19 Stability & Resistance: Stability of Community Biomass

Data Type: Tabular Data (within eco_indicators)

Spatial Scope: Maritimes

Duration 1970-2022

Source: Bundy et al. 2017

19.1 Introduction to Indicator

The coefficient of variability (CV) in biomass describes the temporal variability in biomass relative to its mean, here estimated in a 5-year moving average (Bundy, Gomez, and Cook 2017). Using the inverse of CV, a decrease in this indicator represents greater biomass variability from year to year in the community, and an increase represents lower biomass variability.

19.2 View Data

library(tidyr)
library(plotly)
library(stringr)

plotly_df <- data@data %>% inner_join(global_cols3)

p <- plot_ly()

regions <- unique(plotly_df$region)

for(r in regions){

  df_sub <- plotly_df %>% filter(region == r)

  group_name <- unique(df_sub$region_group)
  
  linewidth <- unique(df_sub$linewidth)
  linetype <- unique(df_sub$linetype)

  p <- p %>%
    add_lines(
      data = df_sub,
      x = ~year,
      y = ~CVBiomass_value,
      name = r,
      legendgroup = group_name,
      legendgrouptitle = list(text =
        ifelse(group_name == "ESS",
               "Eastern Scotian Shelf Zones",
               "Western Scotian Shelf Zones"
               )
      ),
      line = list(color = unique(df_sub$color),
                  dash = linetype,
                  width = linewidth),
      text = ~paste0("<b>",region,"</b>: ",round(CVBiomass_value,2),"°C"),
      hoverinfo = "x+text"
    )
}

p %>%
  layout(
    title = "Stability of Community Biomass",
    xaxis = list(title = "Year"),
    yaxis = list(title = "1 / Coefficient of Variation in Biomass", fixedrange = TRUE),
    hovermode = "x unified",
    legend = list(
      tracegroupgap = 5,
      groupclick = "toggleitem",
      itemdoubleclick = FALSE
    )
  ) %>%
  config(displayModeBar = FALSE)

Figure 19.1: Coefficient of Variation of biomass in Scotian Shelf Regions; 1970-2022. Use dropdown box to select a target trophic level, and click legend to toggle regions.

19.3 Summary and Trends

Trend and summary values are automatically generated; data were last updated on marea package install on 2026-02-10

Despite variability between individual NAFO regions (Fig. 19.1), the inverse coefficient of variation in biomass significantly decreased in the Western Scotian Shelf and non-significantly decreased in the Eastern Scotian Shelf throughout the sampling span (Fig. 19.2).

Figure 19.2: Overall CV Boimass trends Eastern and Western Scotian Shelf.

19.3.1 Summary Table by Region and Functional Group

Trends in the coefficient of variability of biomass in each NAFO region within the Eastern and Western Scotian Shelf (1970-2022) are shown in the table below (Table 19.1).

Table 19.1: Change trends for Coefficient of Variation of Biomass in NAFO regions within the Eastern and Western Scotian Shelf regions. Asterisks indicate significant trends over time (p < 0.05).

variable	Eastern Scotian Shelf Biomass Trends (kg/year)	Western Scotian Shelf Biomass Trends (kg/year)
CV Biomass	4VN: -2.46e-02 ∗ 4VS: -2.33e-02 4W: 2.60e-04 ESS: -1.84e-02	4X: -6.41e-02 ∗ WSS: -5.20e-02 ∗

19.4 Relevance to Research and Stock Assessments

Decreases in inverse coefficient of variability represent increases in the variability of biomass in the community from year to year, and lower ecosystem stability in the marine community (Bundy, Gomez, and Cook 2017) as community biomass becomes more volatile or exhibits “boom and bust” patterns from year to year.

19.5 Variable Definitions

variable	description	unit
year	Year of data collection
region	Region over which data are summarized
CVBiomass_value	Coefficient of variation in Biomass

19.6 Additional Data

Distribution of Fishing Pressure (within eco_indicators) contains data for 4VN, 4VS, 4W, 4X, ESS, and WSS. All are shown on this page, but note that NAFO divisions are nested within Scotian Shelf regions.

19.7 Get the Data

library(marea)
data('eco_indicators')
plot(eco_indicators)

References

Bundy, Alida, Catalina Gomez, and Adam M. Cook. 2017. “Guidance Framework for the Selection and Evaluation of Ecological Indicators.” Canadian Technical Report of Fisheries and Aquatic Sciences 3232. Dartmouth, Nova Scotia, Canada: Fisheries; Oceans Canada, Bedford Institute of Oceanography. https://waves-vagues.dfo-mpo.gc.ca/Library/40648886.pdf.