Ecology and Vulnerability

Atlantic Halibut

A growing number of studies provide strong evidence that marine fish and invertebrate species are responding 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 the majority of 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 in comparison to range shifts in aquatic species because observations need to have 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 is 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 Range, Elevation, or Depth

Between the periods of 1974-1977 to 2019-2022, the spring range of Atlantic halibut across the Northeast continental shelf region has shifted 0.55 degrees (62.18 km) north and its range has expanded by 0.21 degrees (23.92 km); conversely during the fall season, its fall range has moved 0.18 degrees (20.26 km) south and contracted by 1.02 degrees (112.8 km) between the periods of 1974-1976 to 2019-2022. Atlantic halibut has shifted to shallower depths in both spring and fall by 5 meters and 31.2 meters, respectively (NOAA Fisheries 2022).

Atlantic halibut is projected to experience significant losses of relative biomass during spring and fall by 2050 across the Northeast continental shelf under mean model projections using the RCP 8.5 scenario (Allyn et al., 2020). There is low certainty that Atlantic Halibut is projected to shift the centroid of their range along the coast of eastern Canada by 122.1 km under RCP 2.6 and medium uncertainty they will shift 440.9 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 -18.6% under RCP 8.5 when compared to the period of 2006-2020 (Morely et al., 2018).

Changes to Morphology or Physiology

Multiple studies have shown that Atlantic Halibut is sensitive to the effects of ocean acidification and warming water temperatures. Health effects include reduced growth rates (Grans et al., 2014), metabolism increases and apoptosis signaling in gills and blood plasma (Bresolin et al., 2014). Juvenile Atlantic Halibut showed increased immune system responses under varying conditions (5-18 °C and pH of 8.0 and 7.6) that caused increased oxidative damage (Almroth et al., 2019) and may impact their ability to acclimatize (de Souza et al., 2016).