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Northward range shifts are increasingly being identified in mobile animals that are responding to climate change. Range shifts are consequential to animal ecology, ecosystem function, and conservation goals, yet for many species these cannot be characterised without means of synoptically measuring their distribution. The distribution of critically endangered North Atlantic right whale (Eubalaena glacialis; NARW) north of 45°N has been largely unknown due to a lack of systematic monitoring. The objectives of this study were to characterize the spatial and temporal variation in NARW acoustic occurrence in the northern portion of their foraging range. In addition, we sought to identify relevant NARW migratory corridors and explore potential previously unidentified high-use habitats beyond the highly surveyed Gulf of St. Lawrence (GSL). To achieve this, passive acoustic monitoring data were collected and analyzed from 67 moorings and 13 gliders deployed (across 38 recording stations) throughout the Atlantic Canadian continental shelf, between 42°N and 58°N during 2015 through 2017. The results support that while a portion of the population has moved northward into the GSL, this shift was constrained to temperate latitudinal ranges < 52°N during the study period. NARWs were not detected in the Labrador Sea and Newfoundland Shelf, despite their preferred prey occurring in those areas. NARWs were present on the Scotian Shelf (45°N) nearly year-round, but only from May through December in the Cabot Strait (50°N). These results indicate that the northern range of the population is probably influenced by energetic requirements to minimize the distance between suitable foraging habitat and low latitude calving grounds, rather than an absence of suitable foraging conditions in high latitude waters, or other environmental or physiological factors. This work provides critical information to conserve the species and mitigate human-induced risks.

Ocean warming linked to anthropogenic climate change is impacting the ecology of marine species around the world. In 2010, the Gulf of Maine and Scotian Shelf regions of the Northwest Atlantic underwent an unprecedented regime shift. Forced by climate-driven changes in the Gulf Stream, warm slope waters entered the region and created a less favorable foraging environment for the endangered North Atlantic right whale population. By mid-decade, right whales had shifted their late spring/summer foraging grounds from the Gulf of Maine and the western Scotian Shelf to the Gulf of St. Lawrence. The population also began exhibiting unusually high mortality in 2017. Here, we report that climate-driven changes in ocean circulation have altered the foraging environment and habitat use of right whales, reducing the population’s calving rate and exposing it to greater mortality risks from ship strikes and fishing gear entanglement. The case of the North Atlantic right whale provides a cautionary tale for the management of protected species in a changing ocean.

North Atlantic right whales Eubalaena glacialis (hereafter right whales) have recently shifted their distribution away from some protected feeding habitats, which suggests large-scale changes in food supply have occurred. Quantifying the nature and extent of the apparent shift is key to exploring this hypothesis and planning or revising conservation strategies. This paper characterizes decadal right whale occurrence in the Bay of Fundy summer feeding habitat using data derived from 7522 h of survey effort collected over 30 yr (1987 to 2016) that yielded 11483 right whale sightings. Eight occurrence descriptors were derived to quantify temporal variation in right whale presence, encounter rates and time of arrival in the Bay. Time of arrival was modeled using linear and power function models fit to annual discovery curves. Principal component analysis showed 2 modes that explained 58 and 14% of the variation in occurrence, respectively. The first mode captured a significant decline in summertime right whale occurrence beginning in 2010. The second mode captured a decadal-scale cycle in seasonal timing of occurrence, which highlighted a sharp change from early to late occupancy at the turn of the millennium. Annual occurrence during the 2010-2016 period was anomalously low in both the Grand Manan Basin critical habitat and the Bay of Fundy Traffic Separation Scheme (shipping lanes), whereas encounters in the region NW of the critical habitat containing Owen Basin and The Wolves islands may be increasing due to a distributional shift within the Bay. We discuss the consequences of these changes for both population dynamics and future conservation of the species.

