Gearing up: Methods for quantifying gear density for fixed-gear commercial fisheries in the U.S. Atlantic

Fixed-gear commercial fisheries are unique due to their occupancy nature, claiming areas of the ocean for discrete periods. As space conflicts arise from competing ocean uses, there is an increased need to understand and categorize fixed-gear fisheries to incorporate into marine spatial planning (MSP) efforts. We used fishery-dependent data and input from stakeholders to discern fleet dynamics of all gillnet and trap/pot fisheries in U.S. waters of the Northwest Atlantic Ocean. A Fixed-Gear Fishery Layer (FGFL) was developed combining fishery subgroups that were categorized around gear type, gear configuration, and species landed. Fishing effort from each subgroup was spatially allocated onto a 1 sq nm (1.9 sq km) grid using methods that relied on the level of detail available from trip reporting and monitoring, each with differing degrees of spatial resolution. This stepwise process allowed trips reported with minimal spatial detail to be included while not compromising trips where greater spatial precision existed. We demonstrate how the FGFL has been used for two MSP projects focused on protected species conservation and wind energy development.

Methods
Fixed-gear fisheries existing in the Northwest Atlantic from Maine to Florida were summarized and allocated spatiotemporally based on the level of spatial precision in trip reports and vessel monitoring data. While the data used in the manuscript is not publicly available due to confidentiality restrictions, we provide simulated example fisheries trip reports (vtr_data_example.Rdata) and vessel monitoring system data (vms_data_example.Rdata) to demonstrate the methods described in the manuscript. These methods for allocating this example fixed-gear fisheries data are available and carried out in R and may be adapted to other areas and data worldwide. A central part of the methods utilizes a gridded data frame (MapRef.Rdata) that summarizes spatial variables within each grid cell and acts as a reference to fisheries data in the allocation process. This file is specific to the U.S. Atlantic waters, but similar grids could be generated for a given study area. Additional data files include shapefiles and other spatial and supporting data used in the methods and described in the R code and manuscript. The BuildFGFLMethods.R file is the main code used to perform the analysis.