This series of maps broadly characterizes monkfish commercial fishing vessel activity in the Northeast based on Vessel Monitoring System (VMS)1 data from 2006 through 2016 (full calendar years). The relative amount of vessel activity is indicated qualitatively from high (red) to low (blue). The National Marine Fisheries Service (NMFS) describes VMS as “a satellite surveillance system primarily used to monitor the location and movement of commercial fishing vessels in the U.S.”

The maps do not necessarily distinguish between fishing activity, vessel transit, and other vessel activities. Some maps show vessel activity at less than four knots—a speed threshold that was determined with industry input to attempt to better highlight fishing areas. Nevertheless, those maps still likely show non-fishing activities that occur at low speeds, such as processing catch, sorting, drifting, or idling in port. The most accurate interpretation of these maps is that they indicate relative levels of vessel presence.

The lack of historical data and relatively short timeframe of this map preclude consideration of historical fishing areas. It also does not illustrate more recent or future changes in fishing activity resulting from changing environmental and economic conditions, fisheries management, and other important factors.

Data Considerations

The data provided by NMFS contained the day/month/year, the geographic coordinates of the vessel at the time of transmission, and the vessel’s declaration code, which may signify fishery plan, program within that plan, and associated area identifier or gear-type information. These data then were aggregated by combining all program codes within each fishery plan.

The limitations of the data used to produce these maps should be understood prior to interpretation of this map.

These data are from vessels operating in certain fishery management plans and certain programs within those plans. This map displays data for limited access monkfish vessels electing to fish in the Offshore Fishery Program (50 CFR 648.10).

It is important to note that these data include all trips using a Monkfish VMS code by vessels with these permits, and as such, may include trips that target other fisheries but use such a Monkfish VMS declaration for another fishery as a management and reporting mechanism. Additionally, certain monkfish trips are not captured by this data. There are many New England fisheries not described through any VMS-derived maps.

VMS data are subject to strict confidentiality restrictions. Therefore, the map shows the density of vessel locations following the removal of individually identifiable vessel positions. The process of removing sensitive vessel locations followed the “rule of three” mandated by NMFS Office of Law Enforcement (OLE) by using a screening grid to identify which grid cells contained three or more VMS records. VMS records within cells that contain fewer than three VMS records were not included in the analysis. A statistical method to normalize data was used on the subsequent density grids and data values represent standard deviations. While legends are consistent across products, values represent high or low areas of vessel activity specific to each dataset. Detailed information on processing techniques is outlined in the metadata. This process can result in activity that seems anomalous, e.g., single data points in areas where multispecies fishing isn’t common, because three data points occur in a given 100m by 100m square. This is usually because of transit lines that overlap in a given cell, while nearby cells contain fewer than three data points.


These data were updated and posted on Northeast Ocean Data in spring 2018, and they will continue to be updated as described in the 2016 Northeast Ocean Plan.

Support for Regional Ocean Planning

For information about how these data and maps were developed with stakeholder input and will be used to support regional ocean planning, please see the 2016 Northeast Ocean Plan at www.neoceanplanning.org.

1 In general, vessels holding permits in certain fisheries are required to use VMS. See www.greateratlantic.fisheries.noaa.gov/vms/regs/index.html for additional information, including a link to federal regulations describing requirements for the use of VMS. Fisheries with vessels required to use VMS include: full-time or part-time limited access scallop; limited access monkfish/occasional scallop or combination permit electing to provide VMS notifications; limited access multispecies (groundfish; e.g., cod, flounder species, haddock, pollock, plaice, halibut, redfish, ocean pout, hake) permit when fishing on a category A or B day at sea (DAS); surfclam or ocean quahog open access permit; Maine mahogany quahog limited access permit; limited access monkfish vessel electing to fish in the Offshore Fishery Program; limited access herring permit; limited access squid permit; limited access mackerel permit.