aggregation are a source of concern. Until satisfactory data on the beluga population in the northern part of the Sea of Okhotsk or the Shelikhov population are obtained, it is necessary to limit its use to meeting the needs of northern minorities and research organisations.

Conclusion

Annual removals of belugas in the Sea of Okhotsk for research and educational purposes is determined by the unflagging demand for them in dolphinariums and aquariums all over the world, in countries that do not prohibit the entry of wild-caught whales. Up to now annual removals in the Sakhalin Gulf amounted to an average of 22 individuals (44 maximum) and did not do much damage to their population. The demand for these belugas has grown in the last few years, and quotas for their removal have increased substantially. However, catching teams still concentrate all of their efforts in the limited part in the north of the Sea of Okhotsk – the southern part of the Sakhalin Gulf.

We believe that such an approach to the use of this biological resource will produce negative consequences for the Sakhalin-Amur beluga population. Not only the amount of live-capture removals but also deaths during transportation and temporary holding, strict age census of caught belugas, preferences of customers on their sex and presumable pronounced discomfort of the local aggregation are a source of concern. According to our satellite monitoring data, photos and visual observations, belugas near the islands of Chkalov and Baidukov are prone to staying in the same areas and have their own fixed home sections. The actions of catching teams that are simultaneously operating in the south of the gulf for a long period of time are likely to upset the existing sex and age balance and create stress in resident groups.

Recently, there have been many discussions about the need to resume the hunting of sea mammals in order to regulate their growing populations, which are causing the imbalance of marine ecosystems because of high consumption of fish and competition for resources with humans. However, fish consumption by mammals has not been studied. We have not heard of any research on the potential capacity of ecosystems for sea mammals in Russia. The structure and numerical growth, not only of separate groups but even whole populations of belugas and other sea mammals, have not been analysed. The beluga populations that were once hunted are likely to recover gradually. However, some of them may find it hard to recover their initial structure and strength due to climate change, anthropogenic activities, diseases and other factors. The absence of reliable counts over many years often makes it impossible to determine the dynamics of reproduction.

Comprehensive studies of the populations of sea mammals and monitoring of their use are still outstanding issues. It is necessary to elaborate and enforce standard methods of rational management of these resources.

The review of research and ensuing recommendations for one beluga aggregation in the Sea of Okhotsk illustrate a potential approach to the sustainable use of resource types of marine mammals.