Variation in water mass transport is a key driver of variability in zooplankton ecology. Data distribution (e.g., sparseness) is often an important factor limiting robust delineation of zooplankton-water mass associations. Mobile autonomous profiling gliders can help address the sparseness issue because gliders can sample across water mass domains spanning tens to hundreds of kilometers at high frequency during a single deployment. The goal of our study was to research the use of gliders as a tool to increase the spatiotemporal scale and robustness of zooplankton-water mass datasets. An autonomous ocean glider was deployed in Roseway Basin, Scotian Shelf, Canada for 2 months along a set of transects that crossed two water masses, a cold-fresh coastal water mass, and a warm-salty continental slope water mass. Zooplankton backscatter was measured with a single frequency Imagenex 300 kHz hydroacoustic echosounder mounted to the underside of the glider at an angle of 26°, such that it was directed vertically downward on the glider downcast. During the deployment, an unusual basin flushing event occurred, where the slope water mass that is typically present in the deep water of Scotian Shelf basins was almost completely replaced by coastal water at all depths. This unique event offered an opportunity to study how extreme changes in water mass affected zooplankton distribution. The impact of basin flushing on both diel- and non-diel-vertically migrating zooplankton communities within the basin was investigated using General Linear Models. The analysis demonstrated some key relationships exist among zooplankton acoustic scattering layers, water mass properties, and basin bathymetry. Zooplankton backscatter was higher in the slope water mass, and declined substantially during the basin flushing event, suggesting that coastal water is not zooplankton habitat for either community. Spatial gradients in the extent of flushing provided local refuge for zooplankton within one margin of the Basin. These patterns would be challenging to measure using conventional shipboard surveys. Our study provides guidance on the use of gliders to supplement shipboard research on biophysical coupling in the plankton, which is of value as the use of gliders for this purpose is proliferating.

Rising global temperatures are causing a poleward shift in species distribution. Range shift velocities are higher in the marine environment, with observed rates of 30–130 km per decade. Both protected and exploited species will be at risk if marine species management policies are not structured to anticipate these range shifts. The 2017 mass mortality event of the North Atlantic right whale showcases the detrimental impact of unanticipated climate-mediated behavior in a species protected by geographically and seasonally fixed policies. Based on the results of a demographic capture-​recapture model, right whales may face extinction in fewer than 30 years unless protective policies are expanded to cover their shifting distribution. Increased support of long-term monitoring programs paired with environmental modeling research is critical to developing more proactive conservation management strategies and preventing further ecological crises.

Oceanographic surveys were conducted in Roseway Basin, western Scotian Shelf, during late-summer from 2007 through 2009 to measure the magnitude of interannual variation in the spatial distribution of diapausing copepods Calanus finmarchicus and C. hyperboreus and associated water mass characteristics. Calanus spp. abundance, energy density and hydrography were measured at depths > 50 m along transects using a Towed Underwater Biological Sampling System equipped with an Optical Plankton Counter (OPC) and a conductivity-temperature-depth (CTD) sensor, as well as at fixed stations using a Biological Net and Environmental Sampling System equipped with nets, OPC and CTD. Water mass density and in some cases salinity explained variation in the deep copepod layer across both time and space, whereas temperature did not. Water mass density, copepod energy density and thickness of the copepod layer were statistically lower during 2008 than 2007 or 2009. The copepod layer was absent from the western Basin margin during 2008 where low density continental water resided that year, whereas during 2007 and 2009 higher density continental slope water and copepods were each present along the western margin. Our results suggest that water mass density is an important characteristic defining the spatial and interannual ecology of the deep copepod layer in Roseway Basin. The 26 σ t isopycnal may be a lower density limit to diapausing Calanus spp. habitat on continental shelves with shallow bathymetry, that helps the animals maintain neutral buoyancy during diapause.

The Roseway and Grand Manan basins on the Canadian Atlantic coast are neighboring late-summer critical feeding habitats for endangered North Atlantic right whales. Although in late summer these habitats regularly contain thick aggregations of right whale food – the copepod Calanus spp. – right whales periodically abandon one or both habitats in the same year. The causes of abandonments, their relationship to food supply, and the locations of whales during abandonment periods are unclear. The goals of this study were to explain variation in right whale abundance indices from a habitat perspective, and to determine whether or not oceanographic variation in the habitats influences occupancy. Four indices of whale abundance and habitat occupancy, including sightings per unit effort (SPUE), photographic sightings of known individuals, population size and habitat transition probabilities, were analyzed in relation to unique datasets of Calanus concentration and water mass characteristics in each basin over the period 1987 through 2009. Calanus concentration, water mass sources and various hydrographic properties each varied coherently between basins. Calanus concentration showed an increasing trend over time in each habitat, although a short-lived reduction in Calanus may have caused right whales to abandon Roseway Basin during the mid-1990s. Food supply explained variation in right whale sightings and population size in Roseway Basin, but not in Grand Manan Basin, suggesting that the Grand Manan Basin has important habitat characteristics in addition to food supply. Changes in the distribution of whale abundance indices during years when oceanographic conditions were associated with reduced food supply in the Scotia-Fundy region suggest that other suitable feeding habitats may not have existed during such years and resulted in negative effects on whale health and reproduction.

