Trends in Spring Species Distribution
The species of the Northeast Shelf ecosystem have shown changes in distribution over recent decades. Individual species have shifted distribution for a number of reasons and these shifts can be characterized in a number of different ways. Two metrics that have been used to characterize distribution on the NE Shelf include: 1) the position in the ecosystem along an axis oriented from the southwest to the northeast, referred to as the along shelf distance; and 2) the depth of occurrence. Along shelf distances range from 0 to 1360, which relates to positions along the axis from the origin in the southwest to the northeast in kilometer units. Depth ranges from 0 to -260, which relates to depth of occurrence in meters. The table below shows the species analyzed. The mean along shelf distance and depth of occurrence for all species by year are shown in the two graphs, with the 2016 values marked with a dashed red line. As a group, these species had an along shelf distance of approximately 790 km at the beginning of the time series. They now have a distance of over 880 km. There has been little change in the depth distribution of these species during the spring survey.
Click species name to see the along-shelf distance and depth distribution trends.
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(File Modified Oct. 25 2016)
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