Aquaculture category description form
Please submit a separate form for each type of culture to be described and try to obtain
information on as many of the variables listed below as possible
Information provider
Name: Helmut Thetmeyer
Affiliation or address: IFM-GEOMAR, Kiel, Germany
Source of information: Phytoplankton monitoring report, Warnsignale aus dem Wattenmeer
(Lozan et al. 1994), Wadden Sea Newsletter, personal communications, WWW.
Part 1 – General description
a. Country: Germany
b. Environment
 Coastal
 Offshore
 Estuarine
 Other (please specify)
c. Type of organisms produced
 Finfish
 Shellfish
 Algae
d. Availability of support for research (please specify
what equipment, facilities are available: use of small research vessel and standard lab facilities
for handling of benthos and water samples can be arranged. For details see:
http://www.awi-bremerhaven.de/BAH/sylt.html
For mobility on sea, there are two possibilities: a ship of the Wadden Sea Station in List on the
island of Sylt (belongs to Alfred Wegener Institute, Bremerhaven) or perhaps an authority boat.
The "Mya" research catamaran
and how far these are from the proposed study site): The locations of areas for mussel farming
varies from year to year. Typically, there is a location on the west side of Sylt which can be
reached by boat from List (location of Wadden Sea Station) in less than an hour.
e. Relationship of the local staff with the fish farm operator (good, bad, other): Karsten Reise and
his staff from the Wadden Sea Station Sylt have described negative environmental effects of
mussel farming, so the relationship with farmers could be troubled. The officer responsible for
mussel farming of the regional authority, Maarten Ruth, has little provisos against mussel
farming and seems to have a good relationship with mussel farmers.
Part 2 – Detailed farm description
a. Species produced: blue mussel (Mytilus edulis)
b. Annual production level: 8,000 to 25,000 tonnes per year, depends on availability of spat.
c. Gear used (net pens, long lines, etc.): sublittoral bottom culture; highly specialized vessels;
seed is collected and mussels are harvested with dredges
d. Distance to nearby aquaculture farms (how many other farms?: depends on the mussel bed we
select, some are isolated others are very close (a few hundred meters) together. Location of
mussel beds varies from year to year.
e. Environmental conditions & ecological information
 Depth: 2.5 to 10 m below charted low water line
 Sediment type: mud and sand
 Water conditions (calm, rough): relatively calm (in comparison to open North Sea) due to
low water depth and shelter from islands and tidal flats, strong tidal currents
 Water quality (all relevant information, e.g. dissolved oxygen, nutrients, etc)
o dissolved oxygen: I don’t have monitoring data but I have never heard that
oxygen depletion in the water column is a severe problem in the Wadden Sea. It
can be supposed that dredging causes oxygen depletion locally.
o nutrients levels in 2004: maximum values are found during winter:
PO4 1.1 µM, Si: 35 – 37 µM, NO3 67 µM, NO2 ca. 2.2 µM, NH4 8 – 10 µM. During
the spring bloom the concentration of NH4, Si and PO4 is below 1 µM.
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Range of chlorophyll a levels: Data for 2003 and 2004
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Air and water temperature, annual range:
o Air Temperature on the Island of Sylt (based on 30 years of temperature
recordings): mean monthly temperature ranges from 0.4 °C in February to 16.6 °C
in August. Average minimum temperature ranges from -1,6 °C in February to
14.1 °C in August. Average maximum temperature ranges from 8.6 °C in January
to 19.4 °C in August (Source: http://www.sylt-wetter.de/progn/progn3.html).
o Water Temperature, North of Sylt in 2004: in January and February water
temperature ranged from 0 to 4 °C. In August a maximum temperature of 21 °C
was measured (Source: Annual Report of Phythoplankton Monitoring, J. van
Beusekom, M. Elbrächter, H. Halliger, und T. Romanova).
