The role of the European lobster (Homarus gammarus) in the ecosystem: An inventory as part of a feasibility study for passive fisheries on European lobster Homarus gammarus in offshore wind farms

Homarus gammarus (European lobster) is a commercially valuable lobster species that is distributed around the European continent and appears to be a viable target species for passive fisheries. In the Win-Wind project, possibilities for passive fishing on H. gammarus in offshore wind farms are being investigated. Since H. gammarus occurrence at offshore wind farms on the Dutch continental shelf appears uncertain, with few to no specimens found in previous monitoring activities, stocking of lobsters will likely be required to achieve harvestable populations. Accordingly, a demand arose to further investigate the role of H. gammarus within its ecosystem to better understand the implications of adding the species to the environment. Hence, a literature review of both the ecology of H. gammarus and the (benthic) ecosystem of the North Sea is presented, followed by a comparison of H. gammarus with other decapod species for which more work is available, through principal component analysis (PCA). It appears that H. gammarus progresses up the food web as it develops from opportunistic larva, to a scavenging juvenile, to an active predator as an adult. Although H. gammarus larvae and early benthic settlers are vulnerable to predation, adult H. gammarus is not a target species for predators. It is suggested that H. gammarus inhabits top-down control on the benthic ecosystem by predation and is controlled bottom-up by food availability. Albeit dependent on the presence of prey and competing species as well as the frequency and intensity of restocking activities, it appears that a sudden increase in H. gammarus may have at least temporary inhibitory effects on the benthos population through predation and consequently indirectly on ecologically related species, such as the brown crab. Further investigation is however required as robust data on the dietary diversity of H. gammarus as well as comprehensive population monitoring programmes in OWFs on the DCS are currently lacking.