The importance of artificial hard substrates in the North sea for the ecology of the ichthyofauna

Completed: January 2009 - December 2013

In the year 2008 the kick off for the construction of the first windmill farm at the Belgian part of the North Sea (BPNS) was given. Within a couple of years three windmill farms and more than a 100 windmills will be present in our North Sea waters.
The foundations of these windmills will act as secondary artificial reefs, attracting different kind of fish species (Arena et al; 2007, Fabi et al.2002, Santos & Monteneiro 2007). Initially, high densities of fishes present at artificial reefs where related to an increased productivity. In 1983 an alternative hypothesis, stating that artificial reefs attract fishes due to behavioral preferences but do not increase productivity, emerged (Bohnsack 1989).
As many fish have a complicated life cycle and are highly migratory it is hard to quantify ‘possible’ net production. For this reason it is important to interpret the dimensions and distribution areas of the populations of fish species involved and to stipulate factors influencing structure (densities) and functionality (production versus dispersion) to quantify net production.
This PhD study aims to determine attraction and/or net productions of the ichthyofauna on the artificial hard substrates of the wind turbines placed at the Thorntonbank. Nearby artificial hard substrates (ship wrecks) and sand banks without windmills will act as reference sites.
The main goals are: to follow-up evolution of fish communities, densities and biomass both on concession area as reference sites after deployment of wind turbines, to determine which mechanisms/processes can result in an
increase of fish producti ( Are differences in physico-chemical characteristics of bottom, water column, hard substrates, … present between various sites? Are differences in condition index present between fish of various sites and what factors influence these differences?) and to determine (daily) migration patterns of some fish species Different techniques will be integrated to understand, quantify and visualize the functional relations between the ichthyofauna and the artificial reef.
Quantification is done using visual (visual census, camera observations) and invasive techniques (gill nets, line fishing). Cod (Gadus morhua) and pouting (Trispoterus luscus) are selected for detailed investigation on
habitat- and food preferences, condition index and migration patterns using different techniques (e.g. stomach content analysis, fatty acid analysis, telemetry).