Part B - Technical instructions 
25 
2 Fish 
Fish surveys involve use of beam trawls in the North Sea and of otter trawls in the Baltic Sea 
(Table 2.1). The surveys have to be accompanied by representative measurements of weather, 
depth, salinity, temperature and oxygen (according to UNESCO 1988), which have to be 
recorded. 
Installation-based surveys are to be carried out corresponding to the current state of technol 
ogy and to the wind farm safety regulations. The concrete scope and methods are determined 
in co-operation with the planning approval/approval authority in the respective study scope. 
In the third year after the end of the baseline study, the studies of fish shall be resumed in this 
section for those areas, where installation of foundations and infield cabling has been com 
pleted. The studies follow the methodology of operation-phase monitoring. 
Table 2.1: Beam trawl/otter trawl survey (wind farm trawl). 
Baseline study 
Construction 
phase 
Operation phase 
Objectives 
Description of fish fauna in the 
project and reference areas. 
Medium and small scale survey 
of status quo, to be used as a 
basis for assessing possible im 
pacts of wind turbines. 
Medium and small scale survey of 
relevant operation phase impacts 
on the fish fauna. 
Survey of small scale impacts on 
fish population in the wind farm 
by state-of-the-art installation- 
based surveys. 
Scope 
Once a year in autumn. In the first year of the baseline study, description of seasonal 
conditions in the project area and reference area requires investigations in spring and 
in autumn. 
In project and reference areas of > 100 km 2 , the minimum number of hauls should be 
30 each when using an otter trawl. 20 hauls each will be sufficient if a beam trawl is 
used. 
In project and reference areas of < 100 km 2 , the minimum number of hauls should be 
no less than 20 each when using an otter trawl. 15 hauls each will be sufficient if a 
beam trawl is used. 
In project and reference areas of < 30 km 2 , the minimum number of hauls should be 
15 each when using an otter trawl. 10 hauls each will be sufficient if a beam trawl is 
used. 
Timing 
At least two consecutive com 
plete seasonal cycles prior to the 
start of construction. 
In the first, third and fifth year of 
the operation phase. 
Method 
Sampling strategy: 
• Equipment standard North Sea: 7 m beam trawl (see p. 44) 
• Equipment standard Baltic Sea: Otter trawl (wind farm trawl) (see p. 46). 
• The same equipment standard must be used both in the project area and in the 
reference area. A change of equipment standard is not permitted! 
• The duration of hauls should be 15 min., and the towing speed 3 to 4 kn. In beam 
trawl surveys, the respective hauls from both sides (starboard/port) must be sur 
veyed. Employing stern trawlers, the duration of hauls must be prolonged to 
30 min., and the respective haul of just one side (starboard or port) must be sur 
veyed. 
• Taking into account the specific conditions of the project, a random station grid is 
to be preferred in principle to a fixed station grid.