Arctic marine ecosystems are among the most rapidly changing on Earth. As sea ice has declined, vessel traffic has expanded into previously inaccessible areas also used by Arctic marine mammals, including ice-associated seals. To date, vessel exposure research has focused on cetaceans during the open-water season, but vessel traffic is also increasing during the ice-covered season, increasing the potential for exposure to ice seals. Ringed seals Pusa hispida depend on sea ice for reproduction and molting, critical periods when they may be particularly vulnerable to disturbances from vessels. We used vessel locations from the Arctic Ship Traffic Database and satellite telemetry locations for 27 ringed seals to estimate potential exposure (i.e. spatial-temporal overlap) to vessels by month in the Pacific Arctic, 2013-2022. Using a 125 km buffer around seal tracks to define monthly areas of potential exposure, 26 seals overlapped with vessels. There were 2172 total potential exposures (average 80, range 14-170 vessels per seal). Seals were potentially exposed to significantly more vessels during the open-water season when vessels traveled at significantly higher maximum speeds than during the ice-covered season. During the ice-covered season, 10 seals overlapped with 27 vessels, which included crude oil tankers, gas tankers, general cargo ships, and ’unknown’ and ’other’ vessel types. Our results suggest that ringed seals in the Pacific Arctic are regularly exposed to all vessel types during the open-water season; however, potential exposure during the ice-covered season is relatively low. Additional research is needed to understand the effects of vessel exposure on ringed seals.
Diel periodicity is a common feature of animal activities and is often shaped by factors related to optimizing resources over daily timescales. Additionally, many terrestrial mammals utilize nighttime periods to avoid diurnal human disturbance; however, examples in marine mammals are limited. Southern resident killer whales (SRKWs) Orcinus orca extensively echolocate to hunt their fish prey. While investigations have documented vessel and noise impacts on SRKWs foraging, with greater effects in females, findings are based on daytime observations. It remains unknown how individuals partition their foraging between day and night periods and whether individuals exploit nighttime periods that coincide with reduced disturbance. Here, we used sound and movement tags to investigate diel periodicity of biosonar-based foraging by classifying SRKW echolocation bouts into 3 foraging phases: (1) search (regular/slow clicking: inter-click interval, ICI > 100 ms), (2) pursuit (fast clicking: 10 ms < ICI ≤ 100 ms), and (3) capture attempts (buzzing: ICI ≤ 10 ms). We often detected crunching sounds following pursuit and/or capture attempts, indicating successful prey capture. SRKWs echolocated at shallower depths at night, reflecting the behavior of their prey. We found no diel effect on the probability of searching. However, females had a lower probability than males of prey pursuit and capture attempts, and the lowest probability of capture attempts at night, implying reduced foraging efficiency even during periods with reduced disturbance. These results, although sample-size limited, advance our understanding of temporal patterns of foraging to better predict consequences of disturbance in coastal cetaceans that rely on sound for energy acquisition.
Extinction risk in sharks threatens to undermine marine ecosystem function, with widespread socio-ecological ramifications. Effective management requires regional evidence regarding species movement, connectivity, and critical habitat use. Angelsharks Squatina squatina are among the most threatened shark species, with several historical populations considered extirpated. Occurrence in both the Canary Islands, Spain, and Cardigan Bay, UK, accordingly presents important conservation opportunities. Here, we detected S. squatina on 3 of 20 baited remote underwater video stations (BRUVS) deployed in September 2024 and June 2025 between 2 Special Areas of Conservation (SAC) in Cardigan Bay: Pen Llŷn a’r Sarnau SAC and Cardigan Bay SAC. This not only represents the first BRUVS detections for this species in the UK but demonstrates repeated habitat use and supports the IUCN Cardigan-Caernarfon Bay Important Shark and Ray Area (ISRA) as an important habitat area. Population status and structure, characteristics, the ecological and environmental drivers of fine-scale habitat use, and whether the study site has specific local ecological importance, are notable knowledge gaps, despite declaration of the IUCN Cardigan-Caernarfon Bay ISRA. Strategies to address this are discussed that would in turn strengthen regional management and conservation benefits for S. squatina .
Over one-third of Critically Endangered North Atlantic right whales (NARWs) occur seasonally (April-November) in the Gulf of St. Lawrence (GSL), Canada, where aerial surveys monitor abundance and distribution to mitigate vessel strike and fishing gear entanglement risks. Reliable risk and abundance estimates require accounting for spatio-temporal variations in diving behaviour. We addressed this by deploying satellite-linked time-depth/fastlocGPS Argos transmitters on 28 NARWs in the GSL during 2019 and 2022-2024, including May-June (n = 4) and July-August (n = 24) deployments. Dive data revealed a pronounced diel pattern: NARWs generally remained near-surface (<15 m) at night and dove near the seafloor during daytime, increasing the potential for encounters with vessels and surface buoylines at night, and bottom-set gear groundlines during daytime. An exception occurred in 2022, with around-the-clock seafloor diving. A state-space model of location data showed that transiting whales were more exposed to potential vessels and surface buoylines and more available to aerial survey platforms, whereas animals demonstrating area-restricted search-like behaviour were more exposed to potential groundlines. Limited spring deployments indicated less frequent near-seafloor diving than in summer, a key consideration for estimating and managing risks from the GSL snow crab fishery, which peaks in spring and may eventually transition from single traps to on-demand groundline-connected strings to reduce vertical and surface buoyline entanglement risks. Together, diel, seasonal, interannual, and behavioural-state differences in diving behaviour underscore the need to integrate these factors into vessel strike and entanglement risk assessments for NARWs in the GSL.
