Abstract
This report describes the results of field work in the Princess Amalia Wind Farm (in Dutch: Prinses Amaliawindpark, or PAWP). It is to realize the requirements of the Monitoring and Evaluation Program, which is part of the Wbr-permit of the wind farm. The objective is to determine if the wind farm functions as a refugium for roundfish. PAWP is expected to act as a refugium because fisheries are excluded in the farm area since 16 October 2007. It is expected that larger and older individuals as well as species vulnerable for fisheries would have a better chance to survive which would result in an increase in numbers and larger individuals. The methods and design of the field work were decided upon by the client and the government and follow closely the protocols of the International Bottom Trawl Survey (IBTS). Following these protocols as close as possible, eight tows in the farm were performed by the Dutch vessel Tridens with the ground gear used in the IBTS. The catches in these eight tows were compared to the catches of the IBTS in the surrounding area in the last 10 years (2004-2013), 43 tows. Unfortunately in 2012 and 2013, only two IBTS tows a year (a French and a Dutch) were made in the vicinity of the wind farm that could be used for the comparison. This provides limited data to perform proper analysis on to conclude on the potential effect of the farm. The catches in the wind farm do not significantly differ from those in the surrounding IBTS, not when all the 43 IBTS tows were combined neither when the comparison was done by year. The analysis were performed on the number of species caught, the total catch per unit of effort (CPUE), and the CPUE of a number of species (herring, sprat, whiting, cod, plaice, dab, greater sand-eel). In total 17 fish species were caught in the eight tows, all of these were also caught in the 43 IBTS tows. The sprat and herring caught in PAWP were larger than those in the 2013 IBTS tows, however the collected data was too limited to explain this larger size. It is more likely that this is caused by catching a school of larger herring and sprat by chance than an effect of the wind farm. Only a single juvenile cod was caught in the farm, while other wind farm studies show a positive effect for cod, mainly due to the attraction to the monopiles. The sampling was, due to safety reasons, not done close to the monopiles but on the sandy bottom in the middle of the farm. The low number of cod is thus as expected comparing it with the catches of the IBTS and not in contrast to the positive findings of the other wind farm studies. There is a suggestion of a positive effect of PAWP on the presence of greater sand-eel. This is a species that is buried in the sediment for a large part of its life and also its eggs stick to the sediments. It might be a species that, if the sediments in the farm are suitable, profits from the refugium function of the farm. However, the data collected are too limited to conclude this. The expectation that larger and older individuals as well as species vulnerable for fisheries would have a better chance to survive and so increase in size and numbers, is not supported nor reject by the data collected. The field work conducted as part of this study is too limited to draw statistically significant conclusions regarding the refugium function of the wind farm for roundfish.