Phocoena phocoena ssp. relicta
|Scientific Name:||Phocoena phocoena ssp. relicta Abel, 1905|
Phocoena phocoena (Linnaeus, 1758) ssp. (Black Sea subpopulation)
|Red List Category & Criteria:||Endangered A1d+4cde ver 3.1|
|Assessor(s):||Birkun Jr., A.A. & Frantzis, A.|
|Reviewer(s):||Brownell Jr., R.L. & Rojas-Bracho, L. (Cetacean Red List Authority)|
The Black Sea Harbour Porpoise, P. p. relicta, qualifies for listing as Endangered (EN) based on criteria A1d and A4cde. The basis for inferences and suspicions leading to that assessment is summarised below.
The estimated generation time is 8-12 years (depending on population status), thus three generations for the Black Sea Harbour Porpoises (using the natural, or pre-disturbance, value of 12) would be 36 years, or 1972-2007.
There are no estimates of unexploited or present total population size, although the available information suggests that present population size is at least several thousands and possibly in the low tens of thousands.
The following information from the last three decades is relevant to the proposed classification. However, it is important to note that very high levels of direct and incidental mortality occurred for a long period before then (from the 1830s and throughout the 20th century) and this undoubtedly would have dramatically reduced the population prior to the 1970s (IWC 2004).
(1) Large directed takes occurred during the years 1976-1983 before the ban on small cetacean hunting was declared in Turkey in 1983. Within that period, the total number of harbour porpoises killed was at least 163,000-211,000. Illegal direct killing of unknown numbers continued in some parts of the Black Sea until 1991.
(2) Regionally extensive incidental mortality of porpoises in bottom-set gillnets is roughly estimated to have been in the thousands annually through the 1980s. The scale of this mortality almost certainly increased in the 1990s-2000s owing to the rapid expansion of illegal, unreported and unregulated fishing in the Black Sea.
(3) A major mass mortality event occurred in the Azov Sea in August 1982 as a result of an explosion at a gas-extraction platform. More than 2,000 porpoises were found on shore following this event.
(4) Two other mass mortality events occurred in 1989 and 1990, attributed to the combined effects of parasitic and bacterial infections. Although difficult to quantify, the mortality of porpoises is believed to have been in the thousands.
(5) Periodically (most recently in November 1993), natural mass mortality events occur as a result of ice entrapment in the Azov Sea. Although no direct estimates are available, these can result in the deaths of several tens or more animals.
(6) There has been general and ongoing degradation of the Black Sea environment (including harbour porpoise habitat) and biodiversity during the 1970s-2000s, with perhaps the most serious period in the late 1980s–early 1990s due to a combination of overfishing, water pollution, eutrophication, demersal fish die-offs caused by hypoxia and the population explosion of harmful alien species. This degradation almost certainly has resulted in a decline in the abundance and quality of Harbour Porpoise prey.
EN: A1d. A reduction in population size of 70% over the past 30 years (see note at end of paragraph) is inferred based on paragraphs (1) and (3) above, i.e. the directed takes and, to a lesser degree, the accident in 1982 (considered ‘actual exploitation’ in the context of IUCN Red List Criteria). These causes were clearly reversible and understood and they have ceased. Despite the absence of abundance estimates for the initial part of the 30-year period, the suspected decline of 70% is based on inferences from a crude extrapolation based on the annual removal levels in the Turkish fishery: a reduction of 70% implies that the population in 1976 must have been at least 233,000-302,000, whereas a reduction of 50% (threshold for Vulnerable) would require a population size of at least 326,000-422,000. The latter seems unrealistic given the duration and intensity of past exploitation. [Note: The numerical analyses were conducted at the Monaco workshop in 2006 and were based on an assumed generation time of 10 rather than 12 years, thus using a 30-year (1976-2006) rather than 36-year interval for three generations.]
