Modeling consequences of spatial closures for offshore energy: Loss of fishing grounds and fishery-independent data

Abstract

Many jurisdictions are currently pursuing renewable sources of energy from the ocean, including offshore wind farms (OWFs). While these could have direct positive effects for global climate change by reducing fossil fuel consumption, there could be unintended consequences for fisheries and conservation. These include the potential loss of fishing grounds (and the consequent spatial displacement of fishing effort) and the potential loss of fishery-independent survey data in OWF areas. Because fishing and other types of vessel traffic are often limited in the OWF area, OWFs may also serve as other effective area-based conservation measures (OECMs), an important type of spatial protection in the context of the Convention on Biological Diversity 30 × 30 initiative. We used spatially explicit population models of groundfish fisheries on an idealized coastline in a management strategy evaluation to investigate the effects of OWF placement on conservation objectives (increased fish biomass) and fishery objectives (maintaining fishery yield). We simulated the loss of fishing grounds on 10% of the coastline, and the concurrent loss of 10% of fishery-independent survey data, introducing uncertainty and bias into stock status estimates. This produced two effects in the model: initial loss of fishery yield due to the closure and reductions in fishing effort when the loss of data triggered precautionary measures in the harvest control rule. Additionally, we assessed scenarios with different placements of the OWF relative to high-quality fish habitat, as OWFs could be placed without fish habitat considerations in mind. As expected (given the sustainable harvest rates we simulated), we found that placing the OWF on high-quality habitat produced the greatest negative effects of fishing grounds and fishery-independent data on fishery yields, but placing the OWF on low-quality habitat caused it to be ineffective as an OECM (in terms of increasing fish population biomass). Additionally, the loss of survey data had a greater effect for less mobile fish species. Our findings highlight the expected trade-offs between the fishery and conservation (i.e., OECM) consequences of OWF expansion and the need to compensate for the loss of fishery-independent data by accounting for species distributions relative to habitat in survey indices.