1 Descriptive Section

1.1 Indicator category

[1] “Fish”

1.2 Indicator name

Bottom trawl survey diversity index

Includes variable(s): NEFSC survey species diversity - FALL, NEFSC survey species diversity - SPRING

1.3 Indicator brief description

Diversity metric for the bottom trawl survey data

1.4 Indicator 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

2 SMART Attribute Section

2.1 Indicator documentation

2.1.1 Are indicators available for others to use (data downloadable)?

Yes

2.1.1.1 Where can indicators be found?

Data: https://noaa-edab.github.io/ecodata/index.html

Description: https://noaa-edab.github.io/catalog/survey_shannon.html

Technical documentation: https://noaa-edab.github.io/tech-doc/survey_shannon.html

2.1.1.2 How often are they updated? Are future updates likely?

[need sequential look at datasets for update frequency. Future requires judgement]

2.1.1.3 Who is the contact?

andrew.beet@noaa.gov

2.1.2 Gather indicator statistics

2.1.2.1 Units

Indicator	Units
NEFSC survey species diversity - FALL	effective Shannon
NEFSC survey species diversity - SPRING	effective Shannon

2.1.2.2 Length of time series, start and end date, periodicity

General overview: SPRING, FALL

Indicator specifics:

Indicator	EPU	StartYear	EndYear	NumYears	MissingYears
NEFSC survey species diversity - FALL	GB	1963	2024	61	1
NEFSC survey species diversity - FALL	GOM	1963	2024	61	1
NEFSC survey species diversity - FALL	MAB	1963	2024	60	2
NEFSC survey species diversity - FALL	SS	1963	2024	61	1
NEFSC survey species diversity - SPRING	GB	1968	2024	56	1
NEFSC survey species diversity - SPRING	GOM	1968	2024	56	1
NEFSC survey species diversity - SPRING	MAB	1968	2024	56	1
NEFSC survey species diversity - SPRING	SS	1968	2024	56	1

2.1.2.3 Spatial location, scale and extent

General overview: EPU

Indicator specifics:

Indicator	EPU
NEFSC survey species diversity - FALL	GB
NEFSC survey species diversity - FALL	GOM
NEFSC survey species diversity - FALL	MAB
NEFSC survey species diversity - FALL	SS
NEFSC survey species diversity - SPRING	GB
NEFSC survey species diversity - SPRING	GOM
NEFSC survey species diversity - SPRING	MAB
NEFSC survey species diversity - SPRING	SS

2.1.2.4 Management scale: all species, FMP level, species level, can it be aggregated or separated to different scales?

[Classify by hand, note gridded data if available could be applied to different species ranges]

2.1.2.5 Uncertainty metrics

Uncertainty is captured in these variables:

character(0)

2.1.3 Are methods clearly documented to obtain source data and calculate indicators?

Yes

2.1.3.1 Can the indicator be calculated from current documentation?

The R package survdat was used in the survey data extraction process.

The Shannon index, \(H^\prime\), was calculated for each Ecological Production Unit (EPU) annually after determining the set of stations surveyed and assigning them to the appropriate EPU.

2.1.3.2 Is code publicly available? up to date?

2.1.3.3 Have methods changed over time?

2.1.4 Are indicator underlying source data linked or easy to find?

Source data are available to qualified researchers upon request (see “Access Information” here).

2.1.4.1 Where are source data stored?

survdat is an R package that allows for queries of the NEFSC survey database (SVDBS).These data are available to qualified researchers upon request. More information on the data request process is available under the “Access Information” field here.

2.1.4.2 How/by whom are source data updated? Are future updates likely?

Andy Beet andrew.beet@noaa.gov

[likelihood of source data updates requires judgement, enter by hand]

2.1.4.3 How often are they updated?

[Update by hand, look for source, may require judgement]

2.2 Indicator analysis/testing or history of use

2.2.1 What decision or advice processes are the indicators currently used in?

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.

2.2.2 What implications of the indicators are currently listed?

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.

2.2.3 Do target, limit, or threshold values already exist for the indicator?

2.2.4 Have the indicators been tested to ensure they respond proportionally to a change in the underlying process?

2.2.5 Are the indicators sensitive to a small change in the process, or what is the threshold of change that is detectable?

Unknown

2.2.6 Is there a time lag between the process change and the indicator change? How long?