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Prospects and opportunities for mussel Mytilus trossulus farming in the southern Baltic Sea (the Gulf of Gdańsk)


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Figure 1

Location of the mussel farms in the Baltic Sea (based on the original map of de Grunt 2019, GIS data: © EuroGeographics for the administrative boundaries; Laboratory of GIS, University of Gdansk for the contour of the Baltic Sea).
Location of the mussel farms in the Baltic Sea (based on the original map of de Grunt 2019, GIS data: © EuroGeographics for the administrative boundaries; Laboratory of GIS, University of Gdansk for the contour of the Baltic Sea).

Figure 2

Location of the experimental mussel farming sites in the Gulf of Gdańsk (source: Sami Alias 2014, modified). Dashed line border of Puck Bay within the gulf.
Location of the experimental mussel farming sites in the Gulf of Gdańsk (source: Sami Alias 2014, modified). Dashed line border of Puck Bay within the gulf.

Figure 3

Diagram of the mussel farming structure in the Gulf of Gdańsk.
Diagram of the mussel farming structure in the Gulf of Gdańsk.

Figure 4

Culture ropes at the MEC site in Puck Bay after two years of exposure.
Culture ropes at the MEC site in Puck Bay after two years of exposure.

Figure 5

Culture ropes after four (a) and 12 months of exposure (b).
Culture ropes after four (a) and 12 months of exposure (b).

Figure 6

Wet biomass, i.e. soft tissue and shell (a) and mean shell length of cultured mussels (b) after different growing periods in the coastal zone of various regions of the Baltic Sea. For comparative purposes, biomass data were normalized to a common unit of kg m−1 of rope, belt or net. The insert map indicates the location of the farms; source of the graph: Minnhagen (2017) based on data from: Engman (2009); Wennström & Engman (2014); Lindahl (2012); Olofsson et al. (2014); Ek Hening & Åslund (2012); Sami Alias (2014); Schröder et al. (2014); Bucefalos project (2015); Moltke Lyngsgaard et al. (2017).
Wet biomass, i.e. soft tissue and shell (a) and mean shell length of cultured mussels (b) after different growing periods in the coastal zone of various regions of the Baltic Sea. For comparative purposes, biomass data were normalized to a common unit of kg m−1 of rope, belt or net. The insert map indicates the location of the farms; source of the graph: Minnhagen (2017) based on data from: Engman (2009); Wennström & Engman (2014); Lindahl (2012); Olofsson et al. (2014); Ek Hening & Åslund (2012); Sami Alias (2014); Schröder et al. (2014); Bucefalos project (2015); Moltke Lyngsgaard et al. (2017).

Figure 7

Long-line farm system (source: https://balticbluegrowth.eu, modified).
Long-line farm system (source: https://balticbluegrowth.eu, modified).

Estimated costs (EUR) of materials (including shipping) required for one 200 m long long-line module and equipment used for mussel harvesting in the long-line system

Componentquantityprice
Polypropylene twisted rope (32 mm diameter) used as the main and anchoring lines (including provision for ties and loops)260 m491
Polypropylene braided hawser rope (32 mm diameter) used as a growing line (including provision for securing ends)2860 m6111
Polypropylene twisted rope (18 mm diameter) for tying up growing lines and buoys440 m265
Polypropylene twisted rope (6 mm diameter) to prepare loop cords for setting attachment points on the mainline220 m15
Submersible buoys with a buoyancy of 35 dm338 items970
Self-made concrete blocks (anchors) of 1.5 t (including the cost of purchasing concrete, materials to build wooden molds, reinforcing bars, stainless steel rods for line attachment loops)4 items703
TOTAL8555
Basic harvesting equipment (stripping and declumping/sorting machines)22374

Selected technical parameters of the culture module in the long-line system

Parameter
Length of supporting line/head rope200m
Length of growing rope (collector)7m
Diameter of head rope32mm
Diameter of growing rope32mm
Buoys buoyancy35dm3
Number of buoys30
Total length of growing ropes2800m

Average length (mm) and growth rate (mm year−1) of mussels on ropes as a function of exposure time, depth zone and location of mussel farming site in the Gulf of Gdańsk in 2009–2012 (Sami Alias 2014, modified)

Exposure time (year)Depth zone (m)MECGLESOP
Mean shell lengthShell growth rate*Mean shell lengthShell growth rateMean shell lengthShell growth rate
13–46.76.75.85.84.24.2
5–66.26.25.45.43.73.7
7–87.07.05.45.43.03.0
9–104.74.74.44.43.23.2
23–49.04.411.35.510.04.9
5–69.64.714.26.99.04.4
7–89.24.511.15.47.23.5
9–1012.46.010.65.19.74.7
33–47.82.613.14.3
5–611.83.98.52.8
7–87.22.413.14.3
9–109.83.27.32.4

Summary of biological parameters of mussels Mytilus trossulus harvested in the Gulf of Gdańsk and other selected Baltic areas. Technical details of the experimental set-up in the Gulf of Gdańsk are given in the text.

Parameter(this study)(Taylor et al. 2019)(Kotta et al. 2020)
Puck Bay (Gulf of Gdańsk)LimfjordenKumlinge (Åland archipelago)Sankt Anna (Östergötland archipelago)Kiel (Bay of Kiel)
farming period2009–20112017–20182010–20122016–20182011–2012
farming technologylong-linelong-linenetsspat catching ropesropes with collector bands
total wet biomass (soft tissue and shell) and SFDW (kg m−1)1.60/0.1420.72/–3.40/–2.5/–
total biomass production (wet soft tissue and shell; t ha−1)22.441.0–90.416.0*20.4*16.7*
mean content of C/N/P in SFDW** (%)48.6/9.8/1.1–/3.2–3.8*** /0.6***–/4.4*** /0.6***–/5.6–7.5*** /0.6***
content of elements in SFDW per 1 m rope (g m−1):C80.5
N16.23.723.322.3
P1.80.31.81.6
yield of elements in one t of harvested mussels (kg):C43.1–43.7
N8.3–8.713.7
P1.00.9
maximum total removal of elements (kg ha−1):C1159
N234600–127083140148
P2640–1006.410.810.8
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Sprache:
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Chemie, andere, Geowissenschaften, Biologie