BSEP116B Biodiversity in the Baltic Sea - Helcom

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predation on nests and nesting adults, predation by white-tailed eagles on nesting adults may affect the number of breeding pairs in some colonies. The total number of barnacle geese in the Baltic is currently estimated at about 25 000 individuals. Reproductive success, measured as the number of fledged young per pair, has been shown to be density-dependent and variable among years (Larsson & Forslund 1994). The amount of high-quality grass available around the colonies for newly hatched chicks in May and June, as well as predation by gulls, determines the production of fledged young. Annual survival rates of adults and fledged young are high. Only limited hunting is permitted in the Baltic region. Many, but not all, large colonies of barnacle geese on Gotland and Öland are situated within protected areas. The colonies in Finland, Estonia, mainland Sweden, Denmark, and Germany range in size from a few pairs to several hundred pairs (Leito 1996, Mortensen & Hansen 1999, SOF 2006, Koop 1998, Mikkola-Roos et al. 2008). Some of the latter colonies have probably been founded by birds of captive origin. However, birds from such colonies usually cannot be distinguished from other birds. Eider (Somateria mollissima) The main breeding areas of the eider in the Baltic Sea are Sweden (270 000–360 000 breeding females, bf, in 1999/2000), Finland (80 000–100 000 bf in 2007), Denmark (25 000 bf 1990–2000), and Estonia (15 000 bf in 1995) (BirdLife International 2004, Desholm et al. 2002, Hario & Rintala 2008). The species also occurs in small numbers in the Russian part of the Gulf of Finland (70–80 bf) and at the German Baltic coast (80–100 bf in 2008). The eider does not breed, or breeds only exceptionally, in Poland, Lithuania, Latvia, and the Kaliningrad region of Russia. The eider population showed a strong long-term increase throughout the 20th century. Simultaneously, it extended its breeding range southwards to the German Baltic coast, where the first breeding was recorded in 1985. However, since the late 1990s, stagnant or even strongly declining population trends have been observed in several countries (Denmark, Sweden, Finland, Estonia; Desholm et al. 2002, Elts et al. 2008, Figure 4.3.5). In Finland, the eider is currently the most rapidly declining seabird species, dropping down from 150 000–180 000 bf in 2001 to only 80 000–100 000 bf in 2007 (Hario & Rintala 2008). This decline is true not only for the Baltic breeding population, but also for the Baltic/Wadden Sea flyway population as a whole. Mid-winter counts suggest that the total population may have fallen from 1.2 million birds in 1991 to 760 000 in 2000, which is a reduction of 36% (Desholm et al. 2002) 5. Although reductions are evident for several breeding areas, the decline of the breeding population along the flyway seems to be less pronounced compared to the winter population. Shortcomings in the monitoring of breeding and wintering numbers, as well as an unknown buffering effect of non-breeders, are probably the reasons for the difference (Desholm at al. 2002). Breeding females 25000 20000 15000 10000 5000 Denmark Estonia The recent population development may be influenced by several factors, among them hunting, predation by mink and white-tailed eagle, bacterial and viral infections, parasite infestations, drowning in fishing gear, and oiling. Low reproductive success and high mortality of ducklings have been reported from several breeding areas in the most recent years. However, several of the factors mentioned above affected the population already in 74 0 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 4.3.5. Development of the eider population in Denmark and Estonia during the 20th century. Data from Desholm et al. (2002), Lyngs (2000 and unpublished), and Elts et al. (2008). 5 These population numbers are probably underestimates because they reflect the counted numbers without any attempt to correct for birds that have not been seen. Noer et al. (1995) estimated a population size of 1.5–2.0 million birds in 1990. However, the estimated decrease of approximately 30%, giving a total population of about 1.0–1.2 million birds in 2000, seems to be realistic (Noer, pers. comm.).
