Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
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<strong>Review</strong> <strong>of</strong> <strong>Cabling</strong> <strong>Techniques</strong> <strong>and</strong> <strong>Environmental</strong> <strong>Effects</strong> <strong>Applicable</strong> to the Offshore Wind<br />
Farm Industry – Technical Report<br />
operations. This is seen as a localised <strong>and</strong> temporary displacement <strong>of</strong> fish, which<br />
in isolation is generally not a significant impact on natural fish resources.<br />
Most species <strong>of</strong> marine fish spawn in the water column <strong>and</strong> so changes to<br />
the seabed through the placement <strong>of</strong> a cable do not have severe long-term<br />
implications. However, disruption to the spawning <strong>of</strong> species that do utilise<br />
the seabed, such as Atlantic herring (Clupea harengus), s<strong>and</strong>eels (Ammodytes<br />
tobianus) <strong>and</strong> dogfish, should be minimised through alternative routing or<br />
timing to avoid spawning areas or periods respectively.<br />
In general, CEFAS recommend that construction on or in the seabed should be<br />
carried out outside <strong>of</strong> the spawning season for substrate spawners e.g. February<br />
to April for spring spawning herring. As this is an important operating window,<br />
it may be prudent to determine the extent <strong>of</strong> spawning areas within the cablelaying<br />
corridor. In the absence <strong>of</strong> data regarding the importance <strong>of</strong> sites for<br />
spawning, additional studies may be required to determine whether mature fish<br />
in spawning condition are present in the area during the spawning season <strong>and</strong>/<br />
or whether eggs <strong>and</strong> larval stages are present (see CEFAS, 2004).<br />
Nursery grounds (areas favoured by juvenile fish) are also important habitats,<br />
although in many locations such habitats may be widespread. If the cable pathway<br />
crosses through an important nursery ground, then the relative importance <strong>of</strong><br />
the site to that region should be assessed.<br />
As most fish species are relatively opportunistic predators, particular feeding<br />
areas are not well defined. However, some species <strong>of</strong> fish may congregate in<br />
certain areas at particular times <strong>of</strong> the year to feed on particular prey species.<br />
The routing <strong>and</strong> laying <strong>of</strong> the cable should therefore minimise disruption to such<br />
sites wherever possible.<br />
Habitat disturbance can be a more significant issue to benthic (associated<br />
with the seabed) mobile fish resources such as many shellfish species. This is<br />
particularly relevant for areas which are important for certain shellfish life stages<br />
where there is reduced mobility, namely crustacean over-wintering areas <strong>and</strong><br />
settlement areas for juvenile shellfish. Settlement areas are discussed further in<br />
‘Smothering’ section below.<br />
The true extent <strong>of</strong> seasonal migration by many fish <strong>and</strong> shellfish species is<br />
becoming better understood. Again the severity <strong>of</strong> impact from cable installation<br />
activities is likely to increase for species that migrate across the seabed, namely<br />
crustacean species such as lobster (Hommarus gammarus), spider crab (Hyas<br />
araneus) <strong>and</strong> edible crab (Cancer pagarus). Routing <strong>and</strong> timing <strong>of</strong> cable-laying<br />
operations to avoid disruption to this seasonal activity may be required. For<br />
example, for the Norfolk (Cromer) Round 1 Offshore Wind Farm, mitigation<br />
cited in the <strong>Environmental</strong> Statement recommended that the export cable, which<br />
covered an inshore area believed to be important for “pairing” (or mating) <strong>of</strong><br />
edible crab, should be installed outside this period (July-September) (Norfolk<br />
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