EN: A4cde. A reduction in population size of 50% over a 30-year period that includes both the past and the future is inferred based on the above paragraphs except (1) and (3). During this period, although direct killing has ceased, the other known or suspected causes of decline (bycatch, habitat degradation, prey depletion, epizootics and adverse climatic circumstances) have not ceased.
|Previously published Red List assessments:|
The subspecies’ range includes the Black Sea proper, Azov Sea, Kerch Strait (e.g., Tzalkin 1938), Marmara Sea, Bosphorus Strait (Öztürk and Öztürk 1997), northern Aegean Sea (Frantzis et al. 2001) and also, very likely, the Dardanelles Straits (Harun Guclusoy 2006, pers. comm. to Frantzis) connecting the Marmara and northern Aegean Seas (see Figure 1 in Supplementary Material). The Black Sea population is completely isolated from the nearest P. phocoena population in the northeastern Atlantic by a wide range hiatus in the Mediterranean Sea (Frantzis et al. 2001). Although there is no agreement on when it happened (Kleinenberg 1956, Frantzis et al. 2001), it is clear that Harbour Porpoises came to the Black Sea via the Mediterranean which, therefore, must have had its own population in the past.
The range of the Black Sea subspecies includes territorial waters and exclusive economic zones of Bulgaria, Georgia, Romania, Russia, Turkey and Ukraine in the Black Sea; internal waters of Ukraine in the Black Sea (including the Dnieper-and-Boug Liman and Karkinitsky Bay); internal waters of Russia and Ukraine in the Azov Sea and Kerch Strait; internal waters of Turkey (TSS, including the Bosphorus Strait, Marmara Sea and, possibly, the Dardanelles); Greek territorial waters in the northern Aegean Sea (Thracian Sea, Kavala Gulf, Strymonikos Gulf, Agiou Orous Gulf, and Thermaikos Gulf); and possibly Turkish territorial waters of the northeastern Aegean Sea, at the exit of the Dardanelles Straits. Occasionally, Harbour Porpoises have been sighted in the Danube, Dnieper, Don and Kuban rivers, their estuaries, deltas and tributaries (e.g., in the Danube in 1984-1989 and 2003 or in the Ingulets, a confluent of the Dnieper, in 1999), and coastal freshwater, brackish and saline lakes and lagoons including the Yalpug and Sivash lakes, Berezansky and Grigorievsky lagoons, Tendrovsky, Yagorlytsky and Jarylgachsky bays, and the Gulf of Taganrog (Tzalkin 1940a, Geptner et al. 1976, Birkun 2006). All of these sites are situated in Ukraine and Russia, on the northern and northwestern coasts of the Black Sea and round the Azov Sea.
The population of P. p. relicta may consist of three or more subpopulations including those that spend much of the year in geographically and ecologically different areas, e.g. the Azov Sea, northwestern Black Sea and Sea of Marmara. The Bosporus Straits, the Sea of Marmara and the Dardanelles Straits serve as conduits between the Black and Aegean Seas. Water flow at the surface is into the Aegean, from the Black Sea (Poulos et al. 1997). If porpoises were to leave the Black Sea, the conditions in the northern Aegean Sea (as compared to other parts of the Mediterranean) would remain similar to those of the Black Sea. The period of greatest similarity would be February and March (Poulos et al. 1997) and five out of the nine records from the Aegean occurred from mid January to the end of March (three were in summer and one in October; all age classes have been found in the small available sample). Further work is needed to determine whether the animals found in the northern Aegean Sea represent a separate resident subpopulation.
[Definition: Territorial waters of all six Black Sea countries are defined as consisting of the 12-mile-wide submerged strip along the coast, and the offshore border of this strip constitutes the marine boundary for each country. In areas where the sea extends inland (gulfs, bays, etc.), the 12-mile rule does not apply. These water bodies constitute the so-called “internal (marine) waters” of the Black Sea countries.]
Native:Bulgaria; Georgia; Romania; Russian Federation; Turkey; Ukraine
|FAO Marine Fishing Areas:|
Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
Total population size is unknown and therefore a synoptic region-wide survey is essential. Past Black Sea region-wide estimates based on strip transect surveys carried out in the USSR (1967-1974; Zemsky and Yablokov 1974) and Turkey (1987; Çelikkale et al. 1989) have been shown to be fundamentally flawed for a number of methodological and analytical reasons, making their use as indicators of absolute abundance unwarranted (e.g., IWC 1992, Buckland et al. 1992). Consideration needs to be given as to whether, despite the identified problems, any of the data from those earlier surveys can be used in comparisons with data from future well-designed surveys to infer population change. Other estimates also suffered from inadequacies of survey design, record keeping and statistical analysis. Nevertheless, it was generally recognized (e.g., Tzalkin 1940, Kleinenberg 1956, Geptner et al. 1976, Yaskin and Yukhov 1997) that during most of the 20th century, the abundance of Harbour Porpoises in the Black Sea was higher than that of Bottlenose Dolphins (Tursiops truncatus ponticus) and lower than that of Common Dolphins (Delphinus delphis ponticus).