7000 6000 Lithuania Estonia Finland 5000 4000 3000 2000 1000 0 1994 1995 1996 1997 1998 1999 Number of individuals 2000 2001 2002 2003 2004 2005 2006 2007 Winter season (January) Figure 4.3.6. Numbers of wintering Steller’s eiders in Estonia and Lithuania, and migrating birds at Hanko-Helsinki, Finland. the past, when the number of eiders in the Baltic was still increasing, and some impacts, such as hunting, used to be even higher than today. The eider is still hunted in several Baltic countries, e.g., Denmark, Sweden, and Finland (see Chapter 6, Hunting). The presence of American minks has caused substantial decreases of breeding bird numbers in those areas where minks reach high densities (e.g., Stockholm archipelago). Furthermore, minks force the eiders to change their nesting habitats, moving from bushy islets to gull colonies or solitary nesting gulls. In 1996 and 2001, outbreaks of avian cholera (caused by the bacteria Pasteurella multocida) affected the population. In Finland in 1996 and 1999, viral infections caused mass mortality among ducklings within the first weeks after hatch. Intestinal acanthocephalan parasite infestation is high among eiders and may have an impact in association with other predisposing factors, such as impaired feeding ability or virus infections (Desholm et al. 2002). Drowning in stationary fishing gear is also an important mortality factor, at least in some wintering areas (I.L.N. & IfAÖ 2005). Steller’s eider (Polysticta stelleri) Steller’s eider is one of the rarest sea duck species, identified as ‘vulnerable’ by the IUCN Red List of Threatened Species. The species nests in Arctic tundra, with the bulk of the Western Palearctic population wintering along the Kola Peninsula and in Varangerfjord in the Barents Sea. A significant proportion of the regional population (10–20%) also winters regularly in the Baltic Sea. Winter distribution in the Baltic is restricted to very few areas: around Saaremaa and Hiiumaa Islands in Estonia, Lithuanian coastal waters off Palanga, and Lågskär Archipelago in Finland. Sightings of Steller’s eiders are also regularly reported from Swedish and Latvian coastal waters. Steller’s eiders were very rare in the Baltic Sea from the beginning of the 20th century until the early 1960s. Then, numbers of Steller’s eiders wintering in the Baltic increased steadily until the mid-1990s (Nygård et al. 1995). This period was followed by a rapid decline of bird abundance across all wintering sites (Žydelis et al. 2006). Peak numbers reaching 5 000 wintering individuals in Estonia and 2 000 in Lithuania dropped to lows of 1 500 and 90, respectively. The number of migrating birds counted in Finland generally also followed the same declining trend (Lehikoinen 2007). The number of wintering birds in Estonia, however, showed signs of increase during the most recent winters (Figure 4.3.6). The reasons for the recent decline of the Baltic wintering population of Steller’s eider are not clear. Most likely, a combination of different factors is in play, including a shift to wintering 75
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Baltic Sea Environment Proceedings
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Published by: Helsinki Commission K
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TABLE OF CONTENTS PREFACE . . . . .
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6.6 Hazardous substances . . . . .
