24 Benthic Invertebrate Indices
Description: Aggregate macrobenthos and megabenthos invertebrate indices from fish stomach contents
Indicator family:
Contributor(s): Sarah Gaichas, James Gartland, Brian E. Smith, Sarah Weisberg, Sean Lucey
Affiliations: NEFSC
24.1 Introduction to Indicator
Benthic invertebrates provide supporting ecosystem services as important prey for many economically important fish species on the Northeast US shelf. Changes to the benthic invertebrate forage base could have important implications for regional food webs. However, we lack direct measurements of benthic invertebrate biomass for most unexploited taxa.
We define Macrobenthos as bottom-dwelling invertebrates retained on a 0.5-1.0 mm sieve. These include polychaete worms, small crustaceans, bivalves (non-commercial), gastropods, nemerteans, tunicates, cnidarians, brittle stars, sea cucumbers, and sand dollars.
We define Megabenthos as sea stars (Echinodermata: Asteroidea) and large Arthropods (horseshoe crabs (Merostomata), mantis shrimp (Crustacea: Stomatopoda), and crabs (Crustacea: Decapoda: Brachyura and Anomura other than hermit crabs)).
The indices developed here use similar methods to the Forage Fish Index. The spatially-explicit macrobenthos and megabenthos indices estimate the combined biomass of 833 and 105 taxa, respectively, using stomach contents information from 88 predator/size combinations from fish collected on bottom trawl surveys.
In addition to an index of benthic invertebrate biomass in each EPU, the coastwide center of gravity for the combined benthic biomass was estimated to evaluate whether distributions of benthic invertebrate biomass have changed over time.
24.2 Key Results and Visualizations
Time series extend from 1980-2023. Macrobenthos and Megabenthos are included on separate plots for each EPU.
Variables plotted are Fall Macrobenthos or Megabenthos Biomass Estimate and Spring Macrobenthos or Megabenthos Biomass Estimate with error bands from Fall Macrobenthos or Megabenthos Biomass Estimate SE and Spring Macrobenthos or Megabenthos Biomass Estimate SE, respectively.
Eastward and Northward components of the Center of Gravity, along with the Center of Gravity SE are plotted for Fall and Spring Macrobenthos or Megabenthos Biomass.
24.3 Indicator statistics
Spatial scale: by EPU and full shelf
Temporal scale: Spring (January-June), Fall (July-December)
Synthesis Theme:
24.4 Implications
Macrobenthos indices show long term declines in spring in all EPUs. In contrast, Megabenthos indices show long term increases in fall in GOM and GB, and in spring in MAB. Megabenthos indices also show a recent trend in spring in GB.
Center of gravity indicators show recent trends towards the north and east in spring for Megabenthos in all EPUs. Macrobenthos center of gravity shows a significant long term trend towards the west over time. This is the opposite direction observed for aggregate forage fish and surveyed fish species in aggregate.
24.5 Get the data
Point of contact: Sarah Gaichas (Sarah.Gaichas@noaa.gov)
ecodata name: ecodata::benthos_index
Variable definitions
Spring Macrobenthos Biomass Estimate = aggregate macrobenthos biomass months 1-6, units relative grams per stomach Spring Macrobenthos Biomass Estimate SE = standard error of aggregate macrobenthos biomass months 1-6, units relative grams per stomach Fall Macrobenthos Biomass Estimate = aggregate macrobenthos biomass months 7-12, units relative grams per stomach Fall Macrobenthos Biomass Estimate SE = standard error of aggregate macrobenthos biomass months 7-12, units relative grams per stomach Fall Eastward Macrobenthos Center of Gravity = average eastward location of macrobenthos biomass months 7-12, units kilometers Fall Eastward Macrobenthos Center of Gravity SE = standard error of average eastward location of macrobenthos biomass months 7-12, units kilometers Fall Northward Macrobenthos Center of Gravity = average northward location of macrobenthos biomass months 7-12, units kilometers Fall Northward Macrobenthos Center of Gravity SE = standard error of average northward location of macrobenthos biomass months 7-12, units kilometers Spring Eastward Macrobenthos Center of Gravity = average eastward location of macrobenthos biomass months 1-6, units kilometers Spring Eastward Macrobenthos Center of Gravity SE = standard error of average eastward location of macrobenthos biomass months 1-6, units kilometers Spring Northward Macrobenthos Center of Gravity = average northward location of macrobenthos biomass months 1-6, units kilometers Spring Northward Macrobenthos Center of Gravity SE = standard error of average northward location of macrobenthos biomass months 1-6, units kilometers Spring Megabenthos Biomass Estimate = aggregate megabenthos biomass months 1-6, units relative grams per stomach Spring Megabenthos Biomass Estimate SE = standard error of aggregate megabenthos biomass months 1-6, units relative grams per stomach Fall Megabenthos Biomass Estimate = aggregate megabenthos biomass months 7-12, units relative grams per stomach Fall Megabenthos Biomass Estimate SE = standard error of aggregate megabenthos biomass months 7-12, units relative grams per stomach Fall Eastward Megabenthos Center of Gravity = average eastward location of megabenthos biomass months 7-12, units kilometers Fall Eastward Megabenthos Center of Gravity SE = standard error of average eastward location of megabenthos biomass months 7-12, units kilometers Fall Northward Megabenthos Center of Gravity = average northward location of megabenthos biomass months 7-12, units kilometers Fall Northward Megabenthos Center of Gravity SE = standard error of average northward location of megabenthos biomass months 7-12, units kilometers Spring Eastward Megabenthos Center of Gravity = average eastward location of megabenthos biomass months 1-6, units kilometers Spring Eastward Megabenthos Center of Gravity SE = standard error of average eastward location of megabenthos biomass months 1-6, units kilometers Spring Northward Megabenthos Center of Gravity = average northward location of megabenthos biomass months 1-6, units kilometers Spring Northward Megabenthos Center of Gravity SE = standard error of average northward location of megabenthos biomass months 1-6, units kilometers
Indicator Category:
24.6 Public Availability
Source data are publicly available. All data and code available on GitHub at https://github.com/NOAA-EDAB/benthosindex
24.7 Accessibility and Constraints
No response
tech-doc link https://noaa-edab.github.io/tech-doc/benthos_index.html