Understanding how distinct populations interact demographically, ecologically and genetically at their boundaries allows us to understand patterns of connectivity and their conservation implications. Here, we build on previous research to evaluate the regional and local population structure of Aotearoa/New Zealand’s endemic and endangered Hector’s dolphin Cephalorhynchus hectori hectori , focusing on distinct areas representing population boundaries. We used DNA profiles comprising genetically identified sex, mitochondrial DNA (mtDNA) haplotype and microsatellite loci for 717 individuals throughout the species’ range, including 266 for which we generated new data. Population structure analyses of both mtDNA and microsatellite data confirmed previously described significant differentiation between the 3 main regions (East, West, and South Coast). There was a clear genetic boundary between the East and West Coast populations, consistent with a previously identified ecological boundary. The Queen Charlotte Sound subpopulation present adjacent to this boundary has very low genetic diversity, consistent with being at the end of a ‘stepping stone’ model of population structure. In contrast, we detected genetic admixture at the boundary between the South and East Coast populations, while confirming genetic differentiation amongst subpopulations in the region. Finally, a deep-water canyon was revealed to be a biogeographic break, with significant genetic differentiation to its north and south. Our results highlight how a single species can have different patterns of gene flow at the boundaries of genetically identifiable populations, likely driven by spatial differences in oceanography and resource distribution.
The Northwest Atlantic population of blue whales Balaenoptera musculus is endangered. Understanding their habitat use off eastern Canada is important for protection and recovery. Passive acoustic monitoring (PAM) has contributed to identifying areas of importance to this population, which include deep slope waters along the edge of the Scotian Shelf off Nova Scotia. Many PAM studies have focused on assessing blue whale acoustic occurrence using infrasonic (A, B, AB) calls, which are produced by males and associated with reproduction or migration. Audible (D, downsweep, arch) calls are less well described but are produced by both sexes and may serve social or foraging functions. We analyzed PAM data collected from Emerald Basin on the central Scotian Shelf from 2015 to 2019 to assess on-shelf blue whale acoustic presence and whether audible calls would contribute to our understanding of their presence. Calls occurred on 39% of recording days, representing year-round presence, with the highest acoustic occurrence observed between September and January (calls occurring on 17-100% of days per month). Of days with calls, 25% of those days contained only infrasonic calls, and 41% contained only audible calls, indicating that blue whale presence would have been underestimated if only infrasonic calls were monitored. These results suggest that Emerald Basin may also be important habitat for blue whales in Atlantic Canada. We recommend that future acoustic studies incorporate both infrasonic and audible call types, as well as further investigation of the Scotian Shelf as potential important habitat.
Vessel strikes account for 25% or more of sea turtle strandings in some regions and are the most common cause of traumatic injury among stranded sea turtles in many developed areas. Vessel strikes are predicted to increase along with human populations and vessel use. Understanding how vessel strikes affect different populations of sea turtles is essential to these species’ conservation. Mote Marine Laboratory’s Stranding Investigations Program responds to stranded sea turtles in southwest Florida and has records of stranded sea turtles dating back to 1987. Historical stranding data collected from 1987 to 2021 were reviewed, and 364 sea turtles with documented wounds consistent with vessel strikes were evaluated. Species studied included loggerhead Caretta caretta , green Chelonia mydas , and Kemp’s ridley Lepidochelys kempii turtles. Wounds were classified by anatomical zones that corresponded with underlying organ systems and other vital anatomy. Analyses examined injury location by species, sex, age, and size class, as well as the likelihood that the vessel strike contributed to the stranding. While there were some significant differences among these demographic categories, the predominant finding of this study is that sea turtles struck by vessels have an exceptionally low survival rate.
Understanding migratory behavior is a fundamental component of conservation biology. However, the migration ecology of Sakhalin taimen Parahucho perryi, one of the largest salmonids and a landmark species for conservation, remains poorly understood. The lifetime migratory patterns of Sakhalin taimen from rivers in northern Hokkaido that had died due to a heat wave were classified into diadromous and fluvial forms, as revealed by transect analysis of otolith microchemistry. Notably, 2 diadromous individuals had migrated to the sea at the age of 0+ yr and subsequently retired from seaward migration, representing the first empirical evidence of a previously predicted migratory pattern. A hierarchical clustering analysis of maternal origins, based on the otolith strontium:calcium ratios from the core to 80 mu m using dynamic time warping analysis, revealed that both post-sea-run migration and post-freshwater residence individuals contribute to offspring production. The migratory patterns revealed a clear difference in the proportion of diadromous forms between the 2 river systems, with a higher occurrence in the Sarufutsu River system, which flows into the Sea of Okhotsk, than in the Teshio River system, which flows into the Sea of Japan. Growth models varied among migratory forms, with diadromous individuals reaching a larger asymptotic fork length than fluvial individuals. These findings suggest that migration to the ocean contributes to size enhancement in Sakhalin taimen. Additionally, the study demonstrated that Sakhalin taimen exhibit diverse growth patterns and migratory behaviors, spanning a wide range of aquatic habitats, from rivers to the ocean, with variations among individuals and river systems.