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1 INTRODUCTION 8 1.1 An integrated
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Box 1.1. Biodiversity The term biod
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of saline water from the North Sea
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14 On a global scale, marine ecosys
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Box 1.2. Regime shifts in the Balti
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2 MARINE LANDSCAPES AND HABITATS 18
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From an ecological point of view, a
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Box 2.1.2. The Baltic marine landsc
Page 26 and 27: • A coherent data set on benthic
Page 28 and 29: Denmark Estonia Finland Germany Lat
Page 30 and 31: Mud-sandflat, Greifswald Lagoon, Ge
Page 32 and 33: 3 COMMUNITIES Communities are assem
Page 34 and 35: 32 Spring bloom index 1200 1000 800
Page 36 and 37: 34 Unusual events and new species i
Page 38 and 39: 36 Depth limit (m) the Gulf of Both
Page 40 and 41: Number of species 16 14 12 10 8 6 4
Page 42 and 43: Figure 3.2.7. Left panel shows pred
Page 44 and 45: Implications for the Baltic Sea Act
Page 46 and 47: Biomass (wet weight, mg per m 2 ) B
Page 48 and 49: the other hand, is not selected by
Page 50 and 51: iomass can be used to assess enviro
Page 52 and 53: Average number of species 20 15 10
Page 54 and 55: 52 Macoma baltica where the influen
Page 56 and 57: the total BT identified for each ma
Page 58 and 59: Recruitment (thousands) 8000000 700
Page 60 and 61: Alien species Several alien fish sp
Page 62 and 63: 4 SPECIES The number of species in
Page 64 and 65: Table 4.1.1. Results of dedicated a
Page 66 and 67: Number of stranded porpoises 180 16
Page 68 and 69: is recommended to survey harbour po
Page 70 and 71: Number of individuals 12000 10000 8
Page 72 and 73: Mean blubber thickness (mm) 40 35 3
Page 74 and 75: Breeding pairs 60000 50000 40000 30
Page 78 and 79: sites outside the Baltic, decreased
Page 80 and 81: Table 4.3.1. Development of the pop
Page 82 and 83: 80 Number of breeding pairs 3000 25
Page 84 and 85: The strategic goal of the BSAP to h
Page 86 and 87: for a given site or area. The secon
Page 88 and 89: Mussel bed reef community, Jasmund,
Page 90 and 91: Table 5.3. Assessment results of th
Page 92 and 93: Aerial photo of harbours seals (Pho
Page 94 and 95: 6 HUMAN PRESSURES ON BIODIVERSITY A
Page 96 and 97: Table 6.1.1. Catch range during the
Page 98 and 99: Baltic herring trawling, Bothnian B
Page 100 and 101: 6.1.3 Major international framework
Page 102 and 103: 100 Oil turnover (millions of tonne
Page 104 and 105: NOx emissions and sewage Macrophyte
Page 106 and 107: Communication links There are a num
Page 108 and 109: Figure 6.3.3. Left: concrete-stone
Page 110 and 111: ecommendations would contribute to
Page 112 and 113: Tourist fishing 110 cial fishery fo
Page 114 and 115: 112 Figure 6.5.1. Integrated classi
Page 116 and 117: can be considered as having been a
Page 118 and 119: Although no direct, dramatic mass m
Page 120 and 121: Bearing in mind the complex hydrogr
Page 122 and 123: Box 6.7.1. Invasion status of the B
Page 124 and 125: Table 6.7.1. Examples of ecological
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munities that formerly consisted of
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6.8.2 Activities generating noise i
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128 and fish in the Baltic Sea area
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800 700 600 bag of the two German B
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Fish swarm on kelp (Laminaria sp.)
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tion of ice cover, either through r
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7 STATUS OF THE NETWORK OF MARINE A
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Box 7.1. Natura 2000 network of pro
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25 20 on how the criteria on ecolog
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estrial, nearshore marine, and offs
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144 >30 psu 18-30 psu 11-18 psu 7.5
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Permission needed Restricted Forbid
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Figure 7.8.a. MARXAN ’best portfo
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The BSPA network is relatively well
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Mammals. Among the mammals, the pop
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154 taxonomic groups and communitie
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156 provided by an ecosystem. Use o
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158 Reduction of human pressures Wh
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160 fishing on fish population dyna
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162 Baden, S., Boström, C. (2001).
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164 Season 2001-2002. Acta Zoologic
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166 Gasiūnaitė, Z.R., Cardoso, A.
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168 HELCOM & OSPAR (2003): Joint HE
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170 ICES (2008c). Report of the Bal
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172 area: density-dependent effects
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174 Noer, H., Clausager, I., Asferg
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176 Scheffer M., Carpenter S.R., Fo
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178 by passive acoustic monitoring.
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180 Warzaw, Poland Vilhunen, Jarmo,
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182 6.7 Alien speices Authors: Lepp
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ANNEX III: CONSERVATION STATUS OF T
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ANNEX IV: HABITAT OR SPECIES DISTRI
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ANNEX V: STATUS OF BREEDING AND WIN
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BSEP116B Biodiversity in the Baltic Sea - Helcom

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