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Technical Documentation, State of the Ecosystem Report

75 Species Density Estimates

Description: Current and Historical Species Distributions

Found in: State of the Ecosystem - Gulf of Maine & Georges Bank (2017, 2018), State of the Ecosystem - Mid-Atlantic (2017, 2018)

Indicator category: Database pull; Database pull with analysis

Contributor: Kevin Friedland

Data steward: Kevin Friedland

Point of contact: Kevin Friedland,

Public availability statement: Source data are publicly available.

75.1 Methods

We used kernel density plots to depict shifts in species’ distributions over time. These figures characterize the probability of a species occurring in a given area based on Northeast Fisheries Science Center (NEFSC) Bottom Trawl Survey data. Kernel density estimates (KDEs) of distributions are shown for the period of 1970-1979 (shaded blue) and most recent three years of survey data (shaded red) (Figures not available). Results are typically visualized for spring and fall bottom trawl surveys seperately.

Three probability levels (25%, 50%, 75%) are shown for each time period, where the 25% region depicts the core area of the distribution and the 75% region shows the area occupied more broadly by the species. A wide array of KDEs for many ecologically and economically important species on the Northeast US Continental Shelf are available here.

75.1.1 Data sources

Current and historical species distributions are based on the NEFSC Bottom Trawl Survey data (aka “Survdat”) and depth strata. Strata are available as shapefiles that can be downloaded here (listed as “strata.shp”).

75.1.2 Data analysis

Code used for species density analysis can be found here.

catalog link No associated catalog page