[Submission]: Species Richness

[Laurels1]

Primary Contact

[email protected]

Secondary Contact

[email protected]

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

Species Richness

Indicator Name (as exists in ecodata)

habitat_diversity

Family (Which group is this indicator associated with?)

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

Data Description

Abundance data were extracted from the NEFSC’s SVDBS database using Survdat for 55 fish species regularly sampled on spring and fall NEFSC bottom trawl surveys (see SOE Tech Doc for a list). Data were converted to presence/absence for species richness modeling.

Species Richness was estimated using “joint” predictions of presence-absence in 100 randomly-drawn assemblages simulated by a joint species distribution model (part of the Northeast Regional Habitat Assessment), which was fitted to observations for 55 common species sampled by the NEFSC bottom trawl survey during the spring and fall of 2000-2019. The model controls for differences in capture efficiency across survey vessels, permitting predictions on a common scale (here calibrated to the Albatross IV). See SOE Tech Doc for details of the model and environmental covariates included.

Introduction to Indicator (Please explain your indicator)

Indices of species richness can indicate the health of the ecosystem as a metric of biodiversity. In this case, looking at a specified set of 55 species that are commonly caught in the NEFSC bottom trawl survey by year and EPU can indicate species distribution shifts as species richness declines in some areas and increases in others.

Key Results and Visualization

Trends of declining richness are seen in the more southerly regions (i.e., the Mid-Atlantic Bight) and increasing richness in the more northerly regions (i.e., the Gulf of Maine). These patterns reflect the decreasing occurrence of cooler-water species in the south and the growing prevalence of warm-water species in the north, likely as a result of warming water temperatures.

Implications

This species richness index provides a summary of how commonly caught fish in the NEFSC bottom trawl survey are changing over time, while controlling for differences in capture efficiency across survey vessels. The shifts of declining species richness in the Mid-Atlantic Bight indicate that fisheries in this region may need to shift away from reliance on these species that may be at the southern edge of their distributions, and may need to expand fisheries to more southerly species. The increase of species richness in the northerly regions such as the Gulf of Maine indicates that there is a likely an influx of southerly species, and management quotas may need to be adjusted between regions. These are likely direct implications that warming water temperatures have on fisheries management.

Spatial Scale

Species richness by EPU

Temporal Scale

Spring (March-May) and fall (September-November) NEFSC bottom trawl surveys from 2000-2019

Synthesis Theme

• Multiple System Drivers
• Regime Shifts
• Ecosystem Reorganization

Define Variables

1. Name: Year, Definition: year of species richness data, 2) Name: Species Richness, Definition: Species richness

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

Chris Haak, Laurel Smith and Tori Kentner

Point(s) of Contact

Laurel Smith ([email protected])

Affiliation

NEFSC

Public Availability

Source data are publicly available.

Accessibility and Constraints

No response

[Laurels1]

@BBeltz1
Please remove Shannon Diversity indices plots

[andybeet]

Plot laurel added

[Laurels1]

@BBeltz1 Please replace the text with the revised text below:
Description:
Species richness is the number of unique species predicted to be captured in NEFSC bottom trawl survey tows, conducted within each of four ecological production units (EPUs) in each year between 2000 and 2019. This is based on simulations from a joint-species distribution model fitted to presence-absence data for 55 species routinely collected by spring and fall surveys during the corresponding time period. Vessel-specific differences in capture efficiency are estimated by the model, and then predictions are generated at the Albatross IV scale. See SOE Tech Doc for details of the model, species considered, and environmental covariates included.
16.1 Introduction to Indicator
Species richness can indicate the health of the ecosystem as a metric of biodiversity, and changes in richness over time may reflect distribution shifts or community reorganization. In the present context, richness in a given EPU is presented in terms of 55 commonly sampled fish species, as they are predicted to be observed (i.e., present or absent) in NEFSC spring and fall bottom trawl surveys each year over the modeled time period (conditional on a common level of gear efficiency across years).
16.2 Key Results and Visualizations
An overall trend of declining richness can be seen in the more southerly Mid-Atlantic Bight (MAB) region during the modeled time period (2000-2019), while the more northerly regions (i.e., the Gulf of Maine and Georges Bank) are characterized by concurrent gains in richness. These patterns reflect the increasingly rare occurrence of cooler-water species (e.g., Atlantic cod, American plaice, and Atlantic pollock) in southern waters and the growing prevalence of warmer-water species (e.g., weakfish, spotted hake, and black sea bass) in the north, likely as a direct result of warming ocean temperatures.
16.3 Indicator statistics
Spatial scale: Ecological production units (4) on the Northeast US continental shelf (as sampled by NEFSC spring and fall bottom trawl surveys)
16.4 Implications
The contrasting EPU-specific trends displayed here highlight changes in the composition of marine fish assemblages that are consistent with expected species distribution shifts under warming water temperatures. It is important to note, however, that these estimates of richness consider only a certain (pre-specified) subset of community members, and are not representative of the entire fish community. For instance, it is probable that southerly (warmer-water) species not included in our analysis may be occurring in the MAB with increased frequency, effectively offsetting richness declines in that region. Still, decreases in the prevalence of cooler water taxa in the MAB may signal that fisheries in this region should reassess any reliance on stocks that are fished near the southern extents of their range, and/or shift fishing effort to more southerly species. Simultaneously, an apparent influx of southerly species in the GOM and GB may eventually necessitate the adjustment of management quotas across regions.

Thank you!