Salinity range: 26 in February 2004 to 31 in August 2004 (Source: Annual Report of
Phythoplankton Monitoring)
Range of current velocities: maximum tidal currents typically range from 0.3-0.5 m/s on
tidal flats to 1.0-1.5 m/s in the gullies. Heavy storms can add wind-driven currents of ca.
1 m/s.
Water exchange rate (residence time): With every tide, there is an exchange of water
between the Wadden Sea basins and the North Sea coast of up to 60%.
Detailed farm description (cont)
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Presence of seagrass beds: In 1991, seagrass beds (Zostera marina and Zostera nolti)
covered an area of 174 km2 in the Eulittoral of the German Wadden Sea. Northern Frisia,
where the island of Sylt is located, is the most important area for seagrass in the Wadden
Sea: 128.8 km2 or 19,8 % of the area of the tidal flats. Only Zostera marina can be found
in the sublittoral zone and due to the high turbidity of the water only down to a depth of
ca. 3 m. However, extensive sublittoral seagrass beds disappeared due to an epidemic
with Labyrinthula zosterae (Myxomycota) in the 1930s and never recovered.
Information on benthic communities: substrate is mud and sand. Hard substrates are
mainly biogeneous, i.e. shells of bivalves and, to a lesser extend, gastropods. In general,
the benthos communities in the gullies and in shallow Wadden Sea areas is less diverse
than in areas of comparable depth in the North Sea outside the Wadden Sea, supposably
due to human activities.
Are there endangered/protected species in the area? what are they? In first half of the 20th
century, there were also (1) sand reefs, produced by the polychaete Sabellaria spinulosa,
(2) banks of the European oyster, Ostrea edulis and (3) wild sublittoral mussel beds and
(4) extensive seagrass beds which all became almost extinct in the Wadden Sea. The
reasons for the (almost) extinction of the first 3 kinds of habitats seem to be direct and
indirect effects of fishing, mussel culture and digging. The primary reason for the
disappearance of sublittoral seagrass beds was a Myxomycota disease, but the human
impacts mentioned above have decreased the probability of a recovery. Many species
belonging to the the communities associated with these habitats are highly endangered or
became locally extinct.
Are there bathymetry data available? yes, but topography is very dynamic
Part 3 – Effects of the environment on aquaculture (WP3)
Problems, actual or anticipated – please rate on scale of 0 (very minor) to 4 (serious) and provide
detailed description of the problem.
 Storm damage 3: Heavy storms can destroy mussel beds by wave action and transport of
sediments. Exposed sites cannot be used for mussel farming.
 Freezing 1: mussel farming is only allowed in the sublittoral zone where no ice occurs.
Freezing may affects intertidal mussel beds and thus spatfall. I have no informations on
this kind of interaction.
 Pollution 2: Mussels accumulate certain toxic pollutants (e.g. lead, cadmium, PCBs).
Frequent consumption of mussels is regarded to be harmful to human health. This is,
however, a general problem of mussels. Mytilus edulis used as bio-indicator to monitor
toxic pollutant in the Wadden Sea, so good data on contamination levels should be
available.
 Harmful Algal Blooms 1: rare, last occurrence of PSP is more than 100 years ago. Toxic
algal blooms occur in the Wadden Sea but normally produce the less dangerous DSP
toxins. Algal blooms and toxicity of mussels is controlled by authorities.
 Disease 2: In the Netherlands and Lower Saxony, in the years after 1948, an epidemic
with the parasitic copepode Mytilicola intestinalis resulted in a low quality of mussels,
making them non-marketable. This resulted in an overfishing of wild mussels in
Schleswig-Holstein. The government of Schleswig-Holstein reacted in 1953 by passing a
stricter law on mussel fishery. In the mid 1950s the Myticoloa epidemic ceased.
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Predators 4: starfish are abundant and feed on all size of mussels. To protect mussels
from predation by starfish, farmers collect mussels from their beds and keep them on
board of their vessel in air for one day. This kills the starfish and many other organisms
associated with the mussels. Crabs and shrimps feed on mussel spat. The low availability
of mussel spat after mild winters could be due to predation by crustaceans.