Line transect surveys have been conducted recently to estimate Harbour Porpoise abundance in different parts of the range. In particular, aerial surveys were conducted in the Azov Sea, Kerch Strait (2001, 2002) and northeastern shelf area of the Black Sea (2002); vessel-based surveys were performed in the Kerch Strait, the entire 12-mile-wide zone of the Ukrainian and Russian Black Sea (2003), Georgian territorial sea (2005), and central part of the Black Sea between the Crimea peninsula, Ukraine, and Sinop province of Turkey (September–October 2005). Results of those surveys (see Table 1 in the Supplementary Material, see below) suggest that present total population size is at least several thousands and possibly in the low tens of thousands.
In the 20th century, the number of Black Sea Harbour Porpoises was dramatically reduced by massive direct killing for the cetacean-processing industry that continued until 1983 (e.g. Smith 1982, IWC 2004). The numbers of animals taken were not recorded accurately; much of the catch data was recorded as numbers of animals undifferentiated to species (all three Black Sea small cetacean species were targeted) and by wet weight aggregates (e.g. pounds or tons of dolphin/porpoise landed). However, it can be inferred that the population size of P. p. relicta was reduced due to the direct kills (totalling some hundreds of thousands) by the time the total ban on dolphin hunting was enforced in the Black Sea region (see section “Threats”). It is strongly suspected that during the subsequent period from 1983-2006, not only did the population not recover but it declined markedly, primarily due to large-scale mortality in bottom-set gillnets (Birkun 2002a). In addition, there are other ongoing threats including human-induced habitat degradation (see “Threats” below). These threats are poorly managed in most Black Sea countries and therefore further decline of the population seems likely. It is also important to consider the effect on population trends of the mass-mortality events mentioned elsewhere in this assessment (gas platform explosion in 1982, die-off from ice conditions in 1993 and the two events in 1989 and 1990 possibly related to parasitic and bacterial infections).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
Harbour Porpoises inhabit mainly shallow waters (0–200 m deep) over the continental shelf around the entire perimeter of the Black Sea, although they also occur quite far offshore in deep water. For instance, in late September – early October 2005, sizeable groups were observed in the central Black Sea, beyond the shelf edge some 38–215 km from the nearest coast in waters 450–2,170 m deep (Krivokhizhin et al. 2006). During warm periods they occur in the Azov Sea and Kerch Strait (Tzalkin 1940a; Kleinenberg 1956; Birkun et al. 2002) and in the Marmara Sea and Bosphorus (Öztürk and Öztürk 1997). Both of these small seas (as well as the northwestern Black Sea shelf zone) may represent geographically disjunct breeding-calving-feeding areas while the straits (Kerch and Bosphorus) connecting the seas serve as migration corridors.
Harbour Porpoises undertake annual migrations, leaving the Azov Sea (Tzalkin 1938) and northwestern Black Sea (Birkun 2006) before winter and returning in spring. Such movements also may occur between the Black Sea and Marmara Sea; in the latter (along with the Bosphorus) there are no records for January-March (Öztürk and Öztürk 1997). The primary wintering areas are in the southeastern Black Sea (Birkun et al. 2006) including southern Georgian territorial waters and (perhaps) eastern Turkish territorial waters. These are also the well-known wintering grounds of Black Sea and Azov Sea populations of the Anchovy (Engraulis encrasicolus ponticus) – a principal prey species for Harbour Porpoises during the cold season (Kleinenberg 1956). Most of the Black Sea porpoise population may congregate there every year. In January 2005 the density estimated for Georgian waters was 1.5 porpoises per km2 ( Birkun et al. 2006), i.e. 6–39 times higher than densities reported for any other Black/Azov Sea area surveyed in summer or autumn.
