[Submission]: survey_shannon

[andybeet]

Primary Contact

[email protected]

Secondary Contact

No response

Data Name (This will be the displayed title in Catalog)

Bottom trawl survey diversity index

Indicator Name (as exists in ecodata)

survey_shannon

Family (Which group is this indicator associated with?)

• Oceanographic
• Habitat
• Lower trophic levels
• Megafauna
• Social
• Economic

Data Description

Diversity metric for the bottom trawl survey data

Introduction to Indicator (Please explain your indicator)

Diversity metrics may be useful in determining shifts in species composition through time. The shannon-diversity index, a way to measure diversity using species richness and evenness is implemented in the attempt to determine changes over time. The index has a maximum value when all species are equally abundant.

Key Results and Visualization

A significant long term decline in the diversity metric is apparent in Georges Bank in both the Spring and the Fall. This is not seen in Gulf of Maine or the Mid Atlantic

Implications

A decline in the shannon diversity index over time could be a result of several factors; a decline in the number of species being found in the system over time or a select few becoming more abundant (relative to the rest) over time. If the number of species remain contant through time, then the decline represents a shift to a more unbalanced, uneven system where some species are more abundannt that others. An increase would represent the opposite, a shift, in direction, to a more balanced, even system.

If the number of species is changing through time, the inference is more complicated since the maximum value of the shannon-index is a function of the number of species.

Spatial Scale

EPU

Temporal Scale

SPRING, FALL

Synthesis Theme

• Multiple System Drivers
• Regime Shifts
• Ecosystem Reorganization

Define Variables

Name: NEFSC survey species diversity (SPRING, FALL)
Units: Shannon index (unitless)

Indicator Category

• Published Methods
• Extensive analysis, not yet published
• Syntheses of published information
• Database pull
• Database pull with analysis
• Other

If other, please specify indicator category

No response

Data Contributors

Andy Beet, Sean Lucey

Point(s) of Contact

[email protected]

Affiliation

NEFSC

Public Availability

Source data are publicly available.

Accessibility and Constraints

No response

[andybeet]

to be completed at a later date

[andybeet]

Filled out missing sections