Birds 2: Oyster catchers and Eider ducks feed on mussels, the latter also in the sublittoral
zone. Harassment is not allowed.
Part 4 – Effects of aquaculture on the environment (WP2)
a. Briefly assess the possible adverse, and/or positive, consequences of aquaculture at this site,
e.g. altered benthic community, increased water column turbidity, wild fish diseases,
eutrophication, risk of escapes and breeding with wild stocks, etc.
 negative: disturbance of benthos communities due to spat fishing and due to maintenance
and harvesting of mussels...
 negative: competition for area with other benthic organisms. The areas are selected for
best culture performance (growth and quality of mussels). These conditions may also be
required by other benthic animals which are endangered or already became locally extinct
(e.g. European oysters)
 positive: mussel culture may reduce turbidity (however dredging temporarily increases
turbidity)
b. List existing marine uses, with emphasis on user-conflicts (e.g. competition for habitat with
wild fisheries) and also such issues as stakeholders disturbed by the view of fish pens or by
boat motors and fumes, etc.
 Nature Conservation (German Wadden Sea is a national park) – most important conflict.
 Fishery – Fishermen (mainly shrimp fishery) cannot fish on mussel beds
 Shipping (authorities and farmers avoid critical locations)
 Tourism (authorities and farmers avoid critical locations)
 Electricity Providers (authorities and farmers avoid critical locations with cables)
Part 5 – Regulatory issues (WP2)
Which tools, models and indicators are currently used by the regulatory agencies (the
"managers") with regard to aquaculture?
The culture takes place in designated areas of two national parks and is strictly regulated, no
mussel culture activities are allowed in the eulittoral zone of the Wadden Sea of SchleswigHolstein and in areas of the national parks with highest status of protection. It is planned to
reduce the culture areas in Schleswig-Holstein from currently 2200 hectare until the end of 2006
to 2000 hectare. The 12 (highly specialised) vessels, used for mussel culture are controlled by a
black box which records position and activities of winches and pumps. There is a close season
for seed collection from 1.5. to 30.6. Landing of adult mussels is prohibited from 15.04.–14.07.
Mussels must be left on the culture beds for two seasons (600 to 650 days), ensuring that they are
not harvested (and transported to other areas) until they reach the market size of ca. 40 mm.
Harassment of seabirds is prohibited.
Regulation and decision finding is quite complex and long-winded with different authorities,
scientific advisors, the society of mussel producers, and NGOs involved. Finally, the regulation
is based on a contract between the Government of Schleswig-Holstein and the producer society.
Part 6 - Dissemination (WP6)
Who are the relevant industry representatives? Who are the aquaculturists? Who are the
regulators? Who are the other stakeholders?
The chairmen of the producer society in Schleswig-Holstein is Peter Ewaldsen (Petersbüll, D 25927 Neukirchen bei Niebüll tel/fax: +494664363).
In the authority for rural affairs (Amt für ländliche Räume) the expert and contact person for
mussel farming is Maarten Ruth (Maarten.Ruth@Fischerei.ALR-Kiel.landsh.de, tel
+494317208016).
The authority responsible for the national park is Landesamt für den Nationalpark SchleswigHolsteinisches Wattenmeer (Schloßgarten 1, 25832 Tönning, tel +4948616160, fax
+49486161669); head of this authority is Helmut Grimm (helmut.grimm@nationalparkamt.de).
Important NGOs are:
Schutzstation Wattenmeer (Grafenstraße 23, 24768 Rendsburg, tel +49433123622, fax
+49433125246, head )
WWF Projektbüro Wattenmeer (Dr. Hans-Ulrich Rösner, Hafenstraße 3, 25813 Husum, tel
+494841668530, fax +494841668539, husum@wwf.de).
list to be continued …