North Atlantic right whales Eubalaena glacialis foraging on deep (>100 m) popula- tions of diapausing Calanus spp. in the Roseway Basin right whale Critical Habitat (south of Nova Scotia, Canada) are most often located along the southern margin of the basin. We investigated the physical and biological oceanographic characteristics that make this margin a lucrative feed- ing ground. Bottom-moored acoustic Doppler current profilers equipped with conductivity, tem- perature, and depth sensors were deployed cross-isobath on the southeastern slope of the basin to simultaneously measure variation in Calanus spp. concentration, current velocity, and water mass characteristics in time and space. Variation in upslope tidal advection of deep-basin water with densities >1026 kg m �3 and containing highly concentrated copepod aggregations was the most important process influencing cross-isobath variation in copepod concentrations on the slope. The aggregations were maintained in the slope region through time despite extensive along-isobath advection, implying the existence of copepod re-supply mechanisms to the southern margin. Pro- posed mechanisms include immigration from surface populations, horizontal advection, and gyre- like re-circulation within the basin. A simple empirically-driven particle tracking model illustrated tidally-forced particle convergence between the 100 and 140 m isobaths on the southeastern slope, followed by upward and along-isobath advection. Cross-isobath 'compression' of copepods coupled with the maintenance of their vertical position through neutral buoyancy is proposed as a mechanism resulting in accumulation on the slope, making the area uniquely beneficial to right whales feeding at depth along the slope margin.

Calanus finmarchicus stage-C5 and C. hyperboreus stage-C4 diapausing in Scotian Shelfbasins are high-quality food sources because they are abundant and high inenergy content. When combined, these two variables are informative for quantify-ing energy density, carrying capacity and energy transfer in marine ecosystems.However, measuring energy content directly can be difficult and expensive. Here,we present energy (caloric) content estimates for two co-located diapausingcopepod species; C. finmarchicus C5 and C. hyperboreus C4 collected during late-summer when their energy content is at or near the annual maximum. We thendevelop several practical energy content calibrations, each designed to estimateenergy content using simple measures of Calanus spp. body size or weight. Weight-specific energy content (energy quality, kJ g

Increasing atmospheric carbon dioxide levels are causing ocean acidification, compromising the ability of some marine organisms to build and maintain support structures. An analysis of mussels from a submarine volcano setting with natural low-pH conditions shows low shell thicknesses and growth rates, but survival over up to four decades. Increasing atmospheric carbon dioxide levels are causing ocean acidification1,2, compromising the ability of some marine organisms to build and maintain support structures3 as the equilibrium state of inorganic carbon moves away from calcium carbonate4. Few marine organisms tolerate conditions where ocean pH falls significantly below today’s value of about 8.1 and aragonite and calcite saturation values below 1 (refs 5, 6). Here we report dense clusters of the vent mussel Bathymodiolus brevior in natural conditions of pH values between 5.36 and 7.29 on northwest Eifuku volcano, Mariana arc, where liquid carbon dioxide and hydrogen sulphide emerge in a hydrothermal setting. We find that both shell thickness and daily growth increments in shells from northwest Eifuku are only about half those recorded from mussels living in water with pH>7.8. Low pH may therefore also be implicated in metabolic impairment7. We identify four-decade-old mussels, but suggest that the mussels can survive for so long only if their protective shell covering remains intact: crabs that could expose the underlying calcium carbonate to dissolution are absent from this setting. The mussels’ ability to precipitate shells in such low-pH conditions is remarkable. Nevertheless, the vulnerability of molluscs to predators is likely to increase in a future ocean with low pH.