The mean group size varies from 1.4 to 7.7 in different areas (Birkun et al. 2002, 2003, 2004; Krivokhizhin et al. 2006) although during their seasonal migration, animals may remain for a few days at different sites (usually bays with abundant fish) forming dense aggregations of some hundreds of individuals, e.g. off the southern coast of Crimea in December-January 1994 (Laspi Bay), March 1995 (near Cape Meganom) and April 2005 (between Cape Aya and Cape Fiolent) (Birkun and Krivokhizhin unpublished data). Sometimes, early and rapid ice formation, arising immediately after an “Indian summer”, can prevent animals leaving the Azov Sea and cause mass mortality due to ice entrapment (Kleinenberg 1956). The last recorded die-off of this kind occurred in November 1993 (Birkun and Krivokhizhin 1997); the number of animals could not be estimated. Black Sea harbour porpoises do not avoid waters with low salinity and high turbidity; they may occur in brackish bays and lagoons, and visit rivers and estuaries (all records occurring at warm times of the year).
The ecology of Black Sea Harbour Porpoises may be considered unusual. It reflects the high degree of geographical isolation of their habitat, relatively low water salinity, significant seasonal fluctuations of water temperature, and large amount of anoxic waters saturated with hydrogen sulphide, H2S, below 100-250 m. At least 14 fish species have been recorded in the stomach contents (Tzalkin 1940, Kleinenberg 1956, Tomilin 1957, Tonay and Öz 1999, Krivokhizhin et al. 2000, Birkun 2006), of which four are considered as the most important prey: Anchovy, Sprat (Sprattus sprattus phalaericus), Whiting (Merlangius merlangus euxinus) and gobies (Gobiidae)
|Movement patterns:||Full Migrant|
Until 1983, unregulated hunting was the primary threat (IWC 1992, 2004). Very large numbers of harbour porpoises, as well as other cetaceans, were taken during the 20th century by all Black Sea countries for a variety of industrial uses (Kleinenberg 1956, Tomilin 1957). Although the total number killed is unknown, it may have been as many as four or five million for all species combined (e.g. see review in Smith 1982). It is widely accepted that all Black Sea cetacean populations, including Harbour Porpoises, were badly reduced by the directed fishery (IWC 1983, 1992, 2004). Catches of Harbour Porpoises were numerically fewer than those of Common Dolphins until 1964 when Harbour Porpoises became predominant (Danilevsky and Tyutyunnikov 1968, Smith 1982). Berkes (1977) reported that in Turkey, approximately 4,400 tons (4,400,000 kg) of cetaceans (all three species combined) were processed annually from 1971-73. He assumed an average weight per carcass of 50 kg (unspecified to species). Importantly, Berkes noted that shooting (the predominant method of dolphin killing in Turkey) could result in about half of the killed animals being lost due to sinking. If, following Berkes, one supposes that in the early 1970s the annual total of removals by the Turkish fishery amounted to 8,800,000 kg (including both processed and lost carcasses), or up to 176,000 animals of which 50% were Harbour Porpoises, this would imply at least 88,000 killed per year (of which 44,000 were landed). These very crude calculations suggest that Turkish catches of Harbour Porpoises in the early 1970s were at least as high as, and possibly much higher than, those estimated for 1976-1981 (34,000-44,000 per year according to IWC, 1983, assuming that harbour porpoises accounted for 80% of the total). At least since 1991, there has been no evidence of illegal directed takes although such takes had been reported before that time (IWC 1992).
At present, incidental mortality in fishing nets is the most serious threat (e.g., Birkun 2002a). Although all three Black Sea cetacean species are 'bycaught', the majority (95%) of recorded cetacean entanglements are of porpoises. Unfortunately, absolute numbers of removals cannot be estimated from the available data. However, there are indications that the annual level of Harbour Porpoise bycatch may be in the thousands. Almost all (99%) of the porpoises are caught in bottom-set gillnets for Turbot (Psetta maeotica), Spiny Dogfish (Squalus acanthias) and sturgeon (Acipenser spp.). The peak occurs from April–June during the Turbot season in the Azov Sea and Kerch Strait and throughout the shelf area of the Black Sea, including territorial waters of all six riparian countries. Almost all (99.9%) recorded bycatches are lethal (BLASDOL 1999). Illegal, unreported or unregulated fishing is widespread in the Black and Azov Seas and a significant proportion of the bycatch may occur in such operations.
An explosion at a gas-drilling platform in the Azov Sea in August 1982 resulted in the deaths of over 2,000 porpoises (Birkun 2002b).
