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Maritimes Ecosystem Indicator Catalogue

5 Bottom Temperature (AZMP)

Data Type: Tabular Data

Spatial Scope: Scotian Shelf (4X, 4V, 4W)

Duration: 1950-2024

Source: DFO Atlantic Zone Monitoring Program via azmpdata

5.1 Introduction to Indicator

AZMP Bottom Temperature data represent derived and regionally summarized data from the Atlantic Zone Monitoring Program (AZMP), accessed via the azmpdata R package. In the DFO Maritimes region, an ecosystem survey across the Scotian Shelf, spanning the Cabot Strait to the Bay of Fundy, is conducted annually during months July and August. During the survey, oceanographic measurements are taken at randomly selected locations.

Temperature data from continuous downcast CTD profiles are interpolated to a defined grid using an objective analysis procedure, and results are spatially weighted for NAFO divisions 4Vn, 4Vs, 4W, and 4X (Layton et al. 2025).

5.2 View Data 

library(plotly)

plotly_df <- data@data %>%
  left_join(global_cols2) # join in colors and region_group df

p <- plot_ly()

regions_order <- c("4Vn","4Vs","4W","4X")

for(r in regions_order){

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

  group_name <- unique(df_sub$region_group)

  p <- p %>%
    add_lines(
      data = df_sub,
      x = ~year,
      y = ~mean_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), width = 2),
      text = ~paste0("<b>",region,"</b>: ",round(mean_value,2),"°C"),
      hoverinfo = "x+text"
    )
}

p %>%
  layout(
    title = "AZMP Bottom Temperature by Region",
    xaxis = list(title = "Year"),
    yaxis = list(title = "Sea Bottom Temperature (°C)", fixedrange = TRUE),
    hovermode = "x unified",
    legend = list(
      tracegroupgap = 5,
      groupclick = "toggleitem",
      itemdoubleclick = FALSE
    )
  ) %>%
  config(displayModeBar = FALSE)

Figure 5.1: AZMP Regional Bottom Temperature in Scotian Shelf Regions; 1950-2024

5.4 Relevance to Research and Stock Assessments

Sea bottom temperature is highly relevant to population dynamics and spatial distributions, particularly for benthic or bottom-associated species. The effects of sea bottom temperature on fisheries is expected to be variable between regions and species, since thermal envelopes vary across species and shifts in temperature can increase or decrease preferred thermal habitat across regions.

In the Scotian Shelf-Bay of Fundy region, warming bottom temperatures have been associated with negative impacts and/or northward distribution shifts to key decapod species, northern shrimp and snow crab, for which this region represents the southernmost extent of both fisheries (Zisserson and Cook 2017; Chang et al. 2025). Alternatively, recent increases in bottom temperature across the Northwestern Atlantic have increased suitable thermal habitat for halibut in most Eastern Canadian NAFO divisons, and models project further increases in abundance within the Canadian range as bottom temperatures continue to increase (Shackell et al. 2022; Czich et al. 2023).

5.5 Variable Definitions

Table 5.2: Column names and definitions in the AZMP_bottom_temperature dataset.
variable description unit
year Year of data collection
region Region over which records are summarized
mean_value Regionally-aggregated annual mean temperature °C

5.6 Additional Data

AZMP Bottom Temperature also contains data for Cabot Strait, E Georges Bank, Emerald Basin, Georges Basin, Lurcher Shoal, Misaine Bank, 4XeGoMBoF and 4XSS, which are not displayed on this page.

5.7 Get the Data 

library(marea)
data('azmp_bottom_temperature')
plot(azmp_bottom_temperature)

References

Chang, Hsiao-Yun, R Anne Richards, David W Townsend, and Yong Chen. 2025. “Temperature and Abundance Effects on Spatial Structures of Northern Shrimp (Pandalus Borealis) at Different Life Stages in the Oceanographically Variable Gulf of Maine.” Fisheries Oceanography 34 (2): e12714.
Czich, Andrew N, RRE Stanley, TS Avery, CE Den Heyer, and NL Shackell. 2023. “Recent and Projected Climate Change–Induced Expansion of Atlantic Halibut in the Northwest Atlantic.” Facets 8: 1–14.
Layton, C, D Brickman, B Greenan, P Galbraith, and JL Shaw. 2025. “Physical Oceanographic Conditions on the Scotian Shelf and in the Gulf of Maine During 2024.” Dartmouth, Nova Scotia: Fisheries; Oceans Canada, Bedford Institute of Oceanography. https://publications.gc.ca/site/eng/9.953493/publication.html.
Shackell, Nancy L, Jonathan AD Fisher, Cornelia E den Heyer, Daniel R Hennen, Andrew C Seitz, Arnault Le Bris, Dominique Robert, et al. 2022. “Spatial Ecology of Atlantic Halibut Across the Northwest Atlantic: A Recovering Species in an Era of Climate Change.” Reviews in Fisheries Science & Aquaculture 30 (3): 281–305.
Zisserson, Ben, and Adam Cook. 2017. “Impact of Bottom Water Temperature Change on the Southernmost Snow Crab Fishery in the Atlantic Ocean.” Fisheries Research 195: 12–18.