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Layer: Intrinsic Seabed Habitat Vulnerability to Fishing - Scallop Dredge, median fishing effort (ID: 73)

Name: Intrinsic Seabed Habitat Vulnerability to Fishing - Scallop Dredge, median fishing effort

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Description: The Intrinsic Seabed Habitat Vulnerability to Fishing layers show the vulnerability of the seabed to each gear type. These datasets constitute a secondary set of outputs from the Northeast Fishing Effects Model (Fishing Effects). The model combines seafloor data (sediment type, energy regime) with parameters related to the interactions between fishing gear and seafloor habitats to generate habitat disturbance estimates in space and time. A higher habitat disturbance percentage suggests that the seafloor in that location is more vulnerable to that fishing gear. Mobile bottom contact gears generate higher benthic habitat disturbance values than fixed bottom contact gears. The intrinsic vulnerability products allow the Council to predict which areas would be vulnerable to impact, even in the absence of existing fishing pressure. <br/> <br/> Data inputs include a benthic sediment/energy map (in Data Explorer category Habitat > Physical) and fishing effort as swept area. Energy classification is based on depth or benthic boundary shear stress data. Data inputs and outputs to Fishing Effects are gridded at a 5 km by 5 km resolution. The model outputs extend only to the shelf break/upper continental slope because this is the limit of fishing activity with bottom-tending gears in the northeast region. The intrinsic habitat vulnerability products apply a spatially and temporally constant level of fishing disturbance for six types of bottom-tending fishing gears: trawl, scallop dredge, hydraulic clam dredge, longline, gillnet, and trap, across all grid cells of the model, at each monthly timestep from 1996-2017. The level of fishing disturbance evaluated for these model runs reflects the median swept area ratio over the entire time series and across all grid cells. Swept area ratio is simply the total swept area within each grid, relative to the grid size. For this model, which has a 25 km2 grid resolution, a swept area of 25 km2 would lead to a swept area ratio of 1, and a swept area of 12.5 km2 would lead to a swept area ratio of 0.5, etc. Values used are described in NEFMC (2019) and vary by gear type; the model report also shows results for the 95th percentile of swept area ratio. <br/> <br/> The maps in the Portal show the estimated percent seabed habitat disturbance for each of these six gear types by grid cell for the final month of the time series (December 2017), This type of product is of value to managers because fishing effort is influenced by numerous factors which are subject to change, including spatial closures that prohibit certain types of gear in specific locations. Every cell in the domain has a modeled value. Larger percentages indicate that a greater percentage of the seafloor is estimated to be impacted at these median levels of fishing disturbance, while smaller percentages indicate a lower impact. All gear types use the same color scale to allow for comparison among gears. While there are modeled differences below a 3% level, those differences are not thought to be especially meaningful in a management context, and are therefore not shown. <br/> <br/> Additional information about the model can be found on the <a href="https://www.nefmc.org/library/fishing-effects-model" target="_blank">New England Fishery Management Council's Fishing Effects</a> page.

Definition Expression: N/A

Copyright Text: New England Fishery Management Council, 2020. For questions contact Michelle Bachman, mbachman@nefmc.org

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