BSEP116B Biodiversity in the Baltic Sea - Helcom

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6 HUMAN PRESSURES ON BIODIVERSITY A human population of approximately 85 million people lives in the catchment or drainage area of the Baltic Sea. A great number of different types of human activities taking place in the catchment area, coastal zone, and open sea exert pressures on Baltic Sea biodiversity. Some pressures act on a local scale, while others act at basin-wide scales. For example, dredging may have a local and short-term impact, while eutrophication affects vast areas and is long lasting. Similarly, certain pressures act at the level of species, while others have an impact at the greater landscape level of biodiversity (Figure 6.1). Many of the pressures also cause synergistic effects, whereby the negative impact of one pressure is exacerbated by another. This chapter addresses the magnitude and impact of different pressures originating from various economic sectors. It mainly covers human activities that are directly associated with the Baltic Sea and that exert multiple pressures on biodiversity, namely, fisheries, maritime traffic, technical installations, and recreational activities. In addition, the chapter provides an overview of the magnitude and known impact of eutrophication, hazardous substances, alien species, noise, and hunting. Projected changes in climate caused by anthropogenic factors are also presented as a case of anticipated future pressure. Pressures addressed in this chapter include the predominant pressures and impacts on Baltic Sea biodiversity. They also largely cover the pressures and impacts listed in Annex III, Table 2 of the EU Marine Strategy Framework Directive (MSFD). 6.1 Fisheries Fisheries have been an important source of livelihood for people of the Baltic countries for centuries. There is archaeological evidence suggesting that fishing was conducted along the Baltic coasts already since before the Middle Ages (e.g., Makowiecki & van Neer 1996). However, the magnitude of landings and fishing effort is mostly documented for the 20th century, while information on the stock status of the eastern Baltic cod population dates back to the 1920s (Eero 2008) and for herring and sprat only to the 1970s (ICES 2008b). There is increasing evidence that fisheries have a substantial impact on the biodiversity and function of the entire Baltic ecosystem. This extends from key abiotic parameters to the upper trophic levels of the food web. The biodiversity segment of the Baltic Sea Action Plan (BSAP) includes a large number of actions targeted to fisheries; in fact, the number of measures related to fisheries in the biodiversity segment is larger than that related to any other human activity. Moreover, the BSAP specifically includes a recommendation to implement the ecosystem approach to fisheries management in the Baltic Sea. Fishing and Fisheries Constructions Eutrophication Physical Environment Communities Species (Genes) and and Hazardous substances Biotopes Water quality Climate Change 6.1.1 Description of fisheries Cod (Gadus morhua callarias), herring (Clupea harengus membras), sprat (Sprattus sprattus) and salmon (Salmo salar) are the most important internationally assessed and managed fish stocks in the Baltic Sea. Most other fish species are mainly of local importance and are therefore managed nationally and/or locally. The assessment and management units of the internationally assessed species are provided in Figure 6.1.1. 92 Hunting Alien Species Maritime Traffic Oil Spills Figure 6.1. Human pressures in the Baltic Sea region act on different levels and scales of biodiversity. Pelagic trawls dominate in the herring and sprat fishery. Usually the catch consists of a mixture of these two species, while their proportion in the catch varies by area and season. Herring is also caught by trapnets/pound-nets and gillnets in coastal areas as well as with bottom trawls. In
addition to clupeids, vendace (Coregonus albula) is caught by pelagic trawls in the northern part of the Bothnian Bay. Cod is mostly caught by demersal trawls, pelagic trawls and gillnets. The importance of longlines has increased recently in cod fisheries at the expense of the gillnet fishery (ICES 2008b). While feeding in the sea, salmon are caught by longlines; during the spawning migration they are caught along the coast, mainly in trapnets and fixed gillnets. The use of drift nets was very important in the salmon fishery up to 2008. In river mouths, set gillnets and trapnets are used (ICES 2008b). A detailed description of the current fisheries by country, sub-basin, and stock is given in ICES (2008b,c). The list of other, mostly locally important, commercial fish includes species such as pikeperch (Sander lucioperca), pike (Esox lucius), perch (Perca fluviatilis), vendace, whitefish (Coregonus lavaretus), burbot (Lota lota) and eel (Anguilla anguilla). Coastal fishing activities take place along the entire coastline of the Baltic Sea. The coastal fishery is usually a mixed fishery. As trawling is prohibited in the coastal zone (shallower than 20 m) in most of the countries, gears used in coastal fisheries include fixed gears (e.g., gill-, pound- and trapnets, and weirs) and Danish seines. The selection of gear depends on the target fish and also on coastal morphology. Although all Baltic countries keep their own national statistics, there are only estimates available on the total coastal fish landings in the Baltic Sea; these amount to about 50 000 tonnes (Lindquist 2001). Figure 6.1.1. Baltic Sea subdivisions of the International Council for the Exploration of the Sea (ICES). Assessment and management units of the main fish species are: Herring: the main Basin (including Gulf of Finland; ICES subdivisions 25–29 and 32; excluding Gulf of Riga); Bothnian Bay (SD 31), Bothnian Sea (SD 30) and Gulf of Riga (SD 28.1); Cod: eastern (SD 25–32) and western (SD 22–24) stocks; Sprat: one single stock (SD 22–32); and Salmon: Main Basin and Gulf of Bothnia stocks (including the following separate assessment units: Northeastern Bothnian Bay; Western Bothnian Bay; Bothnian Sea, Western Main Basin, Eastern Main Basin) (SD 22–31) and Gulf of Finland (SD 32). Baltic herring trawling, Bothnian Bay. Trends in landings Of the major commercial fish stocks, the eastern Baltic cod landings peaked in the 1980s (over 300 000 tonnes annually); they subsequently declined and have remained at very low levels during the past 15 years (the last 5-year mean was ca. 65 000 tonnes). Landings of the western cod exceeded 50 000 tonnes annually from the 1960s until the early 1980s, but have amounted on average to only half of this during the past five years. At the same time, sprat landings substantially increased from less than 50 000 tonnes during the mid-1980s to over 350 000 tonnes recently. The stock of herring in the main basin (including the Gulf of Finland) has steadily decreased from 300 000 tonnes in the late 1970s 93
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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
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• A coherent data set on benthic
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Denmark Estonia Finland Germany Lat
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Mud-sandflat, Greifswald Lagoon, Ge
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3 COMMUNITIES Communities are assem
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32 Spring bloom index 1200 1000 800
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34 Unusual events and new species i
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36 Depth limit (m) the Gulf of Both
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Number of species 16 14 12 10 8 6 4
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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 76 and 77: predation on nests and nesting adul
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 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
Page 126 and 127: munities that formerly consisted of
Page 128 and 129: 6.8.2 Activities generating noise i
Page 130 and 131: 128 and fish in the Baltic Sea area
Page 132 and 133: 800 700 600 bag of the two German B
Page 134 and 135: Fish swarm on kelp (Laminaria sp.)
Page 136 and 137: tion of ice cover, either through r
Page 138 and 139: 7 STATUS OF THE NETWORK OF MARINE A
Page 140 and 141: Box 7.1. Natura 2000 network of pro
Page 142 and 143: 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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