Ecology and Vulnerability

Thorny Skate

Many studies provide strong evidence that marine fish and elasmobranch species respond to climate change through geographical range (Nye et al., 2009) and phenology shifts (Staudinger et al., 2019; Langan et al., 2021). Studies of range shifts generally use long-term federal datasets from spring and fall bottom trawl (NOAA Fisheries, 2022) and ichthyoplankton Ecosystem Monitoring (EcoMon) (Walsh et al., 2015) surveys of the continental shelf or by state and private surveys of regional bays and estuaries (Morson et al., 2019, Snyder et al., 2019; Langan et al., 2021). These extensive monitoring programs have shown that centers of population biomass for most marine fish species are shifting poleward towards higher latitudes and to greater depths at rates that exceed terrestrial species (Lenoir et al., 2020). These general trends are projected to continue under future climate scenarios of modeled habitat abundance (Kleisner et al., 2017), suitable thermal habitat (Morley et al., 2018), and relative population biomass (Allyn et al., 2020).


An analysis of 42 species of marine fish and invertebrates (RSGCN and non-RSGCN species) found in continental shelf waters of the Northeast region between 1974 and 2022, showed the community has shifted on average 0.75 degrees (83.83 km) north during spring, and 0.61 degrees (68.27 km) north during fall. The community also experienced a change in average depth of 22.4 meters and 8.6 meters deeper in spring and fall, respectively (NOAA Fisheries, 2022). Similar to patterns observed at the community scale and for non-RSGCN species, the direction, rate, and magnitude of range shifts varies widely among RSGCN marine fishes and elasmobranchs sampled during this period; responses in range changes span -0.51 km southward in Winter Skate, to 2.25 km northward in Black Sea Bass during spring, and -0.21 km northward in Atlantic Herring to 2.05 km northward in Black Sea Bass during fall. Depth range shifts spanned from -61.08 meters deeper in Atlantic Herring to 12.41 km shallower in Atlantic Cod in spring and -50.88 meters deeper in Atlantic Herring to 31.20 meters shallower in Atlantic Halibut during fall (NOAA Fisheries, 2022).

Shifts in phenology are more difficult to track compared to range shifts in aquatic species because observations need repeated observations within a narrow and set area over multiple decades (Staudinger et al., 2019). Several multi-species analyses have shown phenological shifts in the occurrence of larval phases of demersal groundfishes (Walsh et al., 2015), growth and productivity of population biomass (Henderson et al., 2017), as well as seasonal migration patterns (both ingress and egress) and residence times in estuaries systems such as Narragansett Bay, Rhode Island (Langan et al., 2021).

As species make distributional changes in range and phenology, primarily in response to warming sea surface and bottom temperatures, entire assemblages of marine species are reshuffling and reorganizing across Northeast coastal ecosystems (Weiskopf et al., 2020; Staudinger et al., 2021). Examples of changes in community structure through altered species diversity, population size, and density have been documented across the Northeast continental shelf (Friedland et al., 2020) and in estuaries including Little Egg Inlet, New Jersey (Morson et al., 2019), Narragansett Bay, Rhode Island (Langan et al., 2021), and Long Island Sound off of New York and Connecticut (Snyder et al., 2019). Ensembles of warm-water-associated species that are moving north into temperate habitats are generally replacing cold-water-associated species, which are moving to deeper depths and higher latitudes in search of cold-water refugia (Friedland et al., 2020; Pershing et al., 2021). 

On a global scale, warming has led to a decrease in body size (Sheridan and Bickford 2011) but this varies widely by species and local conditions. The indirect effects of morphological and behavioral changes combined with shifting distributions are changing predator-prey and competitive relationships among associated marine fish species and resulting in novel trophic interactions (Staudinger et al., 2021). Most models that project range shifts currently do not account for species interactions (Pearson and Dawson, 2003; MacPherson et al., 2021); this is an area of active research as changes in trophic relationships are hypothesized to be more important for species survival under future conditions than environmental conditions (Louthan et al., 2015, Staniczenko et al., 2017). In addition, the combined stress from warming ocean temperatures, decreased dissolved oxygen, and ocean acidification is increasing the prevalence and vulnerability to disease and predation.

Shifts in Ranges, Elevation, or Depth

Between the period of 1974-1977 to 2019-2022, Thorny Skate shifted its spring range across the Northeast continental shelf by 0.13 degrees (14.85 km) north and contracted its range by 0.73 degrees (81.52 km). During fall, Thorny Skates also shifted 0.21 degrees (23.51 km) north and contracted its range by 1.2 degrees (133.62 km). Thorny Skates shifted its spring depth distribution by 8.1 meters shallower from 1974-1977 to 2019-2022 and its fall depth by 4.9 meters deeper from 1974-1976 to 2019-2022 (NOAA Fisheries, 2022). Thorny Skate is projected to experience significant losses of relative biomass during spring and fall by 2050 across the Northeast continental shelf, with higher decreases projected in the Southern New England – Mid-Atlantic compared to the Gulf of Maine under mean model projections using the RCP 8.5 scenario (Allyn et al., 2020). There is low certainty that Thorny Skates are projected to shift the centroid of their range across the Northeast continental shelf by 118.2 km under RCP 2.6 and medium uncertainty they will shift 442.1 km under RCP 8.5 by the end of the century (2081-2100), with projected changes of available thermal habitat of 5.5% under a RCP 2.6 and -15.5% under RCP 8.5 when compared to the period of 2006-2020 (Morely et al., 2018).

Changes to Morphology or Physiology

In an experiment of Thorny Skates caught from the Gulf of Maine, this species was sensitive to increases in water temperature of 8℃ (from present-day conditions [9℃] to the highend projections for 2100 [15℃]) with their standard metabolic rate increasing significantly (Schwieterman et al., 2019). Additionally, increasing acidification led to lower hypoxia tolerance and increased standard metabolic rate (Schwieterman et al., 2019), demonstrating how the combination of warmer and more acidic water may have a compounding effect on the physiology of Thorny Skates.

Changes in Populations

Depending on the type of survey data used, models project that Thorny Skates may lose between 60-80% (trawl survey data) or 37% (longline survey data) of their Gulf of Maine and Georges Bank population under the most extreme climate change scenario (Grieve et al., 2020). However, with a more moderate climate change scenario, these numbers fall to 35-45% (trawl) or 22% (longline) percent of population declines (Grieve et al., 2020). Regardless, climate change and warming seawater will likely reduce the habitat availability of the Thorny Skate in the region.