Large-scale pelagic and small-scale coastal fisheries may affect Black Sea harbour porpoises indirectly by reducing their prey populations and degrading their habitat. Primarily, this relates to anchovies and sprats in the Black Sea and gobies in the Azov Sea. In particular, overfishing, eutrophication and the population explosion of an introduced predator, the ctenophore Mnemiopsis leidyi, led to a dramatic (8 to 12-fold) decline of sprat and anchovy abundance in the early 1990s (Prodanov et al. 1997). This reduced prey availability coincided with two mass mortality events (in 1989 and 1990) that, although they affected all three cetacean species, primarily affected porpoises (Birkun 2002c). Severe pulmonary nematodosis, caused by Halocercus spp. and complicated by bacterial super-infection, was recognized as a primary cause of the deaths, which were mainly of young animals. For other species, it has been hypothesised that malnutrition along with immuno-suppression associated with PCB contamination provokes or intensifies the effects of epizootics (e.g. Mediterranean Striped Dolphins; Aguilar and Borrell, 1994). Reported levels of DDTs and HCHs in Black Sea Harbour Porpoises are higher than those in conspecifics elsewhere in the world (Tanabe et al. 1997). Chemical pollution is thus also a potential threat, particularly in the context of epizootics.
Black Sea Harbour Porpoises are also affected in some years by ice entrapment in the Azov Sea (see section “Habitats and Ecology”).
The Black Sea population of Harbour Porpoises has been listed as Vulnerable in the IUCN Red List of Threatened Animals since 1996.
Commercial hunting of Black Sea cetaceans, including Harbour Porpoises, was banned in 1966 in the former USSR (present Georgia, Russia and Ukraine), Bulgaria and Romania, and in 1983 in Turkey. The riparian states assumed international obligations to protect Black Sea cetaceans as contracting parties of the Convention on Biological Diversity (CBD), Convention on the Conservation of Migratory Species of Wild Animals (CMS), Convention on the Conservation of European Wildlife and Natural Habitats (Berne Convention), Convention on the Protection of the Black Sea Against Pollution (Bucharest Convention), Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES, Appendix II), and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS). The Harbour Porpoise, P. phocoena, is mentioned in Annex II of the EC Directive No.92/43/EEC on the conservation of natural habitats of wild fauna and flora. In 1996, the Ministers of Environment of Black Sea countries adopted cetacean conservation and research measures within the framework of the Strategic Action Plan for the Rehabilitation and Protection of the Black Sea (paragraph 62). The Harbour Porpoise is included as Data Deficient in the regional Black Sea Red Data Book (1999). However, in 2002 it was listed as Endangered in the Provisional List of Species of the Black Sea Importance, an annex to the Black Sea Biodiversity and Landscape Conservation Protocol of the Bucharest Convention.
On a national level, Black Sea cetaceans, including harbour porpoises, are protected by environmental laws, governmental decrees and national Red Data Book listings. The harbour porpoise is listed in the Red Data Books of Bulgaria, Russia and Ukraine, which do not use the IUCN categories and criteria. In Russia and Ukraine, inscription in national Red Data Books means that the species should be monitored and managed by appropriate state/national programmes. Such a programme has existed in Ukraine since 1999 (the Delfin-programme adopted by the Ministry of Environment). Action plans for the conservation of Black Sea cetaceans were produced in Ukraine (2001) and Romania (2003) but they have no legal effect. In 2003-05 nine coastal protected areas were joined to form the Ukrainian National Network for Cetacean Conservation, an informal network consisting of 19 institutions (operational units) situated in 17 localities along the seaboard of Ukraine. Those protected areas are (from west to east): the Dunaisky [Danube] Biosphere Reserve, Chernomorsky (Black Sea) Biosphere Reserve, Swan Islands Branch of the Crimean Nature Reserve, Cape Martyan Nature Reserve, Karadag Nature Reserve, Opuk Nature Reserve, Kazantip Nature Reserve, Azov and Sivash National Park, and Meotida Landscape Park. The inventory of cetacean habitats has been completed and a common methodology for cetacean monitoring has been introduced in these protected areas. The ACCOBAMS Implementation Priorities for 2002-06 (Notarbartolo di Sciara 2002) envisage the development of a pilot conservation and management project in the well-defined area between Cape Sarych and Cape Khersones, southern Crimea (Ukraine).
|Citation:||Birkun Jr., A.A. & Frantzis, A. 2008. Phocoena phocoena ssp. relicta. The IUCN Red List of Threatened Species 2008: e.T17030A6737111.Downloaded on 23 